Bump to 0.20.0

Cleanup StringBuilderCache

.github/FUNDING.yml

@@ -0,0 +1,12 @@
+# These are supported funding model platforms
+
+github: [xoofx]
+patreon: # Replace with a single Patreon username
+open_collective: # Replace with a single Open Collective username
+ko_fi: # Replace with a single Ko-fi username
+tidelift: # Replace with a single Tidelift platform-name/package-name e.g., npm/babel
+community_bridge: # Replace with a single Community Bridge project-name e.g., cloud-foundry
+liberapay: # Replace with a single Liberapay username
+issuehunt: # Replace with a single IssueHunt username
+otechie: # Replace with a single Otechie username
+custom: # Replace with up to 4 custom sponsorship URLs e.g., ['link1', 'link2']

.github/workflows/ci.yml

@@ -0,0 +1,61 @@
+name: ci
+
+env:
+  PROJECT_NAME: Markdig
+
+on:
+  push:
+    paths-ignore:
+    - 'doc/**'
+    - 'img/**'
+    - 'changelog.md'
+    - 'readme.md'
+  pull_request:
+
+jobs:
+  build:
+    runs-on: windows-latest
+
+    steps:
+    - name: Checkout
+      uses: actions/checkout@v1
+
+    - name: Install .NET Core
+      uses: actions/setup-dotnet@v1
+      with:
+        dotnet-version: 3.0.100
+
+    - name: Build (Release)
+      run: dotnet build src -c Release
+
+    - name: SpecFileGen
+      run: dotnet src/SpecFileGen/bin/Release/netcoreapp2.1/SpecFileGen.dll
+
+    - name: Test (Release)
+      run: dotnet test src -c Release
+
+    - name: Build & Test (Debug)
+      run: dotnet test src -c Debug
+
+    - name: Coverlet
+      run: dotnet test src -c Release -f netcoreapp2.1 /p:Include=\"[${{env.PROJECT_NAME}}]*\" /p:CollectCoverage=true /p:CoverletOutputFormat=lcov
+
+    - name: Coveralls Upload
+      uses: coverallsapp/github-action@v1.0.1
+      if: github.event_name == 'push'
+      with:
+        github-token: ${{ secrets.GITHUB_TOKEN }}
+        path-to-lcov: src/${{env.PROJECT_NAME}}.Tests/coverage.netcoreapp2.1.info
+
+    - name: Pack
+      run: dotnet pack src -c Release
+
+    - name: Publish
+      if: github.event_name == 'push'
+      run: |      
+          if ( "${{github.ref}}" -match "^refs/tags/[0-9]+\.[0-9]+\.[0-9]+$" ) {
+              dotnet nuget push src\${{env.PROJECT_NAME}}\bin\Release\*.nupkg -s nuget.org -k ${{secrets.NUGET_TOKEN}}
+              dotnet nuget push src\${{env.PROJECT_NAME}}.Signed\bin\Release\*.nupkg -s nuget.org -k ${{secrets.NUGET_TOKEN}}
+          } else {
+              echo "publish is only enabled by tagging with a release tag"
+          }

.gitignore

@@ -7,6 +7,7 @@
 *.userosscache
 *.sln.docstates
 *.nuget.props
+*.nuget.targets
 
 # User-specific files (MonoDevelop/Xamarin Studio)
 *.userprefs

appveyor.yml

@@ -1,57 +0,0 @@
-version: 10.0.{build}
-image: Visual Studio 2017
-configuration: Release
-
-install:
-- ps: >-
-    cd src
-
-    nuget restore Markdig.sln
-
-    $env:MARKDIG_BUILD_NUMBER = ([int]$env:APPVEYOR_BUILD_NUMBER).ToString("000")
-
-    $env:MARKDIG_VERSION_SUFFIX = ""
-
-    $env:appveyor_nuget_push = 'false'
-
-    if(-Not $env:APPVEYOR_PULL_REQUEST_NUMBER) {
-      if($env:appveyor_repo_tag -eq 'True') {
-    	  if($env:appveyor_repo_tag_name -match '^[0-9]') {
-           $env:appveyor_nuget_push = 'true'
-           $env:MARKDIG_VERSION_SUFFIX = ""
-        }
-    	  if($env:appveyor_repo_tag_name -eq 'latest') {
-           $env:appveyor_nuget_push = 'true'
-           $env:MARKDIG_VERSION_SUFFIX = "pre$env:MARKDIG_BUILD_NUMBER"
-        }
-      }
-    }
-
-build:
-  project: src/Markdig.sln
-  verbosity: minimal
-
-after_build:
-- cmd: >-
-    dotnet run --project SpecFileGen/SpecFileGen.csproj -c Release
-
-    dotnet test -v n Markdig.Tests
-
-before_package:
-- cmd: >-
-    msbuild /t:pack /p:VersionSuffix="%MARKDIG_VERSION_SUFFIX%" /p:Configuration=Release Markdig/Markdig.csproj
-
-    msbuild /t:Clean Markdig/Markdig.csproj
-
-    msbuild /t:pack /p:VersionSuffix="%MARKDIG_VERSION_SUFFIX%" /p:Configuration=Release;SignAssembly=true Markdig/Markdig.csproj
-
-artifacts:
-- path: src\Markdig\Bin\Release\*.nupkg
-  name: Markdig Nugets
-
-deploy:
-- provider: NuGet
-  api_key:
-    secure: 7cthHh+wYWZjhqxaxR6QObRaRnstvFkQOY7MkxIsC5kpQEBlKZXuinf0IybbYxJt
-  on:
-    appveyor_nuget_push: true

changelog.md

@@ -1,5 +1,42 @@
 # Changelog
 
+## 0.20.0 (18 Apr 2020)
+- Markdig is now compatible only with `NETStandard 2.0`, `NETStandard 2.1`, `NETCoreApp 2.1` and `NETCoreApp 3.1`.
+- Many performance improvements from [PR #416](https://github.com/lunet-io/markdig/pull/416) 
+[PR #417](https://github.com/lunet-io/markdig/pull/417)
+[PR #418](https://github.com/lunet-io/markdig/pull/418) 
+[PR #421](https://github.com/lunet-io/markdig/pull/421) 
+[PR #422](https://github.com/lunet-io/markdig/pull/422) 
+[PR #410](https://github.com/lunet-io/markdig/pull/410)
+
+## 0.18.3 (8 Mar 2020)
+- Publish NuGet Symbol packages
+
+## 0.18.2 (8 Mar 2020)
+- Optimize LineReader.ReadLine in [PR #393](https://github.com/lunet-io/markdig/pull/393)
+- Use HashSet<T> instead of Dictionary<TKey, TValue> in CharacterMap<T> in [PR #394](https://github.com/lunet-io/markdig/pull/394)
+- Use BitVector128 in CharacterMap<T> in [PR #396](https://github.com/lunet-io/markdig/pull/396)
+- Optimizations in StringLineGroup in [PR #399](https://github.com/lunet-io/markdig/pull/399)
+- Fixed a bug in HeadingRenderer in [PR #402](https://github.com/lunet-io/markdig/pull/402)
+- Fixes issue #303 in [PR #404](https://github.com/lunet-io/markdig/pull/404)
+- Make output of HtmlTableRenderer XML wellformed in [PR #406](https://github.com/lunet-io/markdig/pull/406)
+
+## 0.18.1 (21 Jan 2020)
+- Re-allow emojis and smileys customization, that was broken in [PR #308](https://github.com/lunet-io/markdig/pull/308) ([PR #386](https://github.com/lunet-io/markdig/pull/386))
+- Add `IHostProvider` for medialink customization (#337), support protocol-less url (#135) ([(PR #341)](https://github.com/lunet-io/markdig/pull/341))
+- Add missing Descendants<T> overload ([(PR #387)](https://github.com/lunet-io/markdig/pull/387))
+
+## 0.18.0 (24 Oct 2019)
+- Ignore backslashes in GFM AutoLinks ([(PR #357)](https://github.com/lunet-io/markdig/pull/357))
+- Fix SmartyPants quote matching ([(PR #360)](https://github.com/lunet-io/markdig/pull/360))
+- Fix generic attributes with values of length 1 ([(PR #361)](https://github.com/lunet-io/markdig/pull/361))
+- Fix link text balanced bracket matching ([(PR #375)](https://github.com/lunet-io/markdig/pull/375))
+- Improve overall performance and substantially reduce allocations ([(PR #377)](https://github.com/lunet-io/markdig/pull/377))
+
+## 0.17.1 (04 July 2019)
+- Fix regression when escaping HTML characters ([(PR #340)](https://github.com/lunet-io/markdig/pull/340))
+- Update Emoji Dictionary ([(PR #346)](https://github.com/lunet-io/markdig/pull/346))
+
 ## 0.17.0 (10 May 2019)
 - Update to latest CommonMark specs 0.29 ([(PR #327)](https://github.com/lunet-io/markdig/pull/327))
 - Add `AutoLinkOptions` with `OpenInNewWindow`, `UseHttpsForWWWLinks` ([(PR #327)](https://github.com/lunet-io/markdig/pull/327))

readme.md

@@ -1,4 +1,4 @@
-# Markdig [![Build status](https://ci.appveyor.com/api/projects/status/hk391x8jcskxt1u8?svg=true)](https://ci.appveyor.com/project/xoofx/markdig) [![NuGet](https://img.shields.io/nuget/v/Markdig.svg)](https://www.nuget.org/packages/Markdig/) [![Donate](https://www.paypalobjects.com/en_US/i/btn/btn_donate_SM.gif)](https://www.paypal.com/cgi-bin/webscr?cmd=_s-xclick&hosted_button_id=FRGHXBTP442JL)
+# Markdig [![Build Status](https://github.com/lunet-io/markdig/workflows/ci/badge.svg?branch=master)](https://github.com/lunet-io/markdig/actions) [![Coverage Status](https://coveralls.io/repos/github/lunet-io/markdig/badge.svg?branch=master)](https://coveralls.io/github/lunet-io/markdig?branch=master) [![NuGet](https://img.shields.io/nuget/v/Markdig.svg)](https://www.nuget.org/packages/Markdig/) [![Donate](https://www.paypalobjects.com/en_US/i/btn/btn_donate_SM.gif)](https://www.paypal.com/cgi-bin/webscr?cmd=_s-xclick&hosted_button_id=FRGHXBTP442JL)
 
 <img align="right" width="160px" height="160px" src="img/markdig.png">
 
@@ -21,7 +21,7 @@ You can **try Markdig online** and compare it to other implementations on [babel
   - Even the core Markdown/CommonMark parsing is pluggable, so it allows to disable builtin Markdown/Commonmark parsing (e.g [Disable HTML parsing](https://github.com/lunet-io/markdig/blob/7964bd0160d4c18e4155127a4c863d61ebd8944a/src/Markdig/MarkdownExtensions.cs#L306)) or change behaviour (e.g change matching `#` of a headers with `@`)   
 - Built-in with **20+ extensions**, including:
   - 2 kind of tables:
-    - [**Pipe tables**](src/Markdig.Tests/Specs/PipeTableSpecs.md) (inspired from Github tables and [PanDoc - Pipe Tables](http://pandoc.org/README.html#extension-pipe_tables))
+    - [**Pipe tables**](src/Markdig.Tests/Specs/PipeTableSpecs.md) (inspired from GitHub tables and [PanDoc - Pipe Tables](http://pandoc.org/README.html#extension-pipe_tables))
     - [**Grid tables**](src/Markdig.Tests/Specs/GridTableSpecs.md) (inspired from [Pandoc - Grid Tables](http://pandoc.org/README.html#extension-grid_tables)) 
   - [**Extra emphasis**](src/Markdig.Tests/Specs/EmphasisExtraSpecs.md) (inspired from [Pandoc - Emphasis](http://pandoc.org/README.html#strikeout) and [Markdown-it](https://markdown-it.github.io/)) 
     - strike through `~~`,
@@ -48,9 +48,11 @@ You can **try Markdig online** and compare it to other implementations on [babel
   - [**SmartyPants**](src/Markdig.Tests/Specs/SmartyPantsSpecs.md) (inspired from [Daring Fireball - SmartyPants](https://daringfireball.net/projects/smartypants/))
   - [**Bootstrap**](src/Markdig.Tests/Specs/BootstrapSpecs.md) class (to output bootstrap class)
   - [**Diagrams**](src/Markdig.Tests/Specs/DiagramsSpecs.md) extension whenever a fenced code block contains a special keyword, it will be converted to a div block with the content as-is (currently, supports [`mermaid`](https://knsv.github.io/mermaid/) and [`nomnoml`](https://github.com/skanaar/nomnoml) diagrams)
-  - [**YAML frontmatter**](src/Markdig.Tests/Specs/YamlSpecs.md) to parse without evaluating the frontmatter and to discard it from the HTML output (typically used for previewing without the frontmatter in MarkdownEditor)
+  - [**YAML Front Matter**](src/Markdig.Tests/Specs/YamlSpecs.md) to parse without evaluating the front matter and to discard it from the HTML output (typically used for previewing without the front matter in MarkdownEditor)
   - [**JIRA links**](src/Markdig.Tests/Specs/JiraLinks.md) to automatically generate links for JIRA project references (Thanks to @clarkd: https://github.com/clarkd/MarkdigJiraLinker)
-- Compatible with .NET 3.5, 4.0+ and .NET Core (`netstandard1.1+`)
+- Starting with Markdig version `0.20.0+`, Markdig is compatible only with `NETStandard 2.0`, `NETStandard 2.1`, `NETCoreApp 2.1` and `NETCoreApp 3.1`.
+
+If you are looking for support for an old .NET Framework 3.5 or 4.0, you can download Markdig `0.18.3`.
 	
 ### Third Party Extensions
 
@@ -84,7 +86,7 @@ var result = Markdown.ToHtml("This is a text with some *emphasis*");
 Console.WriteLine(result);   // prints: <p>This is a text with some <em>emphasis</em></p>
 ```
 
-In order to activate most of all advanced extensions (except Emoji, SoftLine as HardLine, JiraLinks and SmartyPants)
+In order to activate most of all advanced extensions (except Emoji, SoftLine as HardLine, Bootstrap, YAML Front Matter, JiraLinks and SmartyPants)
 
 ```csharp
 // Configure the pipeline with all advanced extensions active

src/Markdig.Benchmarks/Markdig.Benchmarks.csproj

@@ -1,43 +1,13 @@
-<?xml version="1.0" encoding="utf-8"?>
-<Project ToolsVersion="14.0" DefaultTargets="Build" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
-  <Import Project="$(MSBuildExtensionsPath)\$(MSBuildToolsVersion)\Microsoft.Common.props" Condition="Exists('$(MSBuildExtensionsPath)\$(MSBuildToolsVersion)\Microsoft.Common.props')" />
+<Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
-    <Configuration Condition=" '$(Configuration)' == '' ">Debug</Configuration>
-    <Platform Condition=" '$(Platform)' == '' ">AnyCPU</Platform>
-    <ProjectGuid>{6A19F040-BC7C-4283-873A-177B5324F1ED}</ProjectGuid>
+    <TargetFrameworks>net471</TargetFrameworks>
     <OutputType>Exe</OutputType>
-    <AppDesignerFolder>Properties</AppDesignerFolder>
-    <RootNamespace>Markdig.Benchmarks</RootNamespace>
-    <AssemblyName>Markdig.Benchmarks</AssemblyName>
-    <TargetFrameworkVersion>v4.6</TargetFrameworkVersion>
-    <FileAlignment>512</FileAlignment>
-    <AutoGenerateBindingRedirects>true</AutoGenerateBindingRedirects>
-    <TargetFrameworkProfile />
-    <CopyNuGetImplementations>true</CopyNuGetImplementations>
-  </PropertyGroup>
-  <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Debug|AnyCPU' ">
-    <PlatformTarget>x86</PlatformTarget>
-    <DebugSymbols>true</DebugSymbols>
-    <DebugType>full</DebugType>
-    <Optimize>false</Optimize>
-    <OutputPath>bin\Debug\</OutputPath>
-    <DefineConstants>DEBUG;TRACE</DefineConstants>
-    <ErrorReport>prompt</ErrorReport>
-    <WarningLevel>4</WarningLevel>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
-    <Prefer32Bit>true</Prefer32Bit>
-  </PropertyGroup>
-  <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Release|AnyCPU' ">
-    <PlatformTarget>x86</PlatformTarget>
-    <DebugType>pdbonly</DebugType>
-    <Optimize>true</Optimize>
-    <OutputPath>bin\Release\</OutputPath>
-    <DefineConstants>TRACE</DefineConstants>
-    <ErrorReport>prompt</ErrorReport>
-    <WarningLevel>4</WarningLevel>
-    <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
-    <Prefer32Bit>true</Prefer32Bit>
+    <IsPackable>false</IsPackable>
   </PropertyGroup>
+  <ItemGroup>
+    <None Remove="spec.md" />
+  </ItemGroup>
   <ItemGroup>
     <Reference Include="CommonMarkNew, Version=0.1.0.0, Culture=neutral, PublicKeyToken=001ef8810438905d, processorArchitecture=MSIL">
       <HintPath>lib\CommonMarkNew.dll</HintPath>
@@ -45,31 +15,12 @@
       <Aliases>newcmark</Aliases>
       <Private>True</Private>
     </Reference>
-    <Reference Include="Microsoft.Build" />
-    <Reference Include="Microsoft.Build.Framework" />
-    <Reference Include="Microsoft.Build.Utilities.v4.0" />
     <Reference Include="MoonShine">
       <HintPath>lib\MoonShine.dll</HintPath>
     </Reference>
     <Reference Include="MarkdownDeep">
       <HintPath>lib\MarkdownDeep.dll</HintPath>
     </Reference>
-    <Reference Include="System" />
-    <Reference Include="System.Core" />
-    <Reference Include="System.Management" />
-    <Reference Include="System.Xml.Linq" />
-    <Reference Include="System.Data.DataSetExtensions" />
-    <Reference Include="Microsoft.CSharp" />
-    <Reference Include="System.Data" />
-    <Reference Include="System.Net.Http" />
-    <Reference Include="System.Xml" />
-  </ItemGroup>
-  <ItemGroup>
-    <Compile Include="CommonMarkLib.cs" />
-    <Compile Include="Program.cs" />
-    <Compile Include="Properties\AssemblyInfo.cs" />
-    <Compile Include="TestMatchPerf.cs" />
-    <Compile Include="TestStringPerf.cs" />
   </ItemGroup>
   <ItemGroup>
     <Content Include="cmark.dll">
@@ -83,21 +34,16 @@
     <Content Include="spec.md">
       <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
     </Content>
-    <None Include="app.config" />
-    <None Include="project.json" />
   </ItemGroup>
   <ItemGroup>
-    <Reference Include="Markdig">
-      <SpecificVersion>False</SpecificVersion>
-      <HintPath>..\Markdig\Bin\$(Configuration)\net40\Markdig.dll</HintPath>
-    </Reference>
+    <PackageReference Include="BenchmarkDotNet" Version="0.10.6" />
+    <PackageReference Include="BenchmarkDotNet.Diagnostics.Windows" Version="0.10.6" />
+    <PackageReference Include="CommonMark.NET" Version="0.15.1" />
+    <PackageReference Include="MarkdownSharp" Version="1.13.0.0" />
+    <PackageReference Include="Microsoft.Diagnostics.Runtime" Version="0.8.31-beta" />
+    <PackageReference Include="Microsoft.Diagnostics.Tracing.TraceEvent" Version="1.0.41.0" />
   </ItemGroup>
-  <Import Project="$(MSBuildToolsPath)\Microsoft.CSharp.targets" />
-  <!-- To modify your build process, add your task inside one of the targets below and uncomment it. 
-       Other similar extension points exist, see Microsoft.Common.targets.
-  <Target Name="BeforeBuild">
-  </Target>
-  <Target Name="AfterBuild">
-  </Target>
-  -->
-</Project>
+  <ItemGroup>
+    <ProjectReference Include="..\Markdig\Markdig.csproj" />
+  </ItemGroup>
+</Project>

src/Markdig.Benchmarks/Properties/AssemblyInfo.cs

@@ -1,36 +0,0 @@
-using System.Reflection;
-using System.Runtime.CompilerServices;
-using System.Runtime.InteropServices;
-
-// General Information about an assembly is controlled through the following 
-// set of attributes. Change these attribute values to modify the information
-// associated with an assembly.
-[assembly: AssemblyTitle("Testamina.Markdig.Benchmarks")]
-[assembly: AssemblyDescription("")]
-[assembly: AssemblyConfiguration("")]
-[assembly: AssemblyCompany("")]
-[assembly: AssemblyProduct("Testamina.Markdig.Benchmarks")]
-[assembly: AssemblyCopyright("Copyright ©  2016")]
-[assembly: AssemblyTrademark("")]
-[assembly: AssemblyCulture("")]
-
-// Setting ComVisible to false makes the types in this assembly not visible 
-// to COM components.  If you need to access a type in this assembly from 
-// COM, set the ComVisible attribute to true on that type.
-[assembly: ComVisible(false)]
-
-// The following GUID is for the ID of the typelib if this project is exposed to COM
-[assembly: Guid("6a19f040-bc7c-4283-873a-177b5324f1ed")]
-
-// Version information for an assembly consists of the following four values:
-//
-//      Major Version
-//      Minor Version 
-//      Build Number
-//      Revision
-//
-// You can specify all the values or you can default the Build and Revision Numbers 
-// by using the '*' as shown below:
-// [assembly: AssemblyVersion("1.0.*")]
-[assembly: AssemblyVersion("1.0.0.0")]
-[assembly: AssemblyFileVersion("1.0.0.0")]

src/Markdig.Benchmarks/Properties/launchSettings.json

@@ -1,8 +0,0 @@
-{
-  "profiles": {
-    "CLASSIC": {
-      "executablePath": "Testamina.Markdig.Benchmarks.dll",
-      "workingDirectory": "..\\..\\artifacts\\bin\\Testamina.Markdig.Benchmarks\\Debug\\net45"
-    }
-  }
-}

src/Markdig.Benchmarks/app.config

@@ -1,3 +0,0 @@
-<?xml version="1.0" encoding="utf-8"?>
-<configuration>
-<startup><supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.6"/></startup></configuration>

src/Markdig.Benchmarks/project.json

@@ -1,29 +0,0 @@
-{
-  "runtimes": {
-    "win-x86": {},
-    "win-x64": {}
-  },
-  "frameworks": {
-    "net46": {
-      "compilationOptions": {
-        "define": [
-          "CLASSIC"
-        ]
-      },
-      "frameworkAssemblies": {
-        "Microsoft.Build": "4.0.0.0",
-        "Microsoft.Build.Framework": "4.0.0.0",
-        "Microsoft.Build.Utilities.v4.0": "4.0.0.0",
-        "System.Management": "4.0.0.0"
-      }
-    }
-  },
-  "dependencies": {
-    "BenchmarkDotNet": "0.10.6",
-    "BenchmarkDotNet.Diagnostics.Windows": "0.10.6",
-    "CommonMark.NET": "0.15.1",
-    "MarkdownSharp": "1.13.0.0",
-    "Microsoft.Diagnostics.Runtime": "0.8.31-beta",
-    "Microsoft.Diagnostics.Tracing.TraceEvent": "1.0.41.0"
-  }
-}

src/Markdig.Signed/Markdig.Signed.csproj

@@ -0,0 +1,13 @@
+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <PackageId>Markdig.Signed</PackageId>
+    <AssemblyOriginatorKeyFile>key.snk</AssemblyOriginatorKeyFile>
+    <SignAssembly>true</SignAssembly>
+  </PropertyGroup>
+  <ItemGroup>
+    <Compile Include="..\Markdig\**\*.cs" Exclude="..\Markdig\obj\**;..\Markdig\bin\**">
+      <Link>%(RecursiveDir)%(Filename)%(Extension)</Link>
+    </Compile>
+  </ItemGroup>
+  <Import Project="..\Markdig\Markdig.targets" />
+</Project>

src/Markdig.Tests/Markdig.Tests.csproj

@@ -1,13 +1,18 @@
-<Project Sdk="Microsoft.NET.Sdk">
+<Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-	<TargetFrameworks>net451;netcoreapp2.1</TargetFrameworks>
+  	<TargetFrameworks>netcoreapp2.1;netcoreapp3.1</TargetFrameworks>
     <OutputType>Library</OutputType>
+    <IsPackable>false</IsPackable>
   </PropertyGroup>
 
   <ItemGroup>
+    <PackageReference Include="coverlet.msbuild" Version="2.8.1">
+      <PrivateAssets>all</PrivateAssets>
+      <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
+    </PackageReference>
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="16.0.1" />
-    <PackageReference Include="NUnit" Version="3.11.0" />
+    <PackageReference Include="NUnit" Version="3.12.0" />
     <PackageReference Include="NUnit3TestAdapter" Version="3.13.0" />
   </ItemGroup>
 

src/Markdig.Tests/MiscTests.cs

@@ -1,5 +1,6 @@
 using System;
 using System.IO;
+using System.Linq;
 using System.Text.RegularExpressions;
 using Markdig.Extensions.AutoLinks;
 using NUnit.Framework;
@@ -8,6 +9,63 @@ namespace Markdig.Tests
 {
     public class MiscTests
     {
+        [TestCase("link [foo [bar]]")] // https://spec.commonmark.org/0.29/#example-508
+        [TestCase("link [foo][bar]")]
+        [TestCase("link [][foo][bar][]")]
+        [TestCase("link [][foo][bar][[]]")]
+        [TestCase("link [foo] [bar]")]
+        [TestCase("link [[foo] [] [bar] [[abc]def]]")]
+        [TestCase("[]")]
+        [TestCase("[ ]")]
+        [TestCase("[bar][]")]
+        [TestCase("[bar][ foo]")]
+        [TestCase("[bar][foo ][]")]
+        [TestCase("[bar][fo[ ]o ][][]")]
+        [TestCase("[a]b[c[d[e]f]g]h")]
+        [TestCase("a[b[c[d]e]f[g]h]i foo [j]k[l[m]n]o")]
+        [TestCase("a[b[c[d]e]f[g]h]i[] [][foo][bar][] foo [j]k[l[m]n]o")]
+        [TestCase("a[b[c[d]e]f[g]h]i foo [j]k[l[m]n]o[][]")]
+        public void LinkTextMayContainBalancedBrackets(string linkText)
+        {
+            string markdown = $"[{linkText}](/uri)";
+            string expected = $@"<p><a href=""/uri"">{linkText}</a></p>";
+
+            TestParser.TestSpec(markdown, expected);
+
+            // Make the link text unbalanced
+            foreach (var bracketIndex in linkText
+                .Select((c, i) => new Tuple<char, int>(c, i))
+                .Where(t => t.Item1 == '[' || t.Item1 == ']')
+                .Select(t => t.Item2))
+            {
+                string brokenLinkText = linkText.Remove(bracketIndex, 1);
+
+                markdown = $"[{brokenLinkText}](/uri)";
+                expected = $@"<p><a href=""/uri"">{brokenLinkText}</a></p>";
+
+                string actual = Markdown.ToHtml(markdown);
+                Assert.AreNotEqual(expected, actual);
+            }
+        }
+
+        [Test]
+        public void IsIssue356Corrected()
+        {
+            string input = @"https://foo.bar/path/\#m4mv5W0GYKZpGvfA.97";
+            string expected = @"<p><a href=""https://foo.bar/path/%5C#m4mv5W0GYKZpGvfA.97"">https://foo.bar/path/\#m4mv5W0GYKZpGvfA.97</a></p>";
+
+            TestParser.TestSpec($"<{input}>", expected);
+            TestParser.TestSpec(input, expected, "autolinks|advanced");
+        }
+
+        [Test]
+        public void TestAltTextIsCorrectlyEscaped()
+        {
+            TestParser.TestSpec(
+                @"![This is image alt text with quotation ' and double quotation ""hello"" world](girl.png)",
+                @"<p><img src=""girl.png"" alt=""This is image alt text with quotation ' and double quotation &quot;hello&quot; world"" /></p>");
+        }
+
         [Test]
         public void TestChangelogPRLinksMatchDescription()
         {

src/Markdig.Tests/Specs/AbbreviationSpecs.generated.cs

@@ -1,4 +1,4 @@
-// Generated: 2019-04-05 16:06:14
+// Generated: 2019-05-15 02:46:55
 
 // --------------------------------
 //           Abbreviations

src/Markdig.Tests/Specs/EmojiSpecs.generated.cs

@@ -1,4 +1,4 @@
-// Generated: 2019-04-15 05:20:50
+// Generated: 2020-01-13 21:08:58
 
 // --------------------------------
 //               Emoji
@@ -18,7 +18,7 @@ namespace Markdig.Tests.Specs.Emoji
         // 
         // ## Emoji
         // 
-        // Emoji and smiley can be converted to their respective unicode characters:
+        // Emoji shortcodes and smileys can be converted to their respective unicode characters:
         [Test]
         public void ExtensionsEmoji_Example001()
         {
@@ -52,7 +52,7 @@ namespace Markdig.Tests.Specs.Emoji
             TestParser.TestSpec("These are not:) an emoji with a:) x:angry:x", "<p>These are not:) an emoji with a:) x:angry:x</p>", "emojis|advanced+emojis");
         }
 
-        // Emoji can be followed by close punctuation (or any other characters):
+        // Emojis can be followed by close punctuation (or any other characters):
         [Test]
         public void ExtensionsEmoji_Example003()
         {
@@ -69,7 +69,7 @@ namespace Markdig.Tests.Specs.Emoji
             TestParser.TestSpec("We all need :), it makes us :muscle:. (and :ok_hand:).", "<p>We all need 😃, it makes us 💪. (and 👌).</p>", "emojis|advanced+emojis");
         }
 
-        // Sentences can end with Emoji:
+        // Sentences can end with emojis:
         [Test]
         public void ExtensionsEmoji_Example004()
         {

src/Markdig.Tests/Specs/EmojiSpecs.md

@@ -4,7 +4,7 @@ This section describes the different extensions supported:
 
 ## Emoji
 
-Emoji and smiley can be converted to their respective unicode characters:
+Emoji shortcodes and smileys can be converted to their respective unicode characters:
 
 ```````````````````````````````` example
 This is a test with a :) and a :angry: smiley
@@ -20,7 +20,7 @@ These are not:) an emoji with a:) x:angry:x
 <p>These are not:) an emoji with a:) x:angry:x</p>
 ````````````````````````````````
 
-Emoji can be followed by close punctuation (or any other characters):
+Emojis can be followed by close punctuation (or any other characters):
 
 ```````````````````````````````` example
 We all need :), it makes us :muscle:. (and :ok_hand:).
@@ -28,7 +28,7 @@ We all need :), it makes us :muscle:. (and :ok_hand:).
 <p>We all need 😃, it makes us 💪. (and 👌).</p>
 ````````````````````````````````
 
-Sentences can end with Emoji:
+Sentences can end with emojis:
 
 ```````````````````````````````` example
 This is a sentence :ok_hand:

src/Markdig.Tests/Specs/GenericAttributesSpecs.generated.cs

@@ -1,4 +1,4 @@
-// Generated: 2019-04-05 16:06:14
+// Generated: 2019-08-01 13:57:17
 
 // --------------------------------
 //        Generic Attributes
@@ -79,5 +79,28 @@ namespace Markdig.Tests.Specs.GenericAttributes
             Console.WriteLine("Example 2\nSection Extensions / Generic Attributes\n");
             TestParser.TestSpec("{#fenced-id .fenced-class}\n~~~\nThis is a fenced with attached attributes\n~~~ ", "<pre><code id=\"fenced-id\" class=\"fenced-class\">This is a fenced with attached attributes\n</code></pre>", "attributes|advanced");
         }
+
+        // Attribute values can be one character long
+        [Test]
+        public void ExtensionsGenericAttributes_Example003()
+        {
+            // Example 3
+            // Section: Extensions / Generic Attributes
+            //
+            // The following Markdown:
+            //     [Foo](url){data-x=1}
+            //     
+            //     [Foo](url){data-x='1'}
+            //     
+            //     [Foo](url){data-x=11}
+            //
+            // Should be rendered as:
+            //     <p><a href="url" data-x="1">Foo</a></p>
+            //     <p><a href="url" data-x="1">Foo</a></p>
+            //     <p><a href="url" data-x="11">Foo</a></p>
+
+            Console.WriteLine("Example 3\nSection Extensions / Generic Attributes\n");
+            TestParser.TestSpec("[Foo](url){data-x=1}\n\n[Foo](url){data-x='1'}\n\n[Foo](url){data-x=11}", "<p><a href=\"url\" data-x=\"1\">Foo</a></p>\n<p><a href=\"url\" data-x=\"1\">Foo</a></p>\n<p><a href=\"url\" data-x=\"11\">Foo</a></p>", "attributes|advanced");
+        }
     }
 }

src/Markdig.Tests/Specs/GenericAttributesSpecs.md

@@ -47,3 +47,17 @@ This is a fenced with attached attributes
 <pre><code id="fenced-id" class="fenced-class">This is a fenced with attached attributes
 </code></pre>
 ````````````````````````````````
+
+Attribute values can be one character long
+
+```````````````````````````````` example
+[Foo](url){data-x=1}
+
+[Foo](url){data-x='1'}
+
+[Foo](url){data-x=11}
+.
+<p><a href="url" data-x="1">Foo</a></p>
+<p><a href="url" data-x="1">Foo</a></p>
+<p><a href="url" data-x="11">Foo</a></p>
+````````````````````````````````

src/Markdig.Tests/Specs/GridTableSpecs.generated.cs

@@ -1,4 +1,4 @@
-// Generated: 2019-04-05 16:06:14
+// Generated: 2020-04-18 06:41:26
 
 // --------------------------------
 //            Grid Tables
@@ -62,8 +62,8 @@ namespace Markdig.Tests.Specs.GridTables
             //
             // Should be rendered as:
             //     <table>
-            //     <col style="width:50%">
-            //     <col style="width:50%">
+            //     <col style="width:50%" />
+            //     <col style="width:50%" />
             //     <tbody>
             //     <tr>
             //     <td>This is</td>
@@ -73,7 +73,7 @@ namespace Markdig.Tests.Specs.GridTables
             //     </table>
 
             Console.WriteLine("Example 1\nSection Extensions / Grid Table\n");
-            TestParser.TestSpec("+---------+---------+\n| This is | a table |", "<table>\n<col style=\"width:50%\">\n<col style=\"width:50%\">\n<tbody>\n<tr>\n<td>This is</td>\n<td>a table</td>\n</tr>\n</tbody>\n</table>", "gridtables|advanced");
+            TestParser.TestSpec("+---------+---------+\n| This is | a table |", "<table>\n<col style=\"width:50%\" />\n<col style=\"width:50%\" />\n<tbody>\n<tr>\n<td>This is</td>\n<td>a table</td>\n</tr>\n</tbody>\n</table>", "gridtables|advanced");
         }
 
         // The following is not a valid row separator 
@@ -112,9 +112,9 @@ namespace Markdig.Tests.Specs.GridTables
             //
             // Should be rendered as:
             //     <table>
-            //     <col style="width:33.33%">
-            //     <col style="width:33.33%">
-            //     <col style="width:33.33%">
+            //     <col style="width:33.33%" />
+            //     <col style="width:33.33%" />
+            //     <col style="width:33.33%" />
             //     <tbody>
             //     <tr>
             //     <td>Col1
@@ -135,7 +135,7 @@ namespace Markdig.Tests.Specs.GridTables
             //     </table>
 
             Console.WriteLine("Example 3\nSection Extensions / Grid Table\n");
-            TestParser.TestSpec("+---------+---------+---------+\n| Col1    | Col2    | Col3    |\n| Col1a   | Col2a   | Col3a   |\n| Col1b             | Col3b   |\n| Col1c                       |", "<table>\n<col style=\"width:33.33%\">\n<col style=\"width:33.33%\">\n<col style=\"width:33.33%\">\n<tbody>\n<tr>\n<td>Col1\nCol1a</td>\n<td>Col2\nCol2a</td>\n<td>Col3\nCol3a</td>\n</tr>\n<tr>\n<td colspan=\"2\">Col1b</td>\n<td>Col3b</td>\n</tr>\n<tr>\n<td colspan=\"3\">Col1c</td>\n</tr>\n</tbody>\n</table>", "gridtables|advanced");
+            TestParser.TestSpec("+---------+---------+---------+\n| Col1    | Col2    | Col3    |\n| Col1a   | Col2a   | Col3a   |\n| Col1b             | Col3b   |\n| Col1c                       |", "<table>\n<col style=\"width:33.33%\" />\n<col style=\"width:33.33%\" />\n<col style=\"width:33.33%\" />\n<tbody>\n<tr>\n<td>Col1\nCol1a</td>\n<td>Col2\nCol2a</td>\n<td>Col3\nCol3a</td>\n</tr>\n<tr>\n<td colspan=\"2\">Col1b</td>\n<td>Col3b</td>\n</tr>\n<tr>\n<td colspan=\"3\">Col1c</td>\n</tr>\n</tbody>\n</table>", "gridtables|advanced");
         }
 
         // A row header is separated using `+========+` instead of `+---------+`:
@@ -152,8 +152,8 @@ namespace Markdig.Tests.Specs.GridTables
             //
             // Should be rendered as:
             //     <table>
-            //     <col style="width:50%">
-            //     <col style="width:50%">
+            //     <col style="width:50%" />
+            //     <col style="width:50%" />
             //     <thead>
             //     <tr>
             //     <th>This is</th>
@@ -163,7 +163,7 @@ namespace Markdig.Tests.Specs.GridTables
             //     </table>
 
             Console.WriteLine("Example 4\nSection Extensions / Grid Table\n");
-            TestParser.TestSpec("+---------+---------+\n| This is | a table |\n+=========+=========+", "<table>\n<col style=\"width:50%\">\n<col style=\"width:50%\">\n<thead>\n<tr>\n<th>This is</th>\n<th>a table</th>\n</tr>\n</thead>\n</table>", "gridtables|advanced");
+            TestParser.TestSpec("+---------+---------+\n| This is | a table |\n+=========+=========+", "<table>\n<col style=\"width:50%\" />\n<col style=\"width:50%\" />\n<thead>\n<tr>\n<th>This is</th>\n<th>a table</th>\n</tr>\n</thead>\n</table>", "gridtables|advanced");
         }
 
         // The last column separator `|` may be omitted:
@@ -179,8 +179,8 @@ namespace Markdig.Tests.Specs.GridTables
             //
             // Should be rendered as:
             //     <table>
-            //     <col style="width:50%">
-            //     <col style="width:50%">
+            //     <col style="width:50%" />
+            //     <col style="width:50%" />
             //     <tbody>
             //     <tr>
             //     <td>This is</td>
@@ -190,7 +190,7 @@ namespace Markdig.Tests.Specs.GridTables
             //     </table>
 
             Console.WriteLine("Example 5\nSection Extensions / Grid Table\n");
-            TestParser.TestSpec("+---------+---------+\n| This is | a table with a longer text in the second column", "<table>\n<col style=\"width:50%\">\n<col style=\"width:50%\">\n<tbody>\n<tr>\n<td>This is</td>\n<td>a table with a longer text in the second column</td>\n</tr>\n</tbody>\n</table>", "gridtables|advanced");
+            TestParser.TestSpec("+---------+---------+\n| This is | a table with a longer text in the second column", "<table>\n<col style=\"width:50%\" />\n<col style=\"width:50%\" />\n<tbody>\n<tr>\n<td>This is</td>\n<td>a table with a longer text in the second column</td>\n</tr>\n</tbody>\n</table>", "gridtables|advanced");
         }
 
         // The respective width of the columns are calculated from the ratio between the total size of the first table row without counting the `+`: `+----+--------+----+` would be divided between:
@@ -215,9 +215,9 @@ namespace Markdig.Tests.Specs.GridTables
             //
             // Should be rendered as:
             //     <table>
-            //     <col style="width:25%">
-            //     <col style="width:50%">
-            //     <col style="width:25%">
+            //     <col style="width:25%" />
+            //     <col style="width:50%" />
+            //     <col style="width:25%" />
             //     <tbody>
             //     <tr>
             //     <td>A</td>
@@ -228,7 +228,7 @@ namespace Markdig.Tests.Specs.GridTables
             //     </table>
 
             Console.WriteLine("Example 6\nSection Extensions / Grid Table\n");
-            TestParser.TestSpec("+----+--------+----+\n| A  |  B C D | E  |\n+----+--------+----+", "<table>\n<col style=\"width:25%\">\n<col style=\"width:50%\">\n<col style=\"width:25%\">\n<tbody>\n<tr>\n<td>A</td>\n<td>B C D</td>\n<td>E</td>\n</tr>\n</tbody>\n</table>", "gridtables|advanced");
+            TestParser.TestSpec("+----+--------+----+\n| A  |  B C D | E  |\n+----+--------+----+", "<table>\n<col style=\"width:25%\" />\n<col style=\"width:50%\" />\n<col style=\"width:25%\" />\n<tbody>\n<tr>\n<td>A</td>\n<td>B C D</td>\n<td>E</td>\n</tr>\n</tbody>\n</table>", "gridtables|advanced");
         }
 
         // Alignment might be specified on the first row using the character `:`:
@@ -245,9 +245,9 @@ namespace Markdig.Tests.Specs.GridTables
             //
             // Should be rendered as:
             //     <table>
-            //     <col style="width:33.33%">
-            //     <col style="width:33.33%">
-            //     <col style="width:33.33%">
+            //     <col style="width:33.33%" />
+            //     <col style="width:33.33%" />
+            //     <col style="width:33.33%" />
             //     <tbody>
             //     <tr>
             //     <td>A</td>
@@ -258,7 +258,7 @@ namespace Markdig.Tests.Specs.GridTables
             //     </table>
 
             Console.WriteLine("Example 7\nSection Extensions / Grid Table\n");
-            TestParser.TestSpec("+-----+:---:+-----+\n|  A  |  B  |  C  |\n+-----+-----+-----+", "<table>\n<col style=\"width:33.33%\">\n<col style=\"width:33.33%\">\n<col style=\"width:33.33%\">\n<tbody>\n<tr>\n<td>A</td>\n<td style=\"text-align: center;\">B</td>\n<td>C</td>\n</tr>\n</tbody>\n</table>", "gridtables|advanced");
+            TestParser.TestSpec("+-----+:---:+-----+\n|  A  |  B  |  C  |\n+-----+-----+-----+", "<table>\n<col style=\"width:33.33%\" />\n<col style=\"width:33.33%\" />\n<col style=\"width:33.33%\" />\n<tbody>\n<tr>\n<td>A</td>\n<td style=\"text-align: center;\">B</td>\n<td>C</td>\n</tr>\n</tbody>\n</table>", "gridtables|advanced");
         }
 
         //  A grid table may have cells spanning both columns and rows:
@@ -279,9 +279,9 @@ namespace Markdig.Tests.Specs.GridTables
             //
             // Should be rendered as:
             //     <table>
-            //     <col style="width:33.33%">
-            //     <col style="width:33.33%">
-            //     <col style="width:33.33%">
+            //     <col style="width:33.33%" />
+            //     <col style="width:33.33%" />
+            //     <col style="width:33.33%" />
             //     <tbody>
             //     <tr>
             //     <td colspan="2">AAAAA</td>
@@ -302,7 +302,7 @@ namespace Markdig.Tests.Specs.GridTables
             //     </table>
 
             Console.WriteLine("Example 8\nSection Extensions / Grid Table\n");
-            TestParser.TestSpec("+---+---+---+\n| AAAAA | B |\n+---+---+ B +\n| D | E | B |\n+ D +---+---+\n| D | CCCCC |\n+---+---+---+", "<table>\n<col style=\"width:33.33%\">\n<col style=\"width:33.33%\">\n<col style=\"width:33.33%\">\n<tbody>\n<tr>\n<td colspan=\"2\">AAAAA</td>\n<td rowspan=\"2\">B\nB\nB</td>\n</tr>\n<tr>\n<td rowspan=\"2\">D\nD\nD</td>\n<td>E</td>\n</tr>\n<tr>\n<td colspan=\"2\">CCCCC</td>\n</tr>\n</tbody>\n</table>", "gridtables|advanced");
+            TestParser.TestSpec("+---+---+---+\n| AAAAA | B |\n+---+---+ B +\n| D | E | B |\n+ D +---+---+\n| D | CCCCC |\n+---+---+---+", "<table>\n<col style=\"width:33.33%\" />\n<col style=\"width:33.33%\" />\n<col style=\"width:33.33%\" />\n<tbody>\n<tr>\n<td colspan=\"2\">AAAAA</td>\n<td rowspan=\"2\">B\nB\nB</td>\n</tr>\n<tr>\n<td rowspan=\"2\">D\nD\nD</td>\n<td>E</td>\n</tr>\n<tr>\n<td colspan=\"2\">CCCCC</td>\n</tr>\n</tbody>\n</table>", "gridtables|advanced");
         }
 
         // A grid table may have cells with both colspan and rowspan:
@@ -323,9 +323,9 @@ namespace Markdig.Tests.Specs.GridTables
             //
             // Should be rendered as:
             //     <table>
-            //     <col style="width:33.33%">
-            //     <col style="width:33.33%">
-            //     <col style="width:33.33%">
+            //     <col style="width:33.33%" />
+            //     <col style="width:33.33%" />
+            //     <col style="width:33.33%" />
             //     <tbody>
             //     <tr>
             //     <td colspan="2" rowspan="2">AAAAA
@@ -345,7 +345,7 @@ namespace Markdig.Tests.Specs.GridTables
             //     </table>
 
             Console.WriteLine("Example 9\nSection Extensions / Grid Table\n");
-            TestParser.TestSpec("+---+---+---+\n| AAAAA | B |\n+ AAAAA +---+\n| AAAAA | C |\n+---+---+---+\n| D | E | F |\n+---+---+---+", "<table>\n<col style=\"width:33.33%\">\n<col style=\"width:33.33%\">\n<col style=\"width:33.33%\">\n<tbody>\n<tr>\n<td colspan=\"2\" rowspan=\"2\">AAAAA\nAAAAA\nAAAAA</td>\n<td>B</td>\n</tr>\n<tr>\n<td>C</td>\n</tr>\n<tr>\n<td>D</td>\n<td>E</td>\n<td>F</td>\n</tr>\n</tbody>\n</table>", "gridtables|advanced");
+            TestParser.TestSpec("+---+---+---+\n| AAAAA | B |\n+ AAAAA +---+\n| AAAAA | C |\n+---+---+---+\n| D | E | F |\n+---+---+---+", "<table>\n<col style=\"width:33.33%\" />\n<col style=\"width:33.33%\" />\n<col style=\"width:33.33%\" />\n<tbody>\n<tr>\n<td colspan=\"2\" rowspan=\"2\">AAAAA\nAAAAA\nAAAAA</td>\n<td>B</td>\n</tr>\n<tr>\n<td>C</td>\n</tr>\n<tr>\n<td>D</td>\n<td>E</td>\n<td>F</td>\n</tr>\n</tbody>\n</table>", "gridtables|advanced");
         }
 
         // A grid table may not have irregularly shaped cells:

src/Markdig.Tests/Specs/GridTableSpecs.md

@@ -42,8 +42,8 @@ The following is a valid row separator
 | This is | a table |
 .
 <table>
-<col style="width:50%">
-<col style="width:50%">
+<col style="width:50%" />
+<col style="width:50%" />
 <tbody>
 <tr>
 <td>This is</td>
@@ -74,9 +74,9 @@ A regular row can continue a previous regular row when column separator `|` are
 | Col1c                       |
 .
 <table>
-<col style="width:33.33%">
-<col style="width:33.33%">
-<col style="width:33.33%">
+<col style="width:33.33%" />
+<col style="width:33.33%" />
+<col style="width:33.33%" />
 <tbody>
 <tr>
 <td>Col1
@@ -105,8 +105,8 @@ A row header is separated using `+========+` instead of `+---------+`:
 +=========+=========+
 .
 <table>
-<col style="width:50%">
-<col style="width:50%">
+<col style="width:50%" />
+<col style="width:50%" />
 <thead>
 <tr>
 <th>This is</th>
@@ -123,8 +123,8 @@ The last column separator `|` may be omitted:
 | This is | a table with a longer text in the second column
 .
 <table>
-<col style="width:50%">
-<col style="width:50%">
+<col style="width:50%" />
+<col style="width:50%" />
 <tbody>
 <tr>
 <td>This is</td>
@@ -150,9 +150,9 @@ So the width would be 4/16 = 25%, 8/16 = 50%, 4/16 = 25%
 +----+--------+----+
 .
 <table>
-<col style="width:25%">
-<col style="width:50%">
-<col style="width:25%">
+<col style="width:25%" />
+<col style="width:50%" />
+<col style="width:25%" />
 <tbody>
 <tr>
 <td>A</td>
@@ -172,9 +172,9 @@ Alignment might be specified on the first row using the character `:`:
 +-----+-----+-----+
 .
 <table>
-<col style="width:33.33%">
-<col style="width:33.33%">
-<col style="width:33.33%">
+<col style="width:33.33%" />
+<col style="width:33.33%" />
+<col style="width:33.33%" />
 <tbody>
 <tr>
 <td>A</td>
@@ -197,9 +197,9 @@ Alignment might be specified on the first row using the character `:`:
 +---+---+---+
 .
 <table>
-<col style="width:33.33%">
-<col style="width:33.33%">
-<col style="width:33.33%">
+<col style="width:33.33%" />
+<col style="width:33.33%" />
+<col style="width:33.33%" />
 <tbody>
 <tr>
 <td colspan="2">AAAAA</td>
@@ -232,9 +232,9 @@ A grid table may have cells with both colspan and rowspan:
 +---+---+---+
 .
 <table>
-<col style="width:33.33%">
-<col style="width:33.33%">
-<col style="width:33.33%">
+<col style="width:33.33%" />
+<col style="width:33.33%" />
+<col style="width:33.33%" />
 <tbody>
 <tr>
 <td colspan="2" rowspan="2">AAAAA

src/Markdig.Tests/Specs/MediaSpecs.generated.cs

@@ -1,4 +1,4 @@
-// Generated: 2019-04-29 18:40:06
+// Generated: 2019-05-15 02:46:20
 
 // --------------------------------
 //               Media
@@ -47,19 +47,19 @@ namespace Markdig.Tests.Specs.Media
             //     ![ok.ru](https://ok.ru/video/26870090463)
             //
             // Should be rendered as:
-            //     <p><iframe src="https://www.youtube.com/embed/mswPy5bt3TQ" width="500" height="281" frameborder="0" allowfullscreen=""></iframe></p>
-            //     <p><iframe src="https://www.youtube.com/embed/mswPy5bt3TQ?start=100" width="500" height="281" frameborder="0" allowfullscreen=""></iframe></p>
-            //     <p><iframe src="https://www.youtube.com/embed/mswPy5bt3TQ" width="500" height="281" frameborder="0" allowfullscreen=""></iframe></p>
-            //     <p><iframe src="https://www.youtube.com/embed/mswPy5bt3TQ?start=100" width="500" height="281" frameborder="0" allowfullscreen=""></iframe></p>
-            //     <p><iframe src="https://www.youtube.com/embed/mswPy5bt3TQ?start=100&amp;rel=0" width="500" height="281" frameborder="0" allowfullscreen=""></iframe></p>
-            //     <p><iframe src="https://www.youtube.com/embed?listType=playlist&amp;list=PLC77007E23FF423C6" width="500" height="281" frameborder="0" allowfullscreen=""></iframe></p>
-            //     <p><iframe src="https://player.vimeo.com/video/8607834" width="500" height="281" frameborder="0" allowfullscreen=""></iframe></p>
+            //     <p><iframe src="https://www.youtube.com/embed/mswPy5bt3TQ" width="500" height="281" class="youtube" frameborder="0" allowfullscreen=""></iframe></p>
+            //     <p><iframe src="https://www.youtube.com/embed/mswPy5bt3TQ?start=100" width="500" height="281" class="youtube" frameborder="0" allowfullscreen=""></iframe></p>
+            //     <p><iframe src="https://www.youtube.com/embed/mswPy5bt3TQ" width="500" height="281" class="youtube" frameborder="0" allowfullscreen=""></iframe></p>
+            //     <p><iframe src="https://www.youtube.com/embed/mswPy5bt3TQ?start=100" width="500" height="281" class="youtube" frameborder="0" allowfullscreen=""></iframe></p>
+            //     <p><iframe src="https://www.youtube.com/embed/mswPy5bt3TQ?start=100&amp;rel=0" width="500" height="281" class="youtube" frameborder="0" allowfullscreen=""></iframe></p>
+            //     <p><iframe src="https://www.youtube.com/embed?listType=playlist&amp;list=PLC77007E23FF423C6" width="500" height="281" class="youtube" frameborder="0" allowfullscreen=""></iframe></p>
+            //     <p><iframe src="https://player.vimeo.com/video/8607834" width="500" height="281" class="vimeo" frameborder="0" allowfullscreen=""></iframe></p>
             //     <p><video width="500" height="281" controls=""><source type="video/mp4" src="https://sample.com/video.mp4"></source></video></p>
-            //     <p><iframe src="https://music.yandex.ru/iframe/#track/4402274/411845/" width="500" height="281" frameborder="0"></iframe></p>
-            //     <p><iframe src="https://ok.ru/videoembed/26870090463" width="500" height="281" frameborder="0" allowfullscreen=""></iframe></p>
+            //     <p><iframe src="https://music.yandex.ru/iframe/#track/4402274/411845/" width="500" height="281" class="yandex" frameborder="0"></iframe></p>
+            //     <p><iframe src="https://ok.ru/videoembed/26870090463" width="500" height="281" class="odnoklassniki" frameborder="0" allowfullscreen=""></iframe></p>
 
             Console.WriteLine("Example 1\nSection Extensions / Media links\n");
-            TestParser.TestSpec("![youtube.com](https://www.youtube.com/watch?v=mswPy5bt3TQ)\n\n![youtube.com with t](https://www.youtube.com/watch?v=mswPy5bt3TQ&t=100)\n\n![youtu.be](https://youtu.be/mswPy5bt3TQ)\n\n![youtu.be with t](https://youtu.be/mswPy5bt3TQ?t=100)\n\n![youtube.com/embed 1](https://www.youtube.com/embed/mswPy5bt3TQ?start=100&rel=0)\n \n![youtube.com/embed 2](https://www.youtube.com/embed?listType=playlist&list=PLC77007E23FF423C6)\n\n![vimeo](https://vimeo.com/8607834)\n\n![static mp4](https://sample.com/video.mp4)\n\n![yandex.ru](https://music.yandex.ru/album/411845/track/4402274)\n\n![ok.ru](https://ok.ru/video/26870090463)", "<p><iframe src=\"https://www.youtube.com/embed/mswPy5bt3TQ\" width=\"500\" height=\"281\" frameborder=\"0\" allowfullscreen=\"\"></iframe></p>\n<p><iframe src=\"https://www.youtube.com/embed/mswPy5bt3TQ?start=100\" width=\"500\" height=\"281\" frameborder=\"0\" allowfullscreen=\"\"></iframe></p>\n<p><iframe src=\"https://www.youtube.com/embed/mswPy5bt3TQ\" width=\"500\" height=\"281\" frameborder=\"0\" allowfullscreen=\"\"></iframe></p>\n<p><iframe src=\"https://www.youtube.com/embed/mswPy5bt3TQ?start=100\" width=\"500\" height=\"281\" frameborder=\"0\" allowfullscreen=\"\"></iframe></p>\n<p><iframe src=\"https://www.youtube.com/embed/mswPy5bt3TQ?start=100&amp;rel=0\" width=\"500\" height=\"281\" frameborder=\"0\" allowfullscreen=\"\"></iframe></p>\n<p><iframe src=\"https://www.youtube.com/embed?listType=playlist&amp;list=PLC77007E23FF423C6\" width=\"500\" height=\"281\" frameborder=\"0\" allowfullscreen=\"\"></iframe></p>\n<p><iframe src=\"https://player.vimeo.com/video/8607834\" width=\"500\" height=\"281\" frameborder=\"0\" allowfullscreen=\"\"></iframe></p>\n<p><video width=\"500\" height=\"281\" controls=\"\"><source type=\"video/mp4\" src=\"https://sample.com/video.mp4\"></source></video></p>\n<p><iframe src=\"https://music.yandex.ru/iframe/#track/4402274/411845/\" width=\"500\" height=\"281\" frameborder=\"0\"></iframe></p>\n<p><iframe src=\"https://ok.ru/videoembed/26870090463\" width=\"500\" height=\"281\" frameborder=\"0\" allowfullscreen=\"\"></iframe></p>", "medialinks|advanced+medialinks");
+            TestParser.TestSpec("![youtube.com](https://www.youtube.com/watch?v=mswPy5bt3TQ)\n\n![youtube.com with t](https://www.youtube.com/watch?v=mswPy5bt3TQ&t=100)\n\n![youtu.be](https://youtu.be/mswPy5bt3TQ)\n\n![youtu.be with t](https://youtu.be/mswPy5bt3TQ?t=100)\n\n![youtube.com/embed 1](https://www.youtube.com/embed/mswPy5bt3TQ?start=100&rel=0)\n \n![youtube.com/embed 2](https://www.youtube.com/embed?listType=playlist&list=PLC77007E23FF423C6)\n\n![vimeo](https://vimeo.com/8607834)\n\n![static mp4](https://sample.com/video.mp4)\n\n![yandex.ru](https://music.yandex.ru/album/411845/track/4402274)\n\n![ok.ru](https://ok.ru/video/26870090463)", "<p><iframe src=\"https://www.youtube.com/embed/mswPy5bt3TQ\" width=\"500\" height=\"281\" class=\"youtube\" frameborder=\"0\" allowfullscreen=\"\"></iframe></p>\n<p><iframe src=\"https://www.youtube.com/embed/mswPy5bt3TQ?start=100\" width=\"500\" height=\"281\" class=\"youtube\" frameborder=\"0\" allowfullscreen=\"\"></iframe></p>\n<p><iframe src=\"https://www.youtube.com/embed/mswPy5bt3TQ\" width=\"500\" height=\"281\" class=\"youtube\" frameborder=\"0\" allowfullscreen=\"\"></iframe></p>\n<p><iframe src=\"https://www.youtube.com/embed/mswPy5bt3TQ?start=100\" width=\"500\" height=\"281\" class=\"youtube\" frameborder=\"0\" allowfullscreen=\"\"></iframe></p>\n<p><iframe src=\"https://www.youtube.com/embed/mswPy5bt3TQ?start=100&amp;rel=0\" width=\"500\" height=\"281\" class=\"youtube\" frameborder=\"0\" allowfullscreen=\"\"></iframe></p>\n<p><iframe src=\"https://www.youtube.com/embed?listType=playlist&amp;list=PLC77007E23FF423C6\" width=\"500\" height=\"281\" class=\"youtube\" frameborder=\"0\" allowfullscreen=\"\"></iframe></p>\n<p><iframe src=\"https://player.vimeo.com/video/8607834\" width=\"500\" height=\"281\" class=\"vimeo\" frameborder=\"0\" allowfullscreen=\"\"></iframe></p>\n<p><video width=\"500\" height=\"281\" controls=\"\"><source type=\"video/mp4\" src=\"https://sample.com/video.mp4\"></source></video></p>\n<p><iframe src=\"https://music.yandex.ru/iframe/#track/4402274/411845/\" width=\"500\" height=\"281\" class=\"yandex\" frameborder=\"0\"></iframe></p>\n<p><iframe src=\"https://ok.ru/videoembed/26870090463\" width=\"500\" height=\"281\" class=\"odnoklassniki\" frameborder=\"0\" allowfullscreen=\"\"></iframe></p>", "medialinks|advanced+medialinks");
         }
     }
 }

src/Markdig.Tests/Specs/MediaSpecs.md

@@ -27,14 +27,14 @@ Allows to embed audio/video links to popular website:
 
 ![ok.ru](https://ok.ru/video/26870090463)
 .
-<p><iframe src="https://www.youtube.com/embed/mswPy5bt3TQ" width="500" height="281" frameborder="0" allowfullscreen=""></iframe></p>
-<p><iframe src="https://www.youtube.com/embed/mswPy5bt3TQ?start=100" width="500" height="281" frameborder="0" allowfullscreen=""></iframe></p>
-<p><iframe src="https://www.youtube.com/embed/mswPy5bt3TQ" width="500" height="281" frameborder="0" allowfullscreen=""></iframe></p>
-<p><iframe src="https://www.youtube.com/embed/mswPy5bt3TQ?start=100" width="500" height="281" frameborder="0" allowfullscreen=""></iframe></p>
-<p><iframe src="https://www.youtube.com/embed/mswPy5bt3TQ?start=100&amp;rel=0" width="500" height="281" frameborder="0" allowfullscreen=""></iframe></p>
-<p><iframe src="https://www.youtube.com/embed?listType=playlist&amp;list=PLC77007E23FF423C6" width="500" height="281" frameborder="0" allowfullscreen=""></iframe></p>
-<p><iframe src="https://player.vimeo.com/video/8607834" width="500" height="281" frameborder="0" allowfullscreen=""></iframe></p>
+<p><iframe src="https://www.youtube.com/embed/mswPy5bt3TQ" width="500" height="281" class="youtube" frameborder="0" allowfullscreen=""></iframe></p>
+<p><iframe src="https://www.youtube.com/embed/mswPy5bt3TQ?start=100" width="500" height="281" class="youtube" frameborder="0" allowfullscreen=""></iframe></p>
+<p><iframe src="https://www.youtube.com/embed/mswPy5bt3TQ" width="500" height="281" class="youtube" frameborder="0" allowfullscreen=""></iframe></p>
+<p><iframe src="https://www.youtube.com/embed/mswPy5bt3TQ?start=100" width="500" height="281" class="youtube" frameborder="0" allowfullscreen=""></iframe></p>
+<p><iframe src="https://www.youtube.com/embed/mswPy5bt3TQ?start=100&amp;rel=0" width="500" height="281" class="youtube" frameborder="0" allowfullscreen=""></iframe></p>
+<p><iframe src="https://www.youtube.com/embed?listType=playlist&amp;list=PLC77007E23FF423C6" width="500" height="281" class="youtube" frameborder="0" allowfullscreen=""></iframe></p>
+<p><iframe src="https://player.vimeo.com/video/8607834" width="500" height="281" class="vimeo" frameborder="0" allowfullscreen=""></iframe></p>
 <p><video width="500" height="281" controls=""><source type="video/mp4" src="https://sample.com/video.mp4"></source></video></p>
-<p><iframe src="https://music.yandex.ru/iframe/#track/4402274/411845/" width="500" height="281" frameborder="0"></iframe></p>
-<p><iframe src="https://ok.ru/videoembed/26870090463" width="500" height="281" frameborder="0" allowfullscreen=""></iframe></p>
+<p><iframe src="https://music.yandex.ru/iframe/#track/4402274/411845/" width="500" height="281" class="yandex" frameborder="0"></iframe></p>
+<p><iframe src="https://ok.ru/videoembed/26870090463" width="500" height="281" class="odnoklassniki" frameborder="0" allowfullscreen=""></iframe></p>
 ````````````````````````````````

src/Markdig.Tests/Specs/SmartyPantsSpecs.generated.cs

@@ -1,4 +1,4 @@
-// Generated: 2019-04-05 16:06:14
+// Generated: 2019-08-01 12:33:23
 
 // --------------------------------
 //           Smarty Pants
@@ -140,13 +140,13 @@ namespace Markdig.Tests.Specs.SmartyPants
             // Section: Extensions / SmartyPants Quotes
             //
             // The following Markdown:
-            //     This is a 'text <<with' a another text>>
+            //     This is 'a "text 'with" a another text'
             //
             // Should be rendered as:
-            //     <p>This is a &lsquo;text &lt;&lt;with&rsquo; a another text&gt;&gt;</p>
+            //     <p>This is &lsquo;a &ldquo;text 'with&rdquo; a another text&rsquo;</p>
 
             Console.WriteLine("Example 8\nSection Extensions / SmartyPants Quotes\n");
-            TestParser.TestSpec("This is a 'text <<with' a another text>>", "<p>This is a &lsquo;text &lt;&lt;with&rsquo; a another text&gt;&gt;</p>", "pipetables+smartypants|advanced+smartypants");
+            TestParser.TestSpec("This is 'a \"text 'with\" a another text'", "<p>This is &lsquo;a &ldquo;text 'with&rdquo; a another text&rsquo;</p>", "pipetables+smartypants|advanced+smartypants");
         }
 
         [Test]
@@ -156,20 +156,36 @@ namespace Markdig.Tests.Specs.SmartyPants
             // Section: Extensions / SmartyPants Quotes
             //
             // The following Markdown:
+            //     This is a 'text <<with' a another text>>
+            //
+            // Should be rendered as:
+            //     <p>This is a &lsquo;text &lt;&lt;with&rsquo; a another text&gt;&gt;</p>
+
+            Console.WriteLine("Example 9\nSection Extensions / SmartyPants Quotes\n");
+            TestParser.TestSpec("This is a 'text <<with' a another text>>", "<p>This is a &lsquo;text &lt;&lt;with&rsquo; a another text&gt;&gt;</p>", "pipetables+smartypants|advanced+smartypants");
+        }
+
+        [Test]
+        public void ExtensionsSmartyPantsQuotes_Example010()
+        {
+            // Example 10
+            // Section: Extensions / SmartyPants Quotes
+            //
+            // The following Markdown:
             //     This is a <<text 'with>> a another text'
             //
             // Should be rendered as:
             //     <p>This is a &laquo;text 'with&raquo; a another text'</p>
 
-            Console.WriteLine("Example 9\nSection Extensions / SmartyPants Quotes\n");
+            Console.WriteLine("Example 10\nSection Extensions / SmartyPants Quotes\n");
             TestParser.TestSpec("This is a <<text 'with>> a another text'", "<p>This is a &laquo;text 'with&raquo; a another text'</p>", "pipetables+smartypants|advanced+smartypants");
         }
 
         // Quotes requires to have the same rules than emphasis `_` regarding left/right frankling rules:
         [Test]
-        public void ExtensionsSmartyPantsQuotes_Example010()
+        public void ExtensionsSmartyPantsQuotes_Example011()
         {
-            // Example 10
+            // Example 11
             // Section: Extensions / SmartyPants Quotes
             //
             // The following Markdown:
@@ -178,24 +194,8 @@ namespace Markdig.Tests.Specs.SmartyPants
             // Should be rendered as:
             //     <p>It's not quotes'</p>
 
-            Console.WriteLine("Example 10\nSection Extensions / SmartyPants Quotes\n");
-            TestParser.TestSpec("It's not quotes'", "<p>It's not quotes'</p>", "pipetables+smartypants|advanced+smartypants");
-        }
-
-        [Test]
-        public void ExtensionsSmartyPantsQuotes_Example011()
-        {
-            // Example 11
-            // Section: Extensions / SmartyPants Quotes
-            //
-            // The following Markdown:
-            //     They are ' not matching quotes '
-            //
-            // Should be rendered as:
-            //     <p>They are ' not matching quotes '</p>
-
             Console.WriteLine("Example 11\nSection Extensions / SmartyPants Quotes\n");
-            TestParser.TestSpec("They are ' not matching quotes '", "<p>They are ' not matching quotes '</p>", "pipetables+smartypants|advanced+smartypants");
+            TestParser.TestSpec("It's not quotes'", "<p>It's not quotes'</p>", "pipetables+smartypants|advanced+smartypants");
         }
 
         [Test]
@@ -205,20 +205,36 @@ namespace Markdig.Tests.Specs.SmartyPants
             // Section: Extensions / SmartyPants Quotes
             //
             // The following Markdown:
+            //     They are ' not matching quotes '
+            //
+            // Should be rendered as:
+            //     <p>They are ' not matching quotes '</p>
+
+            Console.WriteLine("Example 12\nSection Extensions / SmartyPants Quotes\n");
+            TestParser.TestSpec("They are ' not matching quotes '", "<p>They are ' not matching quotes '</p>", "pipetables+smartypants|advanced+smartypants");
+        }
+
+        [Test]
+        public void ExtensionsSmartyPantsQuotes_Example013()
+        {
+            // Example 13
+            // Section: Extensions / SmartyPants Quotes
+            //
+            // The following Markdown:
             //     They are' not matching 'quotes
             //
             // Should be rendered as:
             //     <p>They are' not matching 'quotes</p>
 
-            Console.WriteLine("Example 12\nSection Extensions / SmartyPants Quotes\n");
+            Console.WriteLine("Example 13\nSection Extensions / SmartyPants Quotes\n");
             TestParser.TestSpec("They are' not matching 'quotes", "<p>They are' not matching 'quotes</p>", "pipetables+smartypants|advanced+smartypants");
         }
 
         // An emphasis starting inside left/right quotes will span over the right quote:
         [Test]
-        public void ExtensionsSmartyPantsQuotes_Example013()
+        public void ExtensionsSmartyPantsQuotes_Example014()
         {
-            // Example 13
+            // Example 14
             // Section: Extensions / SmartyPants Quotes
             //
             // The following Markdown:
@@ -227,9 +243,26 @@ namespace Markdig.Tests.Specs.SmartyPants
             // Should be rendered as:
             //     <p>This is &ldquo;a <em>text&rdquo; with an emphasis</em></p>
 
-            Console.WriteLine("Example 13\nSection Extensions / SmartyPants Quotes\n");
+            Console.WriteLine("Example 14\nSection Extensions / SmartyPants Quotes\n");
             TestParser.TestSpec("This is \"a *text\" with an emphasis*", "<p>This is &ldquo;a <em>text&rdquo; with an emphasis</em></p>", "pipetables+smartypants|advanced+smartypants");
         }
+
+        // Multiple sets of quotes can be used
+        [Test]
+        public void ExtensionsSmartyPantsQuotes_Example015()
+        {
+            // Example 15
+            // Section: Extensions / SmartyPants Quotes
+            //
+            // The following Markdown:
+            //     "aaa" "bbb" "ccc" "ddd"
+            //
+            // Should be rendered as:
+            //     <p>&ldquo;aaa&rdquo; &ldquo;bbb&rdquo; &ldquo;ccc&rdquo; &ldquo;ddd&rdquo;</p>
+
+            Console.WriteLine("Example 15\nSection Extensions / SmartyPants Quotes\n");
+            TestParser.TestSpec("\"aaa\" \"bbb\" \"ccc\" \"ddd\"", "<p>&ldquo;aaa&rdquo; &ldquo;bbb&rdquo; &ldquo;ccc&rdquo; &ldquo;ddd&rdquo;</p>", "pipetables+smartypants|advanced+smartypants");
+        }
     }
 
     [TestFixture]
@@ -237,9 +270,9 @@ namespace Markdig.Tests.Specs.SmartyPants
     {
         // ## SmartyPants Separators
         [Test]
-        public void ExtensionsSmartyPantsSeparators_Example014()
+        public void ExtensionsSmartyPantsSeparators_Example016()
         {
-            // Example 14
+            // Example 16
             // Section: Extensions / SmartyPants Separators
             //
             // The following Markdown:
@@ -248,14 +281,14 @@ namespace Markdig.Tests.Specs.SmartyPants
             // Should be rendered as:
             //     <p>This is a &ndash; text</p>
 
-            Console.WriteLine("Example 14\nSection Extensions / SmartyPants Separators\n");
+            Console.WriteLine("Example 16\nSection Extensions / SmartyPants Separators\n");
             TestParser.TestSpec("This is a -- text", "<p>This is a &ndash; text</p>", "pipetables+smartypants|advanced+smartypants");
         }
 
         [Test]
-        public void ExtensionsSmartyPantsSeparators_Example015()
+        public void ExtensionsSmartyPantsSeparators_Example017()
         {
-            // Example 15
+            // Example 17
             // Section: Extensions / SmartyPants Separators
             //
             // The following Markdown:
@@ -264,14 +297,14 @@ namespace Markdig.Tests.Specs.SmartyPants
             // Should be rendered as:
             //     <p>This is a &mdash; text</p>
 
-            Console.WriteLine("Example 15\nSection Extensions / SmartyPants Separators\n");
+            Console.WriteLine("Example 17\nSection Extensions / SmartyPants Separators\n");
             TestParser.TestSpec("This is a --- text", "<p>This is a &mdash; text</p>", "pipetables+smartypants|advanced+smartypants");
         }
 
         [Test]
-        public void ExtensionsSmartyPantsSeparators_Example016()
+        public void ExtensionsSmartyPantsSeparators_Example018()
         {
-            // Example 16
+            // Example 18
             // Section: Extensions / SmartyPants Separators
             //
             // The following Markdown:
@@ -280,15 +313,15 @@ namespace Markdig.Tests.Specs.SmartyPants
             // Should be rendered as:
             //     <p>This is a en ellipsis&hellip;</p>
 
-            Console.WriteLine("Example 16\nSection Extensions / SmartyPants Separators\n");
+            Console.WriteLine("Example 18\nSection Extensions / SmartyPants Separators\n");
             TestParser.TestSpec("This is a en ellipsis...", "<p>This is a en ellipsis&hellip;</p>", "pipetables+smartypants|advanced+smartypants");
         }
 
         // Check that a smartypants are not breaking pipetable parsing:
         [Test]
-        public void ExtensionsSmartyPantsSeparators_Example017()
+        public void ExtensionsSmartyPantsSeparators_Example019()
         {
-            // Example 17
+            // Example 19
             // Section: Extensions / SmartyPants Separators
             //
             // The following Markdown:
@@ -312,15 +345,15 @@ namespace Markdig.Tests.Specs.SmartyPants
             //     </tbody>
             //     </table>
 
-            Console.WriteLine("Example 17\nSection Extensions / SmartyPants Separators\n");
+            Console.WriteLine("Example 19\nSection Extensions / SmartyPants Separators\n");
             TestParser.TestSpec("a  | b\n-- | --\n0  | 1", "<table>\n<thead>\n<tr>\n<th>a</th>\n<th>b</th>\n</tr>\n</thead>\n<tbody>\n<tr>\n<td>0</td>\n<td>1</td>\n</tr>\n</tbody>\n</table>", "pipetables+smartypants|advanced+smartypants");
         }
 
         // Check quotes and dash:
         [Test]
-        public void ExtensionsSmartyPantsSeparators_Example018()
+        public void ExtensionsSmartyPantsSeparators_Example020()
         {
-            // Example 18
+            // Example 20
             // Section: Extensions / SmartyPants Separators
             //
             // The following Markdown:
@@ -329,7 +362,7 @@ namespace Markdig.Tests.Specs.SmartyPants
             // Should be rendered as:
             //     <p>A &ldquo;quote&rdquo; with a &mdash;</p>
 
-            Console.WriteLine("Example 18\nSection Extensions / SmartyPants Separators\n");
+            Console.WriteLine("Example 20\nSection Extensions / SmartyPants Separators\n");
             TestParser.TestSpec("A \"quote\" with a ---", "<p>A &ldquo;quote&rdquo; with a &mdash;</p>", "pipetables+smartypants|advanced+smartypants");
         }
     }

src/Markdig.Tests/Specs/SmartyPantsSpecs.md

@@ -52,6 +52,12 @@ This is a "text 'with" a another text'
 <p>This is a &ldquo;text 'with&rdquo; a another text'</p>
 ````````````````````````````````
 
+```````````````````````````````` example
+This is 'a "text 'with" a another text'
+.
+<p>This is &lsquo;a &ldquo;text 'with&rdquo; a another text&rsquo;</p>
+````````````````````````````````
+
 ```````````````````````````````` example
 This is a 'text <<with' a another text>>
 .
@@ -91,6 +97,14 @@ This is "a *text" with an emphasis*
 <p>This is &ldquo;a <em>text&rdquo; with an emphasis</em></p>
 ````````````````````````````````
 
+Multiple sets of quotes can be used
+
+```````````````````````````````` example
+"aaa" "bbb" "ccc" "ddd"
+.
+<p>&ldquo;aaa&rdquo; &ldquo;bbb&rdquo; &ldquo;ccc&rdquo; &ldquo;ddd&rdquo;</p>
+````````````````````````````````
+
 ## SmartyPants Separators
 
 ```````````````````````````````` example

src/Markdig.Tests/TestContainerBlocks.cs

@@ -0,0 +1,70 @@
+using System;
+using Markdig.Syntax;
+using NUnit.Framework;
+
+namespace Markdig.Tests
+{
+    public class TestContainerBlocks
+    {
+        private class MockContainerBlock : ContainerBlock
+        {
+            public MockContainerBlock()
+                : base(null)
+            {
+
+            }
+        }
+
+        [Test]
+        public void CanBeCleared()
+        {
+            ContainerBlock container = new MockContainerBlock();
+            Assert.AreEqual(0, container.Count);
+            Assert.Null(container.LastChild);
+
+            var paragraph = new ParagraphBlock();
+            Assert.Null(paragraph.Parent);
+
+            container.Add(paragraph);
+
+            Assert.AreEqual(1, container.Count);
+            Assert.AreSame(container, paragraph.Parent);
+            Assert.AreSame(paragraph, container.LastChild);
+
+            container.Clear();
+
+            Assert.AreEqual(0, container.Count);
+            Assert.Null(container.LastChild);
+            Assert.Null(paragraph.Parent);
+        }
+
+        [Test]
+        public void CanBeInsertedInto()
+        {
+            ContainerBlock container = new MockContainerBlock();
+
+            var one = new ParagraphBlock();
+            container.Insert(0, one);
+            Assert.AreEqual(1, container.Count);
+            Assert.AreSame(container[0], one);
+
+            var two = new ParagraphBlock();
+            container.Insert(1, two);
+            Assert.AreEqual(2, container.Count);
+            Assert.AreSame(container[0], one);
+            Assert.AreSame(container[1], two);
+
+            var three = new ParagraphBlock();
+            container.Insert(0, three);
+            Assert.AreEqual(3, container.Count);
+            Assert.AreSame(container[0], three);
+            Assert.AreSame(container[1], one);
+            Assert.AreSame(container[2], two);
+
+            Assert.Throws<ArgumentNullException>(() => container.Insert(0, null));
+            Assert.Throws<ArgumentOutOfRangeException>(() => container.Insert(4, new ParagraphBlock()));
+            Assert.Throws<ArgumentOutOfRangeException>(() => container.Insert(-1, new ParagraphBlock()));
+            Assert.Throws<ArgumentException>(() => container.Insert(0, one)); // one already has a parent
+        }
+    }
+}

src/Markdig.Tests/TestCustomEmojis.cs

@@ -0,0 +1,129 @@
+using System;
+using System.Collections;
+using System.Collections.Generic;
+using Markdig.Extensions.Emoji;
+using NUnit.Framework;
+
+namespace Markdig.Tests
+{
+    [TestFixture]
+    public class TestCustomEmojis
+    {
+        [Test]
+        [TestCase(":smiley:", "<p>♥</p>\n")]
+        [TestCase(":confused:", "<p>:confused:</p>\n")] // default emoji does not work
+        [TestCase(":/", "<p>:/</p>\n")] // default smiley does not work
+        public void TestCustomEmoji(string input, string expected)
+        {
+            var emojiToUnicode = new Dictionary<string, string>();
+            var smileyToEmoji = new Dictionary<string, string>();
+
+            emojiToUnicode[":smiley:"] = "♥";
+
+            var customMapping = new EmojiMapping(emojiToUnicode, smileyToEmoji);
+
+            var pipeline = new MarkdownPipelineBuilder()
+                .UseEmojiAndSmiley(customEmojiMapping: customMapping)
+                .Build();
+
+            var actual = Markdown.ToHtml(input, pipeline);
+            Assert.AreEqual(expected, actual);
+        }
+
+        [Test]
+        [TestCase(":testheart:", "<p>♥</p>\n")]
+        [TestCase("hello", "<p>♥</p>\n")]
+        [TestCase(":confused:", "<p>:confused:</p>\n")] // default emoji does not work
+        [TestCase(":/", "<p>:/</p>\n")] // default smiley does not work
+        public void TestCustomSmiley(string input, string expected)
+        {
+            var emojiToUnicode = new Dictionary<string, string>();
+            var smileyToEmoji = new Dictionary<string, string>();
+
+            emojiToUnicode[":testheart:"] = "♥";
+            smileyToEmoji["hello"] = ":testheart:";
+
+            var customMapping = new EmojiMapping(emojiToUnicode, smileyToEmoji);
+
+            var pipeline = new MarkdownPipelineBuilder()
+                .UseEmojiAndSmiley(customEmojiMapping: customMapping)
+                .Build();
+
+            var actual = Markdown.ToHtml(input, pipeline);
+            Assert.AreEqual(expected, actual);
+        }
+
+        [Test]
+        [TestCase(":smiley:", "<p>♥</p>\n")]
+        [TestCase(":)", "<p>♥</p>\n")]
+        [TestCase(":confused:", "<p>😕</p>\n")] // default emoji still works
+        [TestCase(":/", "<p>😕</p>\n")] // default smiley still works
+        public void TestOverrideDefaultWithCustomEmoji(string input, string expected)
+        {
+            var emojiToUnicode = EmojiMapping.GetDefaultEmojiShortcodeToUnicode();
+            var smileyToEmoji = EmojiMapping.GetDefaultSmileyToEmojiShortcode();
+
+            emojiToUnicode[":smiley:"] = "♥";
+
+            var customMapping = new EmojiMapping(emojiToUnicode, smileyToEmoji);
+
+            var pipeline = new MarkdownPipelineBuilder()
+                .UseEmojiAndSmiley(customEmojiMapping: customMapping)
+                .Build();
+
+            var actual = Markdown.ToHtml(input, pipeline);
+            Assert.AreEqual(expected, actual);
+        }
+
+        [Test]
+        [TestCase(":testheart:", "<p>♥</p>\n")]
+        [TestCase("hello", "<p>♥</p>\n")]
+        [TestCase(":confused:", "<p>😕</p>\n")] // default emoji still works
+        [TestCase(":/", "<p>😕</p>\n")] // default smiley still works
+        public void TestOverrideDefaultWithCustomSmiley(string input, string expected)
+        {
+            var emojiToUnicode = EmojiMapping.GetDefaultEmojiShortcodeToUnicode();
+            var smileyToEmoji = EmojiMapping.GetDefaultSmileyToEmojiShortcode();
+
+            emojiToUnicode[":testheart:"] = "♥";
+            smileyToEmoji["hello"] = ":testheart:";
+
+            var customMapping = new EmojiMapping(emojiToUnicode, smileyToEmoji);
+
+            var pipeline = new MarkdownPipelineBuilder()
+                .UseEmojiAndSmiley(customEmojiMapping: customMapping)
+                .Build();
+
+            var actual = Markdown.ToHtml(input, pipeline);
+            Assert.AreEqual(expected, actual);
+        }
+
+        [Test]
+        public void TestCustomEmojiValidation()
+        {
+            var emojiToUnicode = new Dictionary<string, string>();
+            var smileyToEmoji = new Dictionary<string, string>();
+
+            Assert.Throws<ArgumentNullException>(() => new EmojiMapping(null, smileyToEmoji));
+            Assert.Throws<ArgumentNullException>(() => new EmojiMapping(emojiToUnicode, null));
+
+            emojiToUnicode.Add("null-value", null);
+            Assert.Throws<ArgumentException>(() => new EmojiMapping(emojiToUnicode, smileyToEmoji));
+            emojiToUnicode.Clear();
+
+            smileyToEmoji.Add("null-value", null);
+            Assert.Throws<ArgumentException>(() => new EmojiMapping(emojiToUnicode, smileyToEmoji));
+            smileyToEmoji.Clear();
+
+            smileyToEmoji.Add("foo", "something-that-does-not-exist-in-emojiToUnicode");
+            Assert.Throws<ArgumentException>(() => new EmojiMapping(emojiToUnicode, smileyToEmoji));
+            smileyToEmoji.Clear();
+
+            emojiToUnicode.Add("a", "aaa");
+            emojiToUnicode.Add("b", "bbb");
+            emojiToUnicode.Add("c", "ccc");
+            smileyToEmoji.Add("a", "c"); // "a" already exists in emojiToUnicode
+            Assert.Throws<ArgumentException>(() => new EmojiMapping(emojiToUnicode, smileyToEmoji));
+        }
+    }
+}

src/Markdig.Tests/TestDescendantsOrder.cs

@@ -1,6 +1,7 @@
 using NUnit.Framework;
 using Markdig.Syntax;
 using Markdig.Syntax.Inlines;
+using System;
 using System.Linq;
 using System.Collections.Generic;
 
@@ -12,24 +13,91 @@ namespace Markdig.Tests
         [Test]
         public void TestSchemas()
         {
-            foreach (var markdown in TestParser.SpecsMarkdown)
+            foreach (var syntaxTree in TestParser.SpecsSyntaxTrees)
             {
-                AssertSameDescendantsOrder(markdown);
+                AssertIEnumerablesAreEqual(
+                    Descendants_Legacy(syntaxTree),
+                    syntaxTree.Descendants());
+
+                AssertIEnumerablesAreEqual(
+                    syntaxTree.Descendants().OfType<ParagraphBlock>(),
+                    syntaxTree.Descendants<ParagraphBlock>());
+
+                AssertIEnumerablesAreEqual(
+                    syntaxTree.Descendants().OfType<ParagraphBlock>(),
+                    (syntaxTree as ContainerBlock).Descendants<ParagraphBlock>());
+
+                AssertIEnumerablesAreEqual(
+                    syntaxTree.Descendants().OfType<LiteralInline>(),
+                    syntaxTree.Descendants<LiteralInline>());
+
+                foreach (LiteralInline literalInline in syntaxTree.Descendants<LiteralInline>())
+                {
+                    Assert.AreSame(Array.Empty<ListBlock>(), literalInline.Descendants<ListBlock>());
+                    Assert.AreSame(Array.Empty<ParagraphBlock>(), literalInline.Descendants<ParagraphBlock>());
+                    Assert.AreSame(Array.Empty<ContainerInline>(), literalInline.Descendants<ContainerInline>());
+                }
+
+                foreach (ContainerInline containerInline in syntaxTree.Descendants<ContainerInline>())
+                {
+                    AssertIEnumerablesAreEqual(
+                        containerInline.FindDescendants<LiteralInline>(),
+                        containerInline.Descendants<LiteralInline>());
+
+                    AssertIEnumerablesAreEqual(
+                        containerInline.FindDescendants<LiteralInline>(),
+                        (containerInline as MarkdownObject).Descendants<LiteralInline>());
+
+                    if (containerInline.FirstChild is null)
+                    {
+                        Assert.AreSame(Array.Empty<LiteralInline>(), containerInline.Descendants<LiteralInline>());
+                        Assert.AreSame(Array.Empty<LiteralInline>(), containerInline.FindDescendants<LiteralInline>());
+                        Assert.AreSame(Array.Empty<LiteralInline>(), (containerInline as MarkdownObject).Descendants<LiteralInline>());
+                    }
+
+                    Assert.AreSame(Array.Empty<ListBlock>(), containerInline.Descendants<ListBlock>());
+                    Assert.AreSame(Array.Empty<ParagraphBlock>(), containerInline.Descendants<ParagraphBlock>());
+                }
+
+                foreach (ParagraphBlock paragraphBlock in syntaxTree.Descendants<ParagraphBlock>())
+                {
+                    AssertIEnumerablesAreEqual(
+                        (paragraphBlock as MarkdownObject).Descendants<LiteralInline>(),
+                        paragraphBlock.Descendants<LiteralInline>());
+
+                    Assert.AreSame(Array.Empty<ParagraphBlock>(), paragraphBlock.Descendants<ParagraphBlock>());
+                }
+
+                foreach (ContainerBlock containerBlock in syntaxTree.Descendants<ContainerBlock>())
+                {
+                    AssertIEnumerablesAreEqual(
+                        containerBlock.Descendants<LiteralInline>(),
+                        (containerBlock as MarkdownObject).Descendants<LiteralInline>());
+
+                    AssertIEnumerablesAreEqual(
+                        containerBlock.Descendants<ParagraphBlock>(),
+                        (containerBlock as MarkdownObject).Descendants<ParagraphBlock>());
+
+                    if (containerBlock.Count == 0)
+                    {
+                        Assert.AreSame(Array.Empty<LiteralInline>(), containerBlock.Descendants<LiteralInline>());
+                        Assert.AreSame(Array.Empty<LiteralInline>(), (containerBlock as Block).Descendants<LiteralInline>());
+                        Assert.AreSame(Array.Empty<LiteralInline>(), (containerBlock as MarkdownObject).Descendants<LiteralInline>());
+                    }
+                }
             }
         }
 
-        private void AssertSameDescendantsOrder(string markdown)
+        private static void AssertIEnumerablesAreEqual<T>(IEnumerable<T> first, IEnumerable<T> second)
         {
-            var syntaxTree = Markdown.Parse(markdown, new MarkdownPipelineBuilder().UseAdvancedExtensions().Build());
+            var firstList = new List<T>(first);
+            var secondList = new List<T>(second);
 
-            var descendants_legacy = Descendants_Legacy(syntaxTree).ToList();
-            var descendants_new = syntaxTree.Descendants().ToList();
+            Assert.AreEqual(firstList.Count, secondList.Count);
 
-            Assert.AreEqual(descendants_legacy.Count, descendants_new.Count);
-
-            for (int i = 0; i < descendants_legacy.Count; i++)
+            for (int i = 0; i < firstList.Count; i++)
             {
-                Assert.AreSame(descendants_legacy[i], descendants_new[i]);
+                Assert.AreSame(firstList[i], secondList[i]);
             }
         }
 

src/Markdig.Tests/TestExceptionNotThrown.cs

@@ -0,0 +1,48 @@
+using NUnit.Framework;
+
+namespace Markdig.Tests
+{
+    [TestFixture]
+    public class TestExceptionNotThrown
+    {
+        [Test]
+        public void DoesNotThrowIndexOutOfRangeException1()
+        {
+            Assert.DoesNotThrow(() =>
+            {
+                var pipeline = new MarkdownPipelineBuilder().UseAdvancedExtensions().Build();
+                Markdown.ToHtml("+-\n|\n+", pipeline);
+            });
+        }
+
+        [Test]
+        public void DoesNotThrowIndexOutOfRangeException2()
+        {
+            Assert.DoesNotThrow(() =>
+            {
+                var pipeline = new MarkdownPipelineBuilder().UseAdvancedExtensions().Build();
+                Markdown.ToHtml("+--\n|\n+0", pipeline);
+            });
+        }
+
+        [Test]
+        public void DoesNotThrowIndexOutOfRangeException3()
+        {
+            Assert.DoesNotThrow(() =>
+            {
+                var pipeline = new MarkdownPipelineBuilder().UseAdvancedExtensions().Build();
+                Markdown.ToHtml("+-\n|\n+\n0", pipeline);
+            });
+        }
+
+        [Test]
+        public void DoesNotThrowIndexOutOfRangeException4()
+        {
+            Assert.DoesNotThrow(() =>
+            {
+                var pipeline = new MarkdownPipelineBuilder().UseAdvancedExtensions().Build();
+                Markdown.ToHtml("+-\n|\n+0", pipeline);
+            });
+        }
+    }
+}

src/Markdig.Tests/TestLineReader.cs

@@ -1,4 +1,4 @@
-// Copyright (c) Alexandre Mutel. All rights reserved.
+// Copyright (c) Alexandre Mutel. All rights reserved.
 // This file is licensed under the BSD-Clause 2 license. 
 // See the license.txt file in the project root for more information.
 
@@ -18,60 +18,60 @@ namespace Markdig.Tests
         public void TestEmpty()
         {
             var lineReader = new LineReader("");
-            Assert.Null(lineReader.ReadLine()?.ToString());
+            Assert.Null(lineReader.ReadLine().Text);
         }
 
         [Test]
         public void TestLinesOnlyLf()
         {
             var lineReader = new LineReader("\n\n\n");
-            Assert.AreEqual(string.Empty, lineReader.ReadLine()?.ToString());
+            Assert.AreEqual(string.Empty, lineReader.ReadLine().ToString());
             Assert.AreEqual(1, lineReader.SourcePosition);
-            Assert.AreEqual(string.Empty, lineReader.ReadLine()?.ToString());
+            Assert.AreEqual(string.Empty, lineReader.ReadLine().ToString());
             Assert.AreEqual(2, lineReader.SourcePosition);
-            Assert.AreEqual(string.Empty, lineReader.ReadLine()?.ToString());
-            Assert.Null(lineReader.ReadLine()?.ToString());
+            Assert.AreEqual(string.Empty, lineReader.ReadLine().ToString());
+            Assert.Null(lineReader.ReadLine().Text);
         }
 
         [Test]
         public void TestLinesOnlyCr()
         {
             var lineReader = new LineReader("\r\r\r");
-            Assert.AreEqual(string.Empty, lineReader.ReadLine()?.ToString());
+            Assert.AreEqual(string.Empty, lineReader.ReadLine().ToString());
             Assert.AreEqual(1, lineReader.SourcePosition);
-            Assert.AreEqual(string.Empty, lineReader.ReadLine()?.ToString());
+            Assert.AreEqual(string.Empty, lineReader.ReadLine().ToString());
             Assert.AreEqual(2, lineReader.SourcePosition);
-            Assert.AreEqual(string.Empty, lineReader.ReadLine()?.ToString());
-            Assert.Null(lineReader.ReadLine()?.ToString());
+            Assert.AreEqual(string.Empty, lineReader.ReadLine().ToString());
+            Assert.Null(lineReader.ReadLine().Text);
         }
 
         [Test]
         public void TestLinesOnlyCrLf()
         {
             var lineReader = new LineReader("\r\n\r\n\r\n");
-            Assert.AreEqual(string.Empty, lineReader.ReadLine()?.ToString());
+            Assert.AreEqual(string.Empty, lineReader.ReadLine().ToString());
             Assert.AreEqual(2, lineReader.SourcePosition);
-            Assert.AreEqual(string.Empty, lineReader.ReadLine()?.ToString());
+            Assert.AreEqual(string.Empty, lineReader.ReadLine().ToString());
             Assert.AreEqual(4, lineReader.SourcePosition);
-            Assert.AreEqual(string.Empty, lineReader.ReadLine()?.ToString());
-            Assert.Null(lineReader.ReadLine()?.ToString());
+            Assert.AreEqual(string.Empty, lineReader.ReadLine().ToString());
+            Assert.Null(lineReader.ReadLine().Text);
         }
 
         [Test]
         public void TestNoEndOfLine()
         {
             var lineReader = new LineReader("123");
-            Assert.AreEqual("123", lineReader.ReadLine()?.ToString());
-            Assert.Null(lineReader.ReadLine()?.ToString());
+            Assert.AreEqual("123", lineReader.ReadLine().ToString());
+            Assert.Null(lineReader.ReadLine().Text);
         }
 
         [Test]
         public void TestLf()
         {
             var lineReader = new LineReader("123\n");
-            Assert.AreEqual("123", lineReader.ReadLine()?.ToString());
+            Assert.AreEqual("123", lineReader.ReadLine().ToString());
             Assert.AreEqual(4, lineReader.SourcePosition);
-            Assert.Null(lineReader.ReadLine()?.ToString());
+            Assert.Null(lineReader.ReadLine().Text);
         }
 
         [Test]
@@ -79,29 +79,29 @@ namespace Markdig.Tests
         {
             // When limited == true, we limit the internal buffer exactly after the first new line char '\n'
             var lineReader = new LineReader("123\n456");
-            Assert.AreEqual("123", lineReader.ReadLine()?.ToString());
+            Assert.AreEqual("123", lineReader.ReadLine().ToString());
             Assert.AreEqual(4, lineReader.SourcePosition);
-            Assert.AreEqual("456", lineReader.ReadLine()?.ToString());
-            Assert.Null(lineReader.ReadLine()?.ToString());
+            Assert.AreEqual("456", lineReader.ReadLine().ToString());
+            Assert.Null(lineReader.ReadLine().Text);
         }
 
         [Test]
         public void TestCr()
         {
             var lineReader = new LineReader("123\r");
-            Assert.AreEqual("123", lineReader.ReadLine()?.ToString());
+            Assert.AreEqual("123", lineReader.ReadLine().ToString());
             Assert.AreEqual(4, lineReader.SourcePosition);
-            Assert.Null(lineReader.ReadLine()?.ToString());
+            Assert.Null(lineReader.ReadLine().Text);
         }
 
         [Test]
         public void TestCr2()
         {
             var lineReader = new LineReader("123\r456");
-            Assert.AreEqual("123", lineReader.ReadLine()?.ToString());
+            Assert.AreEqual("123", lineReader.ReadLine().ToString());
             Assert.AreEqual(4, lineReader.SourcePosition);
-            Assert.AreEqual("456", lineReader.ReadLine()?.ToString());
-            Assert.Null(lineReader.ReadLine()?.ToString());
+            Assert.AreEqual("456", lineReader.ReadLine().ToString());
+            Assert.Null(lineReader.ReadLine().Text);
         }
 
         [Test]
@@ -110,19 +110,19 @@ namespace Markdig.Tests
             // When limited == true, we limit the internal buffer exactly after the first new line char '\r'
             // and we check that we don't get a new line for `\n` 
             var lineReader = new LineReader("123\r\n");
-            Assert.AreEqual("123", lineReader.ReadLine()?.ToString());
+            Assert.AreEqual("123", lineReader.ReadLine().ToString());
             Assert.AreEqual(5, lineReader.SourcePosition);
-            Assert.Null(lineReader.ReadLine()?.ToString());
+            Assert.Null(lineReader.ReadLine().Text);
         }
 
         [Test]
         public void TestCrLf2()
         {
             var lineReader = new LineReader("123\r\n456");
-            Assert.AreEqual("123", lineReader.ReadLine()?.ToString());
+            Assert.AreEqual("123", lineReader.ReadLine().ToString());
             Assert.AreEqual(5, lineReader.SourcePosition);
-            Assert.AreEqual("456", lineReader.ReadLine()?.ToString());
-            Assert.Null(lineReader.ReadLine()?.ToString());
+            Assert.AreEqual("456", lineReader.ReadLine().ToString());
+            Assert.Null(lineReader.ReadLine().Text);
         }
     }
 }

src/Markdig.Tests/TestLinkHelper.cs

@@ -322,6 +322,16 @@ namespace Markdig.Tests
             Assert.AreEqual(expectedResult, LinkHelper.Urilize(input, false));
         }
 
+        [TestCase("Header identifiers in HTML", "header-identifiers-in-html")]
+        [TestCase("* Dogs*?--in *my* house?", "-dogs--in-my-house")]
+        [TestCase("[HTML], [S5], or [RTF]?", "html-s5-or-rtf")]
+        [TestCase("3. Applications", "3-applications")]
+        [TestCase("33", "33")]
+        public void TestUrilizeGfm(string input, string expectedResult)
+        {
+            Assert.AreEqual(expectedResult, LinkHelper.UrilizeAsGfm(input));
+        }
+
         [TestCase("abc", "abc")]
         [TestCase("a-c", "a-c")]
         [TestCase("a c", "a-c")]

src/Markdig.Tests/TestMarkdigCoreApi.cs

@@ -0,0 +1,148 @@
+using Markdig.Renderers;
+using Markdig.Syntax;
+using Markdig.Syntax.Inlines;
+using NUnit.Framework;
+using System.IO;
+
+namespace Markdig.Tests
+{
+    public class TestMarkdigCoreApi
+    {
+        [Test]
+        public void TestToHtml()
+        {
+            string html = Markdown.ToHtml("This is a text with some *emphasis*");
+            Assert.AreEqual("<p>This is a text with some <em>emphasis</em></p>\n", html);
+
+            html = Markdown.ToHtml("This is a text with a https://link.tld/");
+            Assert.AreNotEqual("<p>This is a text with a <a href=\"https://link.tld/\">https://link.tld/</a></p>\n", html);
+        }
+
+        [Test]
+        public void TestToHtmlWithPipeline()
+        {
+            var pipeline = new MarkdownPipelineBuilder()
+                .Build();
+
+            string html = Markdown.ToHtml("This is a text with some *emphasis*", pipeline);
+            Assert.AreEqual("<p>This is a text with some <em>emphasis</em></p>\n", html);
+
+            html = Markdown.ToHtml("This is a text with a https://link.tld/", pipeline);
+            Assert.AreNotEqual("<p>This is a text with a <a href=\"https://link.tld/\">https://link.tld/</a></p>\n", html);
+
+            pipeline = new MarkdownPipelineBuilder()
+                .UseAdvancedExtensions()
+                .Build();
+
+            html = Markdown.ToHtml("This is a text with a https://link.tld/", pipeline);
+            Assert.AreEqual("<p>This is a text with a <a href=\"https://link.tld/\">https://link.tld/</a></p>\n", html);
+        }
+
+        [Test]
+        public void TestToHtmlWithWriter()
+        {
+            StringWriter writer = new StringWriter();
+
+            _ = Markdown.ToHtml("This is a text with some *emphasis*", writer);
+            string html = writer.ToString();
+            Assert.AreEqual("<p>This is a text with some <em>emphasis</em></p>\n", html);
+
+            writer = new StringWriter();
+            var pipeline = new MarkdownPipelineBuilder()
+                .UseAdvancedExtensions()
+                .Build();
+
+            _ = Markdown.ToHtml("This is a text with a https://link.tld/", writer, pipeline);
+            html = writer.ToString();
+            Assert.AreEqual("<p>This is a text with a <a href=\"https://link.tld/\">https://link.tld/</a></p>\n", html);
+
+        }
+
+        [Test]
+        public void TestConvert()
+        {
+            StringWriter writer = new StringWriter();
+            HtmlRenderer renderer = new HtmlRenderer(writer);
+
+            _ = Markdown.Convert("This is a text with some *emphasis*", renderer);
+            string html = writer.ToString();
+            Assert.AreEqual("<p>This is a text with some <em>emphasis</em></p>\n", html);
+
+            writer = new StringWriter();
+            renderer = new HtmlRenderer(writer);
+            var pipeline = new MarkdownPipelineBuilder()
+                .UseAdvancedExtensions()
+                .Build();
+
+            _ = Markdown.Convert("This is a text with a https://link.tld/", renderer, pipeline);
+            html = writer.ToString();
+            Assert.AreEqual("<p>This is a text with a <a href=\"https://link.tld/\">https://link.tld/</a></p>\n", html);
+        }
+
+        [Test]
+        public void TestParse()
+        {
+            const string markdown = "This is a text with some *emphasis*";
+
+            var pipeline = new MarkdownPipelineBuilder()
+                .UsePreciseSourceLocation()
+                .Build();
+
+            MarkdownDocument document = Markdown.Parse(markdown, pipeline);
+
+            Assert.AreEqual(1, document.LineCount);
+            Assert.AreEqual(markdown.Length, document.Span.Length);
+            Assert.AreEqual(1, document.LineStartIndexes.Count);
+            Assert.AreEqual(0, document.LineStartIndexes[0]);
+
+            Assert.AreEqual(1, document.Count);
+            ParagraphBlock paragraph = document[0] as ParagraphBlock;
+            Assert.NotNull(paragraph);
+            Assert.AreEqual(markdown.Length, paragraph.Span.Length);
+            LiteralInline literal = paragraph.Inline.FirstChild as LiteralInline;
+            Assert.NotNull(literal);
+            Assert.AreEqual("This is a text with some ", literal.ToString());
+            EmphasisInline emphasis = literal.NextSibling as EmphasisInline;
+            Assert.NotNull(emphasis);
+            Assert.AreEqual("*emphasis*".Length, emphasis.Span.Length);
+            LiteralInline emphasisLiteral = emphasis.FirstChild as LiteralInline;
+            Assert.NotNull(emphasisLiteral);
+            Assert.AreEqual("emphasis", emphasisLiteral.ToString());
+            Assert.Null(emphasisLiteral.NextSibling);
+            Assert.Null(emphasis.NextSibling);
+        }
+
+        [Test]
+        public void TestNormalize()
+        {
+            string normalized = Markdown.Normalize("Heading\n=======");
+            Assert.AreEqual("# Heading", normalized);
+        }
+
+        public void TestNormalizeWithWriter()
+        {
+            StringWriter writer = new StringWriter();
+
+            _ = Markdown.Normalize("Heading\n=======", writer);
+            string normalized = writer.ToString();
+            Assert.AreEqual("# Heading", normalized);
+        }
+
+        [Test]
+        public void TestToPlainText()
+        {
+            string plainText = Markdown.ToPlainText("*Hello*, [world](http://example.com)!");
+            Assert.AreEqual("Hello, world!\n", plainText);
+        }
+
+        [Test]
+        public void TestToPlainTextWithWriter()
+        {
+            StringWriter writer = new StringWriter();
+
+            _ = Markdown.ToPlainText("*Hello*, [world](http://example.com)!", writer);
+            string plainText = writer.ToString();
+            Assert.AreEqual("Hello, world!\n", plainText);
+        }
+    }
+}

src/Markdig.Tests/TestMediaLinks.cs

@@ -0,0 +1,87 @@
+using Markdig.Extensions.MediaLinks;
+using NUnit.Framework;
+using System;
+using System.Text.RegularExpressions;
+
+namespace Markdig.Tests
+{
+    [TestFixture]
+    public class TestMediaLinks
+    {
+        private MarkdownPipeline GetPipeline(MediaOptions options = null)
+        {
+            return new MarkdownPipelineBuilder()
+                 .UseMediaLinks(options)
+                 .Build();
+        }
+
+        [Test]
+        [TestCase("![static mp4](https://sample.com/video.mp4)", "<p><video width=\"500\" height=\"281\" controls=\"\"><source type=\"video/mp4\" src=\"https://sample.com/video.mp4\"></source></video></p>\n")]
+        [TestCase("![static mp4](//sample.com/video.mp4)", "<p><video width=\"500\" height=\"281\" controls=\"\"><source type=\"video/mp4\" src=\"//sample.com/video.mp4\"></source></video></p>\n")]
+        [TestCase(@"![youtube.com](https://www.youtube.com/watch?v=mswPy5bt3TQ)", "<p><iframe src=\"https://www.youtube.com/embed/mswPy5bt3TQ\" width=\"500\" height=\"281\" class=\"youtube\" frameborder=\"0\" allowfullscreen=\"\"></iframe></p>\n")]
+        [TestCase("![yandex.ru](https://music.yandex.ru/album/411845/track/4402274)", "<p><iframe src=\"https://music.yandex.ru/iframe/#track/4402274/411845/\" width=\"500\" height=\"281\" class=\"yandex\" frameborder=\"0\"></iframe></p>\n")]
+        [TestCase("![vimeo](https://vimeo.com/8607834)", "<p><iframe src=\"https://player.vimeo.com/video/8607834\" width=\"500\" height=\"281\" class=\"vimeo\" frameborder=\"0\" allowfullscreen=\"\"></iframe></p>\n")]
+        [TestCase("![ok.ru](https://ok.ru/video/26870090463)", "<p><iframe src=\"https://ok.ru/videoembed/26870090463\" width=\"500\" height=\"281\" class=\"odnoklassniki\" frameborder=\"0\" allowfullscreen=\"\"></iframe></p>\n")]
+        [TestCase("![ok.ru](//ok.ru/video/26870090463)", "<p><iframe src=\"https://ok.ru/videoembed/26870090463\" width=\"500\" height=\"281\" class=\"odnoklassniki\" frameborder=\"0\" allowfullscreen=\"\"></iframe></p>\n")]
+        public void TestBuiltInHosts(string markdown, string expected)
+        {
+            string html = Markdown.ToHtml(markdown, GetPipeline());
+            Assert.AreEqual(html, expected);
+        }
+
+        private class TestHostProvider : IHostProvider
+        {
+            public string Class { get; } = "regex";
+            public bool AllowFullScreen { get; }
+
+            public bool TryHandle(Uri mediaUri, bool isSchemaRelative, out string iframeUrl)
+            {
+                iframeUrl = null;
+                var uri = isSchemaRelative ? "//" + mediaUri.GetComponents(UriComponents.AbsoluteUri & ~UriComponents.Scheme, UriFormat.UriEscaped) : mediaUri.ToString();
+                if (!matcher.IsMatch(uri))
+                    return false;
+                iframeUrl = matcher.Replace(uri, replacement);
+                return true;
+            }
+
+            private Regex matcher;
+            private string replacement;
+
+            public TestHostProvider(string provider, string replace)
+            {
+                matcher = new Regex(provider);
+                replacement = replace;
+            }
+        }
+
+        [Test]
+        [TestCase("![p1](https://sample.com/video.mp4)", "<p><iframe src=\"https://example.com/video.mp4\" width=\"500\" height=\"281\" class=\"regex\" frameborder=\"0\"></iframe></p>\n", @"^https?://sample.com/(.+)$", @"https://example.com/$1")]
+        [TestCase("![p1](//sample.com/video.mp4)", "<p><iframe src=\"https://example.com/video.mp4\" width=\"500\" height=\"281\" class=\"regex\" frameborder=\"0\"></iframe></p>\n", @"^//sample.com/(.+)$", @"https://example.com/$1")]
+        [TestCase("![p1](https://sample.com/video.mp4)", "<p><iframe src=\"https://example.com/video.mp4?token=aaabbb\" width=\"500\" height=\"281\" class=\"regex\" frameborder=\"0\"></iframe></p>\n", @"^https?://sample.com/(.+)$", @"https://example.com/$1?token=aaabbb")]
+        public void TestCustomHostProvider(string markdown, string expected, string provider, string replace)
+        {
+            string html = Markdown.ToHtml(markdown, GetPipeline(new MediaOptions
+            {
+                Hosts =
+                {
+                    new TestHostProvider(provider, replace),
+                }
+            }));
+            Assert.AreEqual(html, expected);
+        }
+
+        [Test]
+        [TestCase("![static mp4](//sample.com/video.mp4)", "<p><video width=\"500\" height=\"281\" controls=\"\"><source type=\"video/mp4\" src=\"//sample.com/video.mp4\"></source></video></p>\n", "")]
+        [TestCase(@"![youtube.com](https://www.youtube.com/watch?v=mswPy5bt3TQ)", "<p><iframe src=\"https://www.youtube.com/embed/mswPy5bt3TQ\" width=\"500\" height=\"281\" class=\"youtube\" frameborder=\"0\" allowfullscreen=\"\"></iframe></p>\n", "")]
+        [TestCase("![static mp4](//sample.com/video.mp4)", "<p><video width=\"500\" height=\"281\" controls=\"\" class=\"k\"><source type=\"video/mp4\" src=\"//sample.com/video.mp4\"></source></video></p>\n", "k")]
+        [TestCase(@"![youtube.com](https://www.youtube.com/watch?v=mswPy5bt3TQ)", "<p><iframe src=\"https://www.youtube.com/embed/mswPy5bt3TQ\" width=\"500\" height=\"281\" class=\"k youtube\" frameborder=\"0\" allowfullscreen=\"\"></iframe></p>\n", "k")]
+        public void TestCustomClass(string markdown, string expected, string klass)
+        {
+            string html = Markdown.ToHtml(markdown, GetPipeline(new MediaOptions
+            {
+                Class = klass,
+            }));
+            Assert.AreEqual(html, expected);
+        }
+    }
+}

src/Markdig.Tests/TestParser.cs

@@ -8,6 +8,7 @@ using System.Linq;
 using System.Text;
 using System.Text.RegularExpressions;
 using Markdig.Extensions.JiraLinks;
+using Markdig.Syntax;
 using NUnit.Framework;
 
 namespace Markdig.Tests
@@ -33,9 +34,9 @@ namespace Markdig.Tests
 
                 // If file creation times aren't preserved by git, add some leeway
                 // If specs have come from git, assume that they were regenerated since CI would fail otherwise
-                testTime = testTime.AddSeconds(2);
+                testTime = testTime.AddMinutes(3);
 
-                // This might not catch a changed spec every time, but should most of the time. Otherwise CI will catch it
+                // This might not catch a changed spec every time, but should at least sometimes. Otherwise CI will catch it
 
                 // This could also trigger, if a user has modified the spec file but reverted the change - can't think of a good workaround
                 Assert.Less(specTime, testTime,
@@ -151,8 +152,20 @@ namespace Markdig.Tests
         /// Contains the markdown source for specification files (order is the same as in <see cref="SpecsFilePaths"/>)
         /// </summary>
         public static readonly string[] SpecsMarkdown;
+        /// <summary>
+        /// Contains the markdown syntax tree for specification files (order is the same as in <see cref="SpecsFilePaths"/>)
+        /// </summary>
+        public static readonly MarkdownDocument[] SpecsSyntaxTrees;
+
         static TestParser()
         {
+            const string RunningInsideVisualStudioPath = "\\src\\.vs\\markdig\\";
+            int index = TestsDirectory.IndexOf(RunningInsideVisualStudioPath);
+            if (index != -1)
+            {
+                TestsDirectory = TestsDirectory.Substring(0, index) + "\\src\\Markdig.Tests";
+            }
+
             SpecsFilePaths = Directory.GetDirectories(TestsDirectory)
                 .Where(dir => dir.EndsWith("Specs"))
                 .SelectMany(dir => Directory.GetFiles(dir)
@@ -161,10 +174,16 @@ namespace Markdig.Tests
                 .ToArray();
 
             SpecsMarkdown = new string[SpecsFilePaths.Length];
+            SpecsSyntaxTrees = new MarkdownDocument[SpecsFilePaths.Length];
+
+            var pipeline = new MarkdownPipelineBuilder()
+                .UseAdvancedExtensions()
+                .Build();
 
             for (int i = 0; i < SpecsFilePaths.Length; i++)
             {
-                SpecsMarkdown[i] = File.ReadAllText(SpecsFilePaths[i]);
+                string markdown = SpecsMarkdown[i] = File.ReadAllText(SpecsFilePaths[i]);
+                SpecsSyntaxTrees[i] = Markdown.Parse(markdown, pipeline);
             }
         }
     }

src/Markdig.Tests/TestPlayParser.cs

@@ -1,5 +1,5 @@
 // Copyright (c) Alexandre Mutel. All rights reserved.
-// This file is licensed under the BSD-Clause 2 license. 
+// This file is licensed under the BSD-Clause 2 license.
 // See the license.txt file in the project root for more information.
 using System;
 using System.Linq;
@@ -19,7 +19,7 @@ namespace Markdig.Tests
             var link = doc.Descendants<ParagraphBlock>().SelectMany(x => x.Inline.Descendants<LinkInline>()).FirstOrDefault(l => l.IsImage);
             Assert.AreEqual("/yoyo", link?.Url);
         }
-        
+
         [Test]
         public void TestListBug2()
         {
@@ -53,11 +53,11 @@ Later in a text we are using HTML and it becomes an abbr tag HTML
         [Test]
         public void TestEmptyLiteral()
         {
-            var text = @"> *some text* 
+            var text = @"> *some text*
 > some other text";
             var doc = Markdown.Parse(text);
 
-            Assert.True(doc.Descendants().OfType<LiteralInline>().All(x => !x.Content.IsEmpty),
+            Assert.True(doc.Descendants<LiteralInline>().All(x => !x.Content.IsEmpty),
                 "There should not have any empty literals");
         }
 
@@ -195,8 +195,8 @@ Paragraph
 ";
 
             var expected = @"<table class=""table"">
-<col style=""width:50%"">
-<col style=""width:50%"">
+<col style=""width:50%"" />
+<col style=""width:50%"" />
 <thead>
 <tr>
 <th>a</th>
@@ -219,7 +219,7 @@ Paragraph
         {
             var pipeline = new MarkdownPipelineBuilder().UseAdvancedExtensions().Build();
 
-            // Reuse the same pipeline 
+            // Reuse the same pipeline
             var result1 = Markdown.ToHtml("This is a \"\"citation\"\"", pipeline);
             var result2 = Markdown.ToHtml("This is a \"\"citation\"\"", pipeline);
 
@@ -269,7 +269,7 @@ Paragraph
         //| Yes                               |
         //| ```                               |
         //+===================================+======================================+
-        //| This is a second line             | 
+        //| This is a second line             |
         //+-----------------------------------+--------------------------------------+
 
         //:::spoiler  {#yessss}

src/Markdig.Tests/TestSmartyPants.cs

@@ -0,0 +1,36 @@
+using Markdig.Extensions.SmartyPants;
+using NUnit.Framework;
+
+namespace Markdig.Tests
+{
+    public class TestSmartyPants
+    {
+        [Test]
+        public void MappingCanBeReconfigured()
+        {
+            SmartyPantOptions options = new SmartyPantOptions();
+            options.Mapping[SmartyPantType.LeftAngleQuote] = "foo";
+            options.Mapping[SmartyPantType.RightAngleQuote] = "bar";
+
+            var pipeline = new MarkdownPipelineBuilder()
+                .UseSmartyPants(options)
+                .Build();
+
+            TestParser.TestSpec("<<test>>", "<p>footestbar</p>", pipeline);
+        }
+
+        [Test]
+        public void MappingCanBeReconfigured_HandlesRemovedMappings()
+        {
+            SmartyPantOptions options = new SmartyPantOptions();
+            options.Mapping.Remove(SmartyPantType.LeftAngleQuote);
+            options.Mapping.Remove(SmartyPantType.RightAngleQuote);
+
+            var pipeline = new MarkdownPipelineBuilder()
+                .UseSmartyPants(options)
+                .Build();
+
+            TestParser.TestSpec("<<test>>", "<p>&laquo;test&raquo;</p>", pipeline);
+        }
+    }
+}

src/Markdig.Tests/TestSourcePosition.cs

@@ -6,8 +6,7 @@ using System;
 using System.Collections.Generic;
 using System.Linq;
 using System.Text;
-using Markdig.Extensions.Footnotes;
-using Markdig.Helpers;
+using Markdig.Extensions.Footnotes;
 using Markdig.Renderers.Html;
 using Markdig.Syntax;
 using Markdig.Syntax.Inlines;
@@ -147,7 +146,7 @@ literal      ( 0, 6)  6-7
         public void TestFootnoteLinkReferenceDefinition()
         {
             //                             01 2 345678
-            var footnote = Markdown.Parse("0\n\n [^1]:", new MarkdownPipelineBuilder().UsePreciseSourceLocation().UseFootnotes().Build()).Descendants().OfType<FootnoteLinkReferenceDefinition>().FirstOrDefault();
+            var footnote = Markdown.Parse("0\n\n [^1]:", new MarkdownPipelineBuilder().UsePreciseSourceLocation().UseFootnotes().Build()).Descendants<FootnoteLinkReferenceDefinition>().FirstOrDefault();
             Assert.NotNull(footnote);
 
             Assert.AreEqual(2, footnote.Line);
@@ -160,7 +159,7 @@ literal      ( 0, 6)  6-7
         {
             //                         0         1
             //                         0123456789012345
-            var link = Markdown.Parse("[234]: /56 'yo' ", new MarkdownPipelineBuilder().UsePreciseSourceLocation().Build()).Descendants().OfType<LinkReferenceDefinition>().FirstOrDefault();
+            var link = Markdown.Parse("[234]: /56 'yo' ", new MarkdownPipelineBuilder().UsePreciseSourceLocation().Build()).Descendants<LinkReferenceDefinition>().FirstOrDefault();
             Assert.NotNull(link);
 
             Assert.AreEqual(0, link.Line);
@@ -175,7 +174,7 @@ literal      ( 0, 6)  6-7
         {
             //                         0          1
             //                         01 2 34567890123456789
-            var link = Markdown.Parse("0\n\n [234]: /56 'yo' ", new MarkdownPipelineBuilder().UsePreciseSourceLocation().Build()).Descendants().OfType<LinkReferenceDefinition>().FirstOrDefault();
+            var link = Markdown.Parse("0\n\n [234]: /56 'yo' ", new MarkdownPipelineBuilder().UsePreciseSourceLocation().Build()).Descendants<LinkReferenceDefinition>().FirstOrDefault();
             Assert.NotNull(link);
 
             Assert.AreEqual(2, link.Line);
@@ -213,7 +212,7 @@ literal      ( 0, 4)  4-5
         {
             //                         0           1
             //                         01 2 3456789012345
-            var link = Markdown.Parse("0\n\n01 [234](/56)", new MarkdownPipelineBuilder().UsePreciseSourceLocation().Build()).Descendants().OfType<LinkInline>().FirstOrDefault();
+            var link = Markdown.Parse("0\n\n01 [234](/56)", new MarkdownPipelineBuilder().UsePreciseSourceLocation().Build()).Descendants<LinkInline>().FirstOrDefault();
             Assert.NotNull(link);
 
             Assert.AreEqual(new SourceSpan(7, 9), link.LabelSpan);
@@ -226,7 +225,7 @@ literal      ( 0, 4)  4-5
         {
             //                         0           1
             //                         01 2 34567890123456789
-            var link = Markdown.Parse("0\n\n01 [234](/56 'yo')", new MarkdownPipelineBuilder().UsePreciseSourceLocation().Build()).Descendants().OfType<LinkInline>().FirstOrDefault();
+            var link = Markdown.Parse("0\n\n01 [234](/56 'yo')", new MarkdownPipelineBuilder().UsePreciseSourceLocation().Build()).Descendants<LinkInline>().FirstOrDefault();
             Assert.NotNull(link);
 
             Assert.AreEqual(new SourceSpan(7, 9), link.LabelSpan);
@@ -240,7 +239,7 @@ literal      ( 0, 4)  4-5
         {
             //                         0           1
             //                         01 2 3456789012345
-            var link = Markdown.Parse("0\n\n01![234](/56)", new MarkdownPipelineBuilder().UsePreciseSourceLocation().Build()).Descendants().OfType<LinkInline>().FirstOrDefault();
+            var link = Markdown.Parse("0\n\n01![234](/56)", new MarkdownPipelineBuilder().UsePreciseSourceLocation().Build()).Descendants<LinkInline>().FirstOrDefault();
             Assert.NotNull(link);
 
             Assert.AreEqual(new SourceSpan(5, 15), link.Span);
@@ -408,7 +407,7 @@ literal      ( 1, 2)  6-6
 6. Bar
 987123. FooBar";
             test = test.Replace("\r\n", "\n");
-            var list = Markdown.Parse(test, new MarkdownPipelineBuilder().UsePreciseSourceLocation().Build()).Descendants().OfType<ListBlock>().FirstOrDefault();
+            var list = Markdown.Parse(test, new MarkdownPipelineBuilder().UsePreciseSourceLocation().Build()).Descendants<ListBlock>().FirstOrDefault();
             Assert.NotNull(list);
 
             Assert.AreEqual(1, list.Line);

src/Markdig.Tests/TestStringSliceList.cs

@@ -1,8 +1,9 @@
-using NUnit.Framework;
+using NUnit.Framework;
 using System.Collections.Generic;
 using System.Text;
 using Markdig.Helpers;
 using Markdig.Syntax;
+using System;
 
 namespace Markdig.Tests
 {
@@ -27,6 +28,8 @@ namespace Markdig.Tests
 
             var chars = ToString(text.ToCharIterator());
             TextAssert.AreEqual("ABC\nE\nF", chars.ToString());
+
+            TextAssert.AreEqual("ABC\nE\nF", text.ToString());
         }
 
         [Test]
@@ -81,8 +84,18 @@ namespace Markdig.Tests
         public void TestSkipWhitespaces()
         {
             var text = new StringLineGroup("             ABC").ToCharIterator();
-            Assert.True(text.TrimStart());
+            Assert.False(text.TrimStart());
             Assert.AreEqual('A', text.CurrentChar);
+
+            text = new StringLineGroup("        ").ToCharIterator();
+            Assert.True(text.TrimStart());
+            Assert.AreEqual('\0', text.CurrentChar);
+
+            var slice = new StringSlice("             ABC");
+            Assert.False(slice.TrimStart());
+
+            slice = new StringSlice("        ");
+            Assert.True(slice.TrimStart());
         }
 
         [Test]
@@ -116,5 +129,31 @@ namespace Markdig.Tests
             var result = ToString(text);
             TextAssert.AreEqual("ABC  \n  DEF ", result);
         }
+
+        [Test]
+        public void TestStringLineGroupIteratorPeekChar()
+        {
+            var iterator = new StringLineGroup(4)
+            {
+                new StringSlice("ABC"),
+                new StringSlice("E"),
+                new StringSlice("F")
+            }.ToCharIterator();
+
+            Assert.AreEqual('A', iterator.CurrentChar);
+            Assert.AreEqual('A', iterator.PeekChar(0));
+            Assert.AreEqual('B', iterator.PeekChar());
+            Assert.AreEqual('B', iterator.PeekChar(1));
+            Assert.AreEqual('C', iterator.PeekChar(2));
+            Assert.AreEqual('\n', iterator.PeekChar(3));
+            Assert.AreEqual('E', iterator.PeekChar(4));
+            Assert.AreEqual('\n', iterator.PeekChar(5));
+            Assert.AreEqual('F', iterator.PeekChar(6));
+            Assert.AreEqual('\0', iterator.PeekChar(7)); // There is no \n appended to the last line
+            Assert.AreEqual('\0', iterator.PeekChar(8));
+            Assert.AreEqual('\0', iterator.PeekChar(100));
+
+            Assert.Throws<ArgumentOutOfRangeException>(() => iterator.PeekChar(-1));
+        }
     }
 }

src/Markdig.WebApp/Markdig.WebApp.csproj

@@ -9,6 +9,7 @@
     <RuntimeFrameworkVersion>2.0.0</RuntimeFrameworkVersion>
     <ApplicationInsightsResourceId>/subscriptions/b6745039-70e7-4641-994b-5457cb220e2a/resourcegroups/Default-ApplicationInsights-EastUS/providers/microsoft.insights/components/Markdig.WebApp</ApplicationInsightsResourceId>
     <ApplicationInsightsAnnotationResourceId>/subscriptions/b6745039-70e7-4641-994b-5457cb220e2a/resourcegroups/Default-ApplicationInsights-EastUS/providers/microsoft.insights/components/Markdig.WebApp</ApplicationInsightsAnnotationResourceId>
+    <IsPackable>false</IsPackable>
   </PropertyGroup>
 
   <ItemGroup>
@@ -22,16 +23,16 @@
   </ItemGroup>
 
   <ItemGroup>
-    <PackageReference Include="Microsoft.ApplicationInsights.AspNetCore" Version="2.1.1" />
-    <PackageReference Include="Microsoft.AspNetCore.Mvc" Version="2.0.0" />
-    <PackageReference Include="Microsoft.AspNetCore.Server.IISIntegration" Version="2.0.0" />
-    <PackageReference Include="Microsoft.AspNetCore.Server.Kestrel" Version="2.0.0" />
-    <PackageReference Include="Microsoft.Extensions.Configuration.EnvironmentVariables" Version="2.0.0" />
-    <PackageReference Include="Microsoft.Extensions.Configuration.FileExtensions" Version="2.0.0" />
-    <PackageReference Include="Microsoft.Extensions.Configuration.Json" Version="2.0.0" />
-    <PackageReference Include="Microsoft.Extensions.Logging" Version="2.0.0" />
-    <PackageReference Include="Microsoft.Extensions.Logging.Console" Version="2.0.0" />
-    <PackageReference Include="Microsoft.Extensions.Logging.Debug" Version="2.0.0" />
+    <PackageReference Include="Microsoft.ApplicationInsights.AspNetCore" Version="2.12.0" />
+    <PackageReference Include="Microsoft.AspNetCore.Mvc" Version="2.2.0" />
+    <PackageReference Include="Microsoft.AspNetCore.Server.IISIntegration" Version="2.2.1" />
+    <PackageReference Include="Microsoft.AspNetCore.Server.Kestrel" Version="2.2.0" />
+    <PackageReference Include="Microsoft.Extensions.Configuration.EnvironmentVariables" Version="3.1.1" />
+    <PackageReference Include="Microsoft.Extensions.Configuration.FileExtensions" Version="3.1.1" />
+    <PackageReference Include="Microsoft.Extensions.Configuration.Json" Version="3.1.1" />
+    <PackageReference Include="Microsoft.Extensions.Logging" Version="3.1.1" />
+    <PackageReference Include="Microsoft.Extensions.Logging.Console" Version="3.1.1" />
+    <PackageReference Include="Microsoft.Extensions.Logging.Debug" Version="3.1.1" />
   </ItemGroup>
 
   <ItemGroup>

src/Markdig.WebApp/Startup.cs

@@ -43,8 +43,8 @@ namespace Markdig.WebApp
         // This method gets called by the runtime. Use this method to configure the HTTP request pipeline
         public void Configure(IApplicationBuilder app, IHostingEnvironment env, ILoggerFactory loggerFactory)
         {
-            loggerFactory.AddConsole(Configuration.GetSection("Logging"));
-            loggerFactory.AddDebug();
+            //loggerFactory.AddConsole(Configuration.GetSection("Logging"));
+            //loggerFactory.AddDebug();
 
             app.UseMvc();
         }

src/Markdig/Directory.Build.props

@@ -1,9 +0,0 @@
-<Project>
-  <PropertyGroup>
-    <PublishRepositoryUrl>true</PublishRepositoryUrl>
-    <AllowedOutputExtensionsInPackageBuildOutputFolder>$(AllowedOutputExtensionsInPackageBuildOutputFolder);.pdb</AllowedOutputExtensionsInPackageBuildOutputFolder>
-  </PropertyGroup>
-  <ItemGroup>
-    <PackageReference Include="Microsoft.SourceLink.GitHub" Version="1.0.0-*" PrivateAssets="All"/>
-  </ItemGroup>
-</Project>

src/Markdig/Extensions/Abbreviations/AbbreviationHelper.cs

@@ -1,8 +1,9 @@
-// Copyright (c) Alexandre Mutel. All rights reserved.
+// Copyright (c) Alexandre Mutel. All rights reserved.
 // This file is licensed under the BSD-Clause 2 license. 
 // See the license.txt file in the project root for more information.
 using System;
 using System.Collections.Generic;
+using Markdig.Helpers;
 using Markdig.Syntax;
 
 namespace Markdig.Extensions.Abbreviations
@@ -21,9 +22,9 @@ namespace Markdig.Extensions.Abbreviations
 
         public static void AddAbbreviation(this MarkdownDocument document, string label, Abbreviation abbr)
         {
-            if (document == null) throw new ArgumentNullException(nameof(document));
-            if (label == null) throw new ArgumentNullException(nameof(label));
-            if (abbr == null) throw new ArgumentNullException(nameof(abbr));
+            if (document == null) ThrowHelper.ArgumentNullException(nameof(document));
+            if (label == null) ThrowHelper.ArgumentNullException_label();
+            if (abbr == null) ThrowHelper.ArgumentNullException(nameof(abbr));
 
             var map = document.GetAbbreviations();
             if (map == null)

src/Markdig/Extensions/Abbreviations/AbbreviationParser.cs

@@ -1,6 +1,7 @@
 // Copyright (c) Alexandre Mutel. All rights reserved.
 // This file is licensed under the BSD-Clause 2 license. 
 // See the license.txt file in the project root for more information.
+using System;
 using System.Collections.Generic;
 using Markdig.Helpers;
 using Markdig.Parsers;
@@ -115,7 +116,7 @@ namespace Markdig.Extensions.Abbreviations
 
                 ValidAbbreviationStart:;
 
-                    if (prefixTree.TryMatchLongest(text, i, content.End - i + 1, out KeyValuePair<string, Abbreviation> abbreviationMatch))
+                    if (prefixTree.TryMatchLongest(text.AsSpan(i, content.End - i + 1), out KeyValuePair<string, Abbreviation> abbreviationMatch))
                     {
                         var match = abbreviationMatch.Key;
                         if (!IsValidAbbreviationEnding(match, content, i))

src/Markdig/Extensions/AutoIdentifiers/AutoIdentifierExtension.cs

@@ -22,6 +22,7 @@ namespace Markdig.Extensions.AutoIdentifiers
     {
         private const string AutoIdentifierKey = "AutoIdentifier";
         private readonly AutoIdentifierOptions options;
+        private readonly StripRendererCache rendererCache = new StripRendererCache();
 
         /// <summary>
         /// Initializes a new instance of the <see cref="AutoIdentifierExtension"/> class.
@@ -159,17 +160,11 @@ namespace Markdig.Extensions.AutoIdentifiers
             }
 
             // Use internally a HtmlRenderer to strip links from a heading
-            var headingWriter = new StringWriter();
-            var stripRenderer = new HtmlRenderer(headingWriter)
-            {
-                // Set to false both to avoid having any HTML tags in the output
-                EnableHtmlForInline = false,
-                EnableHtmlEscape = false
-            };
+            var stripRenderer = rendererCache.Get();
 
             stripRenderer.Render(headingBlock.Inline);
-            var headingText = headingWriter.ToString();
-            headingWriter.GetStringBuilder().Length = 0;
+            var headingText = stripRenderer.Writer.ToString();
+            rendererCache.Release(stripRenderer);
 
             // Urilize the link
             headingText = (options & AutoIdentifierOptions.GitHub) != 0
@@ -195,5 +190,25 @@ namespace Markdig.Extensions.AutoIdentifiers
 
             attributes.Id = headingId;
         }
+
+        private sealed class StripRendererCache : ObjectCache<HtmlRenderer>
+        {
+            protected override HtmlRenderer NewInstance()
+            {
+                var headingWriter = new StringWriter();
+                var stripRenderer = new HtmlRenderer(headingWriter)
+                {
+                    // Set to false both to avoid having any HTML tags in the output
+                    EnableHtmlForInline = false,
+                    EnableHtmlEscape = false
+                };
+                return stripRenderer;
+            }
+
+            protected override void Reset(HtmlRenderer instance)
+            {
+                instance.Reset();
+            }
+        }
     }
 }

src/Markdig/Extensions/AutoLinks/AutoLinkParser.cs

@@ -14,7 +14,7 @@ namespace Markdig.Extensions.AutoLinks
     /// <summary>
     /// The inline parser used to for autolinks.
     /// </summary>
-    /// <seealso cref="Markdig.Parsers.InlineParser" />
+    /// <seealso cref="InlineParser" />
     public class AutoLinkParser : InlineParser
     {
         /// <summary>
@@ -30,10 +30,14 @@ namespace Markdig.Extensions.AutoLinks
                 'f', // for ftp://
                 'm', // for mailto:
                 'w', // for www.
-            };
-        }
-
-        public readonly AutoLinkOptions Options;
+            };
+
+            _listOfCharCache = new ListOfCharCache();
+        }
+
+        public readonly AutoLinkOptions Options;
+
+        private readonly ListOfCharCache _listOfCharCache;
 
         public override bool Match(InlineProcessor processor, ref StringSlice slice)
         {
@@ -44,159 +48,162 @@ namespace Markdig.Extensions.AutoLinks
                 return false;
             }
 
-            List<char> pendingEmphasis;
-            // Check that an autolink is possible in the current context
-            if (!IsAutoLinkValidInCurrentContext(processor, out pendingEmphasis))
-            {
-                return false;
-            }
-
-            var startPosition = slice.Start;
-            int domainOffset = 0;
-
-            var c = slice.CurrentChar;
-            // Precheck URL
-            switch (c)
-            {
-                case 'h':
-                    if (slice.MatchLowercase("ttp://", 1))
-                    {
-                        domainOffset = 7; // http://
-                    }
-                    else if (slice.MatchLowercase("ttps://", 1))
-                    {
-                        domainOffset = 8; // https://
-                    }
-                    else return false;
-                    break;
-                case 'f':
-                    if (!slice.MatchLowercase("tp://", 1))
-                    {
-                        return false;
-                    }
-                    domainOffset = 6; // ftp://
-                    break;
-                case 'm':
-                    if (!slice.MatchLowercase("ailto:", 1))
-                    {
-                        return false;
-                    }
-                    break;
-
-                case 'w':
-                    if (!slice.MatchLowercase("ww.", 1)) // We won't match http:/www. or /www.xxx
-                    {
-                        return false;
-                    }
-                    domainOffset = 4; // www.
-                    break;
-            }
-
-            // Parse URL
-            string link;
-            if (!LinkHelper.TryParseUrl(ref slice, out link, true))
-            {
-                return false;
-            }
-
-
-            // If we have any pending emphasis, remove any pending emphasis characters from the end of the link
-            if (pendingEmphasis != null)
-            {
-                for (int i = link.Length - 1; i >= 0; i--)
-                {
-                    if (pendingEmphasis.Contains(link[i]))
-                    {
-                        slice.Start--;
-                    }
-                    else
-                    {
-                        if (i < link.Length - 1)
-                        {
-                            link = link.Substring(0, i + 1);
-                        }
-                        break;
-                    }
-                }
-            }
-
-            // Post-check URL
-            switch (c)
-            {
-                case 'h':
-                    if (string.Equals(link, "http://", StringComparison.OrdinalIgnoreCase) ||
-                        string.Equals(link, "https://", StringComparison.OrdinalIgnoreCase))
-                    {
-                        return false;
-                    }
-                    break;
-                case 'f':
-                    if (string.Equals(link, "ftp://", StringComparison.OrdinalIgnoreCase))
-                    {
-                        return false;
-                    }
-                    break;
-                case 'm':
-                    int atIndex = link.IndexOf('@');
-                    if (atIndex == -1 ||
-                        atIndex == 7) // mailto:@ - no email part
-                    {
-                        return false;
-                    }
-                    domainOffset = atIndex + 1;
-                    break;
-            }
-
-            if (!LinkHelper.IsValidDomain(link, domainOffset))
+            List<char> pendingEmphasis = _listOfCharCache.Get();
+            try
             {
-                return false;
+                // Check that an autolink is possible in the current context
+                if (!IsAutoLinkValidInCurrentContext(processor, pendingEmphasis))
+                {
+                    return false;
+                }
+
+                var startPosition = slice.Start;
+                int domainOffset = 0;
+
+                var c = slice.CurrentChar;
+                // Precheck URL
+                switch (c)
+                {
+                    case 'h':
+                        if (slice.MatchLowercase("ttp://", 1))
+                        {
+                            domainOffset = 7; // http://
+                        }
+                        else if (slice.MatchLowercase("ttps://", 1))
+                        {
+                            domainOffset = 8; // https://
+                        }
+                        else return false;
+                        break;
+                    case 'f':
+                        if (!slice.MatchLowercase("tp://", 1))
+                        {
+                            return false;
+                        }
+                        domainOffset = 6; // ftp://
+                        break;
+                    case 'm':
+                        if (!slice.MatchLowercase("ailto:", 1))
+                        {
+                            return false;
+                        }
+                        break;
+
+                    case 'w':
+                        if (!slice.MatchLowercase("ww.", 1)) // We won't match http:/www. or /www.xxx
+                        {
+                            return false;
+                        }
+                        domainOffset = 4; // www.
+                        break;
+                }
+
+                // Parse URL
+                if (!LinkHelper.TryParseUrl(ref slice, out string link, true))
+                {
+                    return false;
+                }
+
+
+                // If we have any pending emphasis, remove any pending emphasis characters from the end of the link
+                if (pendingEmphasis.Count > 0)
+                {
+                    for (int i = link.Length - 1; i >= 0; i--)
+                    {
+                        if (pendingEmphasis.Contains(link[i]))
+                        {
+                            slice.Start--;
+                        }
+                        else
+                        {
+                            if (i < link.Length - 1)
+                            {
+                                link = link.Substring(0, i + 1);
+                            }
+                            break;
+                        }
+                    }
+                }
+
+                // Post-check URL
+                switch (c)
+                {
+                    case 'h':
+                        if (string.Equals(link, "http://", StringComparison.OrdinalIgnoreCase) ||
+                            string.Equals(link, "https://", StringComparison.OrdinalIgnoreCase))
+                        {
+                            return false;
+                        }
+                        break;
+                    case 'f':
+                        if (string.Equals(link, "ftp://", StringComparison.OrdinalIgnoreCase))
+                        {
+                            return false;
+                        }
+                        break;
+                    case 'm':
+                        int atIndex = link.IndexOf('@');
+                        if (atIndex == -1 ||
+                            atIndex == 7) // mailto:@ - no email part
+                        {
+                            return false;
+                        }
+                        domainOffset = atIndex + 1;
+                        break;
+                }
+
+                if (!LinkHelper.IsValidDomain(link, domainOffset))
+                {
+                    return false;
+                }
+
+                var inline = new LinkInline()
+                {
+                    Span =
+                    {
+                        Start = processor.GetSourcePosition(startPosition, out int line, out int column),
+                    },
+                    Line = line,
+                    Column = column,
+                    Url = c == 'w' ? ((Options.UseHttpsForWWWLinks ? "https://" : "http://") + link) : link,
+                    IsClosed = true,
+                    IsAutoLink = true,
+                };
+
+                var skipFromBeginning = c == 'm' ? 7 : 0; // For mailto: skip "mailto:" for content
+
+                inline.Span.End = inline.Span.Start + link.Length - 1;
+                inline.UrlSpan = inline.Span;
+                inline.AppendChild(new LiteralInline()
+                {
+                    Span = inline.Span,
+                    Line = line,
+                    Column = column,
+                    Content = new StringSlice(slice.Text, startPosition + skipFromBeginning, startPosition + link.Length - 1),
+                    IsClosed = true
+                });
+                processor.Inline = inline;
+
+                if (Options.OpenInNewWindow)
+                {
+                    inline.GetAttributes().AddPropertyIfNotExist("target", "blank");
+                }
+
+                return true;
             }
-
-            var inline = new LinkInline()
-            {
-                Span =
-                {
-                    Start = processor.GetSourcePosition(startPosition, out int line, out int column),
-                },
-                Line = line,
-                Column = column,
-                Url = c == 'w' ? ((Options.UseHttpsForWWWLinks ? "https://" : "http://") + link) : link,
-                IsClosed = true,
-                IsAutoLink = true,
-            };
-
-            var skipFromBeginning = c == 'm' ? 7 : 0; // For mailto: skip "mailto:" for content
-
-            inline.Span.End = inline.Span.Start + link.Length - 1;
-            inline.UrlSpan = inline.Span;
-            inline.AppendChild(new LiteralInline()
-            {
-                Span = inline.Span,
-                Line = line,
-                Column = column,
-                Content = new StringSlice(slice.Text, startPosition + skipFromBeginning, startPosition + link.Length - 1),
-                IsClosed = true
-            });
-            processor.Inline = inline;
-
-            if (Options.OpenInNewWindow)
+            finally
             {
-                inline.GetAttributes().AddPropertyIfNotExist("target", "blank");
+                _listOfCharCache.Release(pendingEmphasis);
             }
-
-            return true;
         }
 
-        private bool IsAutoLinkValidInCurrentContext(InlineProcessor processor, out List<char> pendingEmphasis)
+        private bool IsAutoLinkValidInCurrentContext(InlineProcessor processor, List<char> pendingEmphasis)
         {
-            pendingEmphasis = null;
-
             // Case where there is a pending HtmlInline <a>
             var currentInline = processor.Inline;
             while (currentInline != null)
             {
-                var htmlInline = currentInline as HtmlInline;
-                if (htmlInline != null)
+                if (currentInline is HtmlInline htmlInline)
                 {
                     // If we have a </a> we don't expect nested <a>
                     if (htmlInline.Tag.StartsWith("</a", StringComparison.OrdinalIgnoreCase))
@@ -211,7 +218,7 @@ namespace Markdig.Extensions.AutoLinks
                     }
                 }
 
-                // Check previous sibling and parents in the tree 
+                // Check previous sibling and parents in the tree
                 currentInline = currentInline.PreviousSibling ?? currentInline.Parent;
             }
 
@@ -221,8 +228,7 @@ namespace Markdig.Extensions.AutoLinks
             int countBrackets = 0;
             while (currentInline != null)
             {
-                var linkDelimiterInline = currentInline as LinkDelimiterInline;
-                if (linkDelimiterInline != null && linkDelimiterInline.IsActive)
+                if (currentInline is LinkDelimiterInline linkDelimiterInline && linkDelimiterInline.IsActive)
                 {
                     if (linkDelimiterInline.Type == DelimiterType.Open)
                     {
@@ -236,14 +242,8 @@ namespace Markdig.Extensions.AutoLinks
                 else
                 {
                     // Record all pending characters for emphasis
-                    var emphasisDelimiter = currentInline as EmphasisDelimiterInline;
-                    if (emphasisDelimiter != null)
+                    if (currentInline is EmphasisDelimiterInline emphasisDelimiter)
                     {
-                        if (pendingEmphasis == null)
-                        {
-                            // Not optimized for GC, but we don't expect this case much
-                            pendingEmphasis = new List<char>();
-                        }
                         if (!pendingEmphasis.Contains(emphasisDelimiter.DelimiterChar))
                         {
                             pendingEmphasis.Add(emphasisDelimiter.DelimiterChar);
@@ -254,6 +254,14 @@ namespace Markdig.Extensions.AutoLinks
             }
 
             return countBrackets <= 0;
+        }
+
+        private sealed class ListOfCharCache : DefaultObjectCache<List<char>>
+        {
+            protected override void Reset(List<char> instance)
+            {
+                instance.Clear();
+            }
         }
     }
 }

src/Markdig/Extensions/Bootstrap/BootstrapExtension.cs

@@ -1,4 +1,4 @@
-// Copyright (c) Alexandre Mutel. All rights reserved.
+// Copyright (c) Alexandre Mutel. All rights reserved.
 // This file is licensed under the BSD-Clause 2 license. 
 // See the license.txt file in the project root for more information.
 
@@ -51,8 +51,7 @@ namespace Markdig.Extensions.Bootstrap
                 }
                 else if (node is Inline)
                 {
-                    var link = node as LinkInline;
-                    if (link != null && link.IsImage)
+                    if (node is LinkInline link && link.IsImage)
                     {
                         link.GetAttributes().AddClass("img-fluid");
                     }

src/Markdig/Extensions/Emoji/EmojiExtension.cs

@@ -7,24 +7,24 @@ using Markdig.Renderers;
 namespace Markdig.Extensions.Emoji
 {
     /// <summary>
-    /// Extension to allow emoji and smiley replacement.
+    /// Extension to allow emoji shortcodes and smileys replacement.
     /// </summary>
     /// <seealso cref="Markdig.IMarkdownExtension" />
     public class EmojiExtension : IMarkdownExtension
     {
-        public EmojiExtension(bool enableSmiley = true)
-        {
-            EnableSmiley = enableSmiley;
+        public EmojiExtension(EmojiMapping emojiMapping)
+        {
+            EmojiMapping = emojiMapping;
         }
-
-        public bool EnableSmiley { get; set; }
-
+
+        public EmojiMapping EmojiMapping { get; }
+
         public void Setup(MarkdownPipelineBuilder pipeline)
         {
             if (!pipeline.InlineParsers.Contains<EmojiParser>())
             {
                 // Insert the parser before any other parsers
-                pipeline.InlineParsers.Insert(0, new EmojiParser(EnableSmiley));
+                pipeline.InlineParsers.Insert(0, new EmojiParser(EmojiMapping));
             }
         }
 

src/Markdig/Extensions/Emoji/EmojiInline.cs

@@ -1,4 +1,4 @@
-// Copyright (c) Alexandre Mutel. All rights reserved.
+// Copyright (c) Alexandre Mutel. All rights reserved.
 // This file is licensed under the BSD-Clause 2 license. 
 // See the license.txt file in the project root for more information.
 
@@ -8,7 +8,7 @@ using Markdig.Syntax.Inlines;
 namespace Markdig.Extensions.Emoji
 {
     /// <summary>
-    /// An emoji inline 
+    /// An emoji inline.
     /// </summary>
     /// <seealso cref="Markdig.Syntax.Inlines.Inline" />
     public class EmojiInline : LiteralInline
@@ -32,7 +32,7 @@ namespace Markdig.Extensions.Emoji
         }
 
         /// <summary>
-        /// Gets or sets the original match string (either an emoji or a text smiley)
+        /// Gets or sets the original match string (either an emoji shortcode or a text smiley)
         /// </summary>
         public string Match { get; set; }
     }

src/Markdig/Extensions/GenericAttributes/GenericAttributesExtension.cs

@@ -1,4 +1,4 @@
-// Copyright (c) Alexandre Mutel. All rights reserved.
+// Copyright (c) Alexandre Mutel. All rights reserved.
 // This file is licensed under the BSD-Clause 2 license. 
 // See the license.txt file in the project root for more information.
 
@@ -16,7 +16,7 @@ namespace Markdig.Extensions.GenericAttributes
     /// Extension that allows to attach HTML attributes to the previous <see cref="Inline"/> or current <see cref="Block"/>.
     /// This extension should be enabled last after enabling other extensions.
     /// </summary>
-    /// <seealso cref="Markdig.IMarkdownExtension" />
+    /// <seealso cref="IMarkdownExtension" />
     public class GenericAttributesExtension : IMarkdownExtension
     {
         public void Setup(MarkdownPipelineBuilder pipeline)
@@ -29,8 +29,7 @@ namespace Markdig.Extensions.GenericAttributes
             // Plug into all IAttributesParseable
             foreach (var parser in pipeline.BlockParsers)
             {
-                var attributesParseable = parser as IAttributesParseable;
-                if (attributesParseable != null)
+                if (parser is IAttributesParseable attributesParseable)
                 {
                     attributesParseable.TryParseAttributes = TryProcessAttributesForHeading;
                 }
@@ -53,8 +52,7 @@ namespace Markdig.Extensions.GenericAttributes
                     var copy = line;
                     copy.Start = indexOfAttributes;
                     var startOfAttributes = copy.Start;
-                    HtmlAttributes attributes;
-                    if (GenericAttributesParser.TryParse(ref copy, out attributes))
+                    if (GenericAttributesParser.TryParse(ref copy, out HtmlAttributes attributes))
                     {
                         var htmlAttributes = block.GetAttributes();
                         attributes.CopyTo(htmlAttributes);

src/Markdig/Extensions/GenericAttributes/GenericAttributesParser.cs

@@ -14,7 +14,7 @@ namespace Markdig.Extensions.GenericAttributes
     /// <summary>
     /// An inline parser used to parse a HTML attributes that can be attached to the previous <see cref="Inline"/> or current <see cref="Block"/>.
     /// </summary>
-    /// <seealso cref="Markdig.Parsers.InlineParser" />
+    /// <seealso cref="InlineParser" />
     public class GenericAttributesParser : InlineParser
     {
         /// <summary>
@@ -27,9 +27,8 @@ namespace Markdig.Extensions.GenericAttributes
 
         public override bool Match(InlineProcessor processor, ref StringSlice slice)
         {
-            HtmlAttributes attributes;
             var startPosition = slice.Start;
-            if (TryParse(ref slice, out attributes))
+            if (TryParse(ref slice, out HtmlAttributes attributes))
             {
                 var inline = processor.Inline;
 
@@ -50,8 +49,10 @@ namespace Markdig.Extensions.GenericAttributes
 
                 // If the current block is a Paragraph, but only the HtmlAttributes is used,
                 // Try to attach the attributes to the following block
-                var paragraph = objectToAttach as ParagraphBlock;
-                if (paragraph != null && paragraph.Inline.FirstChild == null && processor.Inline == null && slice.IsEmptyOrWhitespace())
+                if (objectToAttach is ParagraphBlock paragraph &&
+                    paragraph.Inline.FirstChild == null &&
+                    processor.Inline == null &&
+                    slice.IsEmptyOrWhitespace())
                 {
                     var parent = paragraph.Parent;
                     var indexOfParagraph = parent.IndexOf(paragraph);
@@ -67,9 +68,7 @@ namespace Markdig.Extensions.GenericAttributes
                 attributes.CopyTo(currentHtmlAttributes, true, false);
 
                 // Update the position of the attributes
-                int line;
-                int column;
-                currentHtmlAttributes.Span.Start = processor.GetSourcePosition(startPosition, out line, out column);
+                currentHtmlAttributes.Span.Start = processor.GetSourcePosition(startPosition, out int line, out int column);
                 currentHtmlAttributes.Line = line;
                 currentHtmlAttributes.Column = column;
                 currentHtmlAttributes.Span.End = currentHtmlAttributes.Span.Start + slice.Start - startPosition - 1;
@@ -223,6 +222,7 @@ namespace Markdig.Extensions.GenericAttributes
                     {
                         // Parse until we match a space or a special html character
                         startValue = line.Start;
+                        bool valid = false;
                         while (true)
                         {
                             if (c == '\0')
@@ -234,9 +234,10 @@ namespace Markdig.Extensions.GenericAttributes
                                 break;
                             }
                             c = line.NextChar();
+                            valid = true;
                         }
                         endValue = line.Start - 1;
-                        if (endValue == startValue)
+                        if (!valid)
                         {
                             break;
                         }

src/Markdig/Extensions/Globalization/GlobalizationExtension.cs

@@ -38,7 +38,7 @@ namespace Markdig.Extensions.Globalization
                     var attributes = node.GetAttributes();
                     attributes.AddPropertyIfNotExist("dir", "rtl");
 
-                    if (node is Table table)
+                    if (node is Table)
                     {
                         attributes.AddPropertyIfNotExist("align", "right");
                     }
@@ -71,19 +71,16 @@ namespace Markdig.Extensions.Globalization
             }
             else if (item is LiteralInline literal)
             {
-                return StartsWithRtlCharacter(literal.ToString());
+                return StartsWithRtlCharacter(literal.Content);
             }
 
-            foreach (var descendant in item.Descendants())
+            foreach (var paragraph in item.Descendants<ParagraphBlock>())
             {
-                if (descendant is ParagraphBlock p)
+                foreach (var inline in paragraph.Inline)
                 {
-                    foreach (var i in p.Inline)
+                    if (inline is LiteralInline literal)
                     {
-                        if (i is LiteralInline l)
-                        {
-                            return StartsWithRtlCharacter(l.ToString());
-                        }
+                        return StartsWithRtlCharacter(literal.Content);
                     }
                 }
             }
@@ -91,9 +88,9 @@ namespace Markdig.Extensions.Globalization
             return false;
         }
 
-        private bool StartsWithRtlCharacter(string text)
+        private bool StartsWithRtlCharacter(StringSlice slice)
         {
-            foreach (var c in CharHelper.ToUtf32(text))
+            foreach (var c in CharHelper.ToUtf32(slice))
             {
                 if (CharHelper.IsRightToLeft(c))
                     return true;

src/Markdig/Extensions/ListExtras/ListExtraItemParser.cs

@@ -1,4 +1,4 @@
-// Copyright (c) Alexandre Mutel. All rights reserved.
+// Copyright (c) Alexandre Mutel. All rights reserved.
 // This file is licensed under the BSD-Clause 2 license. 
 // See the license.txt file in the project root for more information.
 
@@ -45,16 +45,16 @@ namespace Markdig.Extensions.ListExtras
             if ((isRomanLow || isRomanUp) && (pendingBulletType == '\0' || pendingBulletType == 'i' || pendingBulletType == 'I'))
             {
                 int startChar = state.Start;
-                int endChar = 0;
                 // With a roman, we can have multiple characters
                 // Note that we don't validate roman numbers
-                while (isRomanLow ? CharHelper.IsRomanLetterLowerPartial(c) : CharHelper.IsRomanLetterUpperPartial(c))
+                do
                 {
-                    endChar = state.Start;
                     c = state.NextChar();
                 }
+                while (isRomanLow ? CharHelper.IsRomanLetterLowerPartial(c) : CharHelper.IsRomanLetterUpperPartial(c));
 
-                result.OrderedStart = CharHelper.RomanToArabic(state.Line.Text.Substring(startChar, endChar - startChar + 1)).ToString();
+                int orderValue = CharHelper.RomanToArabic(state.Line.Text.AsSpan(startChar, state.Start - startChar));
+                result.OrderedStart = CharHelper.SmallNumberToString(orderValue);
                 result.BulletType = isRomanLow ? 'i' : 'I';
                 result.DefaultOrderedStart = isRomanLow ? "i" : "I";
             }
@@ -62,7 +62,7 @@ namespace Markdig.Extensions.ListExtras
             {
                 // otherwise we expect a regular alpha lettered list with a single character.
                 var isUpper = c.IsAlphaUpper();
-                result.OrderedStart = (Char.ToUpperInvariant(c) - 64).ToString();
+                result.OrderedStart = CharHelper.SmallNumberToString((c | 0x20) - 'a' + 1);
                 result.BulletType = isUpper ? 'A' : 'a';
                 result.DefaultOrderedStart = isUpper ? "A" : "a";
                 state.NextChar();

src/Markdig/Extensions/MediaLinks/HostProviderBuilder.cs

@@ -0,0 +1,139 @@
+// Copyright (c) Alexandre Mutel. All rights reserved.
+// This file is licensed under the BSD-Clause 2 license.
+// See the license.txt file in the project root for more information.
+
+using Markdig.Helpers;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+
+namespace Markdig.Extensions.MediaLinks
+{
+    public class HostProviderBuilder
+    {
+        private sealed class DelegateProvider : IHostProvider
+        {
+            public string HostPrefix { get; set; }
+            public Func<Uri, string> Delegate { get; set; }
+            public bool AllowFullScreen { get; set; } = true;
+            public string Class { get; set; }
+
+            public bool TryHandle(Uri mediaUri, bool isSchemaRelative, out string iframeUrl)
+            {
+                if (!mediaUri.Host.StartsWith(HostPrefix, StringComparison.OrdinalIgnoreCase))
+                {
+                    iframeUrl = null;
+                    return false;
+                }
+                iframeUrl = Delegate(mediaUri);
+                return !string.IsNullOrEmpty(iframeUrl);
+            }
+        }
+
+        /// <summary>
+        /// Create a <see cref="IHostProvider"/> with delegate handler.
+        /// </summary>
+        /// <param name="hostPrefix">Prefix of host that can be handled.</param>
+        /// <param name="handler">Handler that generate iframe url, if uri cannot be handled, it can return <see langword="null"/>.</param>
+        /// <param name="allowFullScreen">Should the generated iframe has allowfullscreen attribute.</param>
+        /// <param name="iframeClass">"class" attribute of generated iframe.</param>
+        /// <returns>A <see cref="IHostProvider"/> with delegate handler.</returns>
+        public static IHostProvider Create(string hostPrefix, Func<Uri, string> handler, bool allowFullScreen = true, string iframeClass = null)
+        {
+            if (string.IsNullOrEmpty(hostPrefix))
+                ThrowHelper.ArgumentException("hostPrefix is null or empty.", nameof(hostPrefix));
+            if (handler == null)
+                ThrowHelper.ArgumentNullException(nameof(handler));
+
+            return new DelegateProvider { HostPrefix = hostPrefix, Delegate = handler, AllowFullScreen = allowFullScreen, Class = iframeClass };
+        }
+
+        internal static Dictionary<string, IHostProvider> KnownHosts { get; }
+            = new Dictionary<string, IHostProvider>(StringComparer.OrdinalIgnoreCase)
+            {
+                ["YouTube"] = Create("www.youtube.com", YouTube, iframeClass: "youtube"),
+                ["YouTubeShortened"] = Create("youtu.be", YouTubeShortened, iframeClass: "youtube"),
+                ["Vimeo"] = Create("vimeo.com", Vimeo, iframeClass: "vimeo"),
+                ["Yandex"] = Create("music.yandex.ru", Yandex, allowFullScreen: false, iframeClass: "yandex"),
+                ["Odnoklassniki"] = Create("ok.ru", Odnoklassniki, iframeClass: "odnoklassniki"),
+            };
+
+        #region Known providers
+
+        private static readonly string[] SplitAnd = { "&" };
+        private static string[] SplitQuery(Uri uri)
+        {
+            var query = uri.Query.Substring(uri.Query.IndexOf('?') + 1);
+            return query.Split(SplitAnd, StringSplitOptions.RemoveEmptyEntries);
+        }
+
+        private static string YouTube(Uri uri)
+        {
+            string uriPath = uri.AbsolutePath;
+            if (string.Equals(uriPath, "/embed", StringComparison.OrdinalIgnoreCase) || uriPath.StartsWith("/embed/", StringComparison.OrdinalIgnoreCase))
+            {
+                return uri.ToString();
+            }
+            if (!string.Equals(uriPath, "/watch", StringComparison.OrdinalIgnoreCase) && !uriPath.StartsWith("/watch/", StringComparison.OrdinalIgnoreCase))
+            {
+                return null;
+            }
+            var queryParams = SplitQuery(uri);
+            return BuildYouTubeIframeUrl(
+                queryParams.FirstOrDefault(p => p.StartsWith("v="))?.Substring(2),
+                queryParams.FirstOrDefault(p => p.StartsWith("t="))?.Substring(2)
+            );
+        }
+
+        private static string YouTubeShortened(Uri uri)
+        {
+            return BuildYouTubeIframeUrl(
+                uri.AbsolutePath.Substring(1),
+                SplitQuery(uri).FirstOrDefault(p => p.StartsWith("t="))?.Substring(2)
+            );
+        }
+
+        private static string BuildYouTubeIframeUrl(string videoId, string startTime)
+        {
+            if (string.IsNullOrEmpty(videoId))
+            {
+                return null;
+            }
+            string url = $"https://www.youtube.com/embed/{videoId}";
+            return string.IsNullOrEmpty(startTime) ? url : $"{url}?start={startTime}";
+        }
+
+        private static string Vimeo(Uri uri)
+        {
+            var items = uri.GetComponents(UriComponents.Path, UriFormat.Unescaped).Split('/');
+            return items.Length > 0 ? $"https://player.vimeo.com/video/{ items[items.Length - 1] }" : null;
+        }
+
+        private static string Odnoklassniki(Uri uri)
+        {
+            var items = uri.GetComponents(UriComponents.Path, UriFormat.Unescaped).Split('/');
+            return items.Length > 0 ? $"https://ok.ru/videoembed/{ items[items.Length - 1] }" : null;
+        }
+
+        private static string Yandex(Uri uri)
+        {
+            var items = uri.GetComponents(UriComponents.Path, UriFormat.Unescaped).Split('/');
+            var albumKeyword
+                = items.Skip(0).FirstOrDefault();
+            var albumId
+                = items.Skip(1).FirstOrDefault();
+            var trackKeyword
+                = items.Skip(2).FirstOrDefault();
+            var trackId
+                = items.Skip(3).FirstOrDefault();
+
+            if (albumKeyword != "album" || albumId == null || trackKeyword != "track" || trackId == null)
+            {
+                return null;
+            }
+
+            return $"https://music.yandex.ru/iframe/#track/{trackId}/{albumId}/";
+        }
+        #endregion
+    }
+}

src/Markdig/Extensions/MediaLinks/IHostProvider.cs

@@ -0,0 +1,36 @@
+// Copyright (c) Alexandre Mutel. All rights reserved.
+// This file is licensed under the BSD-Clause 2 license.
+// See the license.txt file in the project root for more information.
+
+using System;
+
+namespace Markdig.Extensions.MediaLinks
+{
+    /// <summary>
+    /// Provides url for media links.
+    /// </summary>
+    public interface IHostProvider
+    {
+        /// <summary>
+        /// "class" attribute of generated iframe.
+        /// </summary>
+        string Class { get; }
+
+        /// <summary>
+        /// Generate url for iframe.
+        /// </summary>
+        /// <param name="mediaUri">Input media uri.</param>
+        /// <param name="isSchemaRelative"><see langword="true"/> if <paramref name="mediaUri"/> is a schema relative uri, i.e. uri starts with "//".</param>
+        /// <param name="iframeUrl">Generated url for iframe.</param>
+        /// <seealso href="https://tools.ietf.org/html/rfc3986#section-4.2"/>
+        bool TryHandle(Uri mediaUri, bool isSchemaRelative, out string iframeUrl);
+
+        /// <summary>
+        /// Should the generated iframe has allowfullscreen attribute.
+        /// </summary>
+        /// <remarks>
+        /// Should be false for audio embedding.
+        /// </remarks>
+        bool AllowFullScreen { get; }
+    }
+}

src/Markdig/Extensions/MediaLinks/MediaLinkExtension.cs

@@ -3,7 +3,6 @@
 // See the license.txt file in the project root for more information.
 
 using System;
-using System.Collections.Generic;
 using System.Linq;
 using Markdig.Renderers;
 using Markdig.Renderers.Html;
@@ -55,18 +54,28 @@ namespace Markdig.Extensions.MediaLinks
             }
 
             Uri uri;
+            bool isSchemaRelative = false;
             // Only process absolute Uri
             if (!Uri.TryCreate(linkInline.Url, UriKind.RelativeOrAbsolute, out uri) || !uri.IsAbsoluteUri)
             {
-                return false;
+                // see https://tools.ietf.org/html/rfc3986#section-4.2
+                // since relative uri doesn't support many properties, "http" is used as a placeholder here.
+                if (linkInline.Url.StartsWith("//") && Uri.TryCreate("http:" + linkInline.Url, UriKind.Absolute, out uri))
+                {
+                    isSchemaRelative = true;
+                }
+                else
+                {
+                    return false;
+                }
             }
 
-            if (TryRenderIframeFromKnownProviders(uri, renderer, linkInline))
+            if (TryRenderIframeFromKnownProviders(uri, isSchemaRelative, renderer, linkInline))
             {
                 return true;
             }
 
-            if (TryGuessAudioVideoFile(uri, renderer, linkInline))
+            if (TryGuessAudioVideoFile(uri, isSchemaRelative, renderer, linkInline))
             {
                 return true;
             }
@@ -86,7 +95,7 @@ namespace Markdig.Extensions.MediaLinks
             return htmlAttributes;
         }
 
-        private bool TryGuessAudioVideoFile(Uri uri, HtmlRenderer renderer, LinkInline linkInline)
+        private bool TryGuessAudioVideoFile(Uri uri, bool isSchemaRelative, HtmlRenderer renderer, LinkInline linkInline)
         {
             var path = uri.GetComponents(UriComponents.Path, UriFormat.Unescaped);
             // Otherwise try to detect if we have an audio/video from the file extension
@@ -106,6 +115,10 @@ namespace Markdig.Extensions.MediaLinks
                     htmlAttributes.AddPropertyIfNotExist("height", Options.Height);
                 }
                 htmlAttributes.AddPropertyIfNotExist("controls", null);
+
+                if (!string.IsNullOrEmpty(Options.Class))
+                    htmlAttributes.AddPropertyIfNotExist("class", Options.Class);
+
                 renderer.WriteAttributes(htmlAttributes);
 
                 renderer.Write($"><source type=\"{mimeType}\" src=\"{linkInline.Url}\"></source></{tagType}>");
@@ -115,38 +128,18 @@ namespace Markdig.Extensions.MediaLinks
             return false;
         }
 
-        #region Known providers
-
-        private class KnownProvider
+        private bool TryRenderIframeFromKnownProviders(Uri uri, bool isSchemaRelative, HtmlRenderer renderer, LinkInline linkInline)
         {
-            public string HostPrefix { get; set; }
-            public Func<Uri, string> Delegate { get; set; }
-            public bool AllowFullScreen { get; set; } = true; //Should be false for audio embedding
-        }
 
-        private static readonly List<KnownProvider> KnownHosts = new List<KnownProvider>()
-        {
-            new KnownProvider {HostPrefix = "www.youtube.com", Delegate = YouTube},
-            new KnownProvider {HostPrefix = "youtu.be", Delegate = YouTubeShortened},
-            new KnownProvider {HostPrefix = "vimeo.com", Delegate = Vimeo},
-            new KnownProvider {HostPrefix = "music.yandex.ru", Delegate = Yandex, AllowFullScreen = false},
-            new KnownProvider {HostPrefix = "ok.ru", Delegate = Odnoklassniki},
-        };
-
-
-        private bool TryRenderIframeFromKnownProviders(Uri uri, HtmlRenderer renderer, LinkInline linkInline)
-        {
-            var foundProvider =
-                KnownHosts
-                    .Where(pair => uri.Host.StartsWith(pair.HostPrefix, StringComparison.OrdinalIgnoreCase))  // when host is match
-                    .Select(provider =>
-                        new
-                        {
-                            provider.AllowFullScreen,
-                            Result = provider.Delegate(uri) // try to call delegate to get iframeUrl
-                        }
-                        )
-                    .FirstOrDefault(provider => provider.Result != null);                                   // use first success
+            IHostProvider foundProvider = null;
+            string iframeUrl = null;
+            foreach (var provider in Options.Hosts)
+            {
+                if (!provider.TryHandle(uri, isSchemaRelative, out iframeUrl))
+                    continue;
+                foundProvider = provider;
+                break;
+            }
 
             if (foundProvider == null)
             {
@@ -155,17 +148,20 @@ namespace Markdig.Extensions.MediaLinks
 
             var htmlAttributes = GetHtmlAttributes(linkInline);
             renderer.Write("<iframe src=\"");
-            renderer.WriteEscapeUrl(foundProvider.Result);
+            renderer.WriteEscapeUrl(iframeUrl);
             renderer.Write("\"");
 
-            if(!string.IsNullOrEmpty(Options.Width))
+            if (!string.IsNullOrEmpty(Options.Width))
                 htmlAttributes.AddPropertyIfNotExist("width", Options.Width);
 
             if (!string.IsNullOrEmpty(Options.Height))
                 htmlAttributes.AddPropertyIfNotExist("height", Options.Height);
 
-            if (!string.IsNullOrEmpty(Options.Class))
-                htmlAttributes.AddPropertyIfNotExist("class", Options.Class);
+            if (!string.IsNullOrEmpty(Options.Class) || !string.IsNullOrEmpty(foundProvider.Class))
+                htmlAttributes.AddPropertyIfNotExist("class",
+                    (!string.IsNullOrEmpty(Options.Class) && !string.IsNullOrEmpty(foundProvider.Class))
+                    ? Options.Class + " " + foundProvider.Class
+                    : Options.Class + foundProvider.Class);
 
             htmlAttributes.AddPropertyIfNotExist("frameborder", "0");
             if (foundProvider.AllowFullScreen)
@@ -177,81 +173,5 @@ namespace Markdig.Extensions.MediaLinks
 
             return true;
         }
-
-        private static readonly string[] SplitAnd = {"&"};
-        private static string[] SplitQuery(Uri uri)
-        {
-            var query = uri.Query.Substring(uri.Query.IndexOf('?') + 1);
-            return query.Split(SplitAnd, StringSplitOptions.RemoveEmptyEntries);
-        }
-
-        private static string YouTube(Uri uri)
-        {
-            string uriPath = uri.AbsolutePath;
-            if (string.Equals(uriPath, "/embed", StringComparison.OrdinalIgnoreCase) || uriPath.StartsWith("/embed/", StringComparison.OrdinalIgnoreCase))
-            {
-                return uri.ToString();
-            }
-            if (!string.Equals(uriPath, "/watch", StringComparison.OrdinalIgnoreCase) && !uriPath.StartsWith("/watch/", StringComparison.OrdinalIgnoreCase))
-            {
-                return null;
-            }
-            var queryParams = SplitQuery(uri);
-            return BuildYouTubeIframeUrl(
-                queryParams.FirstOrDefault(p => p.StartsWith("v="))?.Substring(2),
-                queryParams.FirstOrDefault(p => p.StartsWith("t="))?.Substring(2)
-            );
-        }
-
-        private static string YouTubeShortened(Uri uri)
-        {
-            return BuildYouTubeIframeUrl(
-                uri.AbsolutePath.Substring(1),
-                SplitQuery(uri).FirstOrDefault(p => p.StartsWith("t="))?.Substring(2)
-            );
-        }
-
-        private static string BuildYouTubeIframeUrl(string videoId, string startTime)
-        {
-            if (string.IsNullOrEmpty(videoId))
-            {
-                return null;
-            }
-            string url = $"https://www.youtube.com/embed/{videoId}";
-            return string.IsNullOrEmpty(startTime) ? url : $"{url}?start={startTime}";
-        }
-
-        private static string Vimeo(Uri uri)
-        {
-            var items = uri.GetComponents(UriComponents.Path, UriFormat.Unescaped).Split('/');
-            return items.Length > 0 ? $"https://player.vimeo.com/video/{items[items.Length - 1]}" : null;
-        }
-
-        private static string Odnoklassniki(Uri uri)
-        {
-            var items = uri.GetComponents(UriComponents.Path, UriFormat.Unescaped).Split('/');
-            return items.Length > 0 ? $"https://ok.ru/videoembed/{items[items.Length - 1]}" : null;
-        }
-
-        private static string Yandex(Uri uri)
-        {
-            var items = uri.GetComponents(UriComponents.Path, UriFormat.Unescaped).Split('/');
-            var albumKeyword
-                = items.Skip(0).FirstOrDefault();
-            var albumId
-                = items.Skip(1).FirstOrDefault();
-            var trackKeyword
-                = items.Skip(2).FirstOrDefault();
-            var trackId
-                = items.Skip(3).FirstOrDefault();
-
-            if (albumKeyword != "album" || albumId == null || trackKeyword != "track" || trackId == null)
-            {
-                return null;
-            }
-
-            return $"https://music.yandex.ru/iframe/#track/{trackId}/{albumId}/";
-        }
-        #endregion
     }
 }

src/Markdig/Extensions/MediaLinks/MediaOptions.cs

@@ -76,12 +76,14 @@ namespace Markdig.Extensions.MediaLinks
                 {".ecelp7470", "audio/vnd.nuera.ecelp7470"},
                 {".ecelp9600", "audio/vnd.nuera.ecelp9600"},
                 {".oga", "audio/ogg"},
+                {".ogg", "audio/ogg"},
                 {".weba", "audio/webm"},
                 {".ram", "audio/x-pn-realaudio"},
                 {".rmp", "audio/x-pn-realaudio-plugin"},
                 {".au", "audio/basic"},
                 {".wav", "audio/x-wav"},
             };
+            Hosts = new List<IHostProvider>(HostProviderBuilder.KnownHosts.Values);
         }
 
         public string Width { get; set; }
@@ -91,5 +93,7 @@ namespace Markdig.Extensions.MediaLinks
         public string Class { get; set; }
 
         public Dictionary<string, string> ExtensionToMimeType { get; }
+
+        public List<IHostProvider> Hosts { get; }
     }
 }

src/Markdig/Extensions/SelfPipeline/SelfPipelineExtension.cs

@@ -1,8 +1,9 @@
-// Copyright (c) Alexandre Mutel. All rights reserved.
+// Copyright (c) Alexandre Mutel. All rights reserved.
 // This file is licensed under the BSD-Clause 2 license. 
 // See the license.txt file in the project root for more information.
 
 using System;
+using Markdig.Helpers;
 using Markdig.Renderers;
 
 namespace Markdig.Extensions.SelfPipeline
@@ -29,7 +30,7 @@ namespace Markdig.Extensions.SelfPipeline
             tag = string.IsNullOrEmpty(tag) ? DefaultTag : tag;
             if (tag.IndexOfAny(new []{'<', '>'}) >= 0)
             {
-                throw new ArgumentException("Tag cannot contain `<`  or `>` characters", nameof(tag));
+                ThrowHelper.ArgumentException("Tag cannot contain `<`  or `>` characters", nameof(tag));
             }
 
             if (defaultExtensions != null)
@@ -57,7 +58,7 @@ namespace Markdig.Extensions.SelfPipeline
             // Make sure that this pipeline has only one extension (itself)
             if (pipeline.Extensions.Count > 1)
             {
-                throw new InvalidOperationException(
+                ThrowHelper.InvalidOperationException(
                     "The SelfPipeline extension cannot be configured with other extensions");
             }
         }
@@ -74,7 +75,7 @@ namespace Markdig.Extensions.SelfPipeline
         /// <exception cref="System.ArgumentNullException"></exception>
         public MarkdownPipeline CreatePipelineFromInput(string inputText)
         {
-            if (inputText == null) throw new ArgumentNullException(nameof(inputText));
+            if (inputText == null) ThrowHelper.ArgumentNullException(nameof(inputText));
 
             var builder = new MarkdownPipelineBuilder();
             string defaultConfig = DefaultExtensions;

src/Markdig/Extensions/SmartyPants/HtmlSmartyPantRenderer.cs

@@ -1,4 +1,4 @@
-// Copyright (c) Alexandre Mutel. All rights reserved.
+// Copyright (c) Alexandre Mutel. All rights reserved.
 // This file is licensed under the BSD-Clause 2 license. 
 // See the license.txt file in the project root for more information.
 using System;
@@ -10,7 +10,7 @@ namespace Markdig.Extensions.SmartyPants
     /// <summary>
     /// A HTML renderer for a <see cref="SmartyPant"/>.
     /// </summary>
-    /// <seealso cref="Markdig.Renderers.Html.HtmlObjectRenderer{SmartyPant}" />
+    /// <seealso cref="HtmlObjectRenderer{SmartyPant}" />
     public class HtmlSmartyPantRenderer : HtmlObjectRenderer<SmartyPant>
     {
         private static readonly SmartyPantOptions DefaultOptions = new SmartyPantOptions();
@@ -21,17 +21,15 @@ namespace Markdig.Extensions.SmartyPants
         /// Initializes a new instance of the <see cref="HtmlSmartyPantRenderer"/> class.
         /// </summary>
         /// <param name="options">The options.</param>
-        /// <exception cref="System.ArgumentNullException"></exception>
+        /// <exception cref="ArgumentNullException"></exception>
         public HtmlSmartyPantRenderer(SmartyPantOptions options)
         {
-            if (options == null) throw new ArgumentNullException(nameof(options));
-            this.options = options;
+            this.options = options ?? throw new ArgumentNullException(nameof(options));
         }
 
         protected override void Write(HtmlRenderer renderer, SmartyPant obj)
         {
-            string text;
-            if (!options.Mapping.TryGetValue(obj.Type, out text))
+            if (!options.Mapping.TryGetValue(obj.Type, out string text))
             {
                 DefaultOptions.Mapping.TryGetValue(obj.Type, out text);
             }

src/Markdig/Extensions/SmartyPants/SmartyPant.cs

@@ -1,4 +1,4 @@
-// Copyright (c) Alexandre Mutel. All rights reserved.
+// Copyright (c) Alexandre Mutel. All rights reserved.
 // This file is licensed under the BSD-Clause 2 license. 
 // See the license.txt file in the project root for more information.
 using System.Diagnostics;
@@ -45,5 +45,15 @@ namespace Markdig.Extensions.SmartyPants
             }
             return OpeningCharacter != 0 ? OpeningCharacter.ToString() : string.Empty;
         }
+
+        public LiteralInline AsLiteralInline()
+        {
+            return new LiteralInline(ToString())
+            {
+                Span = Span,
+                Line = Line,
+                Column = Column,
+            };
+        }
     }
 }

src/Markdig/Extensions/SmartyPants/SmartyPantsExtension.cs

@@ -1,4 +1,4 @@
-// Copyright (c) Alexandre Mutel. All rights reserved.
+// Copyright (c) Alexandre Mutel. All rights reserved.
 // This file is licensed under the BSD-Clause 2 license. 
 // See the license.txt file in the project root for more information.
 
@@ -37,8 +37,7 @@ namespace Markdig.Extensions.SmartyPants
 
         public void Setup(MarkdownPipeline pipeline, IMarkdownRenderer renderer)
         {
-            var htmlRenderer = renderer as HtmlRenderer;
-            if (htmlRenderer != null)
+            if (renderer is HtmlRenderer htmlRenderer)
             {
                 if (!htmlRenderer.ObjectRenderers.Contains<HtmlSmartyPantRenderer>())
                 {

src/Markdig/Extensions/SmartyPants/SmartyPantsInlineParser.cs

@@ -49,7 +49,7 @@ namespace Markdig.Extensions.SmartyPants
             {
                 case '\'':
                     type = SmartyPantType.Quote; // We will resolve them at the end of parsing all inlines
-                    if (slice.PeekChar(1) == '\'')
+                    if (slice.PeekChar() == '\'')
                     {
                         slice.NextChar();
                         type = SmartyPantType.DoubleQuote; // We will resolve them at the end of parsing all inlines
@@ -95,9 +95,7 @@ namespace Markdig.Extensions.SmartyPants
             // Skip char
             c = slice.NextChar();
 
-            bool canOpen;
-            bool canClose;
-            CharHelper.CheckOpenCloseDelimiter(pc, c, false, out canOpen, out canClose);
+            CharHelper.CheckOpenCloseDelimiter(pc, c, false, out bool canOpen, out bool canClose);
 
             bool postProcess = false;
 
@@ -156,11 +154,9 @@ namespace Markdig.Extensions.SmartyPants
             }
 
             // Create the SmartyPant inline
-            int line;
-            int column;
             var pant = new SmartyPant()
             {
-                Span = {Start = processor.GetSourcePosition(startingPosition, out line, out column)},
+                Span = { Start = processor.GetSourcePosition(startingPosition, out int line, out int column) },
                 Line = line,
                 Column = column,
                 OpeningCharacter = openingChar,
@@ -195,96 +191,90 @@ namespace Markdig.Extensions.SmartyPants
             return quotePants;
         }
 
+        private readonly struct Opener
+        {
+            public readonly int Type;
+            public readonly int Index;
+
+            public Opener(int type, int index)
+            {
+                Type = type;
+                Index = index;
+            }
+        }
+
         private void BlockOnProcessInlinesEnd(InlineProcessor processor, Inline inline)
         {
             processor.Block.ProcessInlinesEnd -= BlockOnProcessInlinesEnd;
 
             var pants = (ListSmartyPants) processor.ParserStates[Index];
 
-            // We only change quote into left or right quotes if we find proper balancing
-            var previousIndices = new int[3] {-1, -1, -1};
+            Stack<Opener> openers = new Stack<Opener>(4);
 
             for (int i = 0; i < pants.Count; i++)
             {
                 var quote = pants[i];
+                var quoteType = quote.Type;
 
-                int currentTypeIndex = -1;
-                SmartyPantType expectedLeftQuote = 0;
-                SmartyPantType expectedRightQuote = 0;
+                int type;
+                bool isLeft;
 
-                if (quote.Type == SmartyPantType.LeftQuote || quote.Type == SmartyPantType.RightQuote)
+                if (quoteType == SmartyPantType.LeftQuote || quoteType == SmartyPantType.RightQuote)
                 {
-                    currentTypeIndex = 0;
-                    expectedLeftQuote = SmartyPantType.LeftQuote;
-                    expectedRightQuote = SmartyPantType.RightQuote;
+                    type = 0;
+                    isLeft = quoteType == SmartyPantType.LeftQuote;
                 }
-                else if (quote.Type == SmartyPantType.LeftDoubleQuote || quote.Type == SmartyPantType.RightDoubleQuote)
+                else if (quoteType == SmartyPantType.LeftDoubleQuote || quoteType == SmartyPantType.RightDoubleQuote)
                 {
-                    currentTypeIndex = 1;
-                    expectedLeftQuote = SmartyPantType.LeftDoubleQuote;
-                    expectedRightQuote = SmartyPantType.RightDoubleQuote;
+                    type = 1;
+                    isLeft = quoteType == SmartyPantType.LeftDoubleQuote;
                 }
-                else if (quote.Type == SmartyPantType.LeftAngleQuote || quote.Type == SmartyPantType.RightAngleQuote)
+                else if (quoteType == SmartyPantType.LeftAngleQuote || quoteType == SmartyPantType.RightAngleQuote)
                 {
-                    currentTypeIndex = 2;
-                    expectedLeftQuote = SmartyPantType.LeftAngleQuote;
-                    expectedRightQuote = SmartyPantType.RightAngleQuote;
-                }
-
-                if (currentTypeIndex < 0)
-                {
-                    continue;
-                }
-
-                int previousIndex = previousIndices[currentTypeIndex];
-                var previousQuote = previousIndex >= 0 ? pants[previousIndex] : null;
-                if (previousQuote == null)
-                {
-                    if (quote.Type == expectedLeftQuote)
-                    {
-                        previousIndices[currentTypeIndex] = i;
-                    }
+                    type = 2;
+                    isLeft = quoteType == SmartyPantType.LeftAngleQuote;
                 }
                 else
                 {
-                    if (quote.Type == expectedRightQuote)
-                    {
-                        // Replace all intermediate unmatched left or right SmartyPants to their literal equivalent
-                        pants.RemoveAt(i);
-                        i--;
-                        for (int j = i; j > previousIndex; j--)
-                        {
-                            var toReplace = pants[j];
-                            pants.RemoveAt(j);
-                            toReplace.ReplaceBy(new LiteralInline(toReplace.ToString())
-                            {
-                                Span = toReplace.Span,
-                                Line = toReplace.Line,
-                                Column = toReplace.Column,
-                            });
-                            i--;
-                        }
+                    quote.ReplaceBy(quote.AsLiteralInline());
+                    continue;
+                }
 
-                        // If we matched, we remove left/right quotes from the list
-                        pants.RemoveAt(previousIndex);
-                        previousIndices[currentTypeIndex] = -1;
-                    }
-                    else
+                if (isLeft)
+                {
+                    openers.Push(new Opener(type, i));
+                }
+                else
+                {
+                    bool found = false;
+
+                    while (openers.Count > 0)
                     {
-                        previousIndices[currentTypeIndex] = i;
+                        Opener opener = openers.Pop();
+                        var previousQuote = pants[opener.Index];
+
+                        if (opener.Type == type)
+                        {
+                            found = true;
+                            break;
+                        }
+                        else
+                        {
+                            previousQuote.ReplaceBy(previousQuote.AsLiteralInline());
+                        }
+                    }
+
+                    if (!found)
+                    {
+                        quote.ReplaceBy(quote.AsLiteralInline());
                     }
                 }
             }
 
-            // If we have any quotes lefts, replace them by there literal equivalent
-            foreach (var quote in pants)
+            foreach (var opener in openers)
             {
-                quote.ReplaceBy(new LiteralInline(quote.ToString())
-                {
-                    Span = quote.Span,
-                    Line = quote.Line,
-                    Column = quote.Column,
-                });
+                var quote = pants[opener.Index];
+                quote.ReplaceBy(quote.AsLiteralInline());
             }
 
             pants.Clear();
@@ -294,8 +284,7 @@ namespace Markdig.Extensions.SmartyPants
             bool isFinalProcessing)
         {
             // Don't try to process anything if there are no dash
-            var quotePants = state.ParserStates[Index] as ListSmartyPants;
-            if (quotePants == null || !quotePants.HasDash)
+            if (!(state.ParserStates[Index] is ListSmartyPants quotePants) || !quotePants.HasDash)
             {
                 return true;
             }
@@ -309,10 +298,8 @@ namespace Markdig.Extensions.SmartyPants
                 {
                     var next = child.NextSibling;
 
-                    if (child is LiteralInline)
+                    if (child is LiteralInline literal)
                     {
-                        var literal = (LiteralInline) child;
-
                         var startIndex = 0;
 
                         var indexOfDash = literal.Content.IndexOf("--", startIndex);
@@ -372,7 +359,7 @@ namespace Markdig.Extensions.SmartyPants
         }
 
 
-        private class ListSmartyPants : List<SmartyPant>
+        private sealed class ListSmartyPants : List<SmartyPant>
         {
             public bool HasDash { get; set; }
         }

src/Markdig/Extensions/Tables/GridTableParser.cs

@@ -1,4 +1,4 @@
-
+
 // Copyright (c) Alexandre Mutel. All rights reserved.
 // This file is licensed under the BSD-Clause 2 license. 
 // See the license.txt file in the project root for more information.
@@ -138,7 +138,7 @@ namespace Markdig.Extensions.Tables
         private static void SetRowSpanState(List<GridTableState.ColumnSlice> columns, StringSlice line, out bool isHeaderRow, out bool hasRowSpan)
         {
             var lineStart = line.Start;
-            isHeaderRow = line.PeekChar(1) == '=' || line.PeekChar(2) == '=';
+            isHeaderRow = line.PeekChar() == '=' || line.PeekChar(2) == '=';
             hasRowSpan = false;
             foreach (var columnSlice in columns)
             {

src/Markdig/Extensions/Tables/GridTableState.cs

@@ -10,7 +10,7 @@ namespace Markdig.Extensions.Tables
     /// <summary>
     /// Internal state used by the <see cref="GridTableParser"/>
     /// </summary>
-    internal class GridTableState
+    internal sealed class GridTableState
     {
         public int Start { get; set; }
 

src/Markdig/Extensions/Tables/HtmlTableRenderer.cs

@@ -41,7 +41,7 @@ namespace Markdig.Extensions.Tables
                 {
                     var width = Math.Round(tableColumnDefinition.Width*100)/100;
                     var widthValue = string.Format(CultureInfo.InvariantCulture, "{0:0.##}", width);
-                    renderer.WriteLine($"<col style=\"width:{widthValue}%\">");
+                    renderer.WriteLine($"<col style=\"width:{widthValue}%\" />");
                 }
             }
 
@@ -135,4 +135,4 @@ namespace Markdig.Extensions.Tables
             renderer.WriteLine("</table>");
         }
     }
-}
+}

src/Markdig/Extensions/Tables/PipeTableParser.cs

@@ -30,8 +30,7 @@ namespace Markdig.Extensions.Tables
         /// <param name="options">The options.</param>
         public PipeTableParser(LineBreakInlineParser lineBreakParser, PipeTableOptions options = null)
         {
-            if (lineBreakParser == null) throw new ArgumentNullException(nameof(lineBreakParser));
-            this.lineBreakParser = lineBreakParser;
+            this.lineBreakParser = lineBreakParser ?? throw new ArgumentNullException(nameof(lineBreakParser));
             OpeningCharacters = new[] { '|', '\n' };
             Options = options ?? new PipeTableOptions();
         }

src/Markdig/Extensions/Tables/Table.cs

@@ -58,6 +58,11 @@ namespace Markdig.Extensions.Tables
                     var rowSpan = cell.RowSpan - 1;
                     while (rowSpan > 0)
                     {
+                        if (i+rowSpan > (rows.Length-1))
+                        {
+                            return false;
+                        }
+
                         rows[i + rowSpan] += cell.ColumnSpan;
                         rowSpan--;
                     }

src/Markdig/Helpers/ArrayHelper.cs

@@ -1,17 +0,0 @@
-// Copyright (c) Alexandre Mutel. All rights reserved.
-// This file is licensed under the BSD-Clause 2 license. 
-// See the license.txt file in the project root for more information.
-namespace Markdig.Helpers
-{
-    /// <summary>
-    /// Helper class for defining Empty arrays.
-    /// </summary>
-    /// <typeparam name="T">Type of an element of the array</typeparam>
-    public static class ArrayHelper<T>
-    {
-        /// <summary>
-        /// An empty array.
-        /// </summary>
-        public static readonly T[] Empty = new T[0];
-    }
-}

src/Markdig/Helpers/CharHelper.cs

@@ -2,41 +2,12 @@
 // This file is licensed under the BSD-Clause 2 license. 
 // See the license.txt file in the project root for more information.
 
-
-// The IsHighSurrogate, IsLowSurrogate and ConvertToUtf32 methods are copied from
-// .Net Core source code which is under MIT license. They are copied here because
-// they don't exist in `portable40-net40+sl5+win8+wp8+wpa81`, We probably should remove them
-// once we dropped support for that target platform and use the official .Net methods.
-
-//The MIT License(MIT)
-
-//Copyright(c) .NET Foundation and Contributors
-
-//All rights reserved.
-
-//Permission is hereby granted, free of charge, to any person obtaining a copy
-//of this software and associated documentation files (the "Software"), to deal
-//in the Software without restriction, including without limitation the rights
-//to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
-//copies of the Software, and to permit persons to whom the Software is
-//furnished to do so, subject to the following conditions:
-
-//The above copyright notice and this permission notice shall be included in all
-//copies or substantial portions of the Software.
-
-//THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
-//IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-//FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
-//AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
-//LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
-//OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
-//SOFTWARE.
-
 using System;
 using System.Globalization;
 using System.Collections.Generic;
 using System.Runtime.CompilerServices;
-
+using System.Diagnostics;
+
 namespace Markdig.Helpers
 {
     /// <summary>
@@ -46,20 +17,20 @@ namespace Markdig.Helpers
     {
         public const int TabSize = 4;
 
-        public const char ZeroSafeChar = '\uFFFD';
+        public const char ReplacementChar = '\uFFFD';
 
-        public const string ZeroSafeString = "\uFFFD";
+        public const string ReplacementCharString = "\uFFFD";
 
         private const char HighSurrogateStart = '\ud800';
         private const char HighSurrogateEnd = '\udbff';
         private const char LowSurrogateStart = '\udc00';
         private const char LowSurrogateEnd = '\udfff';
 
-        // The starting codepoint for Unicode plane 1.  Plane 1 contains 0x010000 ~ 0x01ffff.
-        private const int UnicodePlane01Start = 0x10000;
-
         // We don't support LCDM
-        private static readonly Dictionary<char, int> romanMap = new Dictionary<char, int> { { 'I', 1 }, { 'V', 5 }, { 'X', 10 } };
+        private static readonly Dictionary<char, int> romanMap = new Dictionary<char, int>(6) {
+            { 'i', 1 }, { 'v', 5 }, { 'x', 10 },
+            { 'I', 1 }, { 'V', 5 }, { 'X', 10 }
+        };
 
         private static readonly char[] punctuationExceptions = { '−', '-', '†', '‡' };
 
@@ -103,36 +74,35 @@ namespace Markdig.Helpers
             }
         }
 
-        [MethodImpl(MethodImplOptionPortable.AggressiveInlining)]
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public static bool IsRomanLetterPartial(char c)
         {
             // We don't support LCDM
             return IsRomanLetterLowerPartial(c) || IsRomanLetterUpperPartial(c);
         }
 
-        [MethodImpl(MethodImplOptionPortable.AggressiveInlining)]
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public static bool IsRomanLetterLowerPartial(char c)
         {
             // We don't support LCDM
             return c == 'i' || c == 'v' || c == 'x';
         }
 
-        [MethodImpl(MethodImplOptionPortable.AggressiveInlining)]
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public static bool IsRomanLetterUpperPartial(char c)
         {
             // We don't support LCDM
             return c == 'I' || c == 'V' || c == 'X';
         }
 
-        [MethodImpl(MethodImplOptionPortable.AggressiveInlining)]
-        public static int RomanToArabic(string text)
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static int RomanToArabic(ReadOnlySpan<char> text)
         {
             int result = 0;
             for (int i = 0; i < text.Length; i++)
             {
-                var character = Char.ToUpperInvariant(text[i]);
-                var candidate = romanMap[character];
-                if (i + 1 < text.Length && candidate < romanMap[Char.ToUpperInvariant(text[i + 1])])
+                var candidate = romanMap[text[i]];
+                if ((uint)(i + 1) < text.Length && candidate < romanMap[text[i + 1]])
                 {
                     result -= candidate;
                 }
@@ -144,24 +114,26 @@ namespace Markdig.Helpers
             return result;
         }
 
-        [MethodImpl(MethodImplOptionPortable.AggressiveInlining)]
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public static int AddTab(int column)
         {
-            return ((column + TabSize) / TabSize) * TabSize;
+            // return ((column + TabSize) / TabSize) * TabSize;
+            Debug.Assert(TabSize == 4, "Change the AddTab implementation if TabSize is no longer a power of 2");
+            return TabSize + (column & ~(TabSize - 1));
         }
 
-        [MethodImpl(MethodImplOptionPortable.AggressiveInlining)]
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public static bool IsAcrossTab(int column)
         {
             return (column & (TabSize - 1)) != 0;
         }
 
-        [MethodImpl(MethodImplOptionPortable.AggressiveInlining)]
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public static bool Contains(this char[] charList, char c)
         {
-            for (int i = 0; i < charList.Length; i++)
+            foreach (char ch in charList)
             {
-                if (charList[i] == c)
+                if (ch == c)
                 {
                     return true;
                 }
@@ -169,31 +141,31 @@ namespace Markdig.Helpers
             return false;
         }
 
-        [MethodImpl(MethodImplOptionPortable.AggressiveInlining)]
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public static bool IsWhitespace(this char c)
         {
             // 2.1 Characters and lines 
             // A whitespace character is a space(U + 0020), tab(U + 0009), newline(U + 000A), line tabulation (U + 000B), form feed (U + 000C), or carriage return (U + 000D).
-            return c == ' ' || c == '\t' || c == '\n' || c == '\v' || c == '\f' || c == '\r';
+            return c <= ' ' && (c == ' ' || c == '\t' || c == '\n' || c == '\v' || c == '\f' || c == '\r');
         }
 
-        [MethodImpl(MethodImplOptionPortable.AggressiveInlining)]
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public static bool IsControl(this char c)
         {
-            return c < ' ' || Char.IsControl(c);
+            return c < ' ' || char.IsControl(c);
         }
 
-        [MethodImpl(MethodImplOptionPortable.AggressiveInlining)]
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public static bool IsEscapableSymbol(this char c)
         {
             // char.IsSymbol also works with Unicode symbols that cannot be escaped based on the specification.
             return (c > ' ' && c < '0') || (c > '9' && c < 'A') || (c > 'Z' && c < 'a') || (c > 'z' && c < 127) || c == '•';
         }
 
-        //[MethodImpl(MethodImplOptionPortable.AggressiveInlining)]
+        //[MethodImpl(MethodImplOptions.AggressiveInlining)]
         public static bool IsWhiteSpaceOrZero(this char c)
         {
-            return IsWhitespace(c) || IsZero(c);
+            return IsZero(c) || IsWhitespace(c);
         }
 
         // Note that we are not considering the character & as a punctuation in HTML
@@ -250,19 +222,19 @@ namespace Markdig.Helpers
             }
         }
 
-        [MethodImpl(MethodImplOptionPortable.AggressiveInlining)]
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public static bool IsNewLine(this char c)
         {
             return c == '\n';
         }
 
-        [MethodImpl(MethodImplOptionPortable.AggressiveInlining)]
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public static bool IsZero(this char c)
         {
             return c == '\0';
         }
 
-        [MethodImpl(MethodImplOptionPortable.AggressiveInlining)]
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public static bool IsSpace(this char c)
         {
             // 2.1 Characters and lines 
@@ -270,7 +242,7 @@ namespace Markdig.Helpers
             return c == ' ';
         }
 
-        [MethodImpl(MethodImplOptionPortable.AggressiveInlining)]
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public static bool IsTab(this char c)
         {
             // 2.1 Characters and lines 
@@ -278,13 +250,13 @@ namespace Markdig.Helpers
             return c == '\t';
         }
 
-        [MethodImpl(MethodImplOptionPortable.AggressiveInlining)]
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public static bool IsSpaceOrTab(this char c)
         {
             return IsSpace(c) || IsTab(c);
         }
 
-        [MethodImpl(MethodImplOptionPortable.AggressiveInlining)]
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public static char EscapeInsecure(this char c)
         {
             // 2.3 Insecure characters
@@ -292,28 +264,28 @@ namespace Markdig.Helpers
             return c == '\0' ? '\ufffd' : c;
         }
 
-        [MethodImpl(MethodImplOptionPortable.AggressiveInlining)]
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public static bool IsAlphaUpper(this char c)
-        {
-            return c >= 'A' && c <= 'Z';
+        {
+            return (uint)(c - 'A') <= ('Z' - 'A');
         }
 
-        [MethodImpl(MethodImplOptionPortable.AggressiveInlining)]
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public static bool IsAlpha(this char c)
-        {
-            return (c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z');
+        {
+            return (uint)((c - 'A') & ~0x20) <= ('Z' - 'A');
         }
 
-        [MethodImpl(MethodImplOptionPortable.AggressiveInlining)]
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public static bool IsAlphaNumeric(this char c)
         {
             return IsAlpha(c) || IsDigit(c);
         }
 
-        [MethodImpl(MethodImplOptionPortable.AggressiveInlining)]
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public static bool IsDigit(this char c)
         {
-            return c >= '0' && c <= '9';
+            return (uint)(c - '0') <= ('9' - '0');
         }
 
         public static bool IsAsciiPunctuation(this char c)
@@ -359,44 +331,40 @@ namespace Markdig.Helpers
             return false;
         }
 
-        [MethodImpl(MethodImplOptionPortable.AggressiveInlining)]
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public static bool IsEmailUsernameSpecialChar(char c)
         {
             return ".!#$%&'*+/=?^_`{|}~-+.~".IndexOf(c) >= 0;
         }
 
-        [MethodImpl(MethodImplOptionPortable.AggressiveInlining)]
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public static bool IsHighSurrogate(char c)
-        {
-            return ((c >= HighSurrogateStart) && (c <= HighSurrogateEnd));
+        {
+            return IsInInclusiveRange(c, HighSurrogateStart, HighSurrogateEnd);
         }
 
-        [MethodImpl(MethodImplOptionPortable.AggressiveInlining)]
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public static bool IsLowSurrogate(char c)
         {
-            return ((c >= LowSurrogateStart) && (c <= LowSurrogateEnd));
+            return IsInInclusiveRange(c, LowSurrogateStart, LowSurrogateEnd);
         }
 
-        public static int ConvertToUtf32(char highSurrogate, char lowSurrogate)
-        {
-            if (!IsHighSurrogate(highSurrogate))
-            {
-                throw new ArgumentOutOfRangeException(nameof(highSurrogate), "Invalid high surrogate");
-            }
-            if (!IsLowSurrogate(lowSurrogate))
-            {
-                throw new ArgumentOutOfRangeException(nameof(lowSurrogate), "Invalid low surrogate");
-            }
-            return (((highSurrogate - HighSurrogateStart) * 0x400) + (lowSurrogate - LowSurrogateStart) + UnicodePlane01Start);
-        }
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static bool IsInInclusiveRange(char c, char min, char max)
+            => (uint)(c - min) <= (uint)(max - min);
 
-        public static IEnumerable<int> ToUtf32(string text)
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        internal static bool IsInInclusiveRange(int value, uint min, uint max)
+            => ((uint)value - min) <= (max - min);
+
+        public static IEnumerable<int> ToUtf32(StringSlice text)
         {
-            for (int i = 0; i < text.Length; i++)
+            for (int i = text.Start; i <= text.End; i++)
             {
-                if (IsHighSurrogate(text[i]) && i < text.Length - 1 && IsLowSurrogate(text[i + 1]))
-                {
-                    yield return ConvertToUtf32(text[i], text[i + 1]);
+                if (IsHighSurrogate(text[i]) && i < text.End && IsLowSurrogate(text[i + 1]))
+                {
+                    Debug.Assert(char.IsSurrogatePair(text[i], text[i + 1]));
+                    yield return char.ConvertToUtf32(text[i], text[i + 1]);
                 }
                 else
                 {
@@ -777,6 +745,24 @@ namespace Markdig.Helpers
                    c == 0x002128 || c == 0x002395 ||
                    c == 0x01D4A2 || c == 0x01D4BB ||
                    c == 0x01D546;
+        }
+
+        // Used by ListExtraItemParser to format numbers from 1 - 26
+        private static readonly string[] smallNumberStringCache = {
+            "0", "1", "2", "3", "4", "5", "6", "7", "8", "9",
+            "10", "11", "12", "13", "14", "15", "16", "17", "18", "19",
+            "20", "21", "22", "23", "24", "25", "26",
+        };
+
+        internal static string SmallNumberToString(int number)
+        {
+            string[] cache = smallNumberStringCache;
+            if ((uint)number < (uint)cache.Length)
+            {
+                return cache[number];
+            }
+
+            return number.ToString();
         }
     }
 }

src/Markdig/Helpers/CharacterMap.cs

@@ -4,6 +4,7 @@
 
 using System;
 using System.Collections.Generic;
+using System.Diagnostics;
 using System.Linq;
 using System.Runtime.CompilerServices;
 
@@ -16,8 +17,8 @@ namespace Markdig.Helpers
     public class CharacterMap<T> where T : class
     {
         private readonly T[] asciiMap;
-        private readonly Dictionary<char, T> nonAsciiMap;
-        private readonly bool[] isOpeningCharacter;
+        private readonly Dictionary<uint, T> nonAsciiMap;
+        private readonly BoolVector128 isOpeningCharacter;
 
         /// <summary>
         /// Initializes a new instance of the <see cref="CharacterMap{T}"/> class.
@@ -26,56 +27,41 @@ namespace Markdig.Helpers
         /// <exception cref="System.ArgumentNullException"></exception>
         public CharacterMap(IEnumerable<KeyValuePair<char, T>> maps)
         {
-            if (maps == null) throw new ArgumentNullException(nameof(maps));
-            var charCounter = new Dictionary<char, int>();
+            if (maps == null) ThrowHelper.ArgumentNullException(nameof(maps));
+            var charSet = new HashSet<char>();
             int maxChar = 0;
 
             foreach (var map in maps)
             {
                 var openingChar = map.Key;
+                charSet.Add(openingChar);
 
-                if (!charCounter.ContainsKey(openingChar))
+                if (openingChar < 128)
                 {
-                    charCounter[openingChar] = 0;
-                }
-                charCounter[openingChar]++;
-
-                if (openingChar < 127 && openingChar > maxChar)
-                {
-                    maxChar = openingChar;
-                }
-                else if (openingChar >= 127 && nonAsciiMap == null)
-                {
-                    // Initialize only if with have an actual non-ASCII opening character
-                    nonAsciiMap = new Dictionary<char, T>();
-                }
-            }
-            OpeningCharacters = charCounter.Keys.ToArray();
-            Array.Sort(OpeningCharacters);
-
-            asciiMap = new T[maxChar + 1];
-            isOpeningCharacter = new bool[maxChar + 1];
-
-            foreach (var state in maps)
-            {
-                var openingChar = state.Key;
-                T stateByChar;
-                if (openingChar < 127)
-                {
-                    stateByChar = asciiMap[openingChar];
-
-                    if (stateByChar == null)
-                    {
-                        asciiMap[openingChar] = state.Value;
-                    }
-                    isOpeningCharacter[openingChar] = true;
+                    maxChar = Math.Max(maxChar, openingChar);
                 }
                 else
                 {
-                    if (!nonAsciiMap.TryGetValue(openingChar, out stateByChar))
-                    {
-                        nonAsciiMap[openingChar] = state.Value;
-                    }
+                    nonAsciiMap ??= new Dictionary<uint, T>();
+                }
+            }
+
+            OpeningCharacters = charSet.ToArray();
+            Array.Sort(OpeningCharacters);
+
+            asciiMap = new T[maxChar + 1];
+
+            foreach (var state in maps)
+            {
+                char openingChar = state.Key;
+                if (openingChar < 128)
+                {
+                    asciiMap[openingChar] ??= state.Value;
+                    isOpeningCharacter.Set(openingChar);
+                }
+                else if (!nonAsciiMap.ContainsKey(openingChar))
+                {
+                    nonAsciiMap[openingChar] = state.Value;
                 }
             }
         }
@@ -90,24 +76,26 @@ namespace Markdig.Helpers
         /// </summary>
         /// <param name="openingChar">The opening character.</param>
         /// <returns>A list of parsers valid for the specified opening character or null if no parsers registered.</returns>
-        public T this[char openingChar]
+        public T this[uint openingChar]
         {
-            [MethodImpl(MethodImplOptionPortable.AggressiveInlining)]
+            [MethodImpl(MethodImplOptions.AggressiveInlining)]
             get
             {
-                T map = null;
-                if (openingChar < asciiMap.Length)
+                T[] asciiMap = this.asciiMap;
+                if (openingChar < (uint)asciiMap.Length)
                 {
-                    map = asciiMap[openingChar];
+                    return asciiMap[openingChar];
                 }
-                else if (nonAsciiMap != null)
+                else
                 {
-                    nonAsciiMap.TryGetValue(openingChar, out map);
+                    T map = null;
+                    nonAsciiMap?.TryGetValue(openingChar, out map);
+                    return map;
                 }
-                return map;
             }
         }
 
+
         /// <summary>
         /// Searches for an opening character from a registered parser in the specified string.
         /// </summary>
@@ -117,47 +105,112 @@ namespace Markdig.Helpers
         /// <returns>Index position within the string of the first opening character found in the specified text; if not found, returns -1</returns>
         public int IndexOfOpeningCharacter(string text, int start, int end)
         {
-            var maxChar = isOpeningCharacter.Length;
-#if SUPPORT_UNSAFE
-            unsafe
-#endif
+            if (nonAsciiMap is null)
             {
-#if SUPPORT_FIXED_STRING
-            fixed (char* pText = text)
-#else
-                var pText = text;
-#endif
-#if SUPPORT_UNSAFE
-                fixed (bool* openingChars = isOpeningCharacter)
-#else
-                var openingChars = isOpeningCharacter;
-#endif
+#if NETCOREAPP3_1
+                ref char textRef = ref Unsafe.AsRef(in text.GetPinnableReference());
+                for (; start <= end; start++)
                 {
-                    if (nonAsciiMap == null)
+                    if (IntPtr.Size == 4)
                     {
-                        for (int i = start; i <= end; i++)
+                        uint c = Unsafe.Add(ref textRef, start);
+                        if (c < 128 && isOpeningCharacter[c])
                         {
-                            var c = pText[i];
-                            if (c < maxChar && openingChars[c])
-                            {
-                                return i;
-                            }
+                            return start;
                         }
                     }
                     else
+                    {
+                        ulong c = Unsafe.Add(ref textRef, start);
+                        if (c < 128 && isOpeningCharacter[c])
+                        {
+                            return start;
+                        }
+                    }
+                }
+#else
+                unsafe
+                {
+                    fixed (char* pText = text)
                     {
                         for (int i = start; i <= end; i++)
                         {
-                            var c = pText[i];
-                            if ((c < maxChar && openingChars[c]) || nonAsciiMap.ContainsKey(c))
+                            char c = pText[i];
+                            if (c < 128 && isOpeningCharacter[c])
                             {
                                 return i;
                             }
                         }
                     }
                 }
+#endif
+                return -1;
             }
+            else
+            {
+                return IndexOfOpeningCharacterNonAscii(text, start, end);
+            }
+        }
+
+        private int IndexOfOpeningCharacterNonAscii(string text, int start, int end)
+        {
+#if NETCOREAPP3_1
+            ref char textRef = ref Unsafe.AsRef(in text.GetPinnableReference());
+            for (int i = start; i <= end; i++)
+            {
+                char c = Unsafe.Add(ref textRef, i);
+                if (c < 128 ? isOpeningCharacter[c] : nonAsciiMap.ContainsKey(c))
+                {
+                    return i;
+                }
+            }
+#else
+            unsafe
+            {
+                fixed (char* pText = text)
+                {
+                    for (int i = start; i <= end; i++)
+                    {
+                        char c = pText[i];
+                        if (c < 128 ? isOpeningCharacter[c] : nonAsciiMap.ContainsKey(c))
+                        {
+                            return i;
+                        }
+                    }
+                }
+            }
+#endif
             return -1;
         }
     }
+
+    internal unsafe struct BoolVector128
+    {
+        private fixed bool values[128];
+
+        public void Set(char c)
+        {
+            Debug.Assert(c < 128);
+            values[c] = true;
+        }
+
+        public readonly bool this[uint c]
+        {
+            [MethodImpl(MethodImplOptions.AggressiveInlining)]
+            get
+            {
+                Debug.Assert(c < 128);
+                return values[c];
+            }
+        }
+        public readonly bool this[ulong c]
+        {
+            [MethodImpl(MethodImplOptions.AggressiveInlining)]
+            get
+            {
+                Debug.Assert(c < 128 && IntPtr.Size == 8);
+                return values[c];
+            }
+        }
+    }
 }

src/Markdig/Helpers/CompactPrefixTree.cs

@@ -4,6 +4,7 @@ using System;
 using System.Collections;
 using System.Collections.Generic;
 using System.Diagnostics;
+using System.Diagnostics.CodeAnalysis;
 using System.Runtime.CompilerServices;
 
 /*
@@ -25,10 +26,8 @@ namespace Markdig.Helpers
     /// <para>Something between a Trie and a full Radix tree, but stored linearly in memory</para>
     /// </summary>
     /// <typeparam name="TValue">The value associated with the key</typeparam>
-    internal class CompactPrefixTree<TValue>
-//#if !LEGACY
-//        : IReadOnlyDictionary<string, TValue>, IReadOnlyList<KeyValuePair<string, TValue>>
-//#endif
+    [ExcludeFromCodeCoverage]
+    internal sealed class CompactPrefixTree<TValue> : IReadOnlyDictionary<string, TValue>, IReadOnlyList<KeyValuePair<string, TValue>>
     {
         /// <summary>
         /// Used internally to control behavior of insertion
@@ -118,7 +117,7 @@ namespace Markdig.Helpers
                 }
             }
         }
-        [MethodImpl(MethodImplOptionPortable.AggressiveInlining)]
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
         private void EnsureTreeCapacity(int min)
         {
             if (_tree.Length < min)
@@ -167,7 +166,7 @@ namespace Markdig.Helpers
                 }
             }
         }
-        [MethodImpl(MethodImplOptionPortable.AggressiveInlining)]
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
         private void EnsureCapacity(int min)
         {
             // Expansion logic as in System.Collections.Generic.List<T>
@@ -225,7 +224,7 @@ namespace Markdig.Helpers
                 }
             }
         }
-        [MethodImpl(MethodImplOptionPortable.AggressiveInlining)]
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
         private void EnsureChildrenCapacity(int min)
         {
             if (_children.Length < min)
@@ -252,7 +251,7 @@ namespace Markdig.Helpers
 
         // Inspired by Markdig's CharacterMap
 
-        [MethodImpl(MethodImplOptionPortable.AggressiveInlining)]
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
         private bool TryGetRoot(char rootChar, out int rootNodeIndex)
         {
             if (rootChar < 128)
@@ -336,7 +335,7 @@ namespace Markdig.Helpers
         /// <returns>The key/value pair of the element at the specified index</returns>
         public KeyValuePair<string, TValue> this[int index]
         {
-            [MethodImpl(MethodImplOptionPortable.AggressiveInlining)]
+            [MethodImpl(MethodImplOptions.AggressiveInlining)]
             get
             {
                 if ((uint)index >= (uint)Count) ThrowHelper.ThrowIndexOutOfRangeException();
@@ -353,7 +352,7 @@ namespace Markdig.Helpers
         {
             get
             {
-                if (TryMatchExact(key, out KeyValuePair<string, TValue> match))
+                if (TryMatchExact(key.AsSpan(), out KeyValuePair<string, TValue> match))
                     return match.Value;
                 throw new KeyNotFoundException(key);
             }
@@ -365,7 +364,6 @@ namespace Markdig.Helpers
             }
         } // Get, Set
 
-#if NETCORE
         /// <summary>
         /// Gets the value associated with the specified key
         /// </summary>
@@ -380,7 +378,6 @@ namespace Markdig.Helpers
                 throw new KeyNotFoundException(key.ToString());
             }
         } // Get only
-#endif
 
         #endregion this[] accessors
 
@@ -711,50 +708,6 @@ namespace Markdig.Helpers
 
         #region TryMatch longest
 
-        /// <summary>
-        /// Tries to find the longest prefix of text, starting at offset, that is contained in this <see cref="CompactPrefixTree{TValue}"/>
-        /// </summary>
-        /// <param name="text">The text in which to search for the prefix</param>
-        /// <param name="offset">Index of the character at which to start searching</param>
-        /// <param name="match">The found prefix and the corresponding value</param>
-        /// <returns>True if a match was found, false otherwise</returns>
-        public bool TryMatchLongest(string text, int offset, out KeyValuePair<string, TValue> match)
-        {
-#if NETCORE
-            return TryMatchLongest(text.AsSpan(offset), out match);
-#else
-            return TryMatchLongest(text, offset, text.Length - offset, out match);
-#endif
-        }
-
-        /// <summary>
-        /// Tries to find the longest prefix of text, that is contained in this <see cref="CompactPrefixTree{TValue}"/>
-        /// </summary>
-        /// <param name="text">The text in which to search for the prefix</param>
-        /// <param name="match">The found prefix and the corresponding value</param>
-        /// <returns>True if a match was found, false otherwise</returns>
-        public bool TryMatchLongest(string text, out KeyValuePair<string, TValue> match)
-        {
-            if (text == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.text);
-#if NETCORE
-            return TryMatchLongest(text.AsSpan(), out match);
-#else
-            return TryMatchLongest(text, 0, text.Length, out match);
-#endif
-        }
-
-        /// <summary>
-        /// Tries to find the longest prefix of text, starting at offset, that is contained in this <see cref="CompactPrefixTree{TValue}"/>
-        /// </summary>
-        /// <param name="text">The text in which to search for the prefix</param>
-        /// <param name="offset">The offset in text at which to start looking for the prefix</param>
-        /// <param name="length">The longest prefix allowed to match</param>
-        /// <param name="match">The found prefix and the corresponding value</param>
-        /// <returns>True if a match was found, false otherwise</returns>
-#if NETCORE
-        public bool TryMatchLongest(string text, int offset, int length, out KeyValuePair<string, TValue> match)
-            => TryMatchLongest(text.AsSpan(offset, length), out match);
-
         /// <summary>
         /// Tries to find the longest prefix of text, that is contained in this <see cref="CompactPrefixTree{TValue}"/>
         /// </summary>
@@ -766,20 +719,6 @@ namespace Markdig.Helpers
             match = default;
             if (text.Length == 0 || !TryGetRoot(text[0], out int nodeIndex))
                 return false;
-#else
-        public bool TryMatchLongest(string text, int offset, int length, out KeyValuePair<string, TValue> match)
-        {
-            int limit = offset + length;
-            if (text == null)
-                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.text);
-
-            if (offset < 0 || length < 0 || text.Length < limit)
-                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.offsetLength, ExceptionReason.InvalidOffsetLength);
-
-            match = default;
-            if (length == 0 || !TryGetRoot(text[offset], out int nodeIndex))
-                return false;
-#endif
 
             int matchIndex = -1;
             int depth = 1;
@@ -788,11 +727,7 @@ namespace Markdig.Helpers
             if (node.ChildChar == 0) goto LeafNodeFound;
             if (node.MatchIndex != -1) matchIndex = node.MatchIndex;
 
-#if NETCORE
             for (int i = 1; i < text.Length; i++)
-#else
-            for (int i = offset + 1; i < limit; i++)
-#endif
             {
                 char c = text[i];
 
@@ -824,7 +759,6 @@ namespace Markdig.Helpers
 
         LeafNodeFound:;
             ref KeyValuePair<string, TValue> possibleMatch = ref _matches[node.MatchIndex];
-#if NETCORE
             if (possibleMatch.Key.Length <= text.Length)
             {
                 // Check that the rest of the strings match
@@ -833,18 +767,6 @@ namespace Markdig.Helpers
                     matchIndex = node.MatchIndex;
                 }
             }
-#else
-            if (possibleMatch.Key.Length <= length)
-            {
-                // Check that the rest of the strings match
-                for (int i = offset + depth, j = depth; j < possibleMatch.Key.Length; i++, j++)
-                {
-                    if (text[i] != possibleMatch.Key[j])
-                        goto Return;
-                }
-                matchIndex = node.MatchIndex;
-            }
-#endif
 
         Return:;
             if (matchIndex != -1)
@@ -859,50 +781,6 @@ namespace Markdig.Helpers
 
         #region TryMatch exact
 
-        /// <summary>
-        /// Tries to find a suffix of text, starting at offset, that is contained in this <see cref="CompactPrefixTree{TValue}"/> and is exactly (text.Length - offset) characters long
-        /// </summary>
-        /// <param name="text">The text in which to search for the prefix</param>
-        /// <param name="offset">Index of the character at which to start searching</param>
-        /// <param name="match">The found prefix and the corresponding value</param>
-        /// <returns>True if a match was found, false otherwise</returns>
-        public bool TryMatchExact(string text, int offset, out KeyValuePair<string, TValue> match)
-        {
-#if NETCORE
-            return TryMatchExact(text.AsSpan(offset), out match);
-#else
-            return TryMatchExact(text, offset, text.Length - offset, out match);
-#endif
-        }
-
-        /// <summary>
-        /// Tries to find a prefix of text, that is contained in this <see cref="CompactPrefixTree{TValue}"/> and is exactly text.Length characters long
-        /// </summary>
-        /// <param name="text">The text in which to search for the prefix</param>
-        /// <param name="match">The found prefix and the corresponding value</param>
-        /// <returns>True if a match was found, false otherwise</returns>
-        public bool TryMatchExact(string text, out KeyValuePair<string, TValue> match)
-        {
-            if (text == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.text);
-#if NETCORE
-            return TryMatchExact(text.AsSpan(), out match);
-#else
-            return TryMatchExact(text, 0, text.Length, out match);
-#endif
-        }
-
-        /// <summary>
-        /// Tries to find a prefix of text, starting at offset, that is contained in this <see cref="CompactPrefixTree{TValue}"/> and is exactly length characters long
-        /// </summary>
-        /// <param name="text">The text in which to search for the prefix</param>
-        /// <param name="offset">The offset in text at which to start looking for the prefix</param>
-        /// <param name="length">The longest prefix allowed to match</param>
-        /// <param name="match">The found prefix and the corresponding value</param>
-        /// <returns>True if a match was found, false otherwise</returns>
-#if NETCORE
-        public bool TryMatchExact(string text, int offset, int length, out KeyValuePair<string, TValue> match)
-            => TryMatchExact(text.AsSpan(offset, length), out match);
-
         /// <summary>
         /// Tries to find a prefix of text, that is contained in this <see cref="CompactPrefixTree{TValue}"/> and is exactly text.Length characters long
         /// </summary>
@@ -914,39 +792,18 @@ namespace Markdig.Helpers
             match = default;
             if (text.Length == 0 || !TryGetRoot(text[0], out int nodeIndex))
                 return false;
-#else
-        public bool TryMatchExact(string text, int offset, int length, out KeyValuePair<string, TValue> match)
-        {
-            int limit = offset + length;
-            if (text == null)
-                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.text);
 
-            if (offset < 0 || length < 0 || text.Length < limit)
-                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.offsetLength, ExceptionReason.InvalidOffsetLength);
-
-            match = default;
-            if (length == 0 || !TryGetRoot(text[offset], out int nodeIndex))
-                return false;
-#endif
             int depth = 1;
 
             ref Node node = ref _tree[nodeIndex];
             if (node.ChildChar == 0) goto LeafNodeFound;
-#if NETCORE
             if (node.MatchIndex != -1 && text.Length == 1)
-#else
-            if (node.MatchIndex != -1 && length == 1)
-#endif
             {
                 match = _matches[node.MatchIndex];
                 return true;
             }
 
-#if NETCORE
             for (int i = 1; i < text.Length; i++)
-#else
-            for (int i = offset + 1; i < limit; i++)
-#endif
             {
                 char c = text[i];
 
@@ -975,81 +832,20 @@ namespace Markdig.Helpers
 
             if (node.MatchIndex == -1) return false;
             match = _matches[node.MatchIndex];
-#if NETCORE
             Debug.Assert(match.Key.Length == text.Length);
-#else
-            Debug.Assert(match.Key.Length == length);
-#endif
             return true;
 
         LeafNodeFound:;
             match = _matches[node.MatchIndex];
-#if NETCORE
+
             return match.Key.Length == text.Length &&
                 text.Slice(depth).Equals(match.Key.AsSpan(depth), StringComparison.Ordinal);
-#else
-            if (match.Key.Length == length)
-            {
-                // Check that the rest of the strings match
-                for (int i = offset + depth, j = depth; j < match.Key.Length; i++, j++)
-                {
-                    if (text[i] != match.Key[j])
-                        return false;
-                }
-                return true;
-            }
-            return false;
-#endif
         }
 
         #endregion TryMatch exact
 
         #region TryMatch shortest
 
-        /// <summary>
-        /// Tries to find the shortest prefix of text, starting at offset, that is contained in this <see cref="CompactPrefixTree{TValue}"/>
-        /// </summary>
-        /// <param name="text">The text in which to search for the prefix</param>
-        /// <param name="offset">Index of the character at which to start searching</param>
-        /// <param name="match">The found prefix and the corresponding value</param>
-        /// <returns>True if a match was found, false otherwise</returns>
-        public bool TryMatchShortest(string text, int offset, out KeyValuePair<string, TValue> match)
-        {
-#if NETCORE
-            return TryMatchShortest(text.AsSpan(offset), out match);
-#else
-            return TryMatchShortest(text, offset, text.Length - offset, out match);
-#endif
-        }
-
-        /// <summary>
-        /// Tries to find the shortest prefix of text, that is contained in this <see cref="CompactPrefixTree{TValue}"/>
-        /// </summary>
-        /// <param name="text">The text in which to search for the prefix</param>
-        /// <param name="match">The found prefix and the corresponding value</param>
-        /// <returns>True if a match was found, false otherwise</returns>
-        public bool TryMatchShortest(string text, out KeyValuePair<string, TValue> match)
-        {
-            if (text == null) ThrowHelper.ThrowArgumentNullException(ExceptionArgument.text);
-#if NETCORE
-            return TryMatchShortest(text.AsSpan(), out match);
-#else
-            return TryMatchShortest(text, 0, text.Length, out match);
-#endif
-        }
-
-        /// <summary>
-        /// Tries to find the shortest prefix of text, starting at offset, that is contained in this <see cref="CompactPrefixTree{TValue}"/>
-        /// </summary>
-        /// <param name="text">The text in which to search for the prefix</param>
-        /// <param name="offset">The offset in text at which to start looking for the prefix</param>
-        /// <param name="length">The longest prefix allowed to match</param>
-        /// <param name="match">The found prefix and the corresponding value</param>
-        /// <returns>True if a match was found, false otherwise</returns>
-#if NETCORE
-        public bool TryMatchShortest(string text, int offset, int length, out KeyValuePair<string, TValue> match)
-            => TryMatchShortest(text.AsSpan(offset, length), out match);
-
         /// <summary>
         /// Tries to find the shortest prefix of text, that is contained in this <see cref="CompactPrefixTree{TValue}"/>
         /// </summary>
@@ -1061,20 +857,7 @@ namespace Markdig.Helpers
             match = default;
             if (text.Length == 0 || !TryGetRoot(text[0], out int nodeIndex))
                 return false;
-#else
-        public bool TryMatchShortest(string text, int offset, int length, out KeyValuePair<string, TValue> match)
-        {
-            int limit = offset + length;
-            if (text == null)
-                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.text);
 
-            if (offset < 0 || length < 0 || text.Length < limit)
-                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.offsetLength, ExceptionReason.InvalidOffsetLength);
-
-            match = default;
-            if (length == 0 || !TryGetRoot(text[offset], out int nodeIndex))
-                return false;
-#endif
             ref Node node = ref _tree[nodeIndex];
             if (node.MatchIndex != -1)
             {
@@ -1082,11 +865,7 @@ namespace Markdig.Helpers
                 return true;
             }
 
-#if NETCORE
             for (int i = 1; i < text.Length; i++)
-#else
-            for (int i = offset + 1; i < limit; i++)
-#endif
             {
                 char c = text[i];
 
@@ -1129,7 +908,7 @@ namespace Markdig.Helpers
         /// <param name="key">The key to locate in this <see cref="CompactPrefixTree{TValue}"/></param>
         /// <returns>True if the key is contained in this PrefixTree, false otherwise.</returns>
         public bool ContainsKey(string key)
-            => TryMatchExact(key, out _);
+            => TryMatchExact(key.AsSpan(), out _);
 
         /// <summary>
         /// Gets the value associated with the specified key
@@ -1139,7 +918,7 @@ namespace Markdig.Helpers
         /// <returns>True if the key is contained in this PrefixTree, false otherwise.</returns>
         public bool TryGetValue(string key, out TValue value)
         {
-            bool ret = TryMatchExact(key, out KeyValuePair<string, TValue> match);
+            bool ret = TryMatchExact(key.AsSpan(), out KeyValuePair<string, TValue> match);
             value = match.Value;
             return ret;
         }
@@ -1173,9 +952,8 @@ namespace Markdig.Helpers
         /// </summary>
         /// <returns></returns>
         public IEnumerator<KeyValuePair<string, TValue>> GetEnumerator() => new Enumerator(_matches);
-//#if !LEGACY
-        //IEnumerator IEnumerable.GetEnumerator() => new Enumerator(_matches);
-//#endif
+
+        IEnumerator IEnumerable.GetEnumerator() => new Enumerator(_matches);
 
         /// <summary>
         /// Enumerates the elements of a <see cref="CompactPrefixTree{TValue}"/>

src/Markdig/Helpers/CustomArrayPool.cs

@@ -0,0 +1,86 @@
+using System.Threading;
+
+namespace Markdig.Helpers
+{
+    internal sealed class CustomArrayPool<T>
+    {
+        private sealed class Bucket
+        {
+            private readonly T[][] _buffers;
+
+            private int _index;
+            private int _lock;
+
+            public Bucket(int numberOfBuffers)
+            {
+                _buffers = new T[numberOfBuffers][];
+            }
+
+            public T[] Rent()
+            {
+                T[][] buffers = _buffers;
+                T[] buffer = null;
+                if (Interlocked.CompareExchange(ref _lock, 1, 0) == 0)
+                {
+                    int index = _index;
+                    if ((uint)index < (uint)buffers.Length)
+                    {
+                        buffer = buffers[index];
+                        buffers[index] = null;
+                        _index = index + 1;
+                    }
+                    Interlocked.Decrement(ref _lock);
+                }
+                return buffer;
+            }
+
+            public void Return(T[] array)
+            {
+                var buffers = _buffers;
+                if (Interlocked.CompareExchange(ref _lock, 1, 0) == 0)
+                {
+                    int index = _index - 1;
+                    if ((uint)index < (uint)buffers.Length)
+                    {
+                        buffers[index] = array;
+                        _index = index;
+                    }
+                    Interlocked.Decrement(ref _lock);
+                }
+            }
+        }
+
+        private readonly Bucket _bucket4, _bucket8, _bucket16, _bucket32;
+
+        public CustomArrayPool(int size4, int size8, int size16, int size32)
+        {
+            _bucket4 = new Bucket(size4);
+            _bucket8 = new Bucket(size8);
+            _bucket16 = new Bucket(size16);
+            _bucket32 = new Bucket(size32);
+        }
+
+        private Bucket SelectBucket(int length)
+        {
+            switch (length)
+            {
+                case 4: return _bucket4;
+                case 8: return _bucket8;
+                case 16: return _bucket16;
+                case 32: return _bucket32;
+
+                default: return null;
+            }
+        }
+
+        public T[] Rent(int length)
+        {
+            return SelectBucket(length)?.Rent() ?? new T[length];
+        }
+
+        public void Return(T[] array)
+        {
+            SelectBucket(array.Length)?.Return(array);
+        }
+    }
+}

src/Markdig/Helpers/EntityHelper.cs

@@ -1,4 +1,4 @@
-// Copyright (c) Alexandre Mutel. All rights reserved.
+// Copyright (c) Alexandre Mutel. All rights reserved.
 // This file is licensed under the BSD-Clause 2 license. 
 // See the license.txt file in the project root for more information.
 
@@ -33,6 +33,7 @@
 
 using System;
 using System.Collections.Generic;
+using System.Text;
 
 namespace Markdig.Helpers
 {
@@ -46,11 +47,10 @@ namespace Markdig.Helpers
         /// </summary>
         /// <param name="entity">The entity without <c>&amp;</c> and <c>;</c> symbols, for example, <c>copy</c>.</param>
         /// <returns>The unicode character set or <c>null</c> if the entity was not recognized.</returns>
-        public static string DecodeEntity(string entity)
+        public static string DecodeEntity(ReadOnlySpan<char> entity)
         {
-            string result;
-            if (EntityMap.TryGetValue(entity, out result))
-                return result;
+            if (EntityMap.TryMatchExact(entity, out KeyValuePair<string, string> result))
+                return result.Value;
 
             return null;
         }
@@ -61,25 +61,49 @@ namespace Markdig.Helpers
         /// <returns>The unicode character set or <c>null</c> if the entity was not recognized.</returns>
         public static string DecodeEntity(int utf32)
         {
-            if (utf32 < 0 || utf32 > 1114111 || (utf32 >= 55296 && utf32 <= 57343))
-                return null;
+            if (!CharHelper.IsInInclusiveRange(utf32, 1, 1114111) || CharHelper.IsInInclusiveRange(utf32, 55296, 57343))
+                return CharHelper.ReplacementCharString;
 
             if (utf32 < 65536)
                 return char.ToString((char)utf32);
 
             utf32 -= 65536;
-            return new string(new char[]
+            return new string(
+#if NETCORE
+                stackalloc
+#else
+                new
+#endif
+                char[]
             {
-                (char)(utf32 / 1024 + 55296),
-                (char)(utf32 % 1024 + 56320)
+                (char)((uint)utf32 / 1024 + 55296),
+                (char)((uint)utf32 % 1024 + 56320)
             });
         }
 
-        #region [ EntityMap ]
+        public static void DecodeEntity(int utf32, StringBuilder sb)
+        {
+            if (!CharHelper.IsInInclusiveRange(utf32, 1, 1114111) || CharHelper.IsInInclusiveRange(utf32, 55296, 57343))
+            {
+                sb.Append(CharHelper.ReplacementChar);
+            }
+            else if (utf32 < 65536)
+            {
+                sb.Append((char)utf32);
+            }
+            else
+            {
+                utf32 -= 65536;
+                sb.Append((char)((uint)utf32 / 1024 + 55296));
+                sb.Append((char)((uint)utf32 % 1024 + 56320));
+            }
+        }
+
+#region [ EntityMap ]
         /// <summary>
         /// Source: http://www.w3.org/html/wg/drafts/html/master/syntax.html#named-character-references
         /// </summary>
-        private static readonly Dictionary<string, string> EntityMap = new Dictionary<string, string>(2125, StringComparer.Ordinal)
+        private static readonly CompactPrefixTree<string> EntityMap = new CompactPrefixTree<string>(2125, 3385, 3510)
         {
             { "Aacute", "\u00C1" },
             { "aacute", "\u00E1" },
@@ -2207,6 +2231,6 @@ namespace Markdig.Helpers
             { "zwj", "\u200D" },
             { "zwnj", "\u200C" }
         };
-        #endregion
+#endregion
     }
 }

src/Markdig/Helpers/HtmlHelper.cs

@@ -51,7 +51,7 @@ namespace Markdig.Helpers
 
         public static bool TryParseHtmlTag(ref StringSlice text, StringBuilder builder)
         {
-            if (builder == null) throw new ArgumentNullException(nameof(builder));
+            if (builder == null) ThrowHelper.ArgumentNullException(nameof(builder));
             var c = text.CurrentChar;
             if (c != '<')
             {
@@ -373,7 +373,7 @@ namespace Markdig.Helpers
             }
             builder.Append('-');
             builder.Append('-');
-            if (text.PeekChar(1) == '>')
+            if (text.PeekChar() == '>')
             {
                 return false;
             }
@@ -450,11 +450,7 @@ namespace Markdig.Helpers
 
             while ((searchPos = text.IndexOfAny(search, searchPos)) != -1)
             {
-                if (sb == null)
-                {
-                    sb = StringBuilderCache.Local();
-                    sb.Length = 0;
-                }
+                sb ??= StringBuilderCache.Local();
                 c = text[searchPos];
                 if (removeBackSlash && c == '\\')
                 {
@@ -472,10 +468,7 @@ namespace Markdig.Helpers
                 }
                 else if (c == '&')
                 {
-                    int entityNameStart;
-                    int entityNameLength;
-                    int numericEntity;
-                    var match = ScanEntity(new StringSlice(text, searchPos, text.Length - 1), out numericEntity, out entityNameStart, out entityNameLength);
+                    var match = ScanEntity(new StringSlice(text, searchPos, text.Length - 1), out int numericEntity, out int entityNameStart, out int entityNameLength);
                     if (match == 0)
                     {
                         searchPos++;
@@ -486,8 +479,7 @@ namespace Markdig.Helpers
 
                         if (entityNameLength > 0)
                         {
-                            var namedEntity = new StringSlice(text, entityNameStart, entityNameStart + entityNameLength - 1);
-                            var decoded = EntityHelper.DecodeEntity(namedEntity.ToString());
+                            var decoded = EntityHelper.DecodeEntity(text.AsSpan(entityNameStart, entityNameLength));
                             if (decoded != null)
                             {
                                 sb.Append(text, lastPos, searchPos - match - lastPos);
@@ -498,36 +490,18 @@ namespace Markdig.Helpers
                         else if (numericEntity >= 0)
                         {
                             sb.Append(text, lastPos, searchPos - match - lastPos);
-                            if (numericEntity == 0)
-                            {
-                                sb.Append('\0'.EscapeInsecure());
-                            }
-                            else
-                            {
-                                var decoded = EntityHelper.DecodeEntity(numericEntity);
-                                if (decoded != null)
-                                {
-                                    sb.Append(decoded);
-                                }
-                                else
-                                {
-                                    sb.Append('\uFFFD');
-                                }
-                            }
-
+                            EntityHelper.DecodeEntity(numericEntity, sb);
                             lastPos = searchPos;
                         }
                     }
                 }
             }
 
-            if (sb == null)
+            if (sb == null || lastPos == 0)
                 return text;
 
             sb.Append(text, lastPos, text.Length - lastPos);
-            var result = sb.ToString();
-            sb.Length = 0;
-            return result;
+            return sb.GetStringAndReset();
         }
 
         /// <summary>

src/Markdig/Helpers/LineReader.cs

@@ -1,10 +1,9 @@
-// Copyright (c) Alexandre Mutel. All rights reserved.
+// Copyright (c) Alexandre Mutel. All rights reserved.
 // This file is licensed under the BSD-Clause 2 license. 
 // See the license.txt file in the project root for more information.
 
 using System;
 using System.IO;
-using System.Text;
 
 namespace Markdig.Helpers
 {
@@ -13,17 +12,19 @@ namespace Markdig.Helpers
     /// </summary>
     public struct LineReader
     {
-        private readonly string text;
+        private readonly string _text;
 
         /// <summary>
         /// Initializes a new instance of the <see cref="LineReader"/> class.
         /// </summary>
-        /// <exception cref="System.ArgumentNullException"></exception>
-        /// <exception cref="System.ArgumentOutOfRangeException">bufferSize cannot be &lt;= 0</exception>
+        /// <exception cref="ArgumentNullException"></exception>
+        /// <exception cref="ArgumentOutOfRangeException">bufferSize cannot be &lt;= 0</exception>
         public LineReader(string text)
         {
-            if (text == null) throw new ArgumentNullException(nameof(text));
-            this.text = text;
+            if (text is null)
+                ThrowHelper.ArgumentNullException_text();
+
+            _text = text;
             SourcePosition = 0;
         }
 
@@ -36,36 +37,31 @@ namespace Markdig.Helpers
         /// Reads a new line from the underlying <see cref="TextReader"/> and update the <see cref="SourcePosition"/> for the next line.
         /// </summary>
         /// <returns>A new line or null if the end of <see cref="TextReader"/> has been reached</returns>
-        public StringSlice? ReadLine()
+        public StringSlice ReadLine()
         {
-            if (SourcePosition >= text.Length)
-            {
-                return null;
-            }
+            string text = _text;
+            int sourcePosition = SourcePosition;
 
-            var startPosition = SourcePosition;
-            var position = SourcePosition;
-            var slice = new StringSlice(text, startPosition, startPosition);
-            for (;position < text.Length; position++)
+            for (int i = sourcePosition; i < text.Length; i++)
             {
-                var c = text[position];
+                char c = text[i];
                 if (c == '\r' || c == '\n')
                 {
-                    slice.End = position - 1;
-                    if (c == '\r' && position + 1 < text.Length && text[position + 1] == '\n')
-                    {
-                        position++;
-                    }
-                    position++;
-                    SourcePosition = position;
+                    var slice = new StringSlice(text, sourcePosition, i - 1);
+
+                    if (c == '\r' && (uint)(i + 1) < (uint)text.Length && text[i + 1] == '\n')
+                        i++;
+
+                    SourcePosition = i + 1;
                     return slice;
                 }
             }
 
-            slice.End = position - 1;
-            SourcePosition = position;
+            if (sourcePosition >= text.Length)
+                return default;
 
-            return slice;
+            SourcePosition = int.MaxValue;
+            return new StringSlice(text, sourcePosition, text.Length - 1);
         }
-   }
+    }
 }

src/Markdig/Helpers/LinkHelper.cs

@@ -101,18 +101,16 @@ namespace Markdig.Helpers
             var headingBuffer = StringBuilderCache.Local();
             for (int i = 0; i < headingText.Length; i++)
             {
-                var c = char.ToLowerInvariant(headingText[i]);
+                var c = headingText[i];
                 if (char.IsLetterOrDigit(c) || c == ' ' || c == '-' || c == '_')
                 {
-                    headingBuffer.Append(c == ' ' ? '-' : c);
+                    headingBuffer.Append(c == ' ' ? '-' : char.ToLowerInvariant(c));
                 }
             }
-            var result = headingBuffer.ToString();
-            headingBuffer.Length = 0;
-            return result;
+            return headingBuffer.GetStringAndReset();
         }
 
-        [MethodImpl(MethodImplOptionPortable.AggressiveInlining)]
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
         private static bool IsReservedPunctuation(char c)
         {
             return c == '_' || c == '-' || c == '.';
@@ -427,7 +425,6 @@ namespace Markdig.Helpers
         {
             bool isValid = false;
             var buffer = StringBuilderCache.Local();
-            buffer.Length = 0;
 
             // a sequence of zero or more characters between straight double-quote characters ("), including a " character only if it is backslash-escaped, or
             // a sequence of zero or more characters between straight single-quote characters ('), including a ' character only if it is backslash-escaped, or
@@ -519,7 +516,6 @@ namespace Markdig.Helpers
         {
             bool isValid = false;
             var buffer = StringBuilderCache.Local();
-            buffer.Length = 0;
 
             var c = text.CurrentChar;
 
@@ -597,20 +593,23 @@ namespace Markdig.Helpers
                         }
                     }
 
-                    if (hasEscape && !c.IsAsciiPunctuation())
+                    if (!isAutoLink)
                     {
-                        buffer.Append('\\');
-                    }
+                        if (hasEscape && !c.IsAsciiPunctuation())
+                        {
+                            buffer.Append('\\');
+                        }
 
-                    // If we have an escape
-                    if (c == '\\')
-                    {
-                        hasEscape = true;
-                        c = text.NextChar();
-                        continue;
-                    }
+                        // If we have an escape
+                        if (c == '\\')
+                        {
+                            hasEscape = true;
+                            c = text.NextChar();
+                            continue;
+                        }
 
-                    hasEscape = false;
+                        hasEscape = false;
+                    }
 
                     if (IsEndOfUri(c, isAutoLink))
                     {
@@ -622,10 +621,7 @@ namespace Markdig.Helpers
                     {
                         if (c == '&')
                         {
-                            int entityNameStart;
-                            int entityNameLength;
-                            int entityValue;
-                            if (HtmlHelper.ScanEntity(text, out entityValue, out entityNameStart, out entityNameLength) > 0)
+                            if (HtmlHelper.ScanEntity(text, out _, out _, out _) > 0)
                             {
                                 isValid = true;
                                 break;
@@ -654,14 +650,14 @@ namespace Markdig.Helpers
             return isValid;
         }
 
-        [MethodImpl(MethodImplOptionPortable.AggressiveInlining)]
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
         private static bool IsTrailingUrlStopCharacter(char c)
         {
             // Trailing punctuation (specifically, ?, !, ., ,, :, *, _, and ~) will not be considered part of the autolink, though they may be included in the interior of the link:
             return c == '?' || c == '!' || c == '.' || c == ',' || c == ':' || c == '*' || c == '*' || c == '_' || c == '~';
         }
 
-        [MethodImpl(MethodImplOptionPortable.AggressiveInlining)]
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
         private static bool IsEndOfUri(char c, bool isAutoLink)
         {
             return c == '\0' || c.IsSpaceOrTab() || c.IsControl() || (isAutoLink && c == '<'); // TODO: specs unclear. space is strict or relaxed? (includes tabs?)

src/Markdig/Helpers/MethodImplOptionPortable.cs

@@ -1,15 +0,0 @@
-// Copyright (c) Alexandre Mutel. All rights reserved.
-// This file is licensed under the BSD-Clause 2 license. 
-// See the license.txt file in the project root for more information.
-using System.Runtime.CompilerServices;
-
-namespace Markdig.Helpers
-{
-    /// <summary>
-    /// Internal helper to allow to declare a method using AggressiveInlining without being .NET 4.0+
-    /// </summary>
-    internal static class MethodImplOptionPortable
-    {
-        public const MethodImplOptions AggressiveInlining = (MethodImplOptions)256;
-    }
-}

src/Markdig/Helpers/ObjectCache.cs

@@ -1,4 +1,4 @@
-// Copyright (c) Alexandre Mutel. All rights reserved.
+// Copyright (c) Alexandre Mutel. All rights reserved.
 // This file is licensed under the BSD-Clause 2 license. 
 // See the license.txt file in the project root for more information.
 using System;
@@ -57,7 +57,7 @@ namespace Markdig.Helpers
         /// <exception cref="System.ArgumentNullException">if instance is null</exception>
         public void Release(T instance)
         {
-            if (instance == null) throw new ArgumentNullException(nameof(instance));
+            if (instance == null) ThrowHelper.ArgumentNullException(nameof(instance));
             Reset(instance);
             lock (builders)
             {

src/Markdig/Helpers/OrderedList.cs

@@ -22,85 +22,85 @@ namespace Markdig.Helpers
         {
         }
 
-        public bool InsertBefore<TElement>(T element) where TElement : T
+        public bool InsertBefore<TItem>(T item) where TItem : T
         {
-            if (element == null) throw new ArgumentNullException(nameof(element));
+            if (item == null) ThrowHelper.ArgumentNullException_item();
             for (int i = 0; i < Count; i++)
             {
-                if (this[i] is TElement)
+                if (this[i] is TItem)
                 {
-                    Insert(i, element);
+                    Insert(i, item);
                     return true;
                 }
             }
             return false;
         }
 
-        public TElement Find<TElement>() where TElement : T
+        public TItem Find<TItem>() where TItem : T
         {
             for (int i = 0; i < Count; i++)
             {
-                if (this[i] is TElement)
+                if (this[i] is TItem)
                 {
-                    return (TElement)this[i];
+                    return (TItem)this[i];
                 }
             }
             return default;
         }
 
-        public bool TryFind<TElement>(out TElement element) where TElement : T
+        public bool TryFind<TItem>(out TItem item) where TItem : T
         {
-            element = Find<TElement>();
-            return element != null;
+            item = Find<TItem>();
+            return item != null;
         }
 
-        public TElement FindExact<TElement>() where TElement : T
+        public TItem FindExact<TItem>() where TItem : T
         {
             for (int i = 0; i < Count; i++)
             {
-                if (this[i].GetType() == typeof(TElement))
+                if (this[i].GetType() == typeof(TItem))
                 {
-                    return (TElement)this[i];
+                    return (TItem)this[i];
                 }
             }
             return default;
         }
 
-        public void AddIfNotAlready<TElement>() where TElement : class, T, new()
+        public void AddIfNotAlready<TItem>() where TItem : class, T, new()
         {
-            if (!Contains<TElement>())
+            if (!Contains<TItem>())
             {
-                Add(new TElement());
+                Add(new TItem());
             }
         }
 
-        public void AddIfNotAlready<TElement>(TElement telement) where TElement : T
+        public void AddIfNotAlready<TItem>(TItem item) where TItem : T
         {
-            if (!Contains<TElement>())
+            if (!Contains<TItem>())
             {
-                Add(telement);
+                Add(item);
             }
         }
 
-        public bool InsertAfter<TElement>(T element) where TElement : T
+        public bool InsertAfter<TItem>(T item) where TItem : T
         {
-            if (element == null) throw new ArgumentNullException(nameof(element));
+            if (item == null) ThrowHelper.ArgumentNullException_item();
             for (int i = 0; i < Count; i++)
             {
-                if (this[i] is TElement)
+                if (this[i] is TItem)
                 {
-                    Insert(i + 1, element);
+                    Insert(i + 1, item);
                     return true;
                 }
             }
             return false;
         }
 
-        public bool Contains<TElement>() where TElement : T
+        public bool Contains<TItem>() where TItem : T
         {
             for (int i = 0; i < Count; i++)
             {
-                if (this[i] is TElement)
+                if (this[i] is TItem)
                 {
                     return true;
                 }
@@ -109,16 +109,16 @@ namespace Markdig.Helpers
         }
 
         /// <summary>
-        /// Replaces <typeparamref name="TElement"/> with <paramref name="replacement"/>.
+        /// Replaces <typeparamref name="TItem"/> with <paramref name="replacement"/>.
         /// </summary>
-        /// <typeparam name="TElement">Element type to find in the list</typeparam>
-        /// <param name="replacement">Object to replace this element with</param>
+        /// <typeparam name="TItem">Item type to find in the list</typeparam>
+        /// <param name="replacement">Object to replace this item with</param>
         /// <returns><c>true</c> if a replacement was made; otherwise <c>false</c>.</returns>
-        public bool Replace<TElement>(T replacement) where TElement : T
+        public bool Replace<TItem>(T replacement) where TItem : T
         {
             for (var i = 0; i < Count; i++)
             {
-                if (this[i] is TElement)
+                if (this[i] is TItem)
                 {
                     RemoveAt(i);
                     Insert(i, replacement);
@@ -129,28 +129,28 @@ namespace Markdig.Helpers
         }
 
         /// <summary>
-        /// Replaces <typeparamref name="TElement"/> with <paramref name="newElement"/> or adds <paramref name="newElement"/>.
+        /// Replaces <typeparamref name="TItem"/> with <paramref name="newItem"/> or adds <paramref name="newItem"/>.
         /// </summary>
-        /// <typeparam name="TElement">Element type to find in the list</typeparam>
-        /// <param name="newElement">Object to add/replace the found element with</param>
+        /// <typeparam name="TItem">Item type to find in the list</typeparam>
+        /// <param name="newItem">Object to add/replace the found item with</param>
         /// <returns><c>true</c> if a replacement was made; otherwise <c>false</c>.</returns>
-        public bool ReplaceOrAdd<TElement>(T newElement) where TElement : T
+        public bool ReplaceOrAdd<TItem>(T newItem) where TItem : T
         {
-            if (Replace<TElement>(newElement))
+            if (Replace<TItem>(newItem))
                 return true;
 
-            Add(newElement);
+            Add(newItem);
             return false;
         }
 
         /// <summary>
-        /// Removes the first occurrence of <typeparamref name="TElement"/>
+        /// Removes the first occurrence of <typeparamref name="TItem"/>
         /// </summary>
-        public bool TryRemove<TElement>() where TElement : T
+        public bool TryRemove<TItem>() where TItem : T
         {
             for (int i = 0; i < Count; i++)
             {
-                if (this[i] is TElement)
+                if (this[i] is TItem)
                 {
                     RemoveAt(i);
                     return true;

src/Markdig/Helpers/StringBuilderCache.cs

@@ -1,4 +1,4 @@
-// Copyright (c) Alexandre Mutel. All rights reserved.
+// Copyright (c) Alexandre Mutel. All rights reserved.
 // This file is licensed under the BSD-Clause 2 license. 
 // See the license.txt file in the project root for more information.
 using System;
@@ -6,11 +6,7 @@ using System.Text;
 
 namespace Markdig.Helpers
 {
-    /// <summary>
-    /// An implementation of <see cref="ObjectCache{T}"/> for <see cref="StringBuilder"/>
-    /// </summary>
-    /// <seealso cref="Markdig.Helpers.ObjectCache{StringBuilder}" />
-    public class StringBuilderCache : DefaultObjectCache<StringBuilder>
+    public static class StringBuilderCache
     {
         /// <summary>
         /// A StringBuilder that can be used locally in a method body only.
@@ -31,13 +27,5 @@ namespace Markdig.Helpers
             }
             return sb;
         }
-
-        protected override void Reset(StringBuilder instance)
-        {
-            if (instance.Length > 0)
-            {
-                instance.Length = 0;
-            }
-        }
     }
 }

src/Markdig/Helpers/StringBuilderExtensions.cs

@@ -6,7 +6,7 @@ using System.Text;
 namespace Markdig.Helpers
 {
     /// <summary>
-    /// Extensions for StringBuilder with <see cref="StringSlice"/>
+    /// Extensions for StringBuilder
     /// </summary>
     public static class StringBuilderExtensions
     {
@@ -19,5 +19,12 @@ namespace Markdig.Helpers
         {
             return builder.Append(slice.Text, slice.Start, slice.Length);
         }
+
+        internal static string GetStringAndReset(this StringBuilder builder)
+        {
+            string text = builder.ToString();
+            builder.Length = 0;
+            return text;
+        }
     }
 }

src/Markdig/Helpers/StringLine.cs

@@ -77,7 +77,7 @@ namespace Markdig.Helpers
             return line.Slice;
         }
 
-        public override string ToString()
+        public readonly override string ToString()
         {
             return Slice.ToString();
         }

src/Markdig/Helpers/StringLineGroup.cs

@@ -7,24 +7,27 @@ using System.Collections;
 using System.Collections.Generic;
 using System.Diagnostics;
 using System.Runtime.CompilerServices;
-using Markdig.Extensions.Tables;
 
 namespace Markdig.Helpers
 {
     /// <summary>
     /// A group of <see cref="StringLine"/>.
     /// </summary>
-    /// <seealso cref="System.Collections.IEnumerable" />
+    /// <seealso cref="IEnumerable" />
     public struct StringLineGroup : IEnumerable
     {
+        // Feel free to change these numbers if you see a positive change
+        private static readonly CustomArrayPool<StringLine> _pool
+            = new CustomArrayPool<StringLine>(512, 386, 128, 64);
+
         /// <summary>
         /// Initializes a new instance of the <see cref="StringLineGroup"/> class.
         /// </summary>
         /// <param name="capacity"></param>
-        public StringLineGroup(int capacity)
+        public StringLineGroup(int capacity, bool willRelease = false)
         {
-            if (capacity <= 0) throw new ArgumentOutOfRangeException(nameof(capacity));
-            Lines = new StringLine[capacity];
+            if (capacity <= 0) ThrowHelper.ArgumentOutOfRangeException(nameof(capacity));
+            Lines = _pool.Rent(willRelease ? Math.Max(8, capacity) : capacity);
             Count = 0;
         }
 
@@ -35,7 +38,7 @@ namespace Markdig.Helpers
         /// <exception cref="System.ArgumentNullException"></exception>
         public StringLineGroup(string text)
         {
-            if (text == null) throw new ArgumentNullException(nameof(text));
+            if (text == null) ThrowHelper.ArgumentNullException_text();
             Lines = new StringLine[1];
             Count = 0;
             Add(new StringSlice(text));
@@ -66,23 +69,20 @@ namespace Markdig.Helpers
         /// <param name="index">The index.</param>
         public void RemoveAt(int index)
         {
-            if (Count - 1 == index)
-            {
-                Count--;
-            }
-            else
+            if (index != Count - 1)
             {
                 Array.Copy(Lines, index + 1, Lines, index, Count - index - 1);
-                Lines[Count - 1] = new StringLine();
-                Count--;
             }
+
+            Lines[Count - 1] = new StringLine();
+            Count--;
         }
 
         /// <summary>
         /// Adds the specified line to this instance.
         /// </summary>
         /// <param name="line">The line.</param>
-        [MethodImpl(MethodImplOptionPortable.AggressiveInlining)]
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void Add(ref StringLine line)
         {
             if (Count == Lines.Length) IncreaseCapacity();
@@ -93,14 +93,14 @@ namespace Markdig.Helpers
         /// Adds the specified slice to this instance.
         /// </summary>
         /// <param name="slice">The slice.</param>
-        [MethodImpl(MethodImplOptionPortable.AggressiveInlining)]
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void Add(StringSlice slice)
         {
             if (Count == Lines.Length) IncreaseCapacity();
             Lines[Count++] = new StringLine(ref slice);
         }
 
-        public override string ToString()
+        public readonly override string ToString()
         {
             return ToSlice().ToString();
         }
@@ -110,22 +110,24 @@ namespace Markdig.Helpers
         /// </summary>
         /// <param name="lineOffsets">The position of the `\n` line offsets from the beginning of the returned slice.</param>
         /// <returns>A single slice concatenating the lines of this instance</returns>
-        public StringSlice ToSlice(List<LineOffset> lineOffsets = null)
+        public readonly StringSlice ToSlice(List<LineOffset> lineOffsets = null)
         {
+            // Optimization case for a single line.
+            if (Count == 1)
+            {
+                lineOffsets?.Add(new LineOffset(Lines[0].Position, Lines[0].Column, Lines[0].Slice.Start - Lines[0].Position, Lines[0].Slice.Start, Lines[0].Slice.End + 1));
+                return Lines[0];
+            }
+
             // Optimization case when no lines
             if (Count == 0)
             {
                 return new StringSlice(string.Empty);
             }
 
-            // Optimization case for a single line.
-            if (Count == 1)
+            if (lineOffsets != null && lineOffsets.Capacity < lineOffsets.Count + Count)
             {
-                if (lineOffsets != null)
-                {
-                    lineOffsets.Add(new LineOffset(Lines[0].Position, Lines[0].Column, Lines[0].Slice.Start - Lines[0].Position, Lines[0].Slice.Start, Lines[0].Slice.End + 1));
-                }
-                return Lines[0];
+                lineOffsets.Capacity = Math.Max(lineOffsets.Count + Count, lineOffsets.Capacity * 2);
             }
 
             // Else use a builder
@@ -135,32 +137,25 @@ namespace Markdig.Helpers
             {
                 if (i > 0)
                 {
-                    if (lineOffsets != null)
-                    {
-                        lineOffsets.Add(new LineOffset(Lines[i - 1].Position, Lines[i - 1].Column, Lines[i - 1].Slice.Start - Lines[i - 1].Position, previousStartOfLine, builder.Length));
-                    }
                     builder.Append('\n');
                     previousStartOfLine = builder.Length;
                 }
-                if (!Lines[i].Slice.IsEmpty)
+                ref var line = ref Lines[i];
+                if (!line.Slice.IsEmpty)
                 {
-                    builder.Append(Lines[i].Slice.Text, Lines[i].Slice.Start, Lines[i].Slice.Length);
+                    builder.Append(line.Slice.Text, line.Slice.Start, line.Slice.Length);
                 }
+
+                lineOffsets?.Add(new LineOffset(line.Position, line.Column, line.Slice.Start - line.Position, previousStartOfLine, builder.Length));
             }
-            if (lineOffsets != null)
-            {
-                lineOffsets.Add(new LineOffset(Lines[Count - 1].Position, Lines[Count - 1].Column, Lines[Count - 1].Slice.Start - Lines[Count - 1].Position, previousStartOfLine, builder.Length));
-            }
-            var str = builder.ToString();
-            builder.Length = 0;
-            return new StringSlice(str);
+            return new StringSlice(builder.GetStringAndReset());
         }
 
         /// <summary>
         /// Converts this instance into a <see cref="ICharIterator"/>.
         /// </summary>
         /// <returns></returns>
-        public Iterator ToCharIterator()
+        public readonly Iterator ToCharIterator()
         {
             return new Iterator(this);
         }
@@ -183,14 +178,24 @@ namespace Markdig.Helpers
 
         private void IncreaseCapacity()
         {
-            var newItems = new StringLine[Lines.Length * 2];
+            var newItems = _pool.Rent(Lines.Length * 2);
             if (Count > 0)
             {
                 Array.Copy(Lines, 0, newItems, 0, Count);
+                Array.Clear(Lines, 0, Count);
             }
+            _pool.Return(Lines);
             Lines = newItems;
         }
 
+        internal void Release()
+        {
+            Array.Clear(Lines, 0, Count);
+            _pool.Return(Lines);
+            Lines = null;
+            Count = -1;
+        }
+
         /// <summary>
         /// The iterator used to iterate other the lines.
         /// </summary>
@@ -207,7 +212,7 @@ namespace Markdig.Helpers
                 _offset = -1;
                 SliceIndex = 0;
                 CurrentChar = '\0';
-                End = -2; 
+                End = -2;
                 for (int i = 0; i < lines.Count; i++)
                 {
                     End += lines.Lines[i].Slice.Length + 1; // Add chars
@@ -221,7 +226,7 @@ namespace Markdig.Helpers
 
             public int End { get; private set; }
 
-            public bool IsEmpty => Start > End;
+            public readonly bool IsEmpty => Start > End;
 
             public int SliceIndex { get; private set; }
 
@@ -252,10 +257,10 @@ namespace Markdig.Helpers
             public char NextChar()
             {
                 Start++;
-                _offset++;
                 if (Start <= End)
                 {
-                    var slice = (StringSlice)_lines.Lines[SliceIndex];
+                    var slice = _lines.Lines[SliceIndex].Slice;
+                    _offset++;
                     if (_offset < slice.Length)
                     {
                         CurrentChar = slice[slice.Start + _offset];
@@ -272,43 +277,54 @@ namespace Markdig.Helpers
                     CurrentChar = '\0';
                     Start = End + 1;
                     SliceIndex = _lines.Count;
-                    _offset--;
                 }
                 return CurrentChar;
             }
 
-            public char PeekChar(int offset = 1)
+            public readonly char PeekChar(int offset = 1)
             {
-                if (offset < 0) throw new ArgumentOutOfRangeException("Negative offset are not supported for StringLineGroup", nameof(offset));
+                if (offset < 0) ThrowHelper.ArgumentOutOfRangeException("Negative offset are not supported for StringLineGroup", nameof(offset));
 
                 if (Start + offset > End)
                 {
                     return '\0';
                 }
 
-                var slice = (StringSlice)_lines.Lines[SliceIndex];
-                if (_offset + offset >= slice.Length)
+                offset += _offset;
+
+                int sliceIndex = SliceIndex;
+                var slice = _lines.Lines[sliceIndex].Slice;
+
+                while (offset > slice.Length)
+                {
+                    // We are not peeking at the same line
+                    offset -= slice.Length + 1; // + 1 for new line
+
+                    Debug.Assert(sliceIndex + 1 < _lines.Lines.Length, "'Start + offset > End' check above should prevent us from indexing out of range");
+                    slice = _lines.Lines[++sliceIndex].Slice;
+                }
+
+                if (offset == slice.Length)
                 {
                     return '\n';
                 }
 
-                return slice[slice.Start + _offset + offset];
+                Debug.Assert(offset < slice.Length);
+                return slice[slice.Start + offset];
             }
 
             public bool TrimStart()
             {
                 var c = CurrentChar;
-                bool hasSpaces = false;
                 while (c.IsWhitespace())
                 {
-                    hasSpaces = true;
                     c = NextChar();
                 }
-                return hasSpaces;
+                return IsEmpty;
             }
         }
 
-        public struct LineOffset
+        public readonly struct LineOffset
         {
             public LineOffset(int linePosition, int column, int offset, int start, int end)
             {

src/Markdig/Helpers/StringSlice.cs

@@ -38,7 +38,9 @@ namespace Markdig.Helpers
         /// <exception cref="System.ArgumentNullException"></exception>
         public StringSlice(string text, int start, int end)
         {
-            if (text == null) throw new ArgumentNullException(nameof(text));
+            if (text is null)
+                ThrowHelper.ArgumentNullException_text();
+
             Text = text;
             Start = start;
             End = end;
@@ -52,34 +54,50 @@ namespace Markdig.Helpers
         /// <summary>
         /// Gets or sets the start position within <see cref="Text"/>.
         /// </summary>
-        public int Start { get; set; }
+        public int Start { readonly get; set; }
 
         /// <summary>
         /// Gets or sets the end position (inclusive) within <see cref="Text"/>.
         /// </summary>
-        public int End { get; set; }
+        public int End { readonly get; set; }
 
         /// <summary>
         /// Gets the length.
         /// </summary>
-        public int Length => End - Start + 1;
+        public readonly int Length => End - Start + 1;
 
         /// <summary>
         /// Gets the current character.
         /// </summary>
-        public char CurrentChar => Start <= End ? this[Start] : '\0';
+        public readonly char CurrentChar
+        {
+            get
+            {
+                int start = Start;
+                return start <= End ? Text[start] : '\0';
+            }
+        }
 
         /// <summary>
         /// Gets a value indicating whether this instance is empty.
         /// </summary>
-        public bool IsEmpty => Start > End;
+        public readonly bool IsEmpty
+        {
+            [MethodImpl(MethodImplOptions.AggressiveInlining)]
+            get => Start > End;
+        }
 
         /// <summary>
         /// Gets the <see cref="System.Char"/> at the specified index.
         /// </summary>
         /// <param name="index">The index.</param>
         /// <returns>A character in the slice at the specified index (not from <see cref="Start"/> but from the begining of the slice)</returns>
-        public char this[int index] => Text[index];
+        public readonly char this[int index]
+        {
+            [MethodImpl(MethodImplOptions.AggressiveInlining)]
+            get => Text[index];
+        }
+
 
         /// <summary>
         /// Goes to the next character, incrementing the <see cref="Start" /> position.
@@ -87,16 +105,30 @@ namespace Markdig.Helpers
         /// <returns>
         /// The next character. `\0` is end of the iteration.
         /// </returns>
-        [MethodImpl(MethodImplOptionPortable.AggressiveInlining)]
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public char NextChar()
         {
-            Start++;
-            if (Start > End)
+            int start = Start;
+            if (start >= End)
             {
                 Start = End + 1;
                 return '\0';
             }
-            return Text[Start];
+            start++;
+            Start = start;
+            return Text[start];
+        }
+
+        /// <summary>
+        /// Peeks a character at the offset of 1 from the current <see cref="Start"/> position
+        /// inside the range <see cref="Start"/> and <see cref="End"/>, returns `\0` if outside this range.
+        /// </summary>
+        /// <returns>The character at offset, returns `\0` if none.</returns>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public readonly char PeekChar()
+        {
+            int index = Start + 1;
+            return index <= End ? Text[index] : '\0';
         }
 
         /// <summary>
@@ -105,21 +137,22 @@ namespace Markdig.Helpers
         /// </summary>
         /// <param name="offset">The offset.</param>
         /// <returns>The character at offset, returns `\0` if none.</returns>
-        [MethodImpl(MethodImplOptionPortable.AggressiveInlining)]
-        public char PeekChar(int offset = 1)
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public readonly char PeekChar(int offset)
         {
             var index = Start + offset;
-            return index >= Start && index <= End ? Text[index] : (char) 0;
+            return index >= Start && index <= End ? Text[index] : '\0';
         }
 
         /// <summary>
         /// Peeks a character at the specified offset from the current beginning of the string, without taking into account <see cref="Start"/> and <see cref="End"/>
         /// </summary>
         /// <returns>The character at offset, returns `\0` if none.</returns>
-        [MethodImpl(MethodImplOptionPortable.AggressiveInlining)]
-        public char PeekCharAbsolute(int index)
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public readonly char PeekCharAbsolute(int index)
         {
-            return index >= 0 && index < Text.Length ? Text[index] : (char)0;
+            string text = Text;
+            return (uint)index < (uint)text.Length ? text[index] : '\0';
         }
 
         /// <summary>
@@ -128,11 +161,12 @@ namespace Markdig.Helpers
         /// </summary>
         /// <param name="offset">The offset.</param>
         /// <returns>The character at offset, returns `\0` if none.</returns>
-        [MethodImpl(MethodImplOptionPortable.AggressiveInlining)]
-        public char PeekCharExtra(int offset)
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public readonly char PeekCharExtra(int offset)
         {
             var index = Start + offset;
-            return index >= 0 && index < Text.Length ? Text[index] : (char)0;
+            var text = Text;
+            return (uint)index < (uint)text.Length ? text[index] : '\0';
         }
 
         /// <summary>
@@ -141,7 +175,7 @@ namespace Markdig.Helpers
         /// <param name="text">The text.</param>
         /// <param name="offset">The offset.</param>
         /// <returns><c>true</c> if the text matches; <c>false</c> otherwise</returns>
-        public bool Match(string text, int offset = 0)
+        public readonly bool Match(string text, int offset = 0)
         {
             return Match(text, End, offset);
         }
@@ -153,19 +187,22 @@ namespace Markdig.Helpers
         /// <param name="end">The end.</param>
         /// <param name="offset">The offset.</param>
         /// <returns><c>true</c> if the text matches; <c>false</c> otherwise</returns>
-        public bool Match(string text, int end, int offset)
+        public readonly bool Match(string text, int end, int offset)
         {
             var index = Start + offset;
-            int i = 0;
-            for (; index <= end && i < text.Length; i++, index++)
+
+            if (end - index + 1 < text.Length)
+                return false;
+
+            string sliceText = Text;
+            for (int i = 0; i < text.Length; i++, index++)
             {
-                if (text[i] != Text[index])
+                if (text[i] != sliceText[index])
                 {
                     return false;
                 }
             }
-
-            return i == text.Length;
+            return true;
         }
 
         /// <summary>
@@ -196,7 +233,7 @@ namespace Markdig.Helpers
         /// <param name="text">The text.</param>
         /// <param name="offset">The offset.</param>
         /// <returns><c>true</c> if the text matches; <c>false</c> otherwise</returns>
-        public bool MatchLowercase(string text, int offset = 0)
+        public readonly bool MatchLowercase(string text, int offset = 0)
         {
             return MatchLowercase(text, End, offset);
         }
@@ -208,19 +245,22 @@ namespace Markdig.Helpers
         /// <param name="end">The end.</param>
         /// <param name="offset">The offset.</param>
         /// <returns><c>true</c> if the text matches; <c>false</c> otherwise</returns>
-        public bool MatchLowercase(string text, int end, int offset)
+        public readonly bool MatchLowercase(string text, int end, int offset)
         {
             var index = Start + offset;
-            int i = 0;
-            for (; index <= end && i < text.Length; i++, index++)
+
+            if (end - index + 1 < text.Length)
+                return false;
+
+            string sliceText = Text;
+            for (int i = 0; i < text.Length; i++, index++)
             {
-                if (text[i] != char.ToLowerInvariant(Text[index]))
+                if (text[i] != char.ToLowerInvariant(sliceText[index]))
                 {
                     return false;
                 }
             }
-
-            return i == text.Length;
+            return true;
         }
 
         /// <summary>
@@ -230,46 +270,30 @@ namespace Markdig.Helpers
         /// <param name="offset">The offset.</param>
         /// <param name="ignoreCase">true if ignore case</param>
         /// <returns><c>true</c> if the text was found; <c>false</c> otherwise</returns>
-        public int IndexOf(string text, int offset = 0, bool ignoreCase = false)
+        public readonly int IndexOf(string text, int offset = 0, bool ignoreCase = false)
         {
-            var end = End - text.Length + 1;
-            if (ignoreCase)
-            {
-                for (int i = Start + offset; i <= end; i++)
-                {
-                    if (MatchLowercase(text, End, i - Start))
-                    {
-                        return i; ;
-                    }
-                }
-            }
-            else
-            {
-                for (int i = Start + offset; i <= end; i++)
-                {
-                    if (Match(text, End, i - Start))
-                    {
-                        return i; ;
-                    }
-                }
-            }
-            return -1;
+            offset += Start;
+            int length = End - offset + 1;
+
+            if (length <= 0)
+                return -1;
+
+            return Text.IndexOf(text, offset, length, ignoreCase ? StringComparison.OrdinalIgnoreCase : StringComparison.Ordinal);
         }
 
         /// <summary>
         /// Searches for the specified character within this slice.
         /// </summary>
         /// <returns>A value >= 0 if the character was found, otherwise &lt; 0</returns>
-        public int IndexOf(char c)
+        public readonly int IndexOf(char c)
         {
-            for (int i = Start; i <= End; i++)
-            {
-                if (Text[i] == c)
-                {
-                    return i;
-                }
-            }
-            return -1;
+            int start = Start;
+            int length = End - start + 1;
+
+            if (length <= 0)
+                return -1;
+
+            return Text.IndexOf(c, start, length);
         }
 
         /// <summary>
@@ -280,16 +304,15 @@ namespace Markdig.Helpers
         /// </returns>
         public bool TrimStart()
         {
-            // Strip leading spaces
-            var start = Start;
-            for (; Start <= End; Start++)
-            {
-                if (!Text[Start].IsWhitespace())
-                {
-                    break;
-                }
-            }
-            return start != Start;
+            string text = Text;
+            int end = End;
+            int i = Start;
+
+            while (i <= end && (uint)i < (uint)text.Length && text[i].IsWhitespace())
+                i++;
+
+            Start = i;
+            return i > end;
         }
 
         /// <summary>
@@ -298,16 +321,15 @@ namespace Markdig.Helpers
         /// <param name="spaceCount">The number of spaces trimmed.</param>
         public void TrimStart(out int spaceCount)
         {
-            spaceCount = 0;
-            // Strip leading spaces
-            for (; Start <= End; Start++)
-            {
-                if (!Text[Start].IsWhitespace())
-                {
-                    break;
-                }
-                spaceCount++;
-            }
+            string text = Text;
+            int end = End;
+            int i = Start;
+
+            while (i <= end && (uint)i < (uint)text.Length && text[i].IsWhitespace())
+                i++;
+
+            spaceCount = i - Start;
+            Start = i;
         }
 
         /// <summary>
@@ -316,14 +338,15 @@ namespace Markdig.Helpers
         /// <returns></returns>
         public bool TrimEnd()
         {
-            for (; Start <= End; End--)
-            {
-                if (!Text[End].IsWhitespace())
-                {
-                    break;
-                }
-            }
-            return IsEmpty;
+            string text = Text;
+            int start = Start;
+            int i = End;
+
+            while (start <= i && (uint)i < (uint)text.Length && text[i].IsWhitespace())
+                i--;
+
+            End = i;
+            return start > i;
         }
 
         /// <summary>
@@ -331,40 +354,51 @@ namespace Markdig.Helpers
         /// </summary>
         public void Trim()
         {
-            TrimStart();
-            TrimEnd();
+            string text = Text;
+            int start = Start;
+            int end = End;
+
+            while (start <= end && (uint)start < (uint)text.Length && text[start].IsWhitespace())
+                start++;
+
+            while (start <= end && (uint)end < (uint)text.Length && text[end].IsWhitespace())
+                end--;
+
+            Start = start;
+            End = end;
         }
 
         /// <summary>
-        /// Returns a <see cref="System.String" /> that represents this instance.
+        /// Returns a <see cref="string" /> that represents this instance.
         /// </summary>
         /// <returns>
-        /// A <see cref="System.String" /> that represents this instance.
+        /// A <see cref="string" /> that represents this instance.
         /// </returns>
-        public override string ToString()
+        public readonly override string ToString()
         {
-            if (Text != null && Start <= End)
-            {
-                var length = Length;
-                if (Start == 0 && Text.Length == length)
-                {
-                    return Text;
-                }
+            string text = Text;
+            int start = Start;
+            int length = End - start + 1;
 
-                return Text.Substring(Start, length);
+            if (text is null || length <= 0)
+            {
+                return string.Empty;
             }
-            return string.Empty;
+            return text.Substring(start, length);
         }
 
         /// <summary>
         /// Determines whether this slice is empty or made only of whitespaces.
         /// </summary>
         /// <returns><c>true</c> if this slice is empty or made only of whitespaces; <c>false</c> otherwise</returns>
-        public bool IsEmptyOrWhitespace()
+        public readonly bool IsEmptyOrWhitespace()
         {
-            for (int i = Start; i <= End; i++)
+            string text = Text;
+            int end = End;
+
+            for (int i = Start; i <= end && (uint)i < (uint)text.Length; i++)
             {
-                if (!Text[i].IsWhitespace())
+                if (!text[i].IsWhitespace())
                 {
                     return false;
                 }

src/Markdig/Helpers/ThrowHelper.cs

@@ -1,26 +1,48 @@
 using System;
 using System.Diagnostics;
+using System.Diagnostics.CodeAnalysis;
 
 namespace Markdig.Helpers
 {
     /// <summary>
     /// Inspired by CoreLib, taken from https://github.com/MihaZupan/SharpCollections, cc @MihaZupan
     /// </summary>
+    [ExcludeFromCodeCoverage]
     internal static class ThrowHelper
     {
+        public static void ArgumentNullException(string paramName) => throw new ArgumentNullException(paramName);
+        public static void ArgumentNullException_item() => throw new ArgumentNullException("item");
+        public static void ArgumentNullException_text() => throw new ArgumentNullException("text");
+        public static void ArgumentNullException_label() => throw new ArgumentNullException("label");
+        public static void ArgumentNullException_key() => throw new ArgumentNullException("key");
+        public static void ArgumentNullException_name() => throw new ArgumentNullException("name");
+        public static void ArgumentNullException_markdown() => throw new ArgumentNullException("markdown");
+        public static void ArgumentNullException_writer() => throw new ArgumentNullException("writer");
+        public static void ArgumentNullException_leafBlock() => throw new ArgumentNullException("leafBlock");
+        public static void ArgumentNullException_markdownObject() => throw new ArgumentNullException("markdownObject");
+
+        public static void ArgumentException(string message) => throw new ArgumentException(message);
+        public static void ArgumentException(string message, string paramName) => throw new ArgumentException(message, paramName);
+
+        public static void ArgumentOutOfRangeException(string paramName) => throw new ArgumentOutOfRangeException(paramName);
+        public static void ArgumentOutOfRangeException(string message, string paramName) => throw new ArgumentOutOfRangeException(message, paramName);
+        public static void ArgumentOutOfRangeException_index() => throw new ArgumentOutOfRangeException("index");
+
+        public static void InvalidOperationException(string message) => throw new InvalidOperationException(message);
+
         public static void ThrowArgumentNullException(ExceptionArgument argument)
         {
-            throw new ArgumentNullException(GetArgumentName(argument));
+            throw new ArgumentNullException(argument.ToString());
         }
 
         public static void ThrowArgumentException(ExceptionArgument argument, ExceptionReason reason)
         {
-            throw new ArgumentException(GetArgumentName(argument), GetExceptionReason(reason));
+            throw new ArgumentException(argument.ToString(), GetExceptionReason(reason));
         }
 
         public static void ThrowArgumentOutOfRangeException(ExceptionArgument argument, ExceptionReason reason)
         {
-            throw new ArgumentOutOfRangeException(GetArgumentName(argument), GetExceptionReason(reason));
+            throw new ArgumentOutOfRangeException(argument.ToString(), GetExceptionReason(reason));
         }
 
         public static void ThrowIndexOutOfRangeException()
@@ -28,25 +50,6 @@ namespace Markdig.Helpers
             throw new IndexOutOfRangeException();
         }
 
-        private static string GetArgumentName(ExceptionArgument argument)
-        {
-            switch (argument)
-            {
-                case ExceptionArgument.key:
-                case ExceptionArgument.input:
-                case ExceptionArgument.value:
-                case ExceptionArgument.length:
-                case ExceptionArgument.text:
-                    return argument.ToString();
-
-                case ExceptionArgument.offsetLength:
-                    return "offset and length";
-
-                default:
-                    Debug.Assert(false, "The enum value is not defined, please check the ExceptionArgument Enum.");
-                    return "";
-            }
-        }
         private static string GetExceptionReason(ExceptionReason reason)
         {
             switch (reason)

src/Markdig/Markdig.csproj

@@ -1,84 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk">
-
   <PropertyGroup>
-    <Description>A fast, powerful, CommonMark compliant, extensible Markdown processor for .NET with 20+ builtin extensions (pipetables, footnotes, definition lists... etc.)</Description>
-    <Copyright>Alexandre Mutel</Copyright>
-    <AssemblyTitle>Markdig</AssemblyTitle>
-    <NeutralLanguage>en-US</NeutralLanguage>
-    <VersionPrefix>0.17.0</VersionPrefix>
-    <Authors>Alexandre Mutel</Authors>
-    <TargetFrameworks>net35;net40;netstandard2.0;uap10.0;netcoreapp2.1</TargetFrameworks>
-    <AssemblyName>Markdig</AssemblyName>
     <PackageId>Markdig</PackageId>
-    <PackageId Condition="'$(SignAssembly)' == 'true'">Markdig.Signed</PackageId>
-    <PackageTags>Markdown CommonMark md html md2html</PackageTags>
-    <PackageReleaseNotes>https://github.com/lunet-io/markdig/blob/master/changelog.md</PackageReleaseNotes>
-    <PackageLicenseExpression>BSD-2-Clause</PackageLicenseExpression>
-    <PackageIconUrl>https://raw.githubusercontent.com/lunet-io/markdig/master/img/markdig.png</PackageIconUrl>
-    <PackageProjectUrl>https://github.com/lunet-io/markdig</PackageProjectUrl>
-    <NetStandardImplicitPackageVersion Condition=" '$(TargetFramework)' == 'netstandard1.1' ">1.6.0</NetStandardImplicitPackageVersion>
-    <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
-    <LangVersion>7.3</LangVersion>
   </PropertyGroup>
-
-  <ItemGroup Condition=" '$(TargetFramework)' == 'net35' ">
-    <Reference Include="mscorlib" />
-    <Reference Include="System" />
-    <Reference Include="System.Core" />
-  </ItemGroup>
-
-  <ItemGroup Condition=" '$(TargetFramework)' == 'net40' ">
-    <Reference Include="mscorlib" />
-    <Reference Include="System" />
-    <Reference Include="System.Core" />
-    <Reference Include="Microsoft.CSharp" />
-  </ItemGroup>
-
-  <ItemGroup Condition=" '$(TargetFramework)' == 'portable40-net40+sl5+win8+wp8+wpa81' ">
-    <Reference Include="mscorlib" />
-    <Reference Include="System" />
-    <Reference Include="System.Core" />
-  </ItemGroup>
-
-  <PropertyGroup Condition=" '$(TargetFramework)' == 'net35' ">
-    <DefineConstants>$(DefineConstants);SUPPORT_FIXED_STRING;SUPPORT_UNSAFE</DefineConstants>
-  </PropertyGroup>
-
-  <PropertyGroup Condition=" '$(TargetFramework)' == 'net40' ">
-    <DefineConstants>$(DefineConstants);SUPPORT_FIXED_STRING;SUPPORT_UNSAFE</DefineConstants>
-  </PropertyGroup>
-
-  <PropertyGroup Condition=" '$(TargetFramework)' == 'netstandard2.0' ">
-    <DefineConstants>$(DefineConstants);SUPPORT_FIXED_STRING;SUPPORT_UNSAFE</DefineConstants>
-  </PropertyGroup>
- 
-  <PropertyGroup Condition=" '$(TargetFramework)' == 'netcoreapp2.1' ">
-    <DefineConstants>$(DefineConstants);SUPPORT_FIXED_STRING;SUPPORT_UNSAFE;NETCORE</DefineConstants>
-  </PropertyGroup>
-
-  <PropertyGroup Condition=" '$(TargetFramework)' == 'uap10.0' ">
-    <TargetPlatformIdentifier>UAP</TargetPlatformIdentifier>
-    <TargetPlatformVersion Condition="'$(TargetPlatformVersion)' == ''">10.0.17763.0</TargetPlatformVersion>
-    <TargetPlatformMinVersion Condition="'$(TargetPlatformMinVersion)' == ''">10.0.10240.0</TargetPlatformMinVersion>
-    <DefineConstants>$(DefineConstants);NETSTANDARD_11;SUPPORT_UNSAFE</DefineConstants>
-  </PropertyGroup>
-
-  <PropertyGroup Condition=" '$(Configuration)' == 'Release' ">
-    <NoWarn>$(NoWarn);CS1591</NoWarn>
-    <GenerateDocumentationFile>true</GenerateDocumentationFile>
-  </PropertyGroup>
-
-  <PropertyGroup Condition=" '$(SignAssembly)' == 'true' ">
-    <AssemblyOriginatorKeyFile>key.snk</AssemblyOriginatorKeyFile>
-    <PublicSign Condition=" '$(OS)' != 'Windows_NT' ">true</PublicSign>
-  </PropertyGroup>
-
-  <!-- Special packages and imports for UWP support -->
-  <ItemGroup>
-    <PackageReference Include="MSBuild.Sdk.Extras" Version="1.0.9" PrivateAssets="all" />
-  </ItemGroup>
-  <ItemGroup Condition=" '$(TargetFramework)' == 'uap10.0' ">
-    <PackageReference Include="Microsoft.NETCore.UniversalWindowsPlatform " Version="5.2.2" />
-  </ItemGroup>
-  <Import Project="$(MSBuildSDKExtrasTargets)" Condition="Exists('$(MSBuildSDKExtrasTargets)')" />
+  <Import Project="Markdig.targets" />
 </Project>

src/Markdig/Markdig.targets

@@ -0,0 +1,48 @@
+<?xml version="1.0" encoding="utf-8"?>
+<Project ToolsVersion="15.0" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
+  <PropertyGroup>
+    <Description>A fast, powerful, CommonMark compliant, extensible Markdown processor for .NET with 20+ builtin extensions (pipetables, footnotes, definition lists... etc.)</Description>
+    <Copyright>Alexandre Mutel</Copyright>
+    <NeutralLanguage>en-US</NeutralLanguage>
+    <VersionPrefix>0.20.0</VersionPrefix>
+    <Authors>Alexandre Mutel</Authors>
+    <TargetFrameworks>netstandard2.0;netstandard2.1;netcoreapp2.1;netcoreapp3.1</TargetFrameworks>
+    <PackageTags>Markdown CommonMark md html md2html</PackageTags>
+    <PackageReleaseNotes>https://github.com/lunet-io/markdig/blob/master/changelog.md</PackageReleaseNotes>
+    <PackageLicenseExpression>BSD-2-Clause</PackageLicenseExpression>
+    <PackageIconUrl>https://raw.githubusercontent.com/lunet-io/markdig/master/img/markdig.png</PackageIconUrl>
+    <PackageProjectUrl>https://github.com/lunet-io/markdig</PackageProjectUrl>
+    <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
+    <LangVersion>8.0</LangVersion>
+    <!--Add support for sourcelink-->
+    <PublishRepositoryUrl>true</PublishRepositoryUrl>
+    <IncludeSymbols>true</IncludeSymbols>
+    <SymbolPackageFormat>snupkg</SymbolPackageFormat>
+  </PropertyGroup>
+
+  <ItemGroup Condition=" '$(TargetFramework)' == 'netstandard2.0' ">
+    <PackageReference Include="System.Memory" Version="4.5.4" />
+  </ItemGroup>
+
+  <PropertyGroup Condition=" '$(TargetFramework)' == 'netstandard2.1' ">
+    <DefineConstants>$(DefineConstants);NETCORE</DefineConstants>
+  </PropertyGroup>
+
+  <PropertyGroup Condition=" '$(TargetFramework)' == 'netcoreapp2.1' ">
+    <DefineConstants>$(DefineConstants);NETCORE</DefineConstants>
+  </PropertyGroup>
+
+  <PropertyGroup Condition=" '$(TargetFramework)' == 'netcoreapp3.1' ">
+    <DefineConstants>$(DefineConstants);NETCORE</DefineConstants>
+  </PropertyGroup>
+
+  <PropertyGroup Condition=" '$(Configuration)' == 'Release' ">
+    <NoWarn>$(NoWarn);CS1591</NoWarn>
+    <GenerateDocumentationFile>true</GenerateDocumentationFile>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="Microsoft.SourceLink.GitHub" Version="1.0.*" PrivateAssets="All"/>
+  </ItemGroup>
+
+</Project>

src/Markdig/Markdown.cs

@@ -5,6 +5,7 @@ using System;
 using System.IO;
 using System.Reflection;
 using Markdig.Extensions.SelfPipeline;
+using Markdig.Helpers;
 using Markdig.Parsers;
 using Markdig.Renderers;
 using Markdig.Renderers.Normalize;
@@ -17,11 +18,7 @@ namespace Markdig
     /// </summary>
     public static partial class Markdown
     {
-#if NETSTANDARD_11
-        public static readonly string Version = typeof(Markdown).GetTypeInfo().Assembly.GetCustomAttribute<AssemblyFileVersionAttribute>().Version;
-#else
         public static readonly string Version = ((AssemblyFileVersionAttribute) typeof(Markdown).Assembly.GetCustomAttributes(typeof(AssemblyFileVersionAttribute), false)[0]).Version;
-#endif
 
         /// <summary>
         /// Normalizes the specified markdown to a normalized markdown text.
@@ -72,10 +69,19 @@ namespace Markdig
         /// <exception cref="System.ArgumentNullException">if markdown variable is null</exception>
         public static string ToHtml(string markdown, MarkdownPipeline pipeline = null)
         {
-            if (markdown == null) throw new ArgumentNullException(nameof(markdown));
-            var writer = new StringWriter();
-            ToHtml(markdown, writer, pipeline);
-            return writer.ToString();
+            if (markdown == null) ThrowHelper.ArgumentNullException_markdown();
+            pipeline ??= new MarkdownPipelineBuilder().Build();
+            pipeline = CheckForSelfPipeline(pipeline, markdown);
+
+            var renderer = pipeline.GetCacheableHtmlRenderer();
+
+            var document = Parse(markdown, pipeline);
+            renderer.Render(document);
+            renderer.Writer.Flush();
+
+            string html = renderer.Writer.ToString();
+            pipeline.ReleaseCacheableHtmlRenderer(renderer);
+            return html;
         }
 
         /// <summary>
@@ -89,9 +95,9 @@ namespace Markdig
         /// <exception cref="System.ArgumentNullException">if reader or writer variable are null</exception>
         public static MarkdownDocument ToHtml(string markdown, TextWriter writer, MarkdownPipeline pipeline = null, MarkdownParserContext context = null)
         {
-            if (markdown == null) throw new ArgumentNullException(nameof(markdown));
-            if (writer == null) throw new ArgumentNullException(nameof(writer));
-            pipeline = pipeline ?? new MarkdownPipelineBuilder().Build();
+            if (markdown == null) ThrowHelper.ArgumentNullException_markdown();
+            if (writer == null) ThrowHelper.ArgumentNullException_writer();
+            pipeline ??= new MarkdownPipelineBuilder().Build();
             pipeline = CheckForSelfPipeline(pipeline, markdown);
 
             // We override the renderer with our own writer
@@ -115,9 +121,9 @@ namespace Markdig
         /// <exception cref="System.ArgumentNullException">if markdown or writer variable are null</exception>
         public static object Convert(string markdown, IMarkdownRenderer renderer, MarkdownPipeline pipeline = null, MarkdownParserContext context = null)
         {
-            if (markdown == null) throw new ArgumentNullException(nameof(markdown));
-            if (renderer == null) throw new ArgumentNullException(nameof(renderer));
-            pipeline = pipeline ?? new MarkdownPipelineBuilder().Build();
+            if (markdown == null) ThrowHelper.ArgumentNullException_markdown();
+            if (renderer == null) ThrowHelper.ArgumentNullException(nameof(renderer));
+            pipeline ??= new MarkdownPipelineBuilder().Build();
 
             pipeline = CheckForSelfPipeline(pipeline, markdown);
             var document = Parse(markdown, pipeline, context);
@@ -133,7 +139,7 @@ namespace Markdig
         /// <exception cref="System.ArgumentNullException">if markdown variable is null</exception>
         public static MarkdownDocument Parse(string markdown)
         {
-            if (markdown == null) throw new ArgumentNullException(nameof(markdown));
+            if (markdown == null) ThrowHelper.ArgumentNullException_markdown();
             return Parse(markdown, null);
         }
 
@@ -147,8 +153,8 @@ namespace Markdig
         /// <exception cref="System.ArgumentNullException">if markdown variable is null</exception>
         public static MarkdownDocument Parse(string markdown, MarkdownPipeline pipeline, MarkdownParserContext context = null)
         {
-            if (markdown == null) throw new ArgumentNullException(nameof(markdown));
-            pipeline = pipeline ?? new MarkdownPipelineBuilder().Build();
+            if (markdown == null) ThrowHelper.ArgumentNullException_markdown();
+            pipeline ??= new MarkdownPipelineBuilder().Build();
 
             pipeline = CheckForSelfPipeline(pipeline, markdown);
             return MarkdownParser.Parse(markdown, pipeline, context);
@@ -175,16 +181,17 @@ namespace Markdig
         /// <exception cref="System.ArgumentNullException">if reader or writer variable are null</exception>
         public static MarkdownDocument ToPlainText(string markdown, TextWriter writer, MarkdownPipeline pipeline = null, MarkdownParserContext context = null)
         {
-            if (markdown == null) throw new ArgumentNullException(nameof(markdown));
-            if (writer == null) throw new ArgumentNullException(nameof(writer));
-            pipeline = pipeline ?? new MarkdownPipelineBuilder().Build();
+            if (markdown == null) ThrowHelper.ArgumentNullException_markdown();
+            if (writer == null) ThrowHelper.ArgumentNullException_writer();
+            pipeline ??= new MarkdownPipelineBuilder().Build();
             pipeline = CheckForSelfPipeline(pipeline, markdown);
 
             // We override the renderer with our own writer
             var renderer = new HtmlRenderer(writer)
             {
                 EnableHtmlForBlock = false,
-                EnableHtmlForInline = false
+                EnableHtmlForInline = false,
+                EnableHtmlEscape = false,
             };
             pipeline.Setup(renderer);
 
@@ -205,7 +212,7 @@ namespace Markdig
         /// <exception cref="System.ArgumentNullException">if markdown variable is null</exception>
         public static string ToPlainText(string markdown, MarkdownPipeline pipeline = null, MarkdownParserContext context = null)
         {
-            if (markdown == null) throw new ArgumentNullException(nameof(markdown));
+            if (markdown == null) ThrowHelper.ArgumentNullException_markdown();
             var writer = new StringWriter();
             ToPlainText(markdown, writer, pipeline, context);
             return writer.ToString();

src/Markdig/MarkdownExtensions.cs

@@ -34,7 +34,8 @@ using Markdig.Extensions.Yaml;
 using Markdig.Parsers;
 using Markdig.Parsers.Inlines;
 using Markdig.Extensions.Globalization;
-
+using Markdig.Helpers;
+
 namespace Markdig
 {
     /// <summary>
@@ -92,8 +93,8 @@ namespace Markdig
                 .UseDiagrams()
                 .UseAutoLinks()
                 .UseGenericAttributes(); // Must be last as it is one parser that is modifying other parsers
-        }
-        
+        }
+
         /// <summary>
         /// Uses this extension to enable autolinks from text `http://`, `https://`, `ftp://`, `mailto:`, `www.xxx.yyy`
         /// </summary>
@@ -138,7 +139,7 @@ namespace Markdig
         {
             if (pipeline.Extensions.Count != 0)
             {
-                throw new InvalidOperationException("The SelfPipeline extension cannot be used with other extensions");
+                ThrowHelper.InvalidOperationException("The SelfPipeline extension cannot be used with other extensions");
             }
 
             pipeline.Extensions.Add(new SelfPipelineExtension(defaultTag, defaultExtensions));
@@ -421,20 +422,35 @@ namespace Markdig
         }
 
         /// <summary>
-        /// Uses the emoji and smiley extension.
+        /// Uses the emojis and smileys extension.
         /// </summary>
         /// <param name="pipeline">The pipeline.</param>
-        /// <param name="enableSmiley">Enable smiley in addition to Emoji, <c>true</c> by default.</param>
+        /// <param name="enableSmileys">Enable smileys in addition to emoji shortcodes, <c>true</c> by default.</param>
         /// <returns>The modified pipeline</returns>
-        public static MarkdownPipelineBuilder UseEmojiAndSmiley(this MarkdownPipelineBuilder pipeline, bool enableSmiley = true)
+        public static MarkdownPipelineBuilder UseEmojiAndSmiley(this MarkdownPipelineBuilder pipeline, bool enableSmileys = true)
         {
             if (!pipeline.Extensions.Contains<EmojiExtension>())
             {
-                pipeline.Extensions.Add(new EmojiExtension(enableSmiley));
+                var emojiMapping = enableSmileys ? EmojiMapping.DefaultEmojisAndSmileysMapping : EmojiMapping.DefaultEmojisOnlyMapping;
+                pipeline.Extensions.Add(new EmojiExtension(emojiMapping));
             }
             return pipeline;
         }
 
+        /// <summary>
+        /// Uses the emojis and smileys extension.
+        /// </summary>
+        /// <param name="pipeline">The pipeline.</param>
+        /// <param name="customEmojiMapping">Enable customization of the emojis and smileys mapping.</param>
+        /// <returns>The modified pipeline</returns>
+        public static MarkdownPipelineBuilder UseEmojiAndSmiley(this MarkdownPipelineBuilder pipeline, EmojiMapping customEmojiMapping)
+        {
+            if (!pipeline.Extensions.Contains<EmojiExtension>())
+            {
+                pipeline.Extensions.Add(new EmojiExtension(customEmojiMapping));
+            }
+            return pipeline;
+        }
         /// <summary>
         /// Add rel=nofollow to all links rendered to HTML.
         /// </summary>

src/Markdig/MarkdownParserContext.cs

@@ -5,7 +5,7 @@ namespace Markdig
     /// <summary>
     /// Provides a context that can be used as part of parsing Markdown documents.
     /// </summary>
-    public sealed class MarkdownParserContext
+    public class MarkdownParserContext
     {
         /// <summary>
         /// Gets or sets the context property collection.

src/Markdig/MarkdownPipeline.cs

@@ -1,4 +1,4 @@
-// Copyright (c) Alexandre Mutel. All rights reserved.
+// Copyright (c) Alexandre Mutel. All rights reserved.
 // This file is licensed under the BSD-Clause 2 license. 
 // See the license.txt file in the project root for more information.
 using System;
@@ -20,15 +20,14 @@ namespace Markdig
         /// <summary>
         /// Initializes a new instance of the <see cref="MarkdownPipeline" /> class.
         /// </summary>
-        internal MarkdownPipeline(OrderedList<IMarkdownExtension> extensions, BlockParserList blockParsers, InlineParserList inlineParsers, StringBuilderCache cache, TextWriter debugLog, ProcessDocumentDelegate documentProcessed)
+        internal MarkdownPipeline(OrderedList<IMarkdownExtension> extensions, BlockParserList blockParsers, InlineParserList inlineParsers, TextWriter debugLog, ProcessDocumentDelegate documentProcessed)
         {
-            if (blockParsers == null) throw new ArgumentNullException(nameof(blockParsers));
-            if (inlineParsers == null) throw new ArgumentNullException(nameof(inlineParsers));
+            if (blockParsers == null) ThrowHelper.ArgumentNullException(nameof(blockParsers));
+            if (inlineParsers == null) ThrowHelper.ArgumentNullException(nameof(inlineParsers));
             // Add all default parsers
             Extensions = extensions;
             BlockParsers = blockParsers;
             InlineParsers = inlineParsers;
-            StringBuilderCache = cache;
             DebugLog = debugLog;
             DocumentProcessed = documentProcessed;
         }
@@ -44,8 +43,6 @@ namespace Markdig
 
         internal InlineParserList InlineParsers { get; }
 
-        internal StringBuilderCache StringBuilderCache { get; }
-
         // TODO: Move the log to a better place
         internal TextWriter DebugLog { get; }
 
@@ -57,11 +54,48 @@ namespace Markdig
         /// <param name="renderer">The markdown renderer to setup</param>
         public void Setup(IMarkdownRenderer renderer)
         {
-            if (renderer == null) throw new ArgumentNullException(nameof(renderer));
+            if (renderer == null) ThrowHelper.ArgumentNullException(nameof(renderer));
             foreach (var extension in Extensions)
             {
                 extension.Setup(this, renderer);
             }
         }
+
+
+        private HtmlRendererCache _rendererCache = null;
+
+        internal HtmlRenderer GetCacheableHtmlRenderer()
+        {
+            if (_rendererCache is null)
+            {
+                _rendererCache = new HtmlRendererCache
+                {
+                    OnNewInstanceCreated = Setup
+                };
+            }
+            return _rendererCache.Get();
+        }
+        internal void ReleaseCacheableHtmlRenderer(HtmlRenderer renderer)
+        {
+            _rendererCache.Release(renderer);
+        }
+
+        private sealed class HtmlRendererCache : ObjectCache<HtmlRenderer>
+        {
+            public Action<HtmlRenderer> OnNewInstanceCreated;
+
+            protected override HtmlRenderer NewInstance()
+            {
+                var writer = new StringWriter();
+                var renderer = new HtmlRenderer(writer);
+                OnNewInstanceCreated(renderer);
+                return renderer;
+            }
+
+            protected override void Reset(HtmlRenderer instance)
+            {
+                instance.Reset();
+            }
+        }
     }
 }

src/Markdig/MarkdownPipelineBuilder.cs

@@ -49,8 +49,6 @@ namespace Markdig
             };
 
             Extensions = new OrderedList<IMarkdownExtension>();
-
-            StringBuilderCache = new StringBuilderCache();
         }
 
         /// <summary>
@@ -68,11 +66,6 @@ namespace Markdig
         /// </summary>
         public OrderedList<IMarkdownExtension> Extensions { get; }
 
-        /// <summary>
-        /// Gets or sets the string builder cache used by the parsers.
-        /// </summary>
-        public StringBuilderCache StringBuilderCache { get; set; }
-
         /// <summary>
         /// Gets or sets a value indicating whether to enable precise source location (slower parsing but accurate position for block and inline elements)
         /// </summary>
@@ -111,7 +104,7 @@ namespace Markdig
             {
                 if (extension == null)
                 {
-                    throw new InvalidOperationException("An extension cannot be null");
+                    ThrowHelper.InvalidOperationException("An extension cannot be null");
                 }
                 extension.Setup(this);
             }
@@ -120,7 +113,6 @@ namespace Markdig
                 new OrderedList<IMarkdownExtension>(Extensions),
                 new BlockParserList(BlockParsers),
                 new InlineParserList(InlineParsers),
-                StringBuilderCache,
                 DebugLog,
                 GetDocumentProcessed)
             {

src/Markdig/Parsers/BlockParser.cs

@@ -25,9 +25,9 @@ namespace Markdig.Parsers
         {
             if (OpeningCharacters != null)
             {
-                for (int i = 0; i < OpeningCharacters.Length; i++)
+                foreach (char openingChar in OpeningCharacters)
                 {
-                    if (OpeningCharacters[i] == c)
+                    if (openingChar == c)
                     {
                         return true;
                     }

src/Markdig/Parsers/BlockProcessor.cs

@@ -24,7 +24,6 @@ namespace Markdig.Parsers
             // These properties are not changing between a parent and a children BlockProcessor
             this.root = root;
             this.parserStateCache = root.parserStateCache;
-            StringBuilders = root.StringBuilders;
             Document = root.Document;
             Parsers = root.Parsers;
 
@@ -41,13 +40,11 @@ namespace Markdig.Parsers
         /// <param name="parsers">The list of parsers.</param>
         /// <exception cref="System.ArgumentNullException">
         /// </exception>
-        public BlockProcessor(StringBuilderCache stringBuilders, MarkdownDocument document, BlockParserList parsers, MarkdownParserContext context)
+        public BlockProcessor(MarkdownDocument document, BlockParserList parsers, MarkdownParserContext context)
         {
-            if (stringBuilders == null) throw new ArgumentNullException(nameof(stringBuilders));
-            if (document == null) throw new ArgumentNullException(nameof(document));
-            if (parsers == null) throw new ArgumentNullException(nameof(parsers));
+            if (document == null) ThrowHelper.ArgumentNullException(nameof(document));
+            if (parsers == null) ThrowHelper.ArgumentNullException(nameof(parsers));
             parserStateCache = new BlockParserStateCache(this);
-            StringBuilders = stringBuilders;
             Document = document;
             document.IsOpen = true;
             Parsers = parsers;
@@ -153,11 +150,6 @@ namespace Markdig.Parsers
         /// </summary>
         public int StartBeforeIndent { get; private set; }
 
-        /// <summary>
-        /// Gets the cache of string builders.
-        /// </summary>
-        public StringBuilderCache StringBuilders { get; }
-
         /// <summary>
         /// Gets the current stack of <see cref="Block"/> being processed.
         /// </summary>
@@ -400,8 +392,8 @@ namespace Markdig.Parsers
         /// <exception cref="System.ArgumentException">The block must be opened</exception>
         public void Open(Block block)
         {
-            if (block == null) throw new ArgumentNullException(nameof(block));
-            if (!block.IsOpen) throw new ArgumentException("The block must be opened", nameof(block));
+            if (block == null) ThrowHelper.ArgumentNullException(nameof(block));
+            if (!block.IsOpen) ThrowHelper.ArgumentException("The block must be opened", nameof(block));
             OpenedBlocks.Add(block);
         }
 
@@ -477,7 +469,7 @@ namespace Markdig.Parsers
         {
             if (this == root)
             {
-                throw new InvalidOperationException("Cannot release the root parser state");
+                ThrowHelper.InvalidOperationException("Cannot release the root parser state");
             }
             parserStateCache.Release(this);
         }
@@ -500,6 +492,11 @@ namespace Markdig.Parsers
                 if (!block.Parser.Close(this, block))
                 {
                     block.Parent?.Remove(block);
+
+                    if (block is LeafBlock leaf)
+                    {
+                        leaf.Lines.Release();
+                    }
                 }
                 else
                 {
@@ -628,7 +625,7 @@ namespace Markdig.Parsers
                 // If a parser is adding a block, it must be the last of the list
                 if ((i + 1) < OpenedBlocks.Count && NewBlocks.Count > 0)
                 {
-                    throw new InvalidOperationException("A pending parser cannot add a new block when it is not the last pending block");
+                    ThrowHelper.InvalidOperationException("A pending parser cannot add a new block when it is not the last pending block");
                 }
 
                 // If we have a leaf block
@@ -675,7 +672,7 @@ namespace Markdig.Parsers
                 // Security check so that the parser can't go into a crazy infinite loop if one extension is messing
                 if (previousStart == Start)
                 {
-                    throw new InvalidOperationException($"The parser is in an invalid infinite loop while trying to parse blocks at line [{LineIndex}] with line [{Line}]");
+                    ThrowHelper.InvalidOperationException($"The parser is in an invalid infinite loop while trying to parse blocks at line [{LineIndex}] with line [{Line}]");
                 }
                 previousStart = Start;
 
@@ -805,7 +802,7 @@ namespace Markdig.Parsers
 
                 if (block.Parser == null)
                 {
-                    throw new InvalidOperationException($"The new block [{block.GetType()}] must have a valid Parser property");
+                    ThrowHelper.InvalidOperationException($"The new block [{block.GetType()}] must have a valid Parser property");
                 }
 
                 block.Line = LineIndex;
@@ -821,7 +818,7 @@ namespace Markdig.Parsers
 
                     if (newBlocks.Count > 0)
                     {
-                        throw new InvalidOperationException(
+                        ThrowHelper.InvalidOperationException(
                             "The NewBlocks is not empty. This is happening if a LeafBlock is not the last to be pushed");
                     }
                 }
@@ -873,7 +870,7 @@ namespace Markdig.Parsers
             NewBlocks.Clear();
         }
 
-        private class BlockParserStateCache : ObjectCache<BlockProcessor>
+        private sealed class BlockParserStateCache : ObjectCache<BlockProcessor>
         {
             private readonly BlockProcessor root;
 

src/Markdig/Parsers/BlockStateExtensions.cs

@@ -1,4 +1,4 @@
-// Copyright (c) Alexandre Mutel. All rights reserved.
+// Copyright (c) Alexandre Mutel. All rights reserved.
 // This file is licensed under the BSD-Clause 2 license. 
 // See the license.txt file in the project root for more information.
 using System.Runtime.CompilerServices;
@@ -16,7 +16,7 @@ namespace Markdig.Parsers
         /// </summary>
         /// <param name="blockState">State of the block.</param>
         /// <returns><c>true</c> if the block state is in discard state</returns>
-        [MethodImpl(MethodImplOptionPortable.AggressiveInlining)]
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public static bool IsDiscard(this BlockState blockState)
         {
             return blockState == BlockState.ContinueDiscard || blockState == BlockState.BreakDiscard;
@@ -27,7 +27,7 @@ namespace Markdig.Parsers
         /// </summary>
         /// <param name="blockState">State of the block.</param>
         /// <returns><c>true</c> if the block state is in continue state</returns>
-        [MethodImpl(MethodImplOptionPortable.AggressiveInlining)]
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public static bool IsContinue(this BlockState blockState)
         {
             return blockState == BlockState.Continue || blockState == BlockState.ContinueDiscard;
@@ -38,7 +38,7 @@ namespace Markdig.Parsers
         /// </summary>
         /// <param name="blockState">State of the block.</param>
         /// <returns><c>true</c> if the block state is in break state</returns>
-        [MethodImpl(MethodImplOptionPortable.AggressiveInlining)]
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public static bool IsBreak(this BlockState blockState)
         {
             return blockState == BlockState.Break || blockState == BlockState.BreakDiscard;

src/Markdig/Parsers/FencedBlockParserBase.cs

@@ -124,7 +124,9 @@ namespace Markdig.Parsers
             }
             else
             {
-                infoString = line.ToString().Trim();
+                var lineCopy = line;
+                lineCopy.Trim();
+                infoString = lineCopy.ToString();
             }
 
             fenced.Info = HtmlHelper.Unescape(infoString);

src/Markdig/Parsers/HtmlBlockParser.cs

@@ -100,7 +100,7 @@ namespace Markdig.Parsers
             if (c == '!')
             {
                 c = line.NextChar();
-                if (c == '-' && line.PeekChar(1) == '-')
+                if (c == '-' && line.PeekChar() == '-')
                 {
                     return CreateHtmlBlock(state, HtmlBlockType.Comment, startColumn, startPosition); // group 2
                 }
@@ -140,7 +140,7 @@ namespace Markdig.Parsers
             }
 
             if (
-                !(c == '>' || (!hasLeadingClose && c == '/' && line.PeekChar(1) == '>') || c.IsWhitespace() ||
+                !(c == '>' || (!hasLeadingClose && c == '/' && line.PeekChar() == '>') || c.IsWhitespace() ||
                   c == '\0'))
             {
                 return BlockState.None;

src/Markdig/Parsers/InlineProcessor.cs

@@ -36,12 +36,10 @@ namespace Markdig.Parsers
         /// <param name="inlineCreated">The inline created event.</param>
         /// <exception cref="System.ArgumentNullException">
         /// </exception>
-        public InlineProcessor(StringBuilderCache stringBuilders, MarkdownDocument document, InlineParserList parsers, bool preciseSourcelocation, MarkdownParserContext context)
+        public InlineProcessor(MarkdownDocument document, InlineParserList parsers, bool preciseSourcelocation, MarkdownParserContext context)
         {
-            if (stringBuilders == null) throw new ArgumentNullException(nameof(stringBuilders));
-            if (document == null) throw new ArgumentNullException(nameof(document));
-            if (parsers == null) throw new ArgumentNullException(nameof(parsers));
-            StringBuilders = stringBuilders;
+            if (document == null) ThrowHelper.ArgumentNullException(nameof(document));
+            if (parsers == null) ThrowHelper.ArgumentNullException(nameof(parsers));
             Document = document;
             Parsers = parsers;
             Context = context;
@@ -91,11 +89,6 @@ namespace Markdig.Parsers
         /// </summary>
         public MarkdownDocument Document { get; }
 
-        /// <summary>
-        /// Gets the cache string builders.
-        /// </summary>
-        public StringBuilderCache StringBuilders { get;  }
-
         /// <summary>
         /// Gets or sets the index of the line from the begining of the document being processed.
         /// </summary>
@@ -176,7 +169,7 @@ namespace Markdig.Parsers
         /// <param name="leafBlock">The leaf block.</param>
         public void ProcessInlineLeaf(LeafBlock leafBlock)
         {
-            if (leafBlock == null) throw new ArgumentNullException(nameof(leafBlock));
+            if (leafBlock == null) ThrowHelper.ArgumentNullException_leafBlock();
 
             // clear parser states
             Array.Clear(ParserStates, 0, ParserStates.Length);
@@ -192,7 +185,7 @@ namespace Markdig.Parsers
             previousLineIndexForSliceOffset = 0;
             lineOffsets.Clear();
             var text = leafBlock.Lines.ToSlice(lineOffsets);
-            leafBlock.Lines = new StringLineGroup();
+            leafBlock.Lines.Release();
 
             int previousStart = -1;
 
@@ -201,7 +194,7 @@ namespace Markdig.Parsers
                 // Security check so that the parser can't go into a crazy infinite loop if one extension is messing
                 if (previousStart == text.Start)
                 {
-                    throw new InvalidOperationException($"The parser is in an invalid infinite loop while trying to parse inlines for block [{leafBlock.GetType().Name}] at position ({leafBlock.ToPositionText()}");
+                    ThrowHelper.InvalidOperationException($"The parser is in an invalid infinite loop while trying to parse inlines for block [{leafBlock.GetType().Name}] at position ({leafBlock.ToPositionText()}");
                 }
                 previousStart = text.Start;