Merge pull request #844 from snnz/fix-gridtables

Prevent GridTableParser from looking beyond the end of a line.

.github/workflows/ci.yml

@@ -11,22 +11,11 @@ on:
 
 jobs:
   build:
-    runs-on: windows-latest
-
-    steps:
-    - name: Checkout
-      uses: actions/checkout@v2
-      with:
-        submodules: true
-        fetch-depth: 0
-
-    - name: Install .NET 6.0
-      uses: actions/setup-dotnet@v1
-      with:
-        dotnet-version: '6.0.x'
-
-    - name: Build, Test, Pack, Publish
-      shell: bash
-      run: |
-        dotnet tool install -g dotnet-releaser
-        dotnet-releaser run --nuget-token "${{secrets.NUGET_TOKEN}}" --github-token "${{secrets.GITHUB_TOKEN}}" src/dotnet-releaser.toml
+    uses: xoofx/.github/.github/workflows/dotnet.yml@main
+    with:
+      dotnet-version: |
+        6.0
+        8.0
+        9.0
+    secrets:
+      NUGET_TOKEN: ${{ secrets.NUGET_TOKEN }}    

.github/workflows/nuget_org_only.config

@@ -0,0 +1,7 @@
+<?xml version="1.0" encoding="utf-8"?>
+<configuration>
+  <packageSources>
+    <clear />
+    <add key="nuget.org" value="https://api.nuget.org/v3/index.json" />
+  </packageSources>
+</configuration>

doc/parsing-extensions.md

@@ -1,6 +1,6 @@
 # Extensions and Parsers
 
-Markdig was [implemented in such a way](http://xoofx.com/blog/2016/06/13/implementing-a-markdown-processor-for-dotnet/) as to be extremely pluggable, with even basic behaviors being mutable and extendable.
+Markdig was [implemented in such a way](http://xoofx.github.io/blog/2016/06/13/implementing-a-markdown-processor-for-dotnet/) as to be extremely pluggable, with even basic behaviors being mutable and extendable.
 
 The basic mechanism for extension of Markdig is the `IMarkdownExtension` interface, which allows any implementing class to be registered with the pipeline builder and thus to directly modify the collections of `BlockParser` and `InlineParser` objects which end up in the pipeline.
 

readme.md

@@ -1,4 +1,4 @@
-# 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/xoofx/markdig/badge.svg?branch=master)](https://coveralls.io/github/xoofx/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)
+# Markdig [![ci](https://github.com/xoofx/markdig/actions/workflows/ci.yml/badge.svg)](https://github.com/xoofx/markdig/actions/workflows/ci.yml) [![Coverage Status](https://coveralls.io/repos/github/xoofx/markdig/badge.svg?branch=master)](https://coveralls.io/github/xoofx/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">
 
@@ -12,7 +12,7 @@ You can **try Markdig online** and compare it to other implementations on [babel
 
 - **Very fast parser and html renderer** (no-regexp), very lightweight in terms of GC pressure. See benchmarks
 - **Abstract Syntax Tree** with precise source code location for syntax tree, useful when building a Markdown editor.
-  - Checkout [MarkdownEditor for Visual Studio](https://visualstudiogallery.msdn.microsoft.com/eaab33c3-437b-4918-8354-872dfe5d1bfe) powered by Markdig!
+  - Checkout [Markdown Editor v2 for Visual Studio 2022](https://marketplace.visualstudio.com/items?itemName=MadsKristensen.MarkdownEditor2) powered by Markdig!
 - Converter to **HTML**
 - Passing more than **600+ tests** from the latest [CommonMark specs (0.30)](http://spec.commonmark.org/)
 - Includes all the core elements of CommonMark:
@@ -48,7 +48,7 @@ You can **try Markdig online** and compare it to other implementations on [babel
   - [**Emoji**](src/Markdig.Tests/Specs/EmojiSpecs.md) support (inspired from [Markdown-it](https://markdown-it.github.io/))
   - [**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)
+  - [**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://mermaid.js.org) and [`nomnoml`](https://github.com/skanaar/nomnoml) diagrams)
   - [**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)
 - 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`.
@@ -70,7 +70,7 @@ If you are looking for support for an old .NET Framework 3.5 or 4.0, you can dow
 
 While there is not yet a dedicated documentation, you can find from the [specs documentation](src/Markdig.Tests/Specs/readme.md) how to use these extensions.
 
-In the meantime, you can have a "behind the scene" article about Markdig in my blog post ["Implementing a Markdown Engine for .NET"](http://xoofx.com/blog/2016/06/13/implementing-a-markdown-processor-for-dotnet/)
+In the meantime, you can have a "behind the scene" article about Markdig in my blog post ["Implementing a Markdown Engine for .NET"](http://xoofx.github.io/blog/2016/06/13/implementing-a-markdown-processor-for-dotnet/)
 
 ## Download
 
@@ -144,12 +144,12 @@ AMD Ryzen 9 5950X, 1 CPU, 32 logical and 16 physical cores
 - Markdig is roughly **x100 times faster than MarkdownSharp**
 - **20% faster than the reference cmark C implementation** 
 
+## Sponsors
 
-## Donate
+Supports this project with a monthly donation and help me continue improving it. \[[Become a sponsor](https://github.com/sponsors/xoofx)\]
 
-If you are using this library and find it useful for your project, please consider a donation for it!
-
-[![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 src="https://github.com/lilith.png?size=200" width="64px;" style="border-radius: 50%" alt="lilith"/>](https://github.com/lilith) Lilith River, author of [Imageflow Server, an easy on-demand
+image editing, optimization, and delivery server](https://github.com/imazen/imageflow-server)
 
 ## Credits
 
@@ -164,4 +164,4 @@ Some decoding part (e.g HTML [EntityHelper.cs](https://github.com/lunet-io/markd
 Thanks to the work done by @clarkd on the JIRA Link extension (https://github.com/clarkd/MarkdigJiraLinker), now included with this project!
 ## Author
 
-Alexandre MUTEL aka [xoofx](http://xoofx.com)
+Alexandre MUTEL aka [xoofx](http://xoofx.github.io)

src/Markdig.Benchmarks/Markdig.Benchmarks.csproj

@@ -1,6 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
-    <TargetFramework>net6.0</TargetFramework>
+    <TargetFramework>net8.0</TargetFramework>
     <OutputType>Exe</OutputType>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
     <IsPackable>false</IsPackable>
@@ -19,12 +19,12 @@
     </Content>
   </ItemGroup>
   <ItemGroup>
-    <PackageReference Include="BenchmarkDotNet" Version="0.13.1" />
-    <PackageReference Include="BenchmarkDotNet.Diagnostics.Windows" Version="0.13.1" />
+    <PackageReference Include="BenchmarkDotNet" Version="0.13.12" />
+    <PackageReference Include="BenchmarkDotNet.Diagnostics.Windows" Version="0.13.12" />
     <PackageReference Include="CommonMark.NET" Version="0.15.1" />
     <PackageReference Include="Markdown" Version="2.2.1" />
     <PackageReference Include="MarkdownSharp" Version="2.0.5" />
-    <PackageReference Include="Microsoft.Diagnostics.Runtime" Version="2.0.226801" />
+    <PackageReference Include="Microsoft.Diagnostics.Runtime" Version="3.1.506101" />
   </ItemGroup>
   <ItemGroup>
     <ProjectReference Include="..\Markdig\Markdig.csproj" />

src/Markdig.Tests/GlobalUsings.cs

@@ -0,0 +1,5 @@
+// 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.
+
+global using Assert = NUnit.Framework.Legacy.ClassicAssert;

src/Markdig.Tests/Markdig.Tests.csproj

@@ -1,19 +1,20 @@
-<Project Sdk="Microsoft.NET.Sdk">
+<Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFramework>net6.0</TargetFramework>
+    <TargetFrameworks>net6.0;net8.0;net9.0</TargetFrameworks>
     <OutputType>Exe</OutputType>
     <IsPackable>false</IsPackable>
     <ImplicitUsings>enable</ImplicitUsings>
+    <LangVersion>13.0</LangVersion>
     <StartupObject>Markdig.Tests.Program</StartupObject>
-    <SpecExecutable>$(MSBuildProjectDirectory)\..\SpecFileGen\bin\$(Configuration)\net6.0\SpecFileGen.dll</SpecExecutable>
-    <SpecTimestamp>$(MSBuildProjectDirectory)\..\SpecFileGen\bin\$(Configuration)\net6.0\SpecFileGen.timestamp</SpecTimestamp>
+    <SpecExecutable>$(MSBuildProjectDirectory)\..\SpecFileGen\bin\$(Configuration)\$(TargetFramework)\SpecFileGen.dll</SpecExecutable>
+    <SpecTimestamp>$(MSBuildProjectDirectory)\..\SpecFileGen\bin\$(Configuration)\$(TargetFramework)\SpecFileGen.timestamp</SpecTimestamp>
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.1.0" />
-    <PackageReference Include="NUnit" Version="3.13.3" />
-    <PackageReference Include="NUnit3TestAdapter" Version="4.2.1" />
+    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.9.0" />
+    <PackageReference Include="NUnit" Version="4.1.0" />
+    <PackageReference Include="NUnit3TestAdapter" Version="4.5.0" />
   </ItemGroup>
 
   <ItemGroup>

src/Markdig.Tests/MiscTests.cs

@@ -1,7 +1,8 @@
 using System.Text.RegularExpressions;
 
 using Markdig.Extensions.AutoLinks;
-
+using Markdig.Extensions.Tables;
+using Markdig.Syntax;
 using NUnit.Framework;
 
 namespace Markdig.Tests;
@@ -198,9 +199,9 @@ $$
 <div class=""math"">
 \begin{align}
 \sqrt{37} & = \sqrt{\frac{73^2-1}{12^2}} \\
- & = \sqrt{\frac{73^2}{12^2}\cdot\frac{73^2-1}{73^2}} \\ 
+ & = \sqrt{\frac{73^2}{12^2}\cdot\frac{73^2-1}{73^2}} \\
  & = \sqrt{\frac{73^2}{12^2}}\sqrt{\frac{73^2-1}{73^2}} \\
- & = \frac{73}{12}\sqrt{1 - \frac{1}{73^2}} \\ 
+ & = \frac{73}{12}\sqrt{1 - \frac{1}{73^2}} \\
  & \approx \frac{73}{12}\left(1 - \frac{1}{2\cdot73^2}\right)
 \end{align}
 </div>
@@ -291,4 +292,98 @@ $$
         TestParser.TestSpec("www.foo.bar", "<p><a href=\"http://www.foo.bar\">www.foo.bar</a></p>", pipeline);
         TestParser.TestSpec("www.foo.bar", "<p><a href=\"https://www.foo.bar\">www.foo.bar</a></p>", httpsPipeline);
     }
+
+    [Test]
+    public void RootInlineHasCorrectSourceSpan()
+    {
+        var pipeline = new MarkdownPipelineBuilder().UsePreciseSourceLocation().Build();
+        pipeline.TrackTrivia = true;
+
+        var document = Markdown.Parse("0123456789\n", pipeline);
+
+        var expectedSourceSpan = new SourceSpan(0, 10);
+        Assert.That(((LeafBlock)document.LastChild).Inline.Span == expectedSourceSpan);
+    }
+
+    [Test]
+    public void RootInlineInTableCellHasCorrectSourceSpan()
+    {
+        var pipeline = new MarkdownPipelineBuilder().UsePreciseSourceLocation().UseAdvancedExtensions().Build();
+        pipeline.TrackTrivia = true;
+
+        var document = Markdown.Parse("| a | b |\n| --- | --- |\n| <span id=\"dest\"></span><span id=\"DEST\"></span>*dest*<br/> | \\[in\\] The address of the result of the operation.<br/> |", pipeline);
+
+        var paragraph = (ParagraphBlock)((TableCell)((TableRow)((Table)document.LastChild).LastChild).First()).LastChild;
+        Assert.That(paragraph.Inline.Span.Start == paragraph.Inline.FirstChild.Span.Start);
+        Assert.That(paragraph.Inline.Span.End == paragraph.Inline.LastChild.Span.End);
+    }
+
+    [Test]
+    public void TestGridTableShortLine()
+    {
+        var input = @"
++--+
+|  |
++-";
+
+        var expected = @"<table>
+<col style=""width:100%"" />
+<tbody>
+<tr>
+<td></td>
+</tr>
+</tbody>
+</table>
+";
+        TestParser.TestSpec(input, expected, new MarkdownPipelineBuilder().UseGridTables().Build());
+    }
+  
+    [Test]
+    public void TestDefinitionListInListItemWithBlankLine()
+    {
+        var input = @"
+- 
+
+  term
+  :   definition
+";
+
+        var expected = @"<ul>
+<li>
+<dl>
+<dt>term</dt>
+<dd>definition</dd>
+</dl>
+</li>
+</ul>
+";
+        TestParser.TestSpec(input, expected, new MarkdownPipelineBuilder().UseDefinitionLists().Build());
+    }
+
+    [Test]
+    public void TestAlertWithinAlertOrNestedBlock()
+    {
+        var input = @"
+>[!NOTE]
+[!NOTE]
+The second one is not a note.
+
+>>[!NOTE]
+Also not a note.
+";
+
+        var expected = @"<div class=""markdown-alert markdown-alert-note"">
+<p class=""markdown-alert-title""><svg viewBox=""0 0 16 16"" version=""1.1"" width=""16"" height=""16"" aria-hidden=""true""><path d=""M0 8a8 8 0 1 1 16 0A8 8 0 0 1 0 8Zm8-6.5a6.5 6.5 0 1 0 0 13 6.5 6.5 0 0 0 0-13ZM6.5 7.75A.75.75 0 0 1 7.25 7h1a.75.75 0 0 1 .75.75v2.75h.25a.75.75 0 0 1 0 1.5h-2a.75.75 0 0 1 0-1.5h.25v-2h-.25a.75.75 0 0 1-.75-.75ZM8 6a1 1 0 1 1 0-2 1 1 0 0 1 0 2Z""></path></svg>Note</p>
+<p>[!NOTE]
+The second one is not a note.</p>
+</div>
+<blockquote>
+<blockquote>
+<p>[!NOTE]
+Also not a note.</p>
+</blockquote>
+</blockquote>
+";
+        TestParser.TestSpec(input, expected, new MarkdownPipelineBuilder().UseAlertBlocks().Build());
+    }
 }

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

@@ -0,0 +1,179 @@
+
+// --------------------------------
+//           Alert Blocks
+// --------------------------------
+
+using System;
+using NUnit.Framework;
+
+namespace Markdig.Tests.Specs.AlertBlocks
+{
+    [TestFixture]
+    public class TestExtensionsAlertBlocks
+    {
+        // # Extensions
+        // 
+        // This section describes the different extensions supported:
+        // 
+        // ## Alert Blocks
+        // 
+        // This is supporting the [GitHub Alert blocks](https://github.com/orgs/community/discussions/16925)
+        [Test]
+        public void ExtensionsAlertBlocks_Example001()
+        {
+            // Example 1
+            // Section: Extensions / Alert Blocks
+            //
+            // The following Markdown:
+            //     > [!NOTE]  
+            //     > Highlights information that users should take into account, even when skimming.
+            //     
+            //     > [!TIP]
+            //     > Optional information to help a user be more successful.
+            //     
+            //     > [!IMPORTANT]  
+            //     > Crucial information necessary for users to succeed.
+            //     
+            //     > [!WARNING]  
+            //     > Critical content demanding immediate user attention due to potential risks.
+            //     
+            //     > [!CAUTION]
+            //     > Negative potential consequences of an action.
+            //
+            // Should be rendered as:
+            //     <div class="markdown-alert markdown-alert-note">
+            //     <p class="markdown-alert-title"><svg viewBox="0 0 16 16" version="1.1" width="16" height="16" aria-hidden="true"><path d="M0 8a8 8 0 1 1 16 0A8 8 0 0 1 0 8Zm8-6.5a6.5 6.5 0 1 0 0 13 6.5 6.5 0 0 0 0-13ZM6.5 7.75A.75.75 0 0 1 7.25 7h1a.75.75 0 0 1 .75.75v2.75h.25a.75.75 0 0 1 0 1.5h-2a.75.75 0 0 1 0-1.5h.25v-2h-.25a.75.75 0 0 1-.75-.75ZM8 6a1 1 0 1 1 0-2 1 1 0 0 1 0 2Z"></path></svg>Note</p>
+            //     <p>Highlights information that users should take into account, even when skimming.</p>
+            //     </div>
+            //     <div class="markdown-alert markdown-alert-tip">
+            //     <p class="markdown-alert-title"><svg viewBox="0 0 16 16" version="1.1" width="16" height="16" aria-hidden="true"><path d="M8 1.5c-2.363 0-4 1.69-4 3.75 0 .984.424 1.625.984 2.304l.214.253c.223.264.47.556.673.848.284.411.537.896.621 1.49a.75.75 0 0 1-1.484.211c-.04-.282-.163-.547-.37-.847a8.456 8.456 0 0 0-.542-.68c-.084-.1-.173-.205-.268-.32C3.201 7.75 2.5 6.766 2.5 5.25 2.5 2.31 4.863 0 8 0s5.5 2.31 5.5 5.25c0 1.516-.701 2.5-1.328 3.259-.095.115-.184.22-.268.319-.207.245-.383.453-.541.681-.208.3-.33.565-.37.847a.751.751 0 0 1-1.485-.212c.084-.593.337-1.078.621-1.489.203-.292.45-.584.673-.848.075-.088.147-.173.213-.253.561-.679.985-1.32.985-2.304 0-2.06-1.637-3.75-4-3.75ZM5.75 12h4.5a.75.75 0 0 1 0 1.5h-4.5a.75.75 0 0 1 0-1.5ZM6 15.25a.75.75 0 0 1 .75-.75h2.5a.75.75 0 0 1 0 1.5h-2.5a.75.75 0 0 1-.75-.75Z"></path></svg>Tip</p>
+            //     <p>Optional information to help a user be more successful.</p>
+            //     </div>
+            //     <div class="markdown-alert markdown-alert-important">
+            //     <p class="markdown-alert-title"><svg viewBox="0 0 16 16" version="1.1" width="16" height="16" aria-hidden="true"><path d="M0 1.75C0 .784.784 0 1.75 0h12.5C15.216 0 16 .784 16 1.75v9.5A1.75 1.75 0 0 1 14.25 13H8.06l-2.573 2.573A1.458 1.458 0 0 1 3 14.543V13H1.75A1.75 1.75 0 0 1 0 11.25Zm1.75-.25a.25.25 0 0 0-.25.25v9.5c0 .138.112.25.25.25h2a.75.75 0 0 1 .75.75v2.19l2.72-2.72a.749.749 0 0 1 .53-.22h6.5a.25.25 0 0 0 .25-.25v-9.5a.25.25 0 0 0-.25-.25Zm7 2.25v2.5a.75.75 0 0 1-1.5 0v-2.5a.75.75 0 0 1 1.5 0ZM9 9a1 1 0 1 1-2 0 1 1 0 0 1 2 0Z"></path></svg>Important</p>
+            //     <p>Crucial information necessary for users to succeed.</p>
+            //     </div>
+            //     <div class="markdown-alert markdown-alert-warning">
+            //     <p class="markdown-alert-title"><svg viewBox="0 0 16 16" version="1.1" width="16" height="16" aria-hidden="true"><path d="M6.457 1.047c.659-1.234 2.427-1.234 3.086 0l6.082 11.378A1.75 1.75 0 0 1 14.082 15H1.918a1.75 1.75 0 0 1-1.543-2.575Zm1.763.707a.25.25 0 0 0-.44 0L1.698 13.132a.25.25 0 0 0 .22.368h12.164a.25.25 0 0 0 .22-.368Zm.53 3.996v2.5a.75.75 0 0 1-1.5 0v-2.5a.75.75 0 0 1 1.5 0ZM9 11a1 1 0 1 1-2 0 1 1 0 0 1 2 0Z"></path></svg>Warning</p>
+            //     <p>Critical content demanding immediate user attention due to potential risks.</p>
+            //     </div>
+            //     <div class="markdown-alert markdown-alert-caution">
+            //     <p class="markdown-alert-title"><svg viewBox="0 0 16 16" version="1.1" width="16" height="16" aria-hidden="true"><path d="M4.47.22A.749.749 0 0 1 5 0h6c.199 0 .389.079.53.22l4.25 4.25c.141.14.22.331.22.53v6a.749.749 0 0 1-.22.53l-4.25 4.25A.749.749 0 0 1 11 16H5a.749.749 0 0 1-.53-.22L.22 11.53A.749.749 0 0 1 0 11V5c0-.199.079-.389.22-.53Zm.84 1.28L1.5 5.31v5.38l3.81 3.81h5.38l3.81-3.81V5.31L10.69 1.5ZM8 4a.75.75 0 0 1 .75.75v3.5a.75.75 0 0 1-1.5 0v-3.5A.75.75 0 0 1 8 4Zm0 8a1 1 0 1 1 0-2 1 1 0 0 1 0 2Z"></path></svg>Caution</p>
+            //     <p>Negative potential consequences of an action.</p>
+            //     </div>
+
+            TestParser.TestSpec("> [!NOTE]  \n> Highlights information that users should take into account, even when skimming.\n\n> [!TIP]\n> Optional information to help a user be more successful.\n\n> [!IMPORTANT]  \n> Crucial information necessary for users to succeed.\n\n> [!WARNING]  \n> Critical content demanding immediate user attention due to potential risks.\n\n> [!CAUTION]\n> Negative potential consequences of an action.", "<div class=\"markdown-alert markdown-alert-note\">\n<p class=\"markdown-alert-title\"><svg viewBox=\"0 0 16 16\" version=\"1.1\" width=\"16\" height=\"16\" aria-hidden=\"true\"><path d=\"M0 8a8 8 0 1 1 16 0A8 8 0 0 1 0 8Zm8-6.5a6.5 6.5 0 1 0 0 13 6.5 6.5 0 0 0 0-13ZM6.5 7.75A.75.75 0 0 1 7.25 7h1a.75.75 0 0 1 .75.75v2.75h.25a.75.75 0 0 1 0 1.5h-2a.75.75 0 0 1 0-1.5h.25v-2h-.25a.75.75 0 0 1-.75-.75ZM8 6a1 1 0 1 1 0-2 1 1 0 0 1 0 2Z\"></path></svg>Note</p>\n<p>Highlights information that users should take into account, even when skimming.</p>\n</div>\n<div class=\"markdown-alert markdown-alert-tip\">\n<p class=\"markdown-alert-title\"><svg viewBox=\"0 0 16 16\" version=\"1.1\" width=\"16\" height=\"16\" aria-hidden=\"true\"><path d=\"M8 1.5c-2.363 0-4 1.69-4 3.75 0 .984.424 1.625.984 2.304l.214.253c.223.264.47.556.673.848.284.411.537.896.621 1.49a.75.75 0 0 1-1.484.211c-.04-.282-.163-.547-.37-.847a8.456 8.456 0 0 0-.542-.68c-.084-.1-.173-.205-.268-.32C3.201 7.75 2.5 6.766 2.5 5.25 2.5 2.31 4.863 0 8 0s5.5 2.31 5.5 5.25c0 1.516-.701 2.5-1.328 3.259-.095.115-.184.22-.268.319-.207.245-.383.453-.541.681-.208.3-.33.565-.37.847a.751.751 0 0 1-1.485-.212c.084-.593.337-1.078.621-1.489.203-.292.45-.584.673-.848.075-.088.147-.173.213-.253.561-.679.985-1.32.985-2.304 0-2.06-1.637-3.75-4-3.75ZM5.75 12h4.5a.75.75 0 0 1 0 1.5h-4.5a.75.75 0 0 1 0-1.5ZM6 15.25a.75.75 0 0 1 .75-.75h2.5a.75.75 0 0 1 0 1.5h-2.5a.75.75 0 0 1-.75-.75Z\"></path></svg>Tip</p>\n<p>Optional information to help a user be more successful.</p>\n</div>\n<div class=\"markdown-alert markdown-alert-important\">\n<p class=\"markdown-alert-title\"><svg viewBox=\"0 0 16 16\" version=\"1.1\" width=\"16\" height=\"16\" aria-hidden=\"true\"><path d=\"M0 1.75C0 .784.784 0 1.75 0h12.5C15.216 0 16 .784 16 1.75v9.5A1.75 1.75 0 0 1 14.25 13H8.06l-2.573 2.573A1.458 1.458 0 0 1 3 14.543V13H1.75A1.75 1.75 0 0 1 0 11.25Zm1.75-.25a.25.25 0 0 0-.25.25v9.5c0 .138.112.25.25.25h2a.75.75 0 0 1 .75.75v2.19l2.72-2.72a.749.749 0 0 1 .53-.22h6.5a.25.25 0 0 0 .25-.25v-9.5a.25.25 0 0 0-.25-.25Zm7 2.25v2.5a.75.75 0 0 1-1.5 0v-2.5a.75.75 0 0 1 1.5 0ZM9 9a1 1 0 1 1-2 0 1 1 0 0 1 2 0Z\"></path></svg>Important</p>\n<p>Crucial information necessary for users to succeed.</p>\n</div>\n<div class=\"markdown-alert markdown-alert-warning\">\n<p class=\"markdown-alert-title\"><svg viewBox=\"0 0 16 16\" version=\"1.1\" width=\"16\" height=\"16\" aria-hidden=\"true\"><path d=\"M6.457 1.047c.659-1.234 2.427-1.234 3.086 0l6.082 11.378A1.75 1.75 0 0 1 14.082 15H1.918a1.75 1.75 0 0 1-1.543-2.575Zm1.763.707a.25.25 0 0 0-.44 0L1.698 13.132a.25.25 0 0 0 .22.368h12.164a.25.25 0 0 0 .22-.368Zm.53 3.996v2.5a.75.75 0 0 1-1.5 0v-2.5a.75.75 0 0 1 1.5 0ZM9 11a1 1 0 1 1-2 0 1 1 0 0 1 2 0Z\"></path></svg>Warning</p>\n<p>Critical content demanding immediate user attention due to potential risks.</p>\n</div>\n<div class=\"markdown-alert markdown-alert-caution\">\n<p class=\"markdown-alert-title\"><svg viewBox=\"0 0 16 16\" version=\"1.1\" width=\"16\" height=\"16\" aria-hidden=\"true\"><path d=\"M4.47.22A.749.749 0 0 1 5 0h6c.199 0 .389.079.53.22l4.25 4.25c.141.14.22.331.22.53v6a.749.749 0 0 1-.22.53l-4.25 4.25A.749.749 0 0 1 11 16H5a.749.749 0 0 1-.53-.22L.22 11.53A.749.749 0 0 1 0 11V5c0-.199.079-.389.22-.53Zm.84 1.28L1.5 5.31v5.38l3.81 3.81h5.38l3.81-3.81V5.31L10.69 1.5ZM8 4a.75.75 0 0 1 .75.75v3.5a.75.75 0 0 1-1.5 0v-3.5A.75.75 0 0 1 8 4Zm0 8a1 1 0 1 1 0-2 1 1 0 0 1 0 2Z\"></path></svg>Caution</p>\n<p>Negative potential consequences of an action.</p>\n</div>", "advanced", context: "Example 1\nSection Extensions / Alert Blocks\n");
+        }
+
+        // Example with code blocks and mix formatting:
+        [Test]
+        public void ExtensionsAlertBlocks_Example002()
+        {
+            // Example 2
+            // Section: Extensions / Alert Blocks
+            //
+            // The following Markdown:
+            //     > [!NOTE]
+            //     > Highlights information that users should take into account, even when skimming.
+            //     > Testing rendering for multiple lines
+            //     > ```csharp
+            //     > var test = "I can also add code to panels
+            //     > ```
+            //     > `Inline code testing`
+            //
+            // Should be rendered as:
+            //     <div class="markdown-alert markdown-alert-note">
+            //     <p class="markdown-alert-title"><svg viewBox="0 0 16 16" version="1.1" width="16" height="16" aria-hidden="true"><path d="M0 8a8 8 0 1 1 16 0A8 8 0 0 1 0 8Zm8-6.5a6.5 6.5 0 1 0 0 13 6.5 6.5 0 0 0 0-13ZM6.5 7.75A.75.75 0 0 1 7.25 7h1a.75.75 0 0 1 .75.75v2.75h.25a.75.75 0 0 1 0 1.5h-2a.75.75 0 0 1 0-1.5h.25v-2h-.25a.75.75 0 0 1-.75-.75ZM8 6a1 1 0 1 1 0-2 1 1 0 0 1 0 2Z"></path></svg>Note</p>
+            //     <p>Highlights information that users should take into account, even when skimming.
+            //     Testing rendering for multiple lines</p>
+            //     <pre><code class="language-csharp">var test = &quot;I can also add code to panels
+            //     </code></pre>
+            //     <p><code>Inline code testing</code></p>
+            //     </div>
+
+            TestParser.TestSpec("> [!NOTE]\n> Highlights information that users should take into account, even when skimming.\n> Testing rendering for multiple lines\n> ```csharp\n> var test = \"I can also add code to panels\n> ```\n> `Inline code testing`", "<div class=\"markdown-alert markdown-alert-note\">\n<p class=\"markdown-alert-title\"><svg viewBox=\"0 0 16 16\" version=\"1.1\" width=\"16\" height=\"16\" aria-hidden=\"true\"><path d=\"M0 8a8 8 0 1 1 16 0A8 8 0 0 1 0 8Zm8-6.5a6.5 6.5 0 1 0 0 13 6.5 6.5 0 0 0 0-13ZM6.5 7.75A.75.75 0 0 1 7.25 7h1a.75.75 0 0 1 .75.75v2.75h.25a.75.75 0 0 1 0 1.5h-2a.75.75 0 0 1 0-1.5h.25v-2h-.25a.75.75 0 0 1-.75-.75ZM8 6a1 1 0 1 1 0-2 1 1 0 0 1 0 2Z\"></path></svg>Note</p>\n<p>Highlights information that users should take into account, even when skimming.\nTesting rendering for multiple lines</p>\n<pre><code class=\"language-csharp\">var test = &quot;I can also add code to panels\n</code></pre>\n<p><code>Inline code testing</code></p>\n</div>", "advanced", context: "Example 2\nSection Extensions / Alert Blocks\n");
+        }
+
+        // Multiline:
+        [Test]
+        public void ExtensionsAlertBlocks_Example003()
+        {
+            // Example 3
+            // Section: Extensions / Alert Blocks
+            //
+            // The following Markdown:
+            //     > [!NOTE]
+            //     > Highlights information that users should take into account, even when skimming.
+            //     > 
+            //     > Testing rendering for multiple lines
+            //     > 
+            //     > `Inline code testing`
+            //     > 
+            //     > Other line
+            //     > 
+            //     > > Nested quote
+            //     > >
+            //     > > Final nested quote line
+            //     > 
+            //     > Final line of alert
+            //
+            // Should be rendered as:
+            //     <div class="markdown-alert markdown-alert-note">
+            //     <p class="markdown-alert-title"><svg viewBox="0 0 16 16" version="1.1" width="16" height="16" aria-hidden="true"><path d="M0 8a8 8 0 1 1 16 0A8 8 0 0 1 0 8Zm8-6.5a6.5 6.5 0 1 0 0 13 6.5 6.5 0 0 0 0-13ZM6.5 7.75A.75.75 0 0 1 7.25 7h1a.75.75 0 0 1 .75.75v2.75h.25a.75.75 0 0 1 0 1.5h-2a.75.75 0 0 1 0-1.5h.25v-2h-.25a.75.75 0 0 1-.75-.75ZM8 6a1 1 0 1 1 0-2 1 1 0 0 1 0 2Z"></path></svg>Note</p>
+            //     <p>Highlights information that users should take into account, even when skimming.</p>
+            //     <p>Testing rendering for multiple lines</p>
+            //     <p><code>Inline code testing</code></p>
+            //     <p>Other line</p>
+            //     <blockquote>
+            //     <p>Nested quote</p>
+            //     <p>Final nested quote line</p>
+            //     </blockquote>
+            //     <p>Final line of alert</p>
+            //     </div>
+
+            TestParser.TestSpec("> [!NOTE]\n> Highlights information that users should take into account, even when skimming.\n> \n> Testing rendering for multiple lines\n> \n> `Inline code testing`\n> \n> Other line\n> \n> > Nested quote\n> >\n> > Final nested quote line\n> \n> Final line of alert", "<div class=\"markdown-alert markdown-alert-note\">\n<p class=\"markdown-alert-title\"><svg viewBox=\"0 0 16 16\" version=\"1.1\" width=\"16\" height=\"16\" aria-hidden=\"true\"><path d=\"M0 8a8 8 0 1 1 16 0A8 8 0 0 1 0 8Zm8-6.5a6.5 6.5 0 1 0 0 13 6.5 6.5 0 0 0 0-13ZM6.5 7.75A.75.75 0 0 1 7.25 7h1a.75.75 0 0 1 .75.75v2.75h.25a.75.75 0 0 1 0 1.5h-2a.75.75 0 0 1 0-1.5h.25v-2h-.25a.75.75 0 0 1-.75-.75ZM8 6a1 1 0 1 1 0-2 1 1 0 0 1 0 2Z\"></path></svg>Note</p>\n<p>Highlights information that users should take into account, even when skimming.</p>\n<p>Testing rendering for multiple lines</p>\n<p><code>Inline code testing</code></p>\n<p>Other line</p>\n<blockquote>\n<p>Nested quote</p>\n<p>Final nested quote line</p>\n</blockquote>\n<p>Final line of alert</p>\n</div>", "advanced", context: "Example 3\nSection Extensions / Alert Blocks\n");
+        }
+
+        // An alert inline (e.g `[!NOTE]`) must come first in a quote block, and must be followed by optional spaces with a new line. If no new lines are found, it will not be considered as an alert block.
+        // 
+        // Followed by space and new line:
+        [Test]
+        public void ExtensionsAlertBlocks_Example004()
+        {
+            // Example 4
+            // Section: Extensions / Alert Blocks
+            //
+            // The following Markdown:
+            //     > [!NOTE] This is invalid because no new line
+            //     > Highlights information that users should take into account, even when skimming.
+            //
+            // Should be rendered as:
+            //     <blockquote>
+            //     <p>[!NOTE] This is invalid because no new line
+            //     Highlights information that users should take into account, even when skimming.</p>
+            //     </blockquote>
+
+            TestParser.TestSpec("> [!NOTE] This is invalid because no new line\n> Highlights information that users should take into account, even when skimming.", "<blockquote>\n<p>[!NOTE] This is invalid because no new line\nHighlights information that users should take into account, even when skimming.</p>\n</blockquote>", "advanced", context: "Example 4\nSection Extensions / Alert Blocks\n");
+        }
+
+        // Must come first in a quote block:
+        [Test]
+        public void ExtensionsAlertBlocks_Example005()
+        {
+            // Example 5
+            // Section: Extensions / Alert Blocks
+            //
+            // The following Markdown:
+            //     > This is not a [!NOTE]
+            //     > Highlights information that users should take into account, even when skimming.
+            //
+            // Should be rendered as:
+            //     <blockquote>
+            //     <p>This is not a [!NOTE]
+            //     Highlights information that users should take into account, even when skimming.</p>
+            //     </blockquote>
+
+            TestParser.TestSpec("> This is not a [!NOTE]\n> Highlights information that users should take into account, even when skimming.", "<blockquote>\n<p>This is not a [!NOTE]\nHighlights information that users should take into account, even when skimming.</p>\n</blockquote>", "advanced", context: "Example 5\nSection Extensions / Alert Blocks\n");
+        }
+    }
+}

src/Markdig.Tests/Specs/AlertBlockSpecs.md

@@ -0,0 +1,127 @@
+# Extensions
+
+This section describes the different extensions supported:
+
+## Alert Blocks
+
+This is supporting the [GitHub Alert blocks](https://github.com/orgs/community/discussions/16925)
+
+```````````````````````````````` example
+> [!NOTE]  
+> Highlights information that users should take into account, even when skimming.
+
+> [!TIP]
+> Optional information to help a user be more successful.
+
+> [!IMPORTANT]  
+> Crucial information necessary for users to succeed.
+
+> [!WARNING]  
+> Critical content demanding immediate user attention due to potential risks.
+
+> [!CAUTION]
+> Negative potential consequences of an action.
+.
+<div class="markdown-alert markdown-alert-note">
+<p class="markdown-alert-title"><svg viewBox="0 0 16 16" version="1.1" width="16" height="16" aria-hidden="true"><path d="M0 8a8 8 0 1 1 16 0A8 8 0 0 1 0 8Zm8-6.5a6.5 6.5 0 1 0 0 13 6.5 6.5 0 0 0 0-13ZM6.5 7.75A.75.75 0 0 1 7.25 7h1a.75.75 0 0 1 .75.75v2.75h.25a.75.75 0 0 1 0 1.5h-2a.75.75 0 0 1 0-1.5h.25v-2h-.25a.75.75 0 0 1-.75-.75ZM8 6a1 1 0 1 1 0-2 1 1 0 0 1 0 2Z"></path></svg>Note</p>
+<p>Highlights information that users should take into account, even when skimming.</p>
+</div>
+<div class="markdown-alert markdown-alert-tip">
+<p class="markdown-alert-title"><svg viewBox="0 0 16 16" version="1.1" width="16" height="16" aria-hidden="true"><path d="M8 1.5c-2.363 0-4 1.69-4 3.75 0 .984.424 1.625.984 2.304l.214.253c.223.264.47.556.673.848.284.411.537.896.621 1.49a.75.75 0 0 1-1.484.211c-.04-.282-.163-.547-.37-.847a8.456 8.456 0 0 0-.542-.68c-.084-.1-.173-.205-.268-.32C3.201 7.75 2.5 6.766 2.5 5.25 2.5 2.31 4.863 0 8 0s5.5 2.31 5.5 5.25c0 1.516-.701 2.5-1.328 3.259-.095.115-.184.22-.268.319-.207.245-.383.453-.541.681-.208.3-.33.565-.37.847a.751.751 0 0 1-1.485-.212c.084-.593.337-1.078.621-1.489.203-.292.45-.584.673-.848.075-.088.147-.173.213-.253.561-.679.985-1.32.985-2.304 0-2.06-1.637-3.75-4-3.75ZM5.75 12h4.5a.75.75 0 0 1 0 1.5h-4.5a.75.75 0 0 1 0-1.5ZM6 15.25a.75.75 0 0 1 .75-.75h2.5a.75.75 0 0 1 0 1.5h-2.5a.75.75 0 0 1-.75-.75Z"></path></svg>Tip</p>
+<p>Optional information to help a user be more successful.</p>
+</div>
+<div class="markdown-alert markdown-alert-important">
+<p class="markdown-alert-title"><svg viewBox="0 0 16 16" version="1.1" width="16" height="16" aria-hidden="true"><path d="M0 1.75C0 .784.784 0 1.75 0h12.5C15.216 0 16 .784 16 1.75v9.5A1.75 1.75 0 0 1 14.25 13H8.06l-2.573 2.573A1.458 1.458 0 0 1 3 14.543V13H1.75A1.75 1.75 0 0 1 0 11.25Zm1.75-.25a.25.25 0 0 0-.25.25v9.5c0 .138.112.25.25.25h2a.75.75 0 0 1 .75.75v2.19l2.72-2.72a.749.749 0 0 1 .53-.22h6.5a.25.25 0 0 0 .25-.25v-9.5a.25.25 0 0 0-.25-.25Zm7 2.25v2.5a.75.75 0 0 1-1.5 0v-2.5a.75.75 0 0 1 1.5 0ZM9 9a1 1 0 1 1-2 0 1 1 0 0 1 2 0Z"></path></svg>Important</p>
+<p>Crucial information necessary for users to succeed.</p>
+</div>
+<div class="markdown-alert markdown-alert-warning">
+<p class="markdown-alert-title"><svg viewBox="0 0 16 16" version="1.1" width="16" height="16" aria-hidden="true"><path d="M6.457 1.047c.659-1.234 2.427-1.234 3.086 0l6.082 11.378A1.75 1.75 0 0 1 14.082 15H1.918a1.75 1.75 0 0 1-1.543-2.575Zm1.763.707a.25.25 0 0 0-.44 0L1.698 13.132a.25.25 0 0 0 .22.368h12.164a.25.25 0 0 0 .22-.368Zm.53 3.996v2.5a.75.75 0 0 1-1.5 0v-2.5a.75.75 0 0 1 1.5 0ZM9 11a1 1 0 1 1-2 0 1 1 0 0 1 2 0Z"></path></svg>Warning</p>
+<p>Critical content demanding immediate user attention due to potential risks.</p>
+</div>
+<div class="markdown-alert markdown-alert-caution">
+<p class="markdown-alert-title"><svg viewBox="0 0 16 16" version="1.1" width="16" height="16" aria-hidden="true"><path d="M4.47.22A.749.749 0 0 1 5 0h6c.199 0 .389.079.53.22l4.25 4.25c.141.14.22.331.22.53v6a.749.749 0 0 1-.22.53l-4.25 4.25A.749.749 0 0 1 11 16H5a.749.749 0 0 1-.53-.22L.22 11.53A.749.749 0 0 1 0 11V5c0-.199.079-.389.22-.53Zm.84 1.28L1.5 5.31v5.38l3.81 3.81h5.38l3.81-3.81V5.31L10.69 1.5ZM8 4a.75.75 0 0 1 .75.75v3.5a.75.75 0 0 1-1.5 0v-3.5A.75.75 0 0 1 8 4Zm0 8a1 1 0 1 1 0-2 1 1 0 0 1 0 2Z"></path></svg>Caution</p>
+<p>Negative potential consequences of an action.</p>
+</div>
+````````````````````````````````
+
+Example with code blocks and mix formatting:
+
+
+```````````````````````````````` example
+> [!NOTE]
+> Highlights information that users should take into account, even when skimming.
+> Testing rendering for multiple lines
+> ```csharp
+> var test = "I can also add code to panels
+> ```
+> `Inline code testing`
+.
+<div class="markdown-alert markdown-alert-note">
+<p class="markdown-alert-title"><svg viewBox="0 0 16 16" version="1.1" width="16" height="16" aria-hidden="true"><path d="M0 8a8 8 0 1 1 16 0A8 8 0 0 1 0 8Zm8-6.5a6.5 6.5 0 1 0 0 13 6.5 6.5 0 0 0 0-13ZM6.5 7.75A.75.75 0 0 1 7.25 7h1a.75.75 0 0 1 .75.75v2.75h.25a.75.75 0 0 1 0 1.5h-2a.75.75 0 0 1 0-1.5h.25v-2h-.25a.75.75 0 0 1-.75-.75ZM8 6a1 1 0 1 1 0-2 1 1 0 0 1 0 2Z"></path></svg>Note</p>
+<p>Highlights information that users should take into account, even when skimming.
+Testing rendering for multiple lines</p>
+<pre><code class="language-csharp">var test = &quot;I can also add code to panels
+</code></pre>
+<p><code>Inline code testing</code></p>
+</div>
+````````````````````````````````
+
+Multiline:
+
+```````````````````````````````` example
+> [!NOTE]
+> Highlights information that users should take into account, even when skimming.
+> 
+> Testing rendering for multiple lines
+> 
+> `Inline code testing`
+> 
+> Other line
+> 
+> > Nested quote
+> >
+> > Final nested quote line
+> 
+> Final line of alert
+.
+<div class="markdown-alert markdown-alert-note">
+<p class="markdown-alert-title"><svg viewBox="0 0 16 16" version="1.1" width="16" height="16" aria-hidden="true"><path d="M0 8a8 8 0 1 1 16 0A8 8 0 0 1 0 8Zm8-6.5a6.5 6.5 0 1 0 0 13 6.5 6.5 0 0 0 0-13ZM6.5 7.75A.75.75 0 0 1 7.25 7h1a.75.75 0 0 1 .75.75v2.75h.25a.75.75 0 0 1 0 1.5h-2a.75.75 0 0 1 0-1.5h.25v-2h-.25a.75.75 0 0 1-.75-.75ZM8 6a1 1 0 1 1 0-2 1 1 0 0 1 0 2Z"></path></svg>Note</p>
+<p>Highlights information that users should take into account, even when skimming.</p>
+<p>Testing rendering for multiple lines</p>
+<p><code>Inline code testing</code></p>
+<p>Other line</p>
+<blockquote>
+<p>Nested quote</p>
+<p>Final nested quote line</p>
+</blockquote>
+<p>Final line of alert</p>
+</div>
+````````````````````````````````
+
+An alert inline (e.g `[!NOTE]`) must come first in a quote block, and must be followed by optional spaces with a new line. If no new lines are found, it will not be considered as an alert block.
+
+Followed by space and new line:
+
+```````````````````````````````` example
+> [!NOTE] This is invalid because no new line
+> Highlights information that users should take into account, even when skimming.
+.
+<blockquote>
+<p>[!NOTE] This is invalid because no new line
+Highlights information that users should take into account, even when skimming.</p>
+</blockquote>
+````````````````````````````````
+
+Must come first in a quote block:
+
+```````````````````````````````` example
+> This is not a [!NOTE]
+> Highlights information that users should take into account, even when skimming.
+.
+<blockquote>
+<p>This is not a [!NOTE]
+Highlights information that users should take into account, even when skimming.</p>
+</blockquote>
+````````````````````````````````
+
+

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

@@ -17,7 +17,7 @@ namespace Markdig.Tests.Specs.Diagrams
         // 
         // ## Mermaid diagrams
         //  
-        // Using a fenced code block with the `mermaid` language info will output a `<div class='mermaid'>` instead of a `pre/code` block:
+        // Using a fenced code block with the `mermaid` language info will output a `<pre class='mermaid'>` block (which is the default for other code block):
         [Test]
         public void ExtensionsMermaidDiagrams_Example001()
         {
@@ -34,14 +34,14 @@ namespace Markdig.Tests.Specs.Diagrams
             //     ```
             //
             // Should be rendered as:
-            //     <div class="mermaid">graph TD;
+            //     <pre class="mermaid">graph TD;
             //         A-->B;
             //         A-->C;
             //         B-->D;
             //         C-->D;
-            //     </div>
+            //     </pre>
 
-            TestParser.TestSpec("```mermaid\ngraph TD;\n    A-->B;\n    A-->C;\n    B-->D;\n    C-->D;\n```", "<div class=\"mermaid\">graph TD;\n    A-->B;\n    A-->C;\n    B-->D;\n    C-->D;\n</div>", "diagrams|advanced", context: "Example 1\nSection Extensions / Mermaid diagrams\n");
+            TestParser.TestSpec("```mermaid\ngraph TD;\n    A-->B;\n    A-->C;\n    B-->D;\n    C-->D;\n```", "<pre class=\"mermaid\">graph TD;\n    A-->B;\n    A-->C;\n    B-->D;\n    C-->D;\n</pre>", "diagrams|advanced", context: "Example 1\nSection Extensions / Mermaid diagrams\n");
         }
     }
 

src/Markdig.Tests/Specs/DiagramsSpecs.md

@@ -4,7 +4,7 @@ Adds support for diagrams extension:
 
 ## Mermaid diagrams
  
-Using a fenced code block with the `mermaid` language info will output a `<div class='mermaid'>` instead of a `pre/code` block:
+Using a fenced code block with the `mermaid` language info will output a `<pre class='mermaid'>` block (which is the default for other code block):
 
 ```````````````````````````````` example
 ```mermaid
@@ -15,12 +15,12 @@ graph TD;
     C-->D;
 ```
 .
-<div class="mermaid">graph TD;
+<pre class="mermaid">graph TD;
     A-->B;
     A-->C;
     B-->D;
     C-->D;
-</div>
+</pre>
 ````````````````````````````````
 
 ## nomnoml diagrams

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

@@ -279,7 +279,7 @@ namespace Markdig.Tests.Specs.Math
     {
         // ## Math Block
         // 
-        // The match block can spawn on multiple lines by having a $$ starting on a line.
+        // The math block can spawn on multiple lines by having a $$ starting on a line.
         // It is working as a fenced code block.
         [Test]
         public void ExtensionsMathBlock_Example017()

src/Markdig.Tests/Specs/MathSpecs.md

@@ -127,7 +127,7 @@ $$ math $$ starting at a line
 
 ## Math Block
 
-The match block can spawn on multiple lines by having a $$ starting on a line.
+The math block can spawn on multiple lines by having a $$ starting on a line.
 It is working as a fenced code block.
 
 ```````````````````````````````` example

src/Markdig.Tests/TestEmphasisPlus.cs

@@ -1,7 +1,10 @@
 // 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 Markdig.Syntax;
+using Markdig.Syntax.Inlines;
+
 namespace Markdig.Tests;
 
 [TestFixture]
@@ -18,4 +21,17 @@ public partial class TestEmphasisPlus
     {
         TestParser.TestSpec("normal ***Strong emphasis*** normal", "<p>normal <em><strong>Strong emphasis</strong></em> normal</p>", "");
     }
+
+    [Test]
+    public void OpenEmphasisHasConvenientContentStringSlice()
+    {
+        var pipeline = new MarkdownPipelineBuilder().Build();
+
+        var document = Markdown.Parse("test*test", pipeline);
+
+        var emphasisDelimiterLiteral = (LiteralInline)((ParagraphBlock)document.LastChild).Inline.ElementAt(1);
+        Assert.That(emphasisDelimiterLiteral.Content.Text == "test*test");
+        Assert.That(emphasisDelimiterLiteral.Content.Start == 4);
+        Assert.That(emphasisDelimiterLiteral.Content.End == 4);
+    }
 }

src/Markdig.Tests/TestLinkHelper.cs

@@ -81,6 +81,22 @@ public class TestLinkHelper
         Assert.AreEqual(' ', text.CurrentChar);
     }
 
+    [Test]
+    public void TestTitleMultiline()
+    {
+        var text = new StringSlice("'this\ris\r\na\ntitle'");
+        Assert.True(LinkHelper.TryParseTitle(ref text, out string title, out _));
+        Assert.AreEqual("this\ris\r\na\ntitle", title);
+    }
+
+    [Test]
+    public void TestTitleMultilineWithSpaceAndBackslash()
+    {
+        var text = new StringSlice("'a\n\\ \\\ntitle'");
+        Assert.True(LinkHelper.TryParseTitle(ref text, out string title, out _));
+        Assert.AreEqual("a\n\\ \\\ntitle", title);
+    }
+
     [Test]
     public void TestUrlAndTitle()
     {
@@ -230,6 +246,13 @@ public class TestLinkHelper
 
     }
 
+    [Test]
+    public void TestlLinkReferenceDefinitionInvalid()
+    {
+        var text = new StringSlice("[foo]: /url (title) x\n");
+        Assert.False(LinkHelper.TryParseLinkReferenceDefinition(ref text, out _, out _, out _, out _, out _, out _));
+    }
+
     [Test]
     public void TestAutoLinkUrlSimple()
     {

src/Markdig.Tests/TestMediaLinks.cs

@@ -25,6 +25,7 @@ public class TestMediaLinks
     [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 short](https://www.youtube.com/shorts/6BUptHVuvyI?feature=share)", "<p><iframe src=\"https://www.youtube.com/embed/6BUptHVuvyI\" class=\"youtubeshort\" width=\"500\" height=\"281\" frameborder=\"0\" allowfullscreen=\"\"></iframe></p>\n")]
     [TestCase(@"![youtube.com](https://www.youtube.com/watch?v=mswPy5bt3TQ)", "<p><iframe src=\"https://www.youtube.com/embed/mswPy5bt3TQ\" class=\"youtube\" width=\"500\" height=\"281\" 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/\" class=\"yandex\" width=\"500\" height=\"281\" frameborder=\"0\"></iframe></p>\n")]
     [TestCase("![vimeo](https://vimeo.com/8607834)", "<p><iframe src=\"https://player.vimeo.com/video/8607834\" class=\"vimeo\" width=\"500\" height=\"281\" frameborder=\"0\" allowfullscreen=\"\"></iframe></p>\n")]
@@ -33,7 +34,7 @@ public class TestMediaLinks
     public void TestBuiltInHosts(string markdown, string expected)
     {
         string html = Markdown.ToHtml(markdown, GetPipeline());
-        Assert.AreEqual(html, expected);
+        Assert.AreEqual(expected, html);
     }
 
     [TestCase("![static video relative path](./video.mp4)",
@@ -43,7 +44,7 @@ public class TestMediaLinks
     public void TestBuiltInHostsWithRelativePaths(string markdown, string expected)
     {
         string html = Markdown.ToHtml(markdown, GetPipeline());
-        Assert.AreEqual(html, expected);
+        Assert.AreEqual(expected, html);
     }
     
     private class TestHostProvider : IHostProvider

src/Markdig.Tests/TestNormalize.cs

@@ -51,6 +51,16 @@ public class TestNormalize
         });
     }
 
+    [Test]
+    public void SyntaxHeadlineLevel7()
+    {
+        AssertSyntax("####### Headline", new HeadingBlock(null) {
+            HeaderChar = '#',
+            Level = 7,
+            Inline = new ContainerInline().AppendChild(new LiteralInline("Headline")),
+        });
+    }
+
     [Test]
     public void SyntaxParagraph()
     {

src/Markdig.Tests/TestPlayParser.cs

@@ -9,6 +9,13 @@ namespace Markdig.Tests;
 [TestFixture]
 public class TestPlayParser
 {
+
+    [Test]
+    public void TestInvalidSetext()
+    {
+        TestParser.TestSpec("test\n===n", "<p>test\n===n</p>", "advanced");
+    }
+
     [Test]
     public void TestBugWithEmphasisAndTable()
     {
@@ -39,6 +46,14 @@ public class TestPlayParser
         Assert.AreEqual("/yoyo", link?.Url);
     }
 
+    [Test]
+    public void TestLinkWithMultipleBackslashesInTitle()
+    {
+        var doc = Markdown.Parse(@"[link](/uri '\\\\127.0.0.1')");
+        var link = doc.Descendants<LinkInline>().FirstOrDefault();
+        Assert.AreEqual(@"\\127.0.0.1", link?.Title);
+    }
+
     [Test]
     public void TestListBug2()
     {

src/Markdig.Tests/TestSourcePosition.cs

@@ -67,6 +67,60 @@ literal      ( 2, 0) 12-21
 ");
     }
 
+    [Test]
+    public void TestParagraphWithEndNewLine()
+    {
+        Check("0123456789\n", @"
+paragraph    ( 0, 0)  0-10
+literal      ( 0, 0)  0-9
+linebreak    ( 0,10) 10-10
+", trackTrivia: true);
+
+        Check("0123456789\r", @"
+paragraph    ( 0, 0)  0-10
+literal      ( 0, 0)  0-9
+linebreak    ( 0,10) 10-10
+", trackTrivia: true);
+
+        Check("0123456789\r\n", @"
+paragraph    ( 0, 0)  0-11
+literal      ( 0, 0)  0-9
+linebreak    ( 0,10) 10-11
+", trackTrivia: true);
+    }
+
+
+    [Test]
+    public void TestMultipleParagraphsWithEndNewLine()
+    {
+        Check("0123456789\n\n0123456789\n\n", @"
+paragraph    ( 0, 0)  0-10
+literal      ( 0, 0)  0-9
+linebreak    ( 0,10) 10-10
+paragraph    ( 2, 0) 12-22
+literal      ( 2, 0) 12-21
+linebreak    ( 2,10) 22-22
+", trackTrivia: true);
+
+        Check("0123456789\r\r0123456789\r\r", @"
+paragraph    ( 0, 0)  0-10
+literal      ( 0, 0)  0-9
+linebreak    ( 0,10) 10-10
+paragraph    ( 2, 0) 12-22
+literal      ( 2, 0) 12-21
+linebreak    ( 2,10) 22-22
+", trackTrivia: true);
+
+        Check("0123456789\r\n\r\n0123456789\r\n\r\n", @"
+paragraph    ( 0, 0)  0-11
+literal      ( 0, 0)  0-9
+linebreak    ( 0,10) 10-11
+paragraph    ( 2, 0) 14-25
+literal      ( 2, 0) 14-23
+linebreak    ( 2,10) 24-25
+", trackTrivia: true);
+    }
+
     [Test]
     public void TestEmphasis()
     {
@@ -106,6 +160,17 @@ literal      ( 0, 8)  8-8
 ");
     }
 
+    [Test]
+    public void TestEmphasis4()
+    {
+        Check("**foo*", @"
+paragraph    ( 0, 0)  0-5
+literal      ( 0, 0)  0-0
+emphasis     ( 0, 1)  1-5
+literal      ( 0, 2)  2-4
+");
+    }
+
     [Test]
     public void TestEmphasisFalse()
     {
@@ -468,13 +533,17 @@ literal      ( 1, 6)  8-9
     [Test]
     public void TestAbbreviations()
     {
-        Check("*[HTML]: Hypertext Markup Language\r\n\r\nLater in a text we are using HTML and it becomes an abbr tag HTML", @"
+        Check("*[HTML]: Hypertext Markup Language\r\n\r\nLater in a text we are using HTML and it becomes an abbr tag HTML\r\n\r\nHTML abbreviation at the beginning of a line", @"
 paragraph    ( 2, 0) 38-102
 container    ( 2, 0) 38-102
 literal      ( 2, 0) 38-66
 abbreviation ( 2,29) 67-70
 literal      ( 2,33) 71-98
 abbreviation ( 2,61) 99-102
+paragraph    ( 4, 0) 107-150
+container    ( 4, 0) 107-150
+abbreviation ( 4, 0) 107-110
+literal      ( 4, 4) 111-150
 ", "abbreviations");
     }
 
@@ -644,14 +713,22 @@ literal      ( 0, 2)  2-3
     [Test]
     public void TestMathematicsInline()
     {
-        //     01 23456789AB
-        Check("0\n012 $abcd$", @"
-paragraph    ( 0, 0)  0-11
+        //     01 23456789ABCDEF
+        Check("0\n012 $abcd$ 321", @"
+paragraph    ( 0, 0)  0-15
 literal      ( 0, 0)  0-0
 linebreak    ( 0, 1)  1-1
 literal      ( 1, 0)  2-5
 math         ( 1, 4)  6-11
 attributes   ( 0, 0)  0--1
+literal      ( 1,10) 12-15
+", "mathematics");
+
+        //     012345678
+        Check("$ abcd $", @"
+paragraph    ( 0, 0)  0-7
+math         ( 0, 0)  0-7
+attributes   ( 0, 0)  0--1
 ", "mathematics");
     }
 
@@ -734,6 +811,29 @@ literal      ( 4, 2) 13-13
 ", "pipetables");
     }
 
+    [Test]
+    public void TestPipeTable3()
+    {
+        //     01234 5678 9ABCD
+        Check("|a|b\n-|-\n0|1|\n", @"
+table        ( 0, 0)  0-12
+tablerow     ( 0, 1)  1-3
+tablecell    ( 0, 1)  1-1
+paragraph    ( 0, 1)  1-1
+literal      ( 0, 1)  1-1
+tablecell    ( 0, 3)  3-3
+paragraph    ( 0, 3)  3-3
+literal      ( 0, 3)  3-3
+tablerow     ( 2, 0)  9-11
+tablecell    ( 2, 0)  9-9
+paragraph    ( 2, 0)  9-9
+literal      ( 2, 0)  9-9
+tablecell    ( 2, 2) 11-11
+paragraph    ( 2, 2) 11-11
+literal      ( 2, 2) 11-11
+", "pipetables");
+    }
+
     [Test]
     public void TestIndentedCode()
     {
@@ -825,9 +925,10 @@ literal      ( 8, 2) 77-92
 ");
     }
 
-    private static void Check(string text, string expectedResult, string extensions = null)
+    private static void Check(string text, string expectedResult, string extensions = null, bool trackTrivia = false)
     {
         var pipelineBuilder = new MarkdownPipelineBuilder().UsePreciseSourceLocation();
+        pipelineBuilder.TrackTrivia = trackTrivia;
         if (extensions != null)
         {
             pipelineBuilder.Configure(extensions);

src/Markdig.Tests/TestStringSliceList.cs

@@ -1,3 +1,4 @@
+using System.Collections;
 using System.Text;
 
 using Markdig.Helpers;
@@ -215,4 +216,27 @@ public class TestStringSliceList
         TextAssert.AreEqual("ABC\r\nD\r\n", chars.ToString());
         TextAssert.AreEqual("ABC\r\nD", text.ToString());
     }
-}
+
+    [Test]
+    public void TestStringLineGroup_EnumeratorReturnsRealLines()
+    {
+        string str = "A\r\n";
+        var text = new StringLineGroup(4)
+        {
+            new StringSlice(str, NewLine.CarriageReturnLineFeed) { Start = 0, End = 0 }
+        };
+
+        var enumerator = ((IEnumerable)text).GetEnumerator();
+        Assert.True(enumerator.MoveNext());
+        StringLine currentLine = (StringLine)enumerator.Current;
+        TextAssert.AreEqual("A", currentLine.ToString());
+        Assert.False(enumerator.MoveNext());
+        
+        var nonBoxedEnumerator = text.GetEnumerator();
+
+        Assert.True(nonBoxedEnumerator.MoveNext());
+        currentLine = (StringLine)nonBoxedEnumerator.Current;
+        TextAssert.AreEqual("A", currentLine.ToString());
+        Assert.False(nonBoxedEnumerator.MoveNext());
+    }
+}

src/Markdig.Tests/TestYamlFrontMatterExtension.cs

@@ -75,8 +75,11 @@ public class TestYamlFrontMatterExtension
             ObjectRenderers = new ObjectRendererCollection();
         }
 
+#pragma warning disable CS0067 // ObjectWriteBefore/ObjectWriteAfter is never used
         public event Action<IMarkdownRenderer, MarkdownObject> ObjectWriteBefore;
         public event Action<IMarkdownRenderer, MarkdownObject> ObjectWriteAfter;
+#pragma warning restore CS0067
+
         public ObjectRendererCollection ObjectRenderers { get; }
         public object Render(MarkdownObject markdownObject)
         {
@@ -104,7 +107,7 @@ public class TestYamlFrontMatterExtension
             }
         }
 
-        Assert.Pass("No exception parsing and iterating through YAML front matter block lines");
+        // No exception parsing and iterating through YAML front matter block lines
     }
 
 }

src/Markdig.WebApp/Markdig.WebApp.csproj

@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk.Web">
 
   <PropertyGroup>
-    <TargetFramework>net6.0</TargetFramework>
+    <TargetFramework>net8.0</TargetFramework>
     <PreserveCompilationContext>true</PreserveCompilationContext>
     <AssemblyName>Markdig.WebApp</AssemblyName>
     <ImplicitUsings>enable</ImplicitUsings>
@@ -14,7 +14,7 @@
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="Microsoft.ApplicationInsights.AspNetCore" Version="2.20.0" />
+    <PackageReference Include="Microsoft.ApplicationInsights.AspNetCore" Version="2.22.0" />
   </ItemGroup>
 
   <ItemGroup>

src/Markdig/Extensions/Abbreviations/AbbreviationParser.cs

@@ -20,7 +20,7 @@ public class AbbreviationParser : BlockParser
     /// </summary>
     public AbbreviationParser()
     {
-        OpeningCharacters = new[] { '*' };
+        OpeningCharacters = ['*'];
     }
 
     public override BlockState TryOpen(BlockProcessor processor)
@@ -89,6 +89,7 @@ public class AbbreviationParser : BlockParser
         {
             var literal = (LiteralInline)processor.Inline!;
             var originalLiteral = literal;
+            var originalSpanEnd = literal.Span.End;
 
             ContainerInline? container = null;
 
@@ -171,7 +172,7 @@ public class AbbreviationParser : BlockParser
                     // Process the remaining literal
                     literal = new LiteralInline()
                     {
-                        Span = new SourceSpan(abbrInline.Span.End + 1, literal.Span.End),
+                        Span = new SourceSpan(abbrInline.Span.End + 1, originalSpanEnd),
                         Line = line,
                         Column = column + match.Length,
                     };

src/Markdig/Extensions/Alerts/AlertBlock.cs

@@ -0,0 +1,33 @@
+// 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 Markdig.Syntax;
+
+namespace Markdig.Extensions.Alerts;
+
+/// <summary>
+/// A block representing an alert quote block.
+/// </summary>
+public class AlertBlock : QuoteBlock
+{
+    /// <summary>
+    /// Creates a new instance of this block.
+    /// </summary>
+    /// <param name="kind"></param>
+    public AlertBlock(StringSlice kind) : base(null)
+    {
+        Kind = kind;
+    }
+
+    /// <summary>
+    /// Gets or sets the kind of the alert block (e.g `NOTE`, `TIP`, `IMPORTANT`, `WARNING`, `CAUTION`)
+    /// </summary>
+    public StringSlice Kind { get; set; }
+
+    /// <summary>
+    /// Gets or sets the trivia space after the kind.
+    /// </summary>
+    public StringSlice TriviaSpaceAfterKind { get; set; }
+}

src/Markdig/Extensions/Alerts/AlertBlockRenderer.cs

@@ -0,0 +1,87 @@
+// 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 Markdig.Renderers;
+using Markdig.Renderers.Html;
+using Markdig.Syntax;
+
+namespace Markdig.Extensions.Alerts;
+
+/// <summary>
+/// A HTML renderer for a <see cref="AlertBlock"/>.
+/// </summary>
+/// <seealso cref="HtmlObjectRenderer{AlertBlock}" />
+public class AlertBlockRenderer : HtmlObjectRenderer<AlertBlock>
+{
+    /// <summary>
+    /// Creates a new instance of this renderer.
+    /// </summary>
+    public AlertBlockRenderer()
+    {
+        RenderKind = DefaultRenderKind;
+    }
+
+    /// <summary>
+    /// Gets of sets a delegate to render the kind of the alert.
+    /// </summary>
+    public Action<HtmlRenderer, StringSlice> RenderKind { get; set; }
+
+
+    /// <inheritdoc />
+    protected override void Write(HtmlRenderer renderer, AlertBlock obj)
+    {
+        renderer.EnsureLine();
+        if (renderer.EnableHtmlForBlock)
+        {
+            renderer.Write("<div");
+            renderer.WriteAttributes(obj);
+            renderer.WriteLine('>');
+        }
+
+        RenderKind(renderer, obj.Kind);
+
+        var savedImplicitParagraph = renderer.ImplicitParagraph;
+        renderer.ImplicitParagraph = false;
+        renderer.WriteChildren(obj);
+        renderer.ImplicitParagraph = savedImplicitParagraph;
+        if (renderer.EnableHtmlForBlock)
+        {
+            renderer.WriteLine("</div>");
+        }
+
+        renderer.EnsureLine();
+    }
+
+
+    /// <summary>
+    /// Renders the kind of the alert.
+    /// </summary>
+    /// <param name="renderer">The HTML renderer.</param>
+    /// <param name="kind">The kind of the alert to render</param>
+    public static void DefaultRenderKind(HtmlRenderer renderer, StringSlice kind)
+    {
+        if (kind.Length >= 16)
+        {
+            return;
+        }
+
+        Span<char> upperKind = stackalloc char[kind.Length];
+        kind.AsSpan().ToUpperInvariant(upperKind);
+        string? html = upperKind switch
+        {
+            "NOTE" => "<p class=\"markdown-alert-title\"><svg viewBox=\"0 0 16 16\" version=\"1.1\" width=\"16\" height=\"16\" aria-hidden=\"true\"><path d=\"M0 8a8 8 0 1 1 16 0A8 8 0 0 1 0 8Zm8-6.5a6.5 6.5 0 1 0 0 13 6.5 6.5 0 0 0 0-13ZM6.5 7.75A.75.75 0 0 1 7.25 7h1a.75.75 0 0 1 .75.75v2.75h.25a.75.75 0 0 1 0 1.5h-2a.75.75 0 0 1 0-1.5h.25v-2h-.25a.75.75 0 0 1-.75-.75ZM8 6a1 1 0 1 1 0-2 1 1 0 0 1 0 2Z\"></path></svg>Note</p>",
+            "TIP" => "<p class=\"markdown-alert-title\"><svg viewBox=\"0 0 16 16\" version=\"1.1\" width=\"16\" height=\"16\" aria-hidden=\"true\"><path d=\"M8 1.5c-2.363 0-4 1.69-4 3.75 0 .984.424 1.625.984 2.304l.214.253c.223.264.47.556.673.848.284.411.537.896.621 1.49a.75.75 0 0 1-1.484.211c-.04-.282-.163-.547-.37-.847a8.456 8.456 0 0 0-.542-.68c-.084-.1-.173-.205-.268-.32C3.201 7.75 2.5 6.766 2.5 5.25 2.5 2.31 4.863 0 8 0s5.5 2.31 5.5 5.25c0 1.516-.701 2.5-1.328 3.259-.095.115-.184.22-.268.319-.207.245-.383.453-.541.681-.208.3-.33.565-.37.847a.751.751 0 0 1-1.485-.212c.084-.593.337-1.078.621-1.489.203-.292.45-.584.673-.848.075-.088.147-.173.213-.253.561-.679.985-1.32.985-2.304 0-2.06-1.637-3.75-4-3.75ZM5.75 12h4.5a.75.75 0 0 1 0 1.5h-4.5a.75.75 0 0 1 0-1.5ZM6 15.25a.75.75 0 0 1 .75-.75h2.5a.75.75 0 0 1 0 1.5h-2.5a.75.75 0 0 1-.75-.75Z\"></path></svg>Tip</p>",
+            "IMPORTANT" => "<p class=\"markdown-alert-title\"><svg viewBox=\"0 0 16 16\" version=\"1.1\" width=\"16\" height=\"16\" aria-hidden=\"true\"><path d=\"M0 1.75C0 .784.784 0 1.75 0h12.5C15.216 0 16 .784 16 1.75v9.5A1.75 1.75 0 0 1 14.25 13H8.06l-2.573 2.573A1.458 1.458 0 0 1 3 14.543V13H1.75A1.75 1.75 0 0 1 0 11.25Zm1.75-.25a.25.25 0 0 0-.25.25v9.5c0 .138.112.25.25.25h2a.75.75 0 0 1 .75.75v2.19l2.72-2.72a.749.749 0 0 1 .53-.22h6.5a.25.25 0 0 0 .25-.25v-9.5a.25.25 0 0 0-.25-.25Zm7 2.25v2.5a.75.75 0 0 1-1.5 0v-2.5a.75.75 0 0 1 1.5 0ZM9 9a1 1 0 1 1-2 0 1 1 0 0 1 2 0Z\"></path></svg>Important</p>",
+            "WARNING" => "<p class=\"markdown-alert-title\"><svg viewBox=\"0 0 16 16\" version=\"1.1\" width=\"16\" height=\"16\" aria-hidden=\"true\"><path d=\"M6.457 1.047c.659-1.234 2.427-1.234 3.086 0l6.082 11.378A1.75 1.75 0 0 1 14.082 15H1.918a1.75 1.75 0 0 1-1.543-2.575Zm1.763.707a.25.25 0 0 0-.44 0L1.698 13.132a.25.25 0 0 0 .22.368h12.164a.25.25 0 0 0 .22-.368Zm.53 3.996v2.5a.75.75 0 0 1-1.5 0v-2.5a.75.75 0 0 1 1.5 0ZM9 11a1 1 0 1 1-2 0 1 1 0 0 1 2 0Z\"></path></svg>Warning</p>",
+            "CAUTION" => "<p class=\"markdown-alert-title\"><svg viewBox=\"0 0 16 16\" version=\"1.1\" width=\"16\" height=\"16\" aria-hidden=\"true\"><path d=\"M4.47.22A.749.749 0 0 1 5 0h6c.199 0 .389.079.53.22l4.25 4.25c.141.14.22.331.22.53v6a.749.749 0 0 1-.22.53l-4.25 4.25A.749.749 0 0 1 11 16H5a.749.749 0 0 1-.53-.22L.22 11.53A.749.749 0 0 1 0 11V5c0-.199.079-.389.22-.53Zm.84 1.28L1.5 5.31v5.38l3.81 3.81h5.38l3.81-3.81V5.31L10.69 1.5ZM8 4a.75.75 0 0 1 .75.75v3.5a.75.75 0 0 1-1.5 0v-3.5A.75.75 0 0 1 8 4Zm0 8a1 1 0 1 1 0-2 1 1 0 0 1 0 2Z\"></path></svg>Caution</p>",
+            _ => null
+        };
+
+        if (html is not null)
+        {
+            renderer.WriteLine(html);
+        }
+    }
+}

src/Markdig/Extensions/Alerts/AlertExtension.cs

@@ -0,0 +1,44 @@
+// 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 Markdig.Parsers.Inlines;
+using Markdig.Renderers;
+using Markdig.Renderers.Html;
+
+namespace Markdig.Extensions.Alerts;
+
+/// <summary>
+/// Extension for adding alerts to a Markdown pipeline.
+/// </summary>
+public class AlertExtension : IMarkdownExtension
+{
+    /// <summary>
+    /// Gets or sets the delegate to render the kind of the alert.
+    /// </summary>
+    public Action<HtmlRenderer, StringSlice>? RenderKind { get; set; }
+
+    /// <inheritdoc />
+    public void Setup(MarkdownPipelineBuilder pipeline)
+    {
+        var inlineParser = pipeline.InlineParsers.Find<AlertInlineParser>();
+        if (inlineParser == null)
+        {
+            pipeline.InlineParsers.InsertBefore<LinkInlineParser>(new AlertInlineParser());
+        }
+    }
+
+    /// <inheritdoc />
+    public void Setup(MarkdownPipeline pipeline, IMarkdownRenderer renderer)
+    {
+        var blockRenderer = renderer.ObjectRenderers.FindExact<AlertBlockRenderer>();
+        if (blockRenderer == null)
+        {
+            renderer.ObjectRenderers.InsertBefore<QuoteBlockRenderer>(new AlertBlockRenderer()
+            {
+                RenderKind = RenderKind ?? AlertBlockRenderer.DefaultRenderKind
+            });
+        }
+    }
+}

src/Markdig/Extensions/Alerts/AlertInlineParser.cs

@@ -0,0 +1,128 @@
+// 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 Markdig.Parsers;
+using Markdig.Renderers.Html;
+using Markdig.Syntax;
+using Markdig.Syntax.Inlines;
+
+namespace Markdig.Extensions.Alerts;
+
+/// <summary>
+/// An inline parser for an alert inline (e.g. `[!NOTE]`).
+/// </summary>
+/// <seealso cref="InlineParser" />
+public class AlertInlineParser : InlineParser
+{
+    /// <summary>
+    /// Initializes a new instance of the <see cref="AlertInlineParser"/> class.
+    /// </summary>
+    public AlertInlineParser()
+    {
+        OpeningCharacters = ['['];
+    }
+
+    public override bool Match(InlineProcessor processor, ref StringSlice slice)
+    {
+        // We expect the alert to be the first child of a quote block. Example:
+        // > [!NOTE]
+        // > This is a note
+        if (processor.Block is not ParagraphBlock paragraphBlock || paragraphBlock.Parent is not QuoteBlock quoteBlock || paragraphBlock.Inline?.FirstChild != null
+            || quoteBlock is AlertBlock || quoteBlock.Parent is not MarkdownDocument)
+        {
+            return false;
+        }
+
+        var saved = slice;
+        var c = slice.NextChar();
+        if (c != '!')
+        {
+            slice = saved;
+            return false;
+        }
+
+        c = slice.NextChar(); // Skip !
+
+        var start = slice.Start;
+        var end = start;
+        while (c.IsAlpha())
+        {
+            end = slice.Start;
+            c = slice.NextChar();
+        }
+
+        // We need at least one character
+        if (c != ']' || start == end)
+        {
+            slice = saved;
+            return false;
+        }
+
+        var alertType = new StringSlice(slice.Text, start, end);
+        c = slice.NextChar(); // Skip ]
+
+        start = slice.Start;
+        while (true)
+        {
+            if (c == '\0' || c == '\n' || c == '\r')
+            {
+                end = slice.Start;
+                if (c == '\r')
+                {
+                    c = slice.NextChar(); // Skip \r
+                    if (c == '\0' || c == '\n')
+                    {
+                        end = slice.Start;
+                        if (c == '\n')
+                        {
+                            slice.NextChar(); // Skip \n
+                        }
+                    }
+                }
+                else if (c == '\n')
+                {
+                    slice.NextChar(); // Skip \n
+                }
+                break;
+            }
+            else if (!c.IsSpaceOrTab())
+            {
+                slice = saved;
+                return false;
+            }
+
+            c = slice.NextChar();
+        }
+
+        var alertBlock = new AlertBlock(alertType)
+        {
+            Span = quoteBlock.Span,
+            TriviaSpaceAfterKind = new StringSlice(slice.Text, start, end),
+            Line = quoteBlock.Line,
+            Column = quoteBlock.Column,
+        };
+
+        alertBlock.GetAttributes().AddClass("markdown-alert");
+        alertBlock.GetAttributes().AddClass($"markdown-alert-{alertType.ToString().ToLowerInvariant()}");
+
+        // Replace the quote block with the alert block
+        var parentQuoteBlock = quoteBlock.Parent!;
+        var indexOfQuoteBlock = parentQuoteBlock.IndexOf(quoteBlock);
+        parentQuoteBlock[indexOfQuoteBlock] = alertBlock;
+
+        while (quoteBlock.Count > 0)
+        {
+            var block = quoteBlock[0];
+            quoteBlock.RemoveAt(0);
+            alertBlock.Add(block);
+        }
+
+        // Workaround to replace the parent container
+        // Experimental API, so we are keeping it internal for now until we are sure it's the way we want to go
+        processor.ReplaceParentContainer(quoteBlock, alertBlock);
+
+        return true;
+    }
+}

src/Markdig/Extensions/AutoIdentifiers/AutoIdentifierExtension.cs

@@ -2,8 +2,6 @@
 // This file is licensed under the BSD-Clause 2 license.
 // See the license.txt file in the project root for more information.
 
-using System.IO;
-
 using Markdig.Helpers;
 using Markdig.Parsers;
 using Markdig.Renderers;
@@ -20,8 +18,10 @@ namespace Markdig.Extensions.AutoIdentifiers;
 public class AutoIdentifierExtension : IMarkdownExtension
 {
     private const string AutoIdentifierKey = "AutoIdentifier";
-    private readonly AutoIdentifierOptions options;
-    private readonly StripRendererCache rendererCache = new StripRendererCache();
+
+    private static readonly StripRendererCache _rendererCache = new();
+
+    private readonly AutoIdentifierOptions _options;
 
     /// <summary>
     /// Initializes a new instance of the <see cref="AutoIdentifierExtension"/> class.
@@ -29,7 +29,7 @@ public class AutoIdentifierExtension : IMarkdownExtension
     /// <param name="options">The options.</param>
     public AutoIdentifierExtension(AutoIdentifierOptions options)
     {
-        this.options = options;
+        _options = options;
     }
 
     public void Setup(MarkdownPipelineBuilder pipeline)
@@ -68,7 +68,7 @@ public class AutoIdentifierExtension : IMarkdownExtension
         }
 
         // If the AutoLink options is set, we register a LinkReferenceDefinition at the document level
-        if ((options & AutoIdentifierOptions.AutoLink) != 0)
+        if ((_options & AutoIdentifierOptions.AutoLink) != 0)
         {
             var headingLine = headingBlock.Lines.Lines[0];
 
@@ -157,16 +157,17 @@ public class AutoIdentifierExtension : IMarkdownExtension
         }
 
         // Use internally a HtmlRenderer to strip links from a heading
-        var stripRenderer = rendererCache.Get();
+        var stripRenderer = _rendererCache.Get();
 
         stripRenderer.Render(headingBlock.Inline);
-        var headingText = stripRenderer.Writer.ToString()!;
-        rendererCache.Release(stripRenderer);
+        ReadOnlySpan<char> rawHeadingText = ((FastStringWriter)stripRenderer.Writer).AsSpan();
 
         // Urilize the link
-        headingText = (options & AutoIdentifierOptions.GitHub) != 0
-            ? LinkHelper.UrilizeAsGfm(headingText)
-            : LinkHelper.Urilize(headingText, (options & AutoIdentifierOptions.AllowOnlyAscii) != 0);
+        string headingText = (_options & AutoIdentifierOptions.GitHub) != 0
+            ? LinkHelper.UrilizeAsGfm(rawHeadingText)
+            : LinkHelper.Urilize(rawHeadingText, (_options & AutoIdentifierOptions.AllowOnlyAscii) != 0);
+
+        _rendererCache.Release(stripRenderer);
 
         // If the heading is empty, use the word "section" instead
         var baseHeadingId = string.IsNullOrEmpty(headingText) ? "section" : headingText;
@@ -197,7 +198,7 @@ public class AutoIdentifierExtension : IMarkdownExtension
     {
         protected override HtmlRenderer NewInstance()
         {
-            var headingWriter = new StringWriter();
+            var headingWriter = new FastStringWriter();
             var stripRenderer = new HtmlRenderer(headingWriter)
             {
                 // Set to false both to avoid having any HTML tags in the output
@@ -209,7 +210,9 @@ public class AutoIdentifierExtension : IMarkdownExtension
 
         protected override void Reset(HtmlRenderer instance)
         {
-            instance.Reset();
+            instance.ResetInternal();
+
+            ((FastStringWriter)instance.Writer).Reset();
         }
     }
 }

src/Markdig/Extensions/AutoLinks/AutoLinkExtension.cs

@@ -11,14 +11,9 @@ namespace Markdig.Extensions.AutoLinks;
 /// Extension to automatically create <see cref="LinkInline"/> when a link url http: or mailto: is found.
 /// </summary>
 /// <seealso cref="IMarkdownExtension" />
-public class AutoLinkExtension : IMarkdownExtension
+public class AutoLinkExtension(AutoLinkOptions? options) : IMarkdownExtension
 {
-    public readonly AutoLinkOptions Options;
-
-    public AutoLinkExtension(AutoLinkOptions? options)
-    {
-        Options = options ?? new AutoLinkOptions();
-    }
+    public readonly AutoLinkOptions Options = options ?? new AutoLinkOptions();
 
     public void Setup(MarkdownPipelineBuilder pipeline)
     {

src/Markdig/Extensions/AutoLinks/AutoLinkParser.cs

@@ -22,14 +22,14 @@ public class AutoLinkParser : InlineParser
     {
         Options = options ?? throw new ArgumentNullException(nameof(options));
 
-        OpeningCharacters = new char[]
-        {
+        OpeningCharacters =
+        [
             'h', // for http:// and https://
             'f', // for ftp://
             'm', // for mailto:
             't', // for tel:
             'w', // for www.
-        };
+        ];
 
         _listOfCharCache = new ListOfCharCache();
     }

src/Markdig/Extensions/Bootstrap/BootstrapExtension.cs

@@ -1,7 +1,9 @@
 // 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.Linq;
+using Markdig.Extensions.Alerts;
 using Markdig.Renderers;
 using Markdig.Renderers.Html;
 using Markdig.Syntax;
@@ -24,10 +26,22 @@ public class BootstrapExtension : IMarkdownExtension
 
     public void Setup(MarkdownPipeline pipeline, IMarkdownRenderer renderer)
     {
+        if (renderer is HtmlRenderer htmlRenderer)
+        {
+            var alertRenderer = htmlRenderer.ObjectRenderers.OfType<AlertBlockRenderer>().FirstOrDefault();
+            if (alertRenderer == null)
+            {
+                alertRenderer = new AlertBlockRenderer();
+                renderer.ObjectRenderers.InsertBefore<QuoteBlockRenderer>(new AlertBlockRenderer());
+            }
+
+            alertRenderer.RenderKind = (_, _) => { };
+        }
     }
 
     private static void PipelineOnDocumentProcessed(MarkdownDocument document)
     {
+        Span<char> upperKind = new char[16];
         foreach (var node in document.Descendants())
         {
             if (node.IsInline)
@@ -43,6 +57,28 @@ public class BootstrapExtension : IMarkdownExtension
                 {
                     node.GetAttributes().AddClass("table");
                 }
+                else if (node is AlertBlock alertBlock) // Needs to be before QuoteBlock
+                {
+                    var attributes = node.GetAttributes();
+                    attributes.AddClass("alert");
+                    attributes.AddProperty("role", "alert");
+                    if (alertBlock.Kind.Length <= upperKind.Length)
+                    {
+                        alertBlock.Kind.AsSpan().ToUpperInvariant(upperKind);
+                        attributes.AddClass(upperKind.Slice(0, alertBlock.Kind.Length) switch
+                        {
+                            "NOTE" => "alert-primary",
+                            "TIP" => "alert-success",
+                            "IMPORTANT" => "alert-info",
+                            "WARNING" => "alert-warning",
+                            "CAUTION" => "alert-danger",
+                            _ => "alert-dark",
+                        });
+                    }
+
+                    var lastParagraph = alertBlock.Descendants().OfType<ParagraphBlock>().LastOrDefault();
+                    lastParagraph?.GetAttributes().AddClass("mb-0");
+                }
                 else if (node is QuoteBlock)
                 {
                     node.GetAttributes().AddClass("blockquote");

src/Markdig/Extensions/CustomContainers/CustomContainerExtension.cs

@@ -30,7 +30,11 @@ public class CustomContainerExtension : IMarkdownExtension
             {
                 if (delimiterCount == 2 && emphasisChar == ':')
                 {
-                    return new CustomContainerInline();
+                    return new CustomContainerInline
+                    {
+                        DelimiterChar = ':',
+                        DelimiterCount = 2
+                    };
                 }
                 return null;
             });

src/Markdig/Extensions/CustomContainers/CustomContainerParser.cs

@@ -17,7 +17,7 @@ public class CustomContainerParser : FencedBlockParserBase<CustomContainer>
     /// </summary>
     public CustomContainerParser()
     {
-        OpeningCharacters = new [] {':'};
+        OpeningCharacters = [':'];
 
         // We don't need a prefix
         InfoPrefix = null;

src/Markdig/Extensions/DefinitionLists/DefinitionListParser.cs

@@ -18,7 +18,7 @@ public class DefinitionListParser : BlockParser
     /// </summary>
     public DefinitionListParser()
     {
-        OpeningCharacters = new [] {':', '~'};
+        OpeningCharacters = [':', '~'];
     }
 
     public override BlockState TryOpen(BlockProcessor processor)
@@ -105,13 +105,20 @@ public class DefinitionListParser : BlockParser
     {
         var index = previousParent.IndexOf(paragraphBlock) - 1;
         if (index < 0) return null;
-        var lastBlock = previousParent[index];
-        if (lastBlock is BlankLineBlock)
+        switch (previousParent[index])
         {
-            lastBlock = previousParent[index - 1];
-            previousParent.RemoveAt(index);
+            case DefinitionList definitionList:
+                return definitionList;
+
+            case BlankLineBlock:
+                if (index > 0 && previousParent[index - 1] is DefinitionList definitionList2)
+                {
+                    previousParent.RemoveAt(index);
+                    return definitionList2;
+                }
+                break;
         }
-        return lastBlock as DefinitionList;
+        return null;
     }
 
     public override BlockState TryContinue(BlockProcessor processor, Block block)

src/Markdig/Extensions/Diagrams/DiagramExtension.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 Markdig.Renderers;
@@ -22,9 +22,8 @@ public class DiagramExtension : IMarkdownExtension
         if (renderer is HtmlRenderer htmlRenderer)
         {
             var codeRenderer = htmlRenderer.ObjectRenderers.FindExact<CodeBlockRenderer>()!;
-            // TODO: Add other well known diagram languages
-            codeRenderer.BlocksAsDiv.Add("mermaid");
+            codeRenderer.BlockMapping["mermaid"] = "pre";
             codeRenderer.BlocksAsDiv.Add("nomnoml");
         }
     }
-}
+}

src/Markdig/Extensions/Emoji/EmojiMapping.cs

@@ -1786,6 +1786,6 @@ public class EmojiMapping
                 ThrowHelper.ArgumentException(string.Format("Smiley {0} is already present in the emoji mapping", smiley.Key));
         }
 
-        OpeningCharacters = new List<char>(firstChars).ToArray();
+        OpeningCharacters = [.. firstChars];
     }
 }

src/Markdig/Extensions/Figures/FigureBlockParser.cs

@@ -18,7 +18,7 @@ public class FigureBlockParser : BlockParser
     /// </summary>
     public FigureBlockParser()
     {
-        OpeningCharacters = new[] { '^' };
+        OpeningCharacters = ['^'];
     }
 
     public override BlockState TryOpen(BlockProcessor processor)

src/Markdig/Extensions/Footers/FooterBlockParser.cs

@@ -19,7 +19,7 @@ public class FooterBlockParser : BlockParser
     /// </summary>
     public FooterBlockParser()
     {
-        OpeningCharacters = new[] {'^'};
+        OpeningCharacters = ['^'];
     }
 
     public override BlockState TryOpen(BlockProcessor processor)

src/Markdig/Extensions/Footnotes/FootnoteParser.cs

@@ -22,7 +22,7 @@ public class FootnoteParser : BlockParser
 
     public FootnoteParser()
     {
-        OpeningCharacters = new [] {'['};
+        OpeningCharacters = ['['];
     }
 
     public override BlockState TryOpen(BlockProcessor processor)
@@ -49,7 +49,7 @@ public class FootnoteParser : BlockParser
 
         // Advance the column
         int deltaColumn = processor.Start - start;
-        processor.Column = processor.Column + deltaColumn;
+        processor.Column += deltaColumn;
 
         processor.NextChar(); // Skip ':'
 
@@ -57,6 +57,8 @@ public class FootnoteParser : BlockParser
         {
             Label = label,
             LabelSpan = labelSpan,
+            Column = processor.Column,
+            Span = new SourceSpan(processor.Start, processor.Line.End),
         };
 
         // Maintain a list of all footnotes at document level
@@ -74,6 +76,7 @@ public class FootnoteParser : BlockParser
         {
             CreateLinkInline = CreateLinkToFootnote,
             Line = processor.LineIndex,
+            Column = saved,
             Span = new SourceSpan(start, processor.Start - 2), // account for ]:
             LabelSpan = labelSpan,
             Label = label
@@ -170,10 +173,8 @@ public class FootnoteParser : BlockParser
                 paragraphBlock = new ParagraphBlock();
                 footnote.Add(paragraphBlock);
             }
-            if (paragraphBlock.Inline == null)
-            {
-                paragraphBlock.Inline = new ContainerInline();
-            }
+
+            paragraphBlock.Inline ??= new ContainerInline();
 
             foreach (var link in footnote.Links)
             {

src/Markdig/Extensions/GenericAttributes/GenericAttributesParser.cs

@@ -23,7 +23,7 @@ public class GenericAttributesParser : InlineParser
     /// </summary>
     public GenericAttributesParser()
     {
-        OpeningCharacters = new[] { '{' };
+        OpeningCharacters = ['{'];
     }
 
     public override bool Match(InlineProcessor processor, ref StringSlice slice)
@@ -136,10 +136,7 @@ public class GenericAttributesParser : InlineParser
                 var text = slice.Text.Substring(start, end - start + 1);
                 if (isClass)
                 {
-                    if (classes is null)
-                    {
-                        classes = new List<string>();
-                    }
+                    classes ??= new List<string>();
                     classes.Add(text);
                 }
                 else

src/Markdig/Extensions/Mathematics/MathBlockParser.cs

@@ -20,7 +20,7 @@ public class MathBlockParser : FencedBlockParserBase<MathBlock>
     /// </summary>
     public MathBlockParser()
     {
-        OpeningCharacters = new [] {'$'};
+        OpeningCharacters = ['$'];
         // We expect to match only a $$, no less, no more
         MinimumMatchCount = 2;
         MaximumMatchCount = 2;

src/Markdig/Extensions/Mathematics/MathInlineParser.cs

@@ -21,7 +21,7 @@ public class MathInlineParser : InlineParser
     /// </summary>
     public MathInlineParser()
     {
-        OpeningCharacters = new[] { '$' };
+        OpeningCharacters = ['$'];
         DefaultClass = "math";
     }
 
@@ -152,7 +152,7 @@ public class MathInlineParser : InlineParser
             // Create a new MathInline
             var inline = new MathInline()
             {
-                Span = new SourceSpan(processor.GetSourcePosition(startPosition, out int line, out int column), processor.GetSourcePosition(slice.End)),
+                Span = new SourceSpan(processor.GetSourcePosition(startPosition, out int line, out int column), processor.GetSourcePosition(slice.Start - 1)),
                 Line = line,
                 Column = column,
                 Delimiter = match,

src/Markdig/Extensions/MediaLinks/HostProviderBuilder.cs

@@ -11,23 +11,19 @@ namespace Markdig.Extensions.MediaLinks;
 
 public class HostProviderBuilder
 {
-    private sealed class DelegateProvider : IHostProvider
+    private sealed class DelegateProvider(
+        string hostPrefix,
+        Func<Uri, string?> handler,
+        bool allowFullscreen = true,
+        string? className = null) : IHostProvider
     {
-        public DelegateProvider(string hostPrefix, Func<Uri, string?> handler, bool allowFullscreen = true, string? className = null)
-        {
-            HostPrefix = hostPrefix;
-            Delegate = handler;
-            AllowFullScreen = allowFullscreen;
-            Class = className;
-        }
+        public string HostPrefix { get; } = hostPrefix;
 
-        public string HostPrefix { get; }
+        public Func<Uri, string?> Delegate { get; } = handler;
 
-        public Func<Uri, string?> Delegate { get; }
+        public bool AllowFullScreen { get; } = allowFullscreen;
 
-        public bool AllowFullScreen { get; }
-
-        public string? Class { get; }
+        public string? Class { get; } = className;
 
         public bool TryHandle(Uri mediaUri, bool isSchemaRelative, [NotNullWhen(true)] out string? iframeUrl)
         {
@@ -62,6 +58,7 @@ public class HostProviderBuilder
     internal static Dictionary<string, IHostProvider> KnownHosts { get; }
         = new Dictionary<string, IHostProvider>(StringComparer.OrdinalIgnoreCase)
         {
+            ["YouTubeShort"] = Create("www.youtube.com", YouTubeShort, iframeClass: "youtubeshort"),
             ["YouTube"] = Create("www.youtube.com", YouTube, iframeClass: "youtube"),
             ["YouTubeShortened"] = Create("youtu.be", YouTubeShortened, iframeClass: "youtube"),
             ["Vimeo"] = Create("vimeo.com", Vimeo, iframeClass: "vimeo"),
@@ -71,7 +68,7 @@ public class HostProviderBuilder
 
     #region Known providers
 
-    private static readonly string[] SplitAnd = { "&" };
+    private static readonly string[] SplitAnd = ["&"];
     private static string[] SplitQuery(Uri uri)
     {
         var query = uri.Query.Substring(uri.Query.IndexOf('?') + 1);
@@ -96,6 +93,19 @@ public class HostProviderBuilder
         );
     }
 
+    private static string? YouTubeShort(Uri uri)
+    {
+        string uriPath = uri.AbsolutePath;
+        bool isYouTubeShort = uriPath.StartsWith("/shorts/", StringComparison.OrdinalIgnoreCase);
+        if (!isYouTubeShort)
+        {
+            return null;
+        }
+
+        var shortId = uriPath.Substring("/shorts/".Length).Split('?').FirstOrDefault(); // the format might be "/shorts/6BUptHVuvyI?feature=share"
+        return BuildYouTubeIframeUrl(shortId, null);
+    }
+
     private static string? YouTubeShortened(Uri uri)
     {
         return BuildYouTubeIframeUrl(

src/Markdig/Extensions/NoRefLinks/NoFollowLinksExtension.cs

@@ -17,7 +17,7 @@ public class NoFollowLinksExtension : IMarkdownExtension
 
     public NoFollowLinksExtension()
     {
-        _referralLinksExtension = new ReferralLinksExtension(new[] { "nofollow" });
+        _referralLinksExtension = new ReferralLinksExtension(["nofollow"]);
     }
 
     public void Setup(MarkdownPipelineBuilder pipeline)

src/Markdig/Extensions/SmartyPants/SmartyPantsInlineParser.cs

@@ -19,7 +19,7 @@ public class SmartyPantsInlineParser : InlineParser, IPostInlineProcessor
     /// </summary>
     public SmartyPantsInlineParser()
     {
-        OpeningCharacters = new[] {'\'', '"', '<', '>', '.', '-'};
+        OpeningCharacters = ['\'', '"', '<', '>', '.', '-'];
     }
 
     public override bool Match(InlineProcessor processor, ref StringSlice slice)

src/Markdig/Extensions/Tables/GridTableParser.cs

@@ -12,7 +12,7 @@ public class GridTableParser : BlockParser
 {
     public GridTableParser()
     {
-        OpeningCharacters = new[] { '+' };
+        OpeningCharacters = ['+'];
     }
 
     public override BlockState TryOpen(BlockProcessor processor)
@@ -135,6 +135,7 @@ public class GridTableParser : BlockParser
     private static void SetRowSpanState(List<GridTableState.ColumnSlice> columns, StringSlice line, out bool isHeaderRow, out bool hasRowSpan)
     {
         var lineStart = line.Start;
+        var lineEnd = line.End;
         isHeaderRow = line.PeekChar() == '=' || line.PeekChar(2) == '=';
         hasRowSpan = false;
         foreach (var columnSlice in columns)
@@ -142,9 +143,9 @@ public class GridTableParser : BlockParser
             if (columnSlice.CurrentCell != null)
             {
                 line.Start = lineStart + columnSlice.Start + 1;
-                line.End = lineStart + columnSlice.End - 1;
+                line.End = Math.Min(lineStart + columnSlice.End - 1, lineEnd);
                 line.Trim();
-                if (line.IsEmptyOrWhitespace() || !IsRowSeperator(line))
+                if (line.IsEmptyOrWhitespace() || !IsRowSeparator(line))
                 {
                     hasRowSpan = true;
                     columnSlice.CurrentCell.RowSpan++;
@@ -158,7 +159,7 @@ public class GridTableParser : BlockParser
         }
     }
 
-    private static bool IsRowSeperator(StringSlice slice)
+    private static bool IsRowSeparator(StringSlice slice)
     {
         char c = slice.CurrentChar;
         do
@@ -256,14 +257,14 @@ public class GridTableParser : BlockParser
                 {
                     sliceForCell.End = line.Start + columnEnd - 1;
                 }
-                else if (line.PeekCharExtra(line.End) == '|')
+                else if (line.PeekCharExtra(line.End - line.Start) == '|')
                 {
                     sliceForCell.End = line.End - 1;
                 }
             }
             sliceForCell.TrimEnd();
 
-            if (!isRowLine || !IsRowSeperator(sliceForCell))
+            if (!isRowLine || !IsRowSeparator(sliceForCell))
             {
                 if (columnSlice.CurrentCell is null)
                 {
@@ -273,10 +274,7 @@ public class GridTableParser : BlockParser
                         ColumnIndex = i
                     };
 
-                    if (columnSlice.BlockProcessor is null)
-                    {
-                        columnSlice.BlockProcessor = processor.CreateChild();
-                    }
+                    columnSlice.BlockProcessor ??= processor.CreateChild();
 
                     // Ensure that the BlockParser is aware that the TableCell is the top-level container
                     columnSlice.BlockProcessor.Open(columnSlice.CurrentCell);

src/Markdig/Extensions/Tables/GridTableState.cs

@@ -10,21 +10,15 @@ namespace Markdig.Extensions.Tables;
 /// <summary>
 /// Internal state used by the <see cref="GridTableParser"/>
 /// </summary>
-internal sealed class GridTableState
+internal sealed class GridTableState(int start, bool expectRow)
 {
-    public GridTableState(int start, bool expectRow)
-    {
-        Start = start;
-        ExpectRow = expectRow;
-    }
-
-    public int Start { get; }
+    public int Start { get; } = start;
 
     public StringLineGroup Lines;
 
     public List<ColumnSlice>? ColumnSlices { get; private set; }
 
-    public bool ExpectRow { get; }
+    public bool ExpectRow { get; } = expectRow;
 
     public int StartRowGroup { get; set; }
 
@@ -45,26 +39,18 @@ internal sealed class GridTableState
         ColumnSlices.Add(new ColumnSlice(start, end, align));
     }
 
-    public sealed class ColumnSlice
+    public sealed class ColumnSlice(int start, int end, TableColumnAlign? align)
     {
-        public ColumnSlice(int start, int end, TableColumnAlign? align)
-        {
-            Start = start;
-            End = end;
-            Align = align;
-            CurrentColumnSpan = -1;
-        }
-
         /// <summary>
         /// Gets or sets the index position of this column (after the |)
         /// </summary>
-        public int Start { get; }
+        public int Start { get; } = start;
 
-        public int End { get; }
+        public int End { get; } = end;
 
-        public TableColumnAlign? Align { get; }
+        public TableColumnAlign? Align { get; } = align;
 
-        public int CurrentColumnSpan { get; set; }
+        public int CurrentColumnSpan { get; set; } = -1;
 
         public int PreviousColumnSpan { get; set; }
 

src/Markdig/Extensions/Tables/PipeTableBlockParser.cs

@@ -22,7 +22,7 @@ public class PipeTableBlockParser : BlockParser
     /// </summary>
     public PipeTableBlockParser()
     {
-        OpeningCharacters = new[] {'-'};
+        OpeningCharacters = ['-'];
     }
 
     public override BlockState TryOpen(BlockProcessor processor)

src/Markdig/Extensions/Tables/PipeTableParser.cs

@@ -25,12 +25,12 @@ public class PipeTableParser : InlineParser, IPostInlineProcessor
     /// <summary>
     /// Initializes a new instance of the <see cref="PipeTableParser" /> class.
     /// </summary>
-    /// <param name="lineBreakParser">The linebreak parser to use</param>
+    /// <param name="lineBreakParser">The line break parser to use</param>
     /// <param name="options">The options.</param>
     public PipeTableParser(LineBreakInlineParser lineBreakParser, PipeTableOptions? options = null)
     {
         this.lineBreakParser = lineBreakParser ?? throw new ArgumentNullException(nameof(lineBreakParser));
-        OpeningCharacters = new[] { '|', '\n', '\r' };
+        OpeningCharacters = ['|', '\n', '\r'];
         Options = options ?? new PipeTableOptions();
     }
 
@@ -280,6 +280,8 @@ public class PipeTableParser : InlineParser, IPostInlineProcessor
             tableState.EndOfLines.Add(endOfTable);
         }
 
+        int lastPipePos = 0;
+
         // Cell loop
         // Reconstruct the table from the delimiters
         TableRow? row = null;
@@ -302,6 +304,12 @@ public class PipeTableParser : InlineParser, IPostInlineProcessor
                 if (pipeSeparator != null && (delimiter.PreviousSibling is null || delimiter.PreviousSibling is LineBreakInline))
                 {
                     delimiter.Remove();
+                    if (table.Span.IsEmpty)
+                    {
+                        table.Span = delimiter.Span;
+                        table.Line = delimiter.Line;
+                        table.Column = delimiter.Column;
+                    }
                     continue;
                 }
             }
@@ -354,6 +362,7 @@ public class PipeTableParser : InlineParser, IPostInlineProcessor
                     // If the delimiter is a pipe, we need to remove it from the tree
                     // so that previous loop looking for a parent will not go further on subsequent cells
                     delimiter.Remove();
+                    lastPipePos = delimiter.Span.End;
                 }
 
                 // We trim whitespace at the beginning and ending of the cell
@@ -421,6 +430,11 @@ public class PipeTableParser : InlineParser, IPostInlineProcessor
             }
         }
 
+        if (lastPipePos > table.Span.End)
+        {
+          table.UpdateSpanEnd(lastPipePos);
+        }
+
         // Once we are done with the cells, we can remove all end of lines in the table tree
         foreach (var endOfLine in tableState.EndOfLines)
         {
@@ -443,6 +457,11 @@ public class PipeTableParser : InlineParser, IPostInlineProcessor
         {
             var paragraph = (ParagraphBlock) cell[0];
             state.PostProcessInlines(postInlineProcessorIndex + 1, paragraph.Inline, null, true);
+            if (paragraph.Inline?.LastChild is not null)
+            {
+                paragraph.Inline.Span.End = paragraph.Inline.LastChild.Span.End;
+                paragraph.UpdateSpanEnd(paragraph.Inline.LastChild.Span.End);
+            }
         }
 
         // Clear cells when we are done
@@ -520,7 +539,7 @@ public class PipeTableParser : InlineParser, IPostInlineProcessor
                 // Create aligns until we may have a header row
 
                 aligns ??= new List<TableColumnDefinition>();
-                
+
                 aligns.Add(new TableColumnDefinition() { Alignment =  align });
 
                 // If this is the last delimiter, we need to check the right side of the `|` delimiter
@@ -632,10 +651,10 @@ public class PipeTableParser : InlineParser, IPostInlineProcessor
 
         public int LineIndex { get; set; }
 
-        public List<Inline> ColumnAndLineDelimiters { get; } = new();
+        public List<Inline> ColumnAndLineDelimiters { get; } = [];
 
-        public List<TableCell> Cells { get; } = new();
+        public List<TableCell> Cells { get; } = [];
 
-        public List<Inline> EndOfLines { get; } = new();
+        public List<Inline> EndOfLines { get; } = [];
     }
 }

src/Markdig/Extensions/TaskLists/TaskListInlineParser.cs

@@ -19,7 +19,7 @@ public class TaskListInlineParser : InlineParser
     /// </summary>
     public TaskListInlineParser()
     {
-        OpeningCharacters = new[] {'['};
+        OpeningCharacters = ['['];
         ListClass = "contains-task-list";
         ListItemClass = "task-list-item";
     }

src/Markdig/Extensions/Yaml/YamlFrontMatterParser.cs

@@ -26,7 +26,7 @@ public class YamlFrontMatterParser : BlockParser
     /// </summary>
     public YamlFrontMatterParser()
     {
-        this.OpeningCharacters = new[] { '-' };
+        OpeningCharacters = ['-'];
     }
 
     /// <summary>

src/Markdig/Helpers/BlockWrapper.cs

@@ -7,14 +7,9 @@ using Markdig.Syntax;
 namespace Markdig.Helpers;
 
 // Used to avoid the overhead of type covariance checks
-internal readonly struct BlockWrapper : IEquatable<BlockWrapper>
+internal readonly struct BlockWrapper(Block block) : IEquatable<BlockWrapper>
 {
-    public readonly Block Block;
-
-    public BlockWrapper(Block block)
-    {
-        Block = block;
-    }
+    public readonly Block Block = block;
 
     public static implicit operator Block(BlockWrapper wrapper) => wrapper.Block;
 
@@ -22,7 +17,7 @@ internal readonly struct BlockWrapper : IEquatable<BlockWrapper>
 
     public bool Equals(BlockWrapper other) => ReferenceEquals(Block, other.Block);
 
-    public override bool Equals(object obj) => Block.Equals(obj);
+    public override bool Equals(object? obj) => Block.Equals(obj);
 
     public override int GetHashCode() => Block.GetHashCode();
 }

src/Markdig/Helpers/CharHelper.cs

@@ -30,15 +30,17 @@ public static class CharHelper
         { 'I', 1 }, { 'V', 5 }, { 'X', 10 }
     };
 
-    private static readonly char[] punctuationExceptions = { '−', '-', '†', '‡' };
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    private static bool IsPunctuationException(char c) =>
+        c is '−' or '-' or '†' or '‡';
 
     public static void CheckOpenCloseDelimiter(char pc, char c, bool enableWithinWord, out bool canOpen, out bool canClose)
     {
         pc.CheckUnicodeCategory(out bool prevIsWhiteSpace, out bool prevIsPunctuation);
         c.CheckUnicodeCategory(out bool nextIsWhiteSpace, out bool nextIsPunctuation);
 
-        var prevIsExcepted = prevIsPunctuation && punctuationExceptions.Contains(pc);
-        var nextIsExcepted = nextIsPunctuation && punctuationExceptions.Contains(c);
+        var prevIsExcepted = prevIsPunctuation && IsPunctuationException(pc);
+        var nextIsExcepted = nextIsPunctuation && IsPunctuationException(c);
 
         // A left-flanking delimiter run is a delimiter run that is
         // (1) not followed by Unicode whitespace, and either
@@ -126,19 +128,6 @@ public static class CharHelper
         return (column & (TabSize - 1)) != 0;
     }
 
-    [MethodImpl(MethodImplOptions.AggressiveInlining)]
-    public static bool Contains(this char[] charList, char c)
-    {
-        foreach (char ch in charList)
-        {
-            if (ch == c)
-            {
-                return true;
-            }
-        }
-        return false;
-    }
-
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
     public static bool IsWhitespace(this char c)
     {
@@ -178,7 +167,7 @@ public static class CharHelper
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
     public static bool IsControl(this char c)
     {
-        return c < ' ' || char.IsControl(c);
+        return char.IsControl(c);
     }
 
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
@@ -211,15 +200,17 @@ public static class CharHelper
         {
             // A Unicode punctuation character is an ASCII punctuation character
             // or anything in the general Unicode categories Pc, Pd, Pe, Pf, Pi, Po, or Ps.
+            const int PunctuationCategoryMask =
+                1 << (int)UnicodeCategory.ConnectorPunctuation |
+                1 << (int)UnicodeCategory.DashPunctuation |
+                1 << (int)UnicodeCategory.OpenPunctuation |
+                1 << (int)UnicodeCategory.ClosePunctuation |
+                1 << (int)UnicodeCategory.InitialQuotePunctuation |
+                1 << (int)UnicodeCategory.FinalQuotePunctuation |
+                1 << (int)UnicodeCategory.OtherPunctuation;
+
             space = false;
-            UnicodeCategory category = CharUnicodeInfo.GetUnicodeCategory(c);
-            punctuation = category == UnicodeCategory.ConnectorPunctuation
-                || category == UnicodeCategory.DashPunctuation
-                || category == UnicodeCategory.OpenPunctuation
-                || category == UnicodeCategory.ClosePunctuation
-                || category == UnicodeCategory.InitialQuotePunctuation
-                || category == UnicodeCategory.FinalQuotePunctuation
-                || category == UnicodeCategory.OtherPunctuation;
+            punctuation = (PunctuationCategoryMask & (1 << (int)CharUnicodeInfo.GetUnicodeCategory(c))) != 0;
         }
     }
 
@@ -236,14 +227,16 @@ public static class CharHelper
         }
         else
         {
-            var category = CharUnicodeInfo.GetUnicodeCategory(c);
-            return category == UnicodeCategory.ConnectorPunctuation
-                || category == UnicodeCategory.DashPunctuation
-                || category == UnicodeCategory.OpenPunctuation
-                || category == UnicodeCategory.ClosePunctuation
-                || category == UnicodeCategory.InitialQuotePunctuation
-                || category == UnicodeCategory.FinalQuotePunctuation
-                || category == UnicodeCategory.OtherPunctuation;
+            const int PunctuationCategoryMask =
+                1 << (int)UnicodeCategory.ConnectorPunctuation |
+                1 << (int)UnicodeCategory.DashPunctuation |
+                1 << (int)UnicodeCategory.OpenPunctuation |
+                1 << (int)UnicodeCategory.ClosePunctuation |
+                1 << (int)UnicodeCategory.InitialQuotePunctuation |
+                1 << (int)UnicodeCategory.FinalQuotePunctuation |
+                1 << (int)UnicodeCategory.OtherPunctuation;
+
+            return (PunctuationCategoryMask & (1 << (int)CharUnicodeInfo.GetUnicodeCategory(c))) != 0;
         }
     }
 
@@ -729,11 +722,11 @@ public static class CharHelper
     }
 
     // Used by ListExtraItemParser to format numbers from 1 - 26
-    private static readonly string[] smallNumberStringCache = {
+    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)
     {

src/Markdig/Helpers/CharacterMap.cs

@@ -2,14 +2,10 @@
 // This file is licensed under the BSD-Clause 2 license. 
 // See the license.txt file in the project root for more information.
 
+using System.Buffers;
 using System.Diagnostics;
 using System.Linq;
 using System.Runtime.CompilerServices;
-#if NETCOREAPP3_1_OR_GREATER
-using System.Numerics;
-using System.Runtime.Intrinsics;
-using System.Runtime.Intrinsics.X86;
-#endif
 
 namespace Markdig.Helpers;
 
@@ -19,13 +15,9 @@ namespace Markdig.Helpers;
 /// <typeparam name="T"></typeparam>
 public sealed class CharacterMap<T> where T : class
 {
-#if NETCOREAPP3_1_OR_GREATER
-    private readonly Vector128<byte> _asciiBitmap;
-#endif
-
-    private readonly T[] asciiMap;
-    private readonly Dictionary<uint, T>? nonAsciiMap;
-    private readonly BoolVector128 isOpeningCharacter;
+    private readonly SearchValues<char> _values;
+    private readonly T[] _asciiMap;
+    private readonly Dictionary<uint, T>? _nonAsciiMap;
 
     /// <summary>
     /// Initializes a new instance of the <see cref="CharacterMap{T}"/> class.
@@ -35,64 +27,38 @@ public sealed class CharacterMap<T> where T : class
     public CharacterMap(IEnumerable<KeyValuePair<char, T>> maps)
     {
         if (maps is 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 (openingChar < 128)
-            {
-                maxChar = Math.Max(maxChar, openingChar);
-
-                if (openingChar == 0)
-                {
-                    ThrowHelper.ArgumentOutOfRangeException("Null is not a valid opening character.", nameof(maps));
-                }
-            }
-            else
-            {
-                nonAsciiMap ??= new Dictionary<uint, T>();
-            }
+            charSet.Add(map.Key);
         }
 
-        OpeningCharacters = charSet.ToArray();
+        OpeningCharacters = [.. charSet];
         Array.Sort(OpeningCharacters);
 
-        asciiMap = new T[maxChar + 1];
+        _asciiMap = new T[128];
 
         foreach (var state in maps)
         {
             char openingChar = state.Key;
             if (openingChar < 128)
             {
-                asciiMap[openingChar] ??= state.Value;
-                isOpeningCharacter.Set(openingChar);
+                _asciiMap[openingChar] ??= state.Value;
             }
-            else if (!nonAsciiMap!.ContainsKey(openingChar))
+            else
             {
-                nonAsciiMap[openingChar] = state.Value;
+                _nonAsciiMap ??= new Dictionary<uint, T>();
+
+                if (!_nonAsciiMap.ContainsKey(openingChar))
+                {
+                    _nonAsciiMap[openingChar] = state.Value;
+                }
             }
         }
 
-#if NETCOREAPP3_1_OR_GREATER
-        if (nonAsciiMap is null)
-        {
-            long bitmap_0_3 = 0;
-            long bitmap_4_7 = 0;
-
-            foreach (char openingChar in OpeningCharacters)
-            {
-                int position = (openingChar >> 4) | ((openingChar & 0x0F) << 3);
-                if (position < 64) bitmap_0_3 |= 1L << position;
-                else bitmap_4_7 |= 1L << (position - 64);
-            }
-
-            _asciiBitmap = Vector128.Create(bitmap_0_3, bitmap_4_7).AsByte();
-        }
-#endif
+        _values = SearchValues.Create(OpeningCharacters);
     }
 
     /// <summary>
@@ -110,7 +76,7 @@ public sealed class CharacterMap<T> where T : class
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         get
         {
-            T[] asciiMap = this.asciiMap;
+            T[] asciiMap = _asciiMap;
             if (openingChar < (uint)asciiMap.Length)
             {
                 return asciiMap[openingChar];
@@ -118,13 +84,12 @@ public sealed class CharacterMap<T> where T : class
             else
             {
                 T? map = null;
-                nonAsciiMap?.TryGetValue(openingChar, out map);
+                _nonAsciiMap?.TryGetValue(openingChar, out map);
                 return map;
             }
         }
     }
 
-
     /// <summary>
     /// Searches for an opening character from a registered parser in the specified string.
     /// </summary>
@@ -132,167 +97,20 @@ public sealed class CharacterMap<T> where T : class
     /// <param name="start">The start.</param>
     /// <param name="end">The end.</param>
     /// <returns>Index position within the string of the first opening character found in the specified text; if not found, returns -1</returns>
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
     public int IndexOfOpeningCharacter(string text, int start, int end)
     {
         Debug.Assert(text is not null);
-        Debug.Assert(start >= 0 && end >= 0);
-        Debug.Assert(end - start + 1 >= 0);
-        Debug.Assert(end - start + 1 <= text.Length);
 
-        if (nonAsciiMap is null)
+        ReadOnlySpan<char> span = text.AsSpan(start, end - start + 1);
+
+        int index = span.IndexOfAny(_values);
+
+        if (index >= 0)
         {
-#if NETCOREAPP3_1_OR_GREATER
-            if (Ssse3.IsSupported && BitConverter.IsLittleEndian)
-            {
-                // Based on http://0x80.pl/articles/simd-byte-lookup.html#universal-algorithm
-                // Optimized for sets in the [1, 127] range
-
-                int lengthMinusOne = end - start;
-                int charsToProcessVectorized = lengthMinusOne & ~(2 * Vector128<short>.Count - 1);
-                int finalStart = start + charsToProcessVectorized;
-
-                if (start < finalStart)
-                {
-                    ref char textStartRef = ref Unsafe.Add(ref Unsafe.AsRef(in text.GetPinnableReference()), start);
-                    Vector128<byte> bitmap = _asciiBitmap;
-                    do
-                    {
-                        // Load 32 bytes (16 chars) into two Vector128<short>s (chars)
-                        // Drop the high byte of each char
-                        // Pack the remaining bytes into a single Vector128<byte>
-                        Vector128<byte> input = Sse2.PackUnsignedSaturate(
-                            Unsafe.ReadUnaligned<Vector128<short>>(ref Unsafe.As<char, byte>(ref textStartRef)),
-                            Unsafe.ReadUnaligned<Vector128<short>>(ref Unsafe.As<char, byte>(ref Unsafe.Add(ref textStartRef, Vector128<short>.Count))));
-
-                        // Extract the higher nibble of each character ((input >> 4) & 0xF)
-                        Vector128<byte> higherNibbles = Sse2.And(Sse2.ShiftRightLogical(input.AsUInt16(), 4).AsByte(), Vector128.Create((byte)0xF));
-
-                        // Lookup the matching higher nibble for each character based on the lower nibble
-                        // PSHUFB will set the result to 0 for any non-ASCII (> 127) character
-                        Vector128<byte> bitsets = Ssse3.Shuffle(bitmap, input);
-
-                        // Calculate a bitmask (1 << (higherNibble % 8)) for each character
-                        Vector128<byte> bitmask = Ssse3.Shuffle(Vector128.Create(0x8040201008040201).AsByte(), higherNibbles);
-
-                        // Check which characters are present in the set
-                        // We are relying on bitsets being zero for non-ASCII characters
-                        Vector128<byte> result = Sse2.And(bitsets, bitmask);
-
-                        if (!result.Equals(Vector128<byte>.Zero))
-                        {
-                            int resultMask = ~Sse2.MoveMask(Sse2.CompareEqual(result, Vector128<byte>.Zero));
-                            return start + BitOperations.TrailingZeroCount((uint)resultMask);
-                        }
-
-                        start += 2 * Vector128<short>.Count;
-                        textStartRef = ref Unsafe.Add(ref textStartRef, 2 * Vector128<short>.Count);
-                    }
-                    while (start != finalStart);
-                }
-            }
-
-            ref char textRef = ref Unsafe.AsRef(in text.GetPinnableReference());
-            for (; start <= end; start++)
-            {
-                if (IntPtr.Size == 4)
-                {
-                    uint c = Unsafe.Add(ref textRef, start);
-                    if (c < 128 && isOpeningCharacter[c])
-                    {
-                        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++)
-                    {
-                        char c = pText[i];
-                        if (c < 128 && isOpeningCharacter[c])
-                        {
-                            return i;
-                        }
-                    }
-                }
-            }
-#endif
-            return -1;
+            index += start;
         }
-        else
-        {
-            return IndexOfOpeningCharacterNonAscii(text, start, end);
-        }
-    }
 
-    private int IndexOfOpeningCharacterNonAscii(string text, int start, int end)
-    {
-#if NETCOREAPP3_1_OR_GREATER
-        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;
+        return index;
     }
 }
-
-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/EntityHelper.cs

@@ -31,6 +31,8 @@
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 // SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
+using System.Text;
+
 namespace Markdig.Helpers;
 
 /// <summary>
@@ -57,41 +59,31 @@ public static class EntityHelper
     /// <returns>The unicode character set or <c>null</c> if the entity was not recognized.</returns>
     public static string DecodeEntity(int utf32)
     {
-        if (!CharHelper.IsInInclusiveRange(utf32, 1, 1114111) || CharHelper.IsInInclusiveRange(utf32, 55296, 57343))
+        if (utf32 == 0 || !UnicodeUtility.IsValidUnicodeScalar((uint)utf32))
             return CharHelper.ReplacementCharString;
 
-        if (utf32 < 65536)
+        if (UnicodeUtility.IsBmpCodePoint((uint)utf32))
             return char.ToString((char)utf32);
 
-        utf32 -= 65536;
-        return new string(
-#if NETSTANDARD2_1_OR_GREATER || NETCOREAPP3_1_OR_GREATER
-            stackalloc
-#else
-            new
-#endif
-            char[]
-        {
-            (char)((uint)utf32 / 1024 + 55296),
-            (char)((uint)utf32 % 1024 + 56320)
-        });
+        UnicodeUtility.GetUtf16SurrogatesFromSupplementaryPlaneScalar((uint)utf32, out char high, out char low);
+        return new string([high, low]);
     }
 
     internal static void DecodeEntity(int utf32, ref ValueStringBuilder sb)
     {
-        if (!CharHelper.IsInInclusiveRange(utf32, 1, 1114111) || CharHelper.IsInInclusiveRange(utf32, 55296, 57343))
+        if (utf32 == 0 || !UnicodeUtility.IsValidUnicodeScalar((uint)utf32))
         {
             sb.Append(CharHelper.ReplacementChar);
         }
-        else if (utf32 < 65536)
+        else if (UnicodeUtility.IsBmpCodePoint((uint)utf32))
         {
             sb.Append((char)utf32);
         }
         else
         {
-            utf32 -= 65536;
-            sb.Append((char)((uint)utf32 / 1024 + 55296));
-            sb.Append((char)((uint)utf32 % 1024 + 56320));
+            UnicodeUtility.GetUtf16SurrogatesFromSupplementaryPlaneScalar((uint)utf32, out char high, out char low);
+            sb.Append(high);
+            sb.Append(low);
         }
     }
 

src/Markdig/Helpers/FastStringWriter.cs

@@ -30,7 +30,7 @@ internal sealed class FastStringWriter : TextWriter
     public override string NewLine
     {
         get => _newLine;
-        set => _newLine = value ?? Environment.NewLine;
+        set => base.NewLine = _newLine = value ?? Environment.NewLine;
     }
 
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
@@ -278,8 +278,7 @@ internal sealed class FastStringWriter : TextWriter
         _pos = 0;
     }
 
-    public override string ToString()
-    {
-        return _chars.AsSpan(0, _pos).ToString();
-    }
+    public override string ToString() => AsSpan().ToString();
+
+    public ReadOnlySpan<char> AsSpan() => _chars.AsSpan(0, _pos);
 }

src/Markdig/Helpers/HexConverter.cs

@@ -0,0 +1,27 @@
+// 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;
+
+// Based on https://github.com/dotnet/runtime/blob/main/src/libraries/Common/src/System/HexConverter.cs
+internal static class HexConverter
+{
+    public enum Casing : uint
+    {
+        Upper = 0,
+        Lower = 0x2020U,
+    }
+
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static void ToCharsBuffer(byte value, Span<char> buffer, int startingIndex = 0, Casing casing = Casing.Upper)
+    {
+        uint difference = (((uint)value & 0xF0U) << 4) + ((uint)value & 0x0FU) - 0x8989U;
+        uint packedResult = ((((uint)(-(int)difference) & 0x7070U) >> 4) + difference + 0xB9B9U) | (uint)casing;
+
+        buffer[startingIndex + 1] = (char)(packedResult & 0xFF);
+        buffer[startingIndex] = (char)(packedResult >> 8);
+    }
+}

src/Markdig/Helpers/HtmlHelper.cs

@@ -12,8 +12,8 @@ namespace Markdig.Helpers;
 /// </summary>
 public static class HtmlHelper
 {
-    private static readonly char[] SearchBackAndAmp = { '\\', '&' };
-    private static readonly char[] SearchAmp = { '&' };
+    private static readonly char[] SearchBackAndAmp = ['\\', '&'];
+    private static readonly char[] SearchAmp = ['&'];
     private static readonly string[] EscapeUrlsForAscii = new string[128];
 
     static HtmlHelper()

src/Markdig/Helpers/LineReader.cs

@@ -53,7 +53,7 @@ public struct LineReader
         else
         {
 #if NETCOREAPP3_1_OR_GREATER
-            ReadOnlySpan<char> span = MemoryMarshal.CreateReadOnlySpan(ref Unsafe.Add(ref Unsafe.AsRef(text.GetPinnableReference()), sourcePosition), end - sourcePosition);
+            ReadOnlySpan<char> span = MemoryMarshal.CreateReadOnlySpan(ref Unsafe.Add(ref Unsafe.AsRef(in text.GetPinnableReference()), sourcePosition), end - sourcePosition);
 #else
             ReadOnlySpan<char> span = text.AsSpan(sourcePosition);
 #endif
@@ -65,7 +65,7 @@ public struct LineReader
                 newSourcePosition = end + 1;
 
 #if NETCOREAPP3_1_OR_GREATER
-                if (Unsafe.Add(ref Unsafe.AsRef(text.GetPinnableReference()), end) == '\r')
+                if (Unsafe.Add(ref Unsafe.AsRef(in text.GetPinnableReference()), end) == '\r')
 #else
                 if ((uint)end < (uint)text.Length && text[end] == '\r')
 #endif

src/Markdig/Helpers/LinkHelper.cs

@@ -19,6 +19,11 @@ public static class LinkHelper
     }
 
     public static string Urilize(string headingText, bool allowOnlyAscii, bool keepOpeningDigits = false)
+    {
+        return Urilize(headingText.AsSpan(), allowOnlyAscii, keepOpeningDigits);
+    }
+
+    public static string Urilize(ReadOnlySpan<char> headingText, bool allowOnlyAscii, bool keepOpeningDigits = false)
     {
         var headingBuffer = new ValueStringBuilder(stackalloc char[ValueStringBuilder.StackallocThreshold]);
         bool hasLetter = keepOpeningDigits && headingText.Length > 0 && char.IsLetterOrDigit(headingText[0]);
@@ -95,15 +100,24 @@ public static class LinkHelper
     }
 
     public static string UrilizeAsGfm(string headingText)
+    {
+        return UrilizeAsGfm(headingText.AsSpan());
+    }
+
+    public static string UrilizeAsGfm(ReadOnlySpan<char> headingText)
     {
         // Following https://github.com/jch/html-pipeline/blob/master/lib/html/pipeline/toc_filter.rb
         var headingBuffer = new ValueStringBuilder(stackalloc char[ValueStringBuilder.StackallocThreshold]);
         for (int i = 0; i < headingText.Length; i++)
         {
             var c = headingText[i];
-            if (char.IsLetterOrDigit(c) || c == ' ' || c == '-' || c == '_')
+            if (char.IsLetterOrDigit(c) || c == '-' || c == '_')
             {
-                headingBuffer.Append(c == ' ' ? '-' : char.ToLowerInvariant(c));
+                headingBuffer.Append(char.ToLowerInvariant(c));
+            }
+            else if (c == ' ')
+            {
+                headingBuffer.Append('-');
             }
         }
         return headingBuffer.ToString();
@@ -531,87 +545,70 @@ public static class LinkHelper
             enclosingCharacter = c;
             var closingQuote = c == '(' ? ')' : c;
             bool hasEscape = false;
-            // -1: undefined
-            //  0: has only spaces
-            //  1: has other characters
-            int hasOnlyWhiteSpacesSinceLastLine = -1;
-            while (true)
+            bool isLineBlank = false; // the first line is never blank
+            while ((c = text.NextChar()) != '\0')
             {
-                c = text.NextChar();
-
                 if (c == '\r' || c == '\n')
                 {
-                    if (hasOnlyWhiteSpacesSinceLastLine >= 0)
+                    if (isLineBlank)
                     {
-                        if (hasOnlyWhiteSpacesSinceLastLine == 1)
-                        {
-                            break;
-                        }
-                        hasOnlyWhiteSpacesSinceLastLine = -1;
+                        break;
                     }
+
+                    if (hasEscape)
+                    {
+                        hasEscape = false;
+                        buffer.Append('\\');
+                    }
+
                     buffer.Append(c);
+
                     if (c == '\r' && text.PeekChar() == '\n')
                     {
                         buffer.Append('\n');
+                        text.SkipChar();
                     }
-                    continue;
-                }
 
-                if (c == '\0')
-                {
-                    break;
+                    isLineBlank = true;
                 }
-
-                if (c == closingQuote)
+                else if (hasEscape)
                 {
-                    if (hasEscape)
+                    hasEscape = false;
+
+                    if (!c.IsAsciiPunctuation())
                     {
-                        buffer.Append(closingQuote);
-                        hasEscape = false;
-                        continue;
+                        buffer.Append('\\');
                     }
 
+                    buffer.Append(c);
+                }
+                else if (c == closingQuote)
+                {
                     // Skip last quote
                     text.SkipChar();
-                    goto ReturnValid;
+                    title = buffer.ToString();
+                    return true;
                 }
-
-                if (hasEscape && !c.IsAsciiPunctuation())
-                {
-                    buffer.Append('\\');
-                }
-
-                if (c == '\\')
+                else if (c == '\\')
                 {
                     hasEscape = true;
-                    continue;
+                    isLineBlank = false;
                 }
-
-                hasEscape = false;
-
-                if (c.IsSpaceOrTab())
+                else
                 {
-                    if (hasOnlyWhiteSpacesSinceLastLine < 0)
+                    if (isLineBlank && !c.IsSpaceOrTab())
                     {
-                        hasOnlyWhiteSpacesSinceLastLine = 1;
+                        isLineBlank = false;
                     }
-                }
-                else if (c != '\n' && c != '\r' && text.PeekChar() != '\n')
-                {
-                    hasOnlyWhiteSpacesSinceLastLine = 0;
-                }
 
-                buffer.Append(c);
+                    buffer.Append(c);
+                }
             }
         }
 
         buffer.Dispose();
         title = null;
         return false;
-
-    ReturnValid:
-        title = buffer.ToString();
-        return true;
     }
 
     public static bool TryParseTitleTrivia<T>(ref T text, out string? title, out char enclosingCharacter) where T : ICharIterator
@@ -627,87 +624,70 @@ public static class LinkHelper
             enclosingCharacter = c;
             var closingQuote = c == '(' ? ')' : c;
             bool hasEscape = false;
-            // -1: undefined
-            //  0: has only spaces
-            //  1: has other characters
-            int hasOnlyWhiteSpacesSinceLastLine = -1;
-            while (true)
+            bool isLineBlank = false; // the first line is never blank
+            while ((c = text.NextChar()) != '\0')
             {
-                c = text.NextChar();
-
                 if (c == '\r' || c == '\n')
                 {
-                    if (hasOnlyWhiteSpacesSinceLastLine >= 0)
+                    if (isLineBlank)
                     {
-                        if (hasOnlyWhiteSpacesSinceLastLine == 1)
-                        {
-                            break;
-                        }
-                        hasOnlyWhiteSpacesSinceLastLine = -1;
+                        break;
                     }
+
+                    if (hasEscape)
+                    {
+                        hasEscape = false;
+                        buffer.Append('\\');
+                    }
+
                     buffer.Append(c);
+
                     if (c == '\r' && text.PeekChar() == '\n')
                     {
                         buffer.Append('\n');
+                        text.SkipChar();
                     }
-                    continue;
-                }
 
-                if (c == '\0')
-                {
-                    break;
+                    isLineBlank = true;
                 }
-
-                if (c == closingQuote)
+                else if (hasEscape)
                 {
-                    if (hasEscape)
+                    hasEscape = false;
+
+                    if (!c.IsAsciiPunctuation())
                     {
-                        buffer.Append(closingQuote);
-                        hasEscape = false;
-                        continue;
+                        buffer.Append('\\');
                     }
 
+                    buffer.Append(c);
+                }
+                else if (c == closingQuote)
+                {
                     // Skip last quote
                     text.SkipChar();
-                    goto ReturnValid;
+                    title = buffer.ToString();
+                    return true;
                 }
-
-                if (hasEscape && !c.IsAsciiPunctuation())
-                {
-                    buffer.Append('\\');
-                }
-
-                if (c == '\\')
+                else if (c == '\\')
                 {
                     hasEscape = true;
-                    continue;
+                    isLineBlank = false;
                 }
-
-                hasEscape = false;
-
-                if (c.IsSpaceOrTab())
+                else
                 {
-                    if (hasOnlyWhiteSpacesSinceLastLine < 0)
+                    if (isLineBlank && !c.IsSpaceOrTab())
                     {
-                        hasOnlyWhiteSpacesSinceLastLine = 1;
+                        isLineBlank = false;
                     }
-                }
-                else if (c != '\n' && c != '\r' && text.PeekChar() != '\n')
-                {
-                    hasOnlyWhiteSpacesSinceLastLine = 0;
-                }
 
-                buffer.Append(c);
+                    buffer.Append(c);
+                }
             }
         }
 
         buffer.Dispose();
         title = null;
         return false;
-
-    ReturnValid:
-        title = buffer.ToString();
-        return true;
     }
 
     public static bool TryParseUrl<T>(T text, [NotNullWhen(true)] out string? link) where T : ICharIterator
@@ -744,12 +724,15 @@ public static class LinkHelper
                     break;
                 }
 
-                if (hasEscape && !c.IsAsciiPunctuation())
+                if (hasEscape)
                 {
-                    buffer.Append('\\');
+                    hasEscape = false;
+                    if (!c.IsAsciiPunctuation())
+                    {
+                        buffer.Append('\\');
+                    }
                 }
-
-                if (c == '\\')
+                else if (c == '\\')
                 {
                     hasEscape = true;
                     continue;
@@ -760,8 +743,6 @@ public static class LinkHelper
                     break;
                 }
 
-                hasEscape = false;
-
                 buffer.Append(c);
 
             } while (c != '\0');
@@ -800,20 +781,21 @@ public static class LinkHelper
 
                 if (!isAutoLink)
                 {
-                    if (hasEscape && !c.IsAsciiPunctuation())
+                    if (hasEscape)
                     {
-                        buffer.Append('\\');
+                        hasEscape = false;
+                        if (!c.IsAsciiPunctuation())
+                        {
+                            buffer.Append('\\');
+                        }
                     }
-
                     // If we have an escape
-                    if (c == '\\')
+                    else if (c == '\\')
                     {
                         hasEscape = true;
                         c = text.NextChar();
                         continue;
                     }
-
-                    hasEscape = false;
                 }
 
                 if (IsEndOfUri(c, isAutoLink))
@@ -891,12 +873,15 @@ public static class LinkHelper
                     break;
                 }
 
-                if (hasEscape && !c.IsAsciiPunctuation())
+                if (hasEscape)
                 {
-                    buffer.Append('\\');
+                    hasEscape = false;
+                    if (!c.IsAsciiPunctuation())
+                    {
+                        buffer.Append('\\');
+                    }
                 }
-
-                if (c == '\\')
+                else if (c == '\\')
                 {
                     hasEscape = true;
                     continue;
@@ -907,8 +892,6 @@ public static class LinkHelper
                     break;
                 }
 
-                hasEscape = false;
-
                 buffer.Append(c);
 
             } while (c != '\0');
@@ -947,20 +930,21 @@ public static class LinkHelper
 
                 if (!isAutoLink)
                 {
-                    if (hasEscape && !c.IsAsciiPunctuation())
+                    if (hasEscape)
                     {
-                        buffer.Append('\\');
+                        hasEscape = false;
+                        if (!c.IsAsciiPunctuation())
+                        {
+                            buffer.Append('\\');
+                        }
                     }
-
                     // If we have an escape
-                    if (c == '\\')
+                    else if (c == '\\')
                     {
                         hasEscape = true;
                         c = text.NextChar();
                         continue;
                     }
-
-                    hasEscape = false;
                 }
 
                 if (IsEndOfUri(c, isAutoLink))
@@ -1145,7 +1129,7 @@ public static class LinkHelper
             c = text.NextChar();
         }
 
-        if (c != '\0' && c != '\n' && c != '\r' && text.PeekChar() != '\n')
+        if (c != '\0' && c != '\n' && c != '\r')
         {
             // If we were able to parse the url but the title doesn't end with space, 
             // we are still returning a valid definition
@@ -1285,7 +1269,7 @@ public static class LinkHelper
             c = text.NextChar();
         }
 
-        if (c != '\0' && c != '\n' && c != '\r' && text.PeekChar() != '\n')
+        if (c != '\0' && c != '\n' && c != '\r')
         {
             // If we were able to parse the url but the title doesn't end with space, 
             // we are still returning a valid definition

src/Markdig/Helpers/ObjectCache.cs

@@ -36,7 +36,7 @@ public abstract class ObjectCache<T> where T : class
     /// <returns></returns>
     public T Get()
     {
-        if (_builders.TryDequeue(out T instance))
+        if (_builders.TryDequeue(out T? instance))
         {
             return instance;
         }

src/Markdig/Helpers/StringLineGroup.cs

@@ -187,9 +187,32 @@ public struct StringLineGroup : IEnumerable
         }
     }
 
-    IEnumerator IEnumerable.GetEnumerator()
+    public struct Enumerator(StringLineGroup parent) : IEnumerator
     {
-        return Lines.GetEnumerator();
+        private readonly StringLineGroup _parent = parent;
+        private int _index = -1;
+
+        public object Current => _parent.Lines[_index];
+
+        public bool MoveNext()
+        {
+            return ++_index < _parent.Count;
+        }
+
+        public void Reset()
+        {
+            _index = -1;
+        }
+    }
+    
+    public Enumerator GetEnumerator()
+    {
+        return new Enumerator(this);
+    }
+
+    IEnumerator IEnumerable.GetEnumerator() 
+    {
+        return GetEnumerator();
     }
 
     private void IncreaseCapacity()
@@ -423,25 +446,21 @@ public struct StringLineGroup : IEnumerable
         }
     }
 
-    public readonly struct LineOffset
+    public readonly struct LineOffset(
+        int linePosition,
+        int column,
+        int offset,
+        int start,
+        int end)
     {
-        public LineOffset(int linePosition, int column, int offset, int start, int end)
-        {
-            LinePosition = linePosition;
-            Column = column;
-            Offset = offset;
-            Start = start;
-            End = end;
-        }
+        public readonly int LinePosition = linePosition;
 
-        public readonly int LinePosition;
+        public readonly int Column = column;
 
-        public readonly int Column;
+        public readonly int Offset = offset;
 
-        public readonly int Offset;
+        public readonly int Start = start;
 
-        public readonly int Start;
-
-        public readonly int End;
+        public readonly int End = end;
     }
-}
+}

src/Markdig/Helpers/StringSlice.cs

@@ -475,7 +475,7 @@ public struct StringSlice : ICharIterator
         }
 
 #if NETCOREAPP3_1_OR_GREATER
-        return MemoryMarshal.CreateReadOnlySpan(ref Unsafe.Add(ref Unsafe.AsRef(text.GetPinnableReference()), start), length);
+        return MemoryMarshal.CreateReadOnlySpan(ref Unsafe.Add(ref Unsafe.AsRef(in text.GetPinnableReference()), start), length);
 #else
         return text.AsSpan(start, length);
 #endif

src/Markdig/Helpers/ThrowHelper.cs

@@ -80,7 +80,7 @@ internal static class ThrowHelper
         if (depth > limit)
             DepthLimitExceeded();
 
-        [MethodImpl(MethodImplOptions.NoInlining)]
+        [DoesNotReturn]
         static void DepthLimitExceeded() => throw new ArgumentException("Markdown elements in the input are too deeply nested - depth limit exceeded. Input is most likely not sensible or is a very large table.");
     }
 

src/Markdig/Helpers/UnicodeUtility.cs

@@ -0,0 +1,30 @@
+// 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;
+using System.Runtime.CompilerServices;
+
+namespace System.Text;
+
+// Based on https://github.com/dotnet/runtime/blob/main/src/libraries/System.Private.CoreLib/src/System/Text/UnicodeUtility.cs
+internal static class UnicodeUtility
+{
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static bool IsBmpCodePoint(uint value) => value <= 0xFFFFu;
+
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static bool IsValidUnicodeScalar(uint value)
+    {
+        return ((value - 0x110000u) ^ 0xD800u) >= 0xFFEF0800u;
+    }
+
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static void GetUtf16SurrogatesFromSupplementaryPlaneScalar(uint value, out char highSurrogateCodePoint, out char lowSurrogateCodePoint)
+    {
+        Debug.Assert(IsValidUnicodeScalar(value) && IsBmpCodePoint(value));
+
+        highSurrogateCodePoint = (char)((value + ((0xD800u - 0x40u) << 10)) >> 10);
+        lowSurrogateCodePoint = (char)((value & 0x3FFu) + 0xDC00u);
+    }
+}

src/Markdig/Markdig.targets

@@ -5,7 +5,7 @@
     <Copyright>Alexandre Mutel</Copyright>
     <NeutralLanguage>en-US</NeutralLanguage>
     <Authors>Alexandre Mutel</Authors>
-    <TargetFrameworks>net462;netstandard2.0;netstandard2.1;net6.0</TargetFrameworks>
+    <TargetFrameworks>net462;netstandard2.0;netstandard2.1;net8.0;net9.0</TargetFrameworks>
     <CheckEolTargetFramework>false</CheckEolTargetFramework>
     <PackageTags>Markdown CommonMark md html md2html</PackageTags>
     <PackageReleaseNotes>https://github.com/lunet-io/markdig/blob/master/changelog.md</PackageReleaseNotes>
@@ -14,7 +14,7 @@
     <PackageIcon>markdig.png</PackageIcon>
     <PackageProjectUrl>https://github.com/lunet-io/markdig</PackageProjectUrl>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
-    <LangVersion>10</LangVersion>
+    <LangVersion>12</LangVersion>
     <Nullable>enable</Nullable>
     <NoWarn>$(NoWarn);CS1591</NoWarn>
     <GenerateDocumentationFile>true</GenerateDocumentationFile>
@@ -24,22 +24,18 @@
     <SymbolPackageFormat>snupkg</SymbolPackageFormat>
   </PropertyGroup>
 
-  <ItemGroup Condition=" '$(TargetFramework)' == 'net462' ">
-    <PackageReference Include="System.Memory" Version="4.5.4" />
+  <ItemGroup Condition=" '$(TargetFramework)' == 'net462' OR  '$(TargetFramework)' == 'netstandard2.0'">
+    <PackageReference Include="System.Memory" Version="4.5.5" />
   </ItemGroup>
 
-  <ItemGroup Condition=" '$(TargetFramework)' == 'netstandard2.0' ">
-    <PackageReference Include="System.Memory" Version="4.5.4" />
-  </ItemGroup>
-  
   <ItemGroup>
     <None Include="../../img/markdig.png" Pack="true" PackagePath="" />
     <None Include="../../readme.md" Pack="true" PackagePath="/"/>
-    <PackageReference Include="MinVer" Version="3.1.0">
+    <PackageReference Include="MinVer" Version="4.3.0">
       <PrivateAssets>all</PrivateAssets>
       <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
     </PackageReference>
-    <PackageReference Include="Microsoft.SourceLink.GitHub" Version="1.1.*" PrivateAssets="All"/>
+    <PackageReference Include="Microsoft.SourceLink.GitHub" Version="8.0.*" PrivateAssets="All"/>
   </ItemGroup>
 
   <Target Name="PatchVersion" AfterTargets="MinVer">

src/Markdig/Markdown.cs

@@ -19,16 +19,10 @@ namespace Markdig;
 /// </summary>
 public static class Markdown
 {
-    public static string Version
-    {
-        get
-        {
-            if (_Version == null)
-                _Version = ((AssemblyFileVersionAttribute)typeof(Markdown).Assembly.GetCustomAttributes(typeof(AssemblyFileVersionAttribute), false).FirstOrDefault())?.Version ?? "Unknown";
-            return _Version;
-        }
-    }
-    private static string? _Version;
+    public static string Version =>
+        s_version ??= typeof(Markdown).Assembly.GetCustomAttribute<AssemblyFileVersionAttribute>()?.Version ?? "Unknown";
+
+    private static string? s_version;
 
     internal static readonly MarkdownPipeline DefaultPipeline = new MarkdownPipelineBuilder().Build();
     private static readonly MarkdownPipeline _defaultTrackTriviaPipeline = new MarkdownPipelineBuilder().EnableTrackTrivia().Build();

src/Markdig/MarkdownExtensions.cs

@@ -3,6 +3,7 @@
 // See the license.txt file in the project root for more information.
 
 using Markdig.Extensions.Abbreviations;
+using Markdig.Extensions.Alerts;
 using Markdig.Extensions.AutoIdentifiers;
 using Markdig.Extensions.AutoLinks;
 using Markdig.Extensions.Bootstrap;
@@ -34,6 +35,7 @@ using Markdig.Extensions.Yaml;
 using Markdig.Helpers;
 using Markdig.Parsers;
 using Markdig.Parsers.Inlines;
+using Markdig.Renderers;
 
 namespace Markdig;
 
@@ -74,6 +76,7 @@ public static class MarkdownExtensions
     public static MarkdownPipelineBuilder UseAdvancedExtensions(this MarkdownPipelineBuilder pipeline)
     {
         return pipeline
+            .UseAlertBlocks()
             .UseAbbreviations()
             .UseAutoIdentifiers()
             .UseCitations()
@@ -94,6 +97,18 @@ public static class MarkdownExtensions
             .UseGenericAttributes(); // Must be last as it is one parser that is modifying other parsers
     }
 
+    /// <summary>
+    /// Uses this extension to enable alert blocks.
+    /// </summary>
+    /// <param name="pipeline">The pipeline.</param>
+    /// <param name="renderKind">Replace the default renderer for the kind with a custom renderer</param>
+    /// <returns>The modified pipeline</returns>
+    public static MarkdownPipelineBuilder UseAlertBlocks(this MarkdownPipelineBuilder pipeline, Action<HtmlRenderer, StringSlice>? renderKind = null)
+    {
+        pipeline.Extensions.ReplaceOrAdd<AlertExtension>(new AlertExtension() { RenderKind = renderKind });
+        return pipeline;
+    }
+    
     /// <summary>
     /// Uses this extension to enable autolinks from text `http://`, `https://`, `ftp://`, `mailto:`, `www.xxx.yyy`
     /// </summary>
@@ -552,6 +567,9 @@ public static class MarkdownExtensions
                 case "advanced":
                     pipeline.UseAdvancedExtensions();
                     break;
+                case "alerts":
+                    pipeline.UseAlertBlocks();
+                    break;
                 case "pipetables":
                     pipeline.UsePipeTables();
                     break;

src/Markdig/MarkdownPipeline.cs

@@ -95,18 +95,14 @@ public sealed class MarkdownPipeline
         return new RentedHtmlRenderer(cache, renderer);
     }
 
-    internal sealed class HtmlRendererCache : ObjectCache<HtmlRenderer>
+    internal sealed class HtmlRendererCache(
+        MarkdownPipeline pipeline,
+        bool customWriter = false) : ObjectCache<HtmlRenderer>
     {
-        private static readonly TextWriter s_dummyWriter = new FastStringWriter();
+        private static readonly FastStringWriter s_dummyWriter = new();
 
-        private readonly MarkdownPipeline _pipeline;
-        private readonly bool _customWriter;
-
-        public HtmlRendererCache(MarkdownPipeline pipeline, bool customWriter = false)
-        {
-            _pipeline = pipeline;
-            _customWriter = customWriter;
-        }
+        private readonly MarkdownPipeline _pipeline = pipeline;
+        private readonly bool _customWriter = customWriter;
 
         protected override HtmlRenderer NewInstance()
         {

src/Markdig/MarkdownPipelineBuilder.cs

@@ -24,8 +24,8 @@ public class MarkdownPipelineBuilder
     public MarkdownPipelineBuilder()
     {
         // Add all default parsers
-        BlockParsers = new OrderedList<BlockParser>()
-        {
+        BlockParsers =
+        [
             new ThematicBreakParser(),
             new HeadingBlockParser(),
             new QuoteBlockParser(),
@@ -35,10 +35,10 @@ public class MarkdownPipelineBuilder
             new FencedCodeBlockParser(),
             new IndentedCodeBlockParser(),
             new ParagraphBlockParser(),
-        };
+        ];
 
-        InlineParsers = new OrderedList<InlineParser>()
-        {
+        InlineParsers =
+        [
             new HtmlEntityParser(),
             new LinkInlineParser(),
             new EscapeInlineParser(),
@@ -46,7 +46,7 @@ public class MarkdownPipelineBuilder
             new CodeInlineParser(),
             new AutolinkInlineParser(),
             new LineBreakInlineParser(),
-        };
+        ];
 
         Extensions = new OrderedList<IMarkdownExtension>();
     }

src/Markdig/Parsers/BlockProcessor.cs

@@ -152,7 +152,7 @@ public class BlockProcessor
     /// <summary>
     /// Gets the current stack of <see cref="Block"/> being processed.
     /// </summary>
-    private List<BlockWrapper> OpenedBlocks { get; } = new();
+    private List<BlockWrapper> OpenedBlocks { get; } = [];
 
     private bool ContinueProcessingLine { get; set; }
 

src/Markdig/Parsers/FencedBlockParserBase.cs

@@ -40,7 +40,8 @@ public abstract class FencedBlockParserBase : BlockParser, IAttributesParseable
 /// <seealso cref="BlockParser" />
 public abstract class FencedBlockParserBase<T> : FencedBlockParserBase where T : Block, IFencedBlock
 {
-    private static readonly TransformedStringCache _infoStringCache = new(static infoString => HtmlHelper.Unescape(infoString));
+    private static readonly TransformedStringCache s_infoStringCache = new(static infoString => HtmlHelper.Unescape(infoString));
+    private static readonly TransformedStringCache s_argumentsStringCache = new(static argumentsString => HtmlHelper.Unescape(argumentsString));
     private TransformedStringCache? _infoPrefixCache;
 
     /// <summary>
@@ -176,7 +177,7 @@ public abstract class FencedBlockParserBase<T> : FencedBlockParserBase where T :
 
     end:
         fenced.TriviaAfterFencedChar = afterFence;
-        fenced.Info = _infoStringCache.Get(info.AsSpan());
+        fenced.Info = s_infoStringCache.Get(info.AsSpan());
         fenced.UnescapedInfo = info;
         fenced.TriviaAfterInfo = afterInfo;
         fenced.Arguments = HtmlHelper.Unescape(arg.ToString());
@@ -197,71 +198,47 @@ public abstract class FencedBlockParserBase<T> : FencedBlockParserBase where T :
     /// <returns><c>true</c> if parsing of the line is successfull; <c>false</c> otherwise</returns>
     public static bool DefaultInfoParser(BlockProcessor state, ref StringSlice line, IFencedBlock fenced, char openingCharacter)
     {
-        // An info string cannot contain any backticks (unless it is a tilde block)
         int firstSpace = -1;
-        if (openingCharacter == '`')
+        ReadOnlySpan<char> lineSpan = line.AsSpan();
+
+        if (!lineSpan.IsEmpty)
         {
-            for (int i = line.Start; i <= line.End; i++)
+            if (openingCharacter == '`')
             {
-                char c = line.Text[i];
-                if (c == '`')
+                firstSpace = lineSpan.IndexOfAny(' ', '\t', '`');
+
+                // An info string cannot contain any backticks (unless it is a tilde block)
+                if (firstSpace >= 0 && lineSpan.Slice(firstSpace).Contains('`'))
                 {
                     return false;
                 }
-
-                if (firstSpace < 0 && c.IsSpaceOrTab())
-                {
-                    firstSpace = i;
-                }
             }
-        }
-        else
-        {
-            for (int i = line.Start; i <= line.End; i++)
+            else
             {
-                if (line.Text[i].IsSpaceOrTab())
-                {
-                    firstSpace = i;
-                    break;
-                }
+                firstSpace = lineSpan.IndexOfAny(' ', '\t');
             }
         }
 
         StringSlice infoStringSlice;
-        string? argString = null;
 
-        if (firstSpace > 0)
+        if (firstSpace >= 0)
         {
+            firstSpace += line.Start;
             infoStringSlice = new StringSlice(line.Text, line.Start, firstSpace - 1);
 
-            // Skip any spaces after info string
-            firstSpace++;
-            while (firstSpace <= line.End)
-            {
-                char c = line[firstSpace];
-                if (c.IsSpaceOrTab())
-                {
-                    firstSpace++;
-                }
-                else
-                {
-                    break;
-                }
-            }
-
             var argStringSlice = new StringSlice(line.Text, firstSpace, line.End);
             argStringSlice.Trim();
-            argString = argStringSlice.ToString();
+            fenced.Arguments = s_argumentsStringCache.Get(argStringSlice.AsSpan());
         }
         else
         {
             infoStringSlice = line;
+            fenced.Arguments = string.Empty;
         }
 
         infoStringSlice.Trim();
 
-        fenced.Info = _infoStringCache.Get(infoStringSlice.AsSpan());
-        fenced.Arguments = HtmlHelper.Unescape(argString);
+        fenced.Info = s_infoStringCache.Get(infoStringSlice.AsSpan());
 
         return true;
     }
@@ -303,17 +280,19 @@ public abstract class FencedBlockParserBase<T> : FencedBlockParserBase where T :
         // Try to parse any attached attributes
         TryParseAttributes?.Invoke(processor, ref line, fenced);
 
-        // If the info parser was not successfull, early exit
+        // If the info parser was not successful, early exit
         if (InfoParser != null && !InfoParser(processor, ref line, fenced, matchChar))
         {
             return BlockState.None;
         }
 
         // Add the language as an attribute by default
-        if (!string.IsNullOrEmpty(fenced.Info))
+        string? info = fenced.Info;
+
+        if (!string.IsNullOrEmpty(info))
         {
             Debug.Assert(_infoPrefixCache is not null || InfoPrefix is null);
-            string infoWithPrefix = _infoPrefixCache?.Get(fenced.Info!) ?? fenced.Info!;
+            string infoWithPrefix = _infoPrefixCache?.Get(info!) ?? info!;
             fenced.GetAttributes().AddClass(infoWithPrefix);
         }
 
@@ -329,34 +308,32 @@ public abstract class FencedBlockParserBase<T> : FencedBlockParserBase where T :
     public override BlockState TryContinue(BlockProcessor processor, Block block)
     {
         var fence = (IFencedBlock)block;
-        var openingCount = fence.OpeningFencedCharCount;
 
         // Match if we have a closing fence
         var line = processor.Line;
         var sourcePosition = processor.Start;
         var closingCount = line.CountAndSkipChar(fence.FencedChar);
-        var diff = openingCount - closingCount;
 
         char c = line.CurrentChar;
-        var lastFenceCharPosition = processor.Start + closingCount;
 
         // If we have a closing fence, close it and discard the current line
         // The line must contain only fence opening character followed only by whitespaces.
         var startBeforeTrim = line.Start;
-        var endBeforeTrim = line.End;
-        var trimmed = line.TrimEnd();
-        if (diff <= 0 && !processor.IsCodeIndent && (c == '\0' || c.IsWhitespace()) && trimmed)
+
+        if (fence.OpeningFencedCharCount <= closingCount &&
+            !processor.IsCodeIndent &&
+            (c == '\0' || c.IsWhitespace()) &&
+            line.TrimEnd())
         {
             block.UpdateSpanEnd(startBeforeTrim - 1);
 
-            var fencedBlock = (IFencedBlock)block;
-            fencedBlock.ClosingFencedCharCount = closingCount;
+            fence.ClosingFencedCharCount = closingCount;
 
             if (processor.TrackTrivia)
             {
-                fencedBlock.NewLine = processor.Line.NewLine;
-                fencedBlock.TriviaBeforeClosingFence = processor.UseTrivia(sourcePosition - 1);
-                fencedBlock.TriviaAfter = new StringSlice(processor.Line.Text, lastFenceCharPosition, endBeforeTrim);
+                fence.NewLine = line.NewLine;
+                fence.TriviaBeforeClosingFence = processor.UseTrivia(sourcePosition - 1);
+                fence.TriviaAfter = new StringSlice(line.Text, processor.Start + closingCount, processor.Line.End);
             }
 
             // Don't keep the last line

src/Markdig/Parsers/FencedCodeBlockParser.cs

@@ -20,7 +20,7 @@ public class FencedCodeBlockParser : FencedBlockParserBase<FencedCodeBlock>
     /// </summary>
     public FencedCodeBlockParser()
     {
-        OpeningCharacters = new[] {'`', '~'};
+        OpeningCharacters = ['`', '~'];
         InfoPrefix = DefaultInfoPrefix;
     }
 

src/Markdig/Parsers/HeadingBlockParser.cs

@@ -20,7 +20,7 @@ public class HeadingBlockParser : BlockParser, IAttributesParseable
     /// </summary>
     public HeadingBlockParser()
     {
-        OpeningCharacters = new[] {'#'};
+        OpeningCharacters = ['#'];
     }
 
     /// <summary>

src/Markdig/Parsers/HtmlBlockParser.cs

@@ -18,7 +18,7 @@ public class HtmlBlockParser : BlockParser
     /// </summary>
     public HtmlBlockParser()
     {
-        OpeningCharacters = new[] { '<' };
+        OpeningCharacters = ['<'];
     }
        
     public override BlockState TryOpen(BlockProcessor processor)

src/Markdig/Parsers/InlineProcessor.cs

@@ -26,9 +26,11 @@ public delegate void ProcessInlineDelegate(InlineProcessor processor, Inline? in
 /// </summary>
 public class InlineProcessor
 {
-    private readonly List<StringLineGroup.LineOffset> lineOffsets = new();
+    private readonly List<StringLineGroup.LineOffset> lineOffsets = [];
     private int previousSliceOffset;
     private int previousLineIndexForSliceOffset;
+    internal ContainerBlock? PreviousContainerToReplace;
+    internal ContainerBlock? NewContainerToReplace;
 
     /// <summary>
     /// Initializes a new instance of the <see cref="InlineProcessor" /> class.
@@ -203,6 +205,24 @@ public class InlineProcessor
         return 0;
     }
 
+    /// <summary>
+    /// Replace a parent container. This method is experimental and should be used with caution.
+    /// </summary>
+    /// <param name="previousParentContainer">The previous parent container to replace</param>
+    /// <param name="newParentContainer">The new parent container</param>
+    /// <exception cref="InvalidOperationException">If a new parent container has been already setup.</exception>
+    internal void ReplaceParentContainer(ContainerBlock previousParentContainer, ContainerBlock newParentContainer)
+    {
+        // Limitation for now, only one parent container can be replaced.
+        if (PreviousContainerToReplace != null)
+        {
+            throw new InvalidOperationException("A block is already being replaced");
+        }
+
+        PreviousContainerToReplace = previousParentContainer;
+        NewContainerToReplace = newParentContainer;
+    }
+
     /// <summary>
     /// Processes the inline of the specified <see cref="LeafBlock"/>.
     /// </summary>
@@ -211,6 +231,9 @@ public class InlineProcessor
     {
         if (leafBlock is null) ThrowHelper.ArgumentNullException_leafBlock();
 
+        PreviousContainerToReplace = null;
+        NewContainerToReplace = null;
+
         // clear parser states
         Array.Clear(ParserStates, 0, ParserStates.Length);
 
@@ -225,6 +248,7 @@ public class InlineProcessor
         previousLineIndexForSliceOffset = 0;
         lineOffsets.Clear();
         var text = leafBlock.Lines.ToSlice(lineOffsets);
+        var textEnd = text.End;
         leafBlock.Lines.Release();
         int previousStart = -1;
 
@@ -319,7 +343,8 @@ public class InlineProcessor
                 var newLine = leafBlock.NewLine;
                 if (newLine != NewLine.None)
                 {
-                    leafBlock.Inline.AppendChild(new LineBreakInline { NewLine = newLine });
+                    var position = GetSourcePosition(textEnd + 1, out int line, out int column);
+                    leafBlock.Inline.AppendChild(new LineBreakInline { NewLine = newLine, Line = line, Column = column, Span = { Start = position, End = position + (newLine == NewLine.CarriageReturnLineFeed ? 1 : 0) } });
                 }
             }
         }
@@ -342,6 +367,12 @@ public class InlineProcessor
         //    DebugLog.WriteLine("** Dump after Emphasis:");
         //    leafBlock.Inline.DumpTo(DebugLog);
         //}
+
+        if (leafBlock.Inline.LastChild is not null)
+        {
+            leafBlock.Inline.Span.End = leafBlock.Inline.LastChild.Span.End;
+            leafBlock.UpdateSpanEnd(leafBlock.Inline.Span.End);
+        }
     }
 
     public void PostProcessInlines(int startingIndex, Inline? root, Inline? lastChild, bool isFinalProcessing)

src/Markdig/Parsers/Inlines/AutolinkInlineParser.cs

@@ -19,7 +19,7 @@ public class AutolinkInlineParser : InlineParser
     /// </summary>
     public AutolinkInlineParser()
     {
-        OpeningCharacters = new[] {'<'};
+        OpeningCharacters = ['<'];
         EnableHtmlParsing = true;
     }
 

src/Markdig/Parsers/Inlines/CodeInlineParser.cs

@@ -21,27 +21,21 @@ public class CodeInlineParser : InlineParser
     /// </summary>
     public CodeInlineParser()
     {
-        OpeningCharacters = new[] { '`' };
+        OpeningCharacters = ['`'];
     }
 
     public override bool Match(InlineProcessor processor, ref StringSlice slice)
     {
-        var match = slice.CurrentChar;
+        char match = slice.CurrentChar;
         if (slice.PeekCharExtra(-1) == match)
         {
             return false;
         }
 
-        var startPosition = slice.Start;
+        Debug.Assert(match is not ('\r' or '\n'));
 
         // Match the opened sticks
         int openSticks = slice.CountAndSkipChar(match);
-        int contentStart = slice.Start;
-        int closeSticks = 0;
-
-        char c = slice.CurrentChar;
-
-        var builder = new ValueStringBuilder(stackalloc char[ValueStringBuilder.StackallocThreshold]);
 
         // A backtick string is a string of one or more backtick characters (`) that is neither preceded nor followed by a backtick.
         // A code span begins with a backtick string and ends with a backtick string of equal length.
@@ -54,91 +48,106 @@ public class CodeInlineParser : InlineParser
         // This allows you to include code that begins or ends with backtick characters, which must be separated by
         // whitespace from the opening or closing backtick strings.
 
-        bool allSpace = true;
-        bool containsNewLine = false;
-        var contentEnd = -1;
+        ReadOnlySpan<char> span = slice.AsSpan();
+        bool containsNewLines = false;
 
-        while (c != '\0')
+        while (true)
         {
-            // Transform '\n' into a single space
-            if (c == '\n')
+            int i = span.IndexOfAny('\r', '\n', match);
+
+            if ((uint)i >= (uint)span.Length)
             {
-                containsNewLine = true;
-                c = ' ';
-            }
-            else if (c == '\r')
-            {
-                containsNewLine = true;
-                slice.SkipChar();
-                c = slice.CurrentChar;
-                continue;
+                // We got to the end of the input before seeing the match character. CodeInline can't match here.
+                return false;
             }
 
-            if (c == match)
+            int closeSticks = 0;
+
+            while ((uint)i < (uint)span.Length && span[i] == match)
             {
-                contentEnd = slice.Start;
-                closeSticks = slice.CountAndSkipChar(match);
-
-                if (openSticks == closeSticks)
-                {
-                    break;
-                }
-
-                allSpace = false;
-                builder.Append(match, closeSticks);
-                c = slice.CurrentChar;
+                closeSticks++;
+                i++;
             }
-            else
+
+            span = span.Slice(i);
+
+            if (openSticks == closeSticks)
             {
-                builder.Append(c);
-                if (c != ' ')
-                {
-                    allSpace = false;
-                }
-                c = slice.NextChar();
+                break;
+            }
+            else if (closeSticks == 0)
+            {
+                containsNewLines = true;
+                span = span.Slice(1);
             }
         }
 
-        bool isMatching = false;
-        if (closeSticks == openSticks)
+        ReadOnlySpan<char> rawContent = slice.AsSpan().Slice(0, slice.Length - span.Length - openSticks);
+
+        var content = containsNewLines
+            ? new LazySubstring(ReplaceNewLines(rawContent)) // Should be the rare path.
+            : new LazySubstring(slice.Text, slice.Start, rawContent.Length);
+
+        // Remove one space from front and back if the string is not all spaces
+        if (rawContent.Length > 2 &&
+            rawContent[0] is ' ' or '\n' &&
+            rawContent[rawContent.Length - 1] is ' ' or '\n' &&
+            rawContent.ContainsAnyExcept(' ', '\r', '\n'))
         {
-            ReadOnlySpan<char> contentSpan = builder.AsSpan();
-
-            var content = containsNewLine
-                ? new LazySubstring(contentSpan.ToString())
-                : new LazySubstring(slice.Text, contentStart, contentSpan.Length);
-
-            Debug.Assert(contentSpan.SequenceEqual(content.AsSpan()));
-
-            // Remove one space from front and back if the string is not all spaces
-            if (!allSpace && contentSpan.Length > 2 && contentSpan[0] == ' ' && contentSpan[contentSpan.Length - 1] == ' ')
-            {
-                content.Offset++;
-                content.Length -= 2;
-            }
-
-            int delimiterCount = Math.Min(openSticks, closeSticks);
-            var spanStart = processor.GetSourcePosition(startPosition, out int line, out int column);
-            var spanEnd = processor.GetSourcePosition(slice.Start - 1);
-            var codeInline = new CodeInline(content)
-            {
-                Delimiter = match,
-                Span = new SourceSpan(spanStart, spanEnd),
-                Line = line,
-                Column = column,
-                DelimiterCount = delimiterCount,
-            };
-
-            if (processor.TrackTrivia)
-            {
-                codeInline.ContentWithTrivia = new StringSlice(slice.Text, contentStart, contentEnd - 1);
-            }
-
-            processor.Inline = codeInline;
-            isMatching = true;
+            content.Offset++;
+            content.Length -= 2;
         }
 
-        builder.Dispose();
-        return isMatching;
+        int startPosition = slice.Start;
+        slice.Start = startPosition + rawContent.Length + openSticks;
+
+        // We've already skipped the opening sticks. Account for that here.
+        startPosition -= openSticks;
+
+        var codeInline = new CodeInline(content)
+        {
+            Delimiter = slice.Text[startPosition],
+            Span = new SourceSpan(processor.GetSourcePosition(startPosition, out int line, out int column), processor.GetSourcePosition(slice.Start - 1)),
+            Line = line,
+            Column = column,
+            DelimiterCount = openSticks,
+        };
+
+        if (processor.TrackTrivia)
+        {
+            // startPosition and slice.Start include the opening/closing sticks.
+            codeInline.ContentWithTrivia = new StringSlice(slice.Text, startPosition + openSticks, slice.Start - openSticks - 1);
+        }
+
+        processor.Inline = codeInline;
+        return true;
+    }
+
+    private static string ReplaceNewLines(ReadOnlySpan<char> content)
+    {
+        var builder = new ValueStringBuilder(stackalloc char[ValueStringBuilder.StackallocThreshold]);
+
+        while (true)
+        {
+            int i = content.IndexOfAny('\r', '\n');
+
+            if ((uint)i >= (uint)content.Length)
+            {
+                builder.Append(content);
+                break;
+            }
+
+            builder.Append(content.Slice(0, i));
+
+            if (content[i] == '\n')
+            {
+                // Transform '\n' into a single space
+                builder.Append(' ');
+            }
+
+            content = content.Slice(i + 1);
+        }
+
+        return builder.ToString();
     }
 }

src/Markdig/Parsers/Inlines/EmphasisInlineParser.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.Diagnostics;
@@ -20,7 +20,7 @@ namespace Markdig.Parsers.Inlines;
 public class EmphasisInlineParser : InlineParser, IPostInlineProcessor
 {
     private CharacterMap<EmphasisDescriptor>? emphasisMap;
-    private readonly DelimitersObjectCache inlinesCache = new DelimitersObjectCache();
+    private readonly DelimitersObjectCache inlinesCache = new();
 
     [Obsolete("Use TryCreateEmphasisInlineDelegate instead", error: false)]
     public delegate EmphasisInline CreateEmphasisInlineDelegate(char emphasisChar, bool isStrong);
@@ -31,11 +31,11 @@ public class EmphasisInlineParser : InlineParser, IPostInlineProcessor
     /// </summary>
     public EmphasisInlineParser()
     {
-        EmphasisDescriptors = new List<EmphasisDescriptor>()
-        {
+        EmphasisDescriptors =
+        [
             new EmphasisDescriptor('*', 1, 2, true),
             new EmphasisDescriptor('_', 1, 2, false)
-        };
+        ];
     }
 
     /// <summary>
@@ -65,7 +65,7 @@ public class EmphasisInlineParser : InlineParser, IPostInlineProcessor
     /// </summary>
     [Obsolete("Use TryCreateEmphasisInlineList instead", error: false)]
     public CreateEmphasisInlineDelegate? CreateEmphasisInline { get; set; }
-    public readonly List<TryCreateEmphasisInlineDelegate> TryCreateEmphasisInlineList = new List<TryCreateEmphasisInlineDelegate>();
+    public readonly List<TryCreateEmphasisInlineDelegate> TryCreateEmphasisInlineList = [];
 
     public override void Initialize()
     {
@@ -109,7 +109,7 @@ public class EmphasisInlineParser : InlineParser, IPostInlineProcessor
         var child = container.FirstChild;
         while (child != null)
         {
-            // Stop the search on the delimitation child 
+            // Stop the search on the delimitation child
             if (child == lastChild)
             {
                 break;
@@ -197,7 +197,7 @@ public class EmphasisInlineParser : InlineParser, IPostInlineProcessor
             if (canOpen) delimiterType |= DelimiterType.Open;
             if (canClose) delimiterType |= DelimiterType.Close;
 
-            var delimiter = new EmphasisDelimiterInline(this, emphasisDesc)
+            var delimiter = new EmphasisDelimiterInline(this, emphasisDesc, new StringSlice(slice.Text, startPosition, slice.Start - 1))
             {
                 DelimiterCount = delimiterCount,
                 Type = delimiterType,
@@ -221,7 +221,7 @@ public class EmphasisInlineParser : InlineParser, IPostInlineProcessor
 
         // TODO: Benchmark difference between using List and LinkedList here since there could be a few Remove calls
 
-        // Move current_position forward in the delimiter stack (if needed) until 
+        // Move current_position forward in the delimiter stack (if needed) until
         // we find the first potential closer with delimiter * or _. (This will be the potential closer closest to the beginning of the input – the first one in parse order.)
         for (int i = 0; i < delimiters.Count; i++)
         {
@@ -237,7 +237,7 @@ public class EmphasisInlineParser : InlineParser, IPostInlineProcessor
             {
                 while (true)
                 {
-                    // Now, look back in the stack (staying above stack_bottom and the openers_bottom for this delimiter type) 
+                    // Now, look back in the stack (staying above stack_bottom and the openers_bottom for this delimiter type)
                     // for the first matching potential opener (“matching” means same delimiter).
                     EmphasisDelimiterInline? openDelimiter = null;
                     int openDelimiterIndex = -1;
@@ -302,13 +302,14 @@ public class EmphasisInlineParser : InlineParser, IPostInlineProcessor
                         var openDelimitercount = openDelimiter.DelimiterCount;
                         var closeDelimitercount = closeDelimiter.DelimiterCount;
 
-                        emphasis!.Span.Start = openDelimiter.Span.Start;
+                        emphasis!.Span.Start = openDelimiter.Span.Start + openDelimitercount - delimiterDelta;
                         emphasis.Line = openDelimiter.Line;
-                        emphasis.Column = openDelimiter.Column;
+                        emphasis.Column = openDelimiter.Column + openDelimitercount - delimiterDelta;
                         emphasis.Span.End = closeDelimiter.Span.End - closeDelimitercount + delimiterDelta;
 
-                        openDelimiter.Span.Start += delimiterDelta;
-                        openDelimiter.Column += delimiterDelta;
+                        openDelimiter.Span.End -= delimiterDelta;
+                        openDelimiter.Content.End -= delimiterDelta;
+                        closeDelimiter.Content.Start += delimiterDelta;
                         closeDelimiter.Span.Start += delimiterDelta;
                         closeDelimiter.Column += delimiterDelta;
 
@@ -331,7 +332,7 @@ public class EmphasisInlineParser : InlineParser, IPostInlineProcessor
                         for (int k = i - 1; k >= openDelimiterIndex + 1; k--)
                         {
                             var literalDelimiter = delimiters[k];
-                            literalDelimiter.ReplaceBy(literalDelimiter.AsLiteralInline());                                
+                            literalDelimiter.ReplaceBy(literalDelimiter.AsLiteralInline());
                             delimiters.RemoveAt(k);
                             i--;
                         }

src/Markdig/Parsers/Inlines/EscapeInlineParser.cs

@@ -15,7 +15,7 @@ public class EscapeInlineParser : InlineParser
 {
     public EscapeInlineParser()
     {
-        OpeningCharacters = new[] {'\\'};
+        OpeningCharacters = ['\\'];
     }
 
     public override bool Match(InlineProcessor processor, ref StringSlice slice)

src/Markdig/Parsers/Inlines/HtmlEntityParser.cs

@@ -21,7 +21,7 @@ public class HtmlEntityParser : InlineParser
     /// </summary>
     public HtmlEntityParser()
     {
-        OpeningCharacters = new[] {'&'};
+        OpeningCharacters = ['&'];
     }
 
     public static bool TryParse(ref StringSlice slice, [NotNullWhen(true)] out string? literal, out int match)

src/Markdig/Parsers/Inlines/LineBreakInlineParser.cs

@@ -18,7 +18,7 @@ public class LineBreakInlineParser : InlineParser
     /// </summary>
     public LineBreakInlineParser()
     {
-        OpeningCharacters = new[] { '\n', '\r' };
+        OpeningCharacters = ['\n', '\r'];
     }
 
     /// <summary>

src/Markdig/Parsers/Inlines/LinkInlineParser.cs

@@ -19,7 +19,7 @@ public class LinkInlineParser : InlineParser
     /// </summary>
     public LinkInlineParser()
     {
-        OpeningCharacters = new[] {'[', ']', '!'};
+        OpeningCharacters = ['[', ']', '!'];
     }
 
     public override bool Match(InlineProcessor processor, ref StringSlice slice)
@@ -137,6 +137,9 @@ public class LinkInlineParser : InlineParser
         if (linkRef.CreateLinkInline != null)
         {
             link = linkRef.CreateLinkInline(state, linkRef, parent.FirstChild);
+            link.Span = new SourceSpan(parent.Span.Start, endPosition);
+            link.Line = parent.Line;
+            link.Column = parent.Column;
         }
 
         // Create a default link if the callback was not found
@@ -145,8 +148,8 @@ public class LinkInlineParser : InlineParser
             // Inline Link
             var linkInline = new LinkInline()
             {
-                Url = HtmlHelper.Unescape(linkRef.Url),
-                Title = HtmlHelper.Unescape(linkRef.Title),
+                Url = HtmlHelper.Unescape(linkRef.Url, removeBackSlash: false),
+                Title = HtmlHelper.Unescape(linkRef.Title, removeBackSlash: false),
                 Label = label,
                 LabelSpan = labelSpan,
                 UrlSpan = linkRef.UrlSpan,
@@ -256,8 +259,8 @@ public class LinkInlineParser : InlineParser
                     // Inline Link
                     link = new LinkInline()
                     {
-                        Url = HtmlHelper.Unescape(url),
-                        Title = HtmlHelper.Unescape(title),
+                        Url = HtmlHelper.Unescape(url, removeBackSlash: false),
+                        Title = HtmlHelper.Unescape(title, removeBackSlash: false),
                         IsImage = openParent.IsImage,
                         LabelSpan = openParent.LabelSpan,
                         UrlSpan = inlineState.GetSourcePositionFromLocalSpan(linkSpan),
@@ -322,7 +325,7 @@ public class LinkInlineParser : InlineParser
 
         if (label != null || LinkHelper.TryParseLabelTrivia(ref text, true, out label, out labelSpan))
         {
-            SourceSpan labelWithTrivia = new SourceSpan(labelSpan.Start, labelSpan.End);
+            var labelWithTrivia = new SourceSpan(labelSpan.Start, labelSpan.End);
             if (isLabelSpanLocal)
             {
                 labelSpan = inlineState.GetSourcePositionFromLocalSpan(labelSpan);
@@ -382,11 +385,11 @@ public class LinkInlineParser : InlineParser
                 return new LinkInline()
                 {
                     TriviaBeforeUrl = wsBeforeLink,
-                    Url = HtmlHelper.Unescape(url),
+                    Url = HtmlHelper.Unescape(url, removeBackSlash: false),
                     UnescapedUrl = unescapedUrl,
                     UrlHasPointyBrackets = urlHasPointyBrackets,
                     TriviaAfterUrl = wsAfterLink,
-                    Title = HtmlHelper.Unescape(title),
+                    Title = HtmlHelper.Unescape(title, removeBackSlash: false),
                     UnescapedTitle = unescapedTitle,
                     TitleEnclosingCharacter = titleEnclosingCharacter,
                     TriviaAfterTitle = wsAfterTitle,

src/Markdig/Parsers/Inlines/LiteralInlineParser.cs

@@ -32,16 +32,12 @@ public sealed class LiteralInlineParser : InlineParser
 
     public override bool Match(InlineProcessor processor, ref StringSlice slice)
     {
-        var text = slice.Text;
+        string text = slice.Text;
 
-        var startPosition = processor.GetSourcePosition(slice.Start, out int line, out int column);
-
-        // Slightly faster to perform our own search for opening characters
-        var nextStart = processor.Parsers.IndexOfOpeningCharacter(text, slice.Start + 1, slice.End);
-        //var nextStart = str.IndexOfAny(processor.SpecialCharacters, slice.Start + 1, slice.Length - 1);
+        int nextStart = processor.Parsers.IndexOfOpeningCharacter(text, slice.Start + 1, slice.End);
         int length;
 
-        if (nextStart < 0)
+        if ((uint)nextStart >= (uint)text.Length)
         {
             nextStart = slice.End + 1;
             length = nextStart - slice.Start;
@@ -50,10 +46,10 @@ public sealed class LiteralInlineParser : InlineParser
         {
             // Remove line endings if the next char is a new line
             length = nextStart - slice.Start;
+
             if (!processor.TrackTrivia)
             {
-                var nextText = text[nextStart];
-                if (nextText == '\n' || nextText == '\r')
+                if (text[nextStart] is '\n' or '\r')
                 {
                     int end = nextStart - 1;
                     while (length > 0 && text[end].IsSpace())
@@ -86,7 +82,7 @@ public sealed class LiteralInlineParser : InlineParser
                 processor.Inline = new LiteralInline
                 {
                     Content = length > 0 ? newSlice : StringSlice.Empty,
-                    Span = new SourceSpan(startPosition, processor.GetSourcePosition(endPosition)),
+                    Span = new SourceSpan(processor.GetSourcePosition(slice.Start, out int line, out int column), processor.GetSourcePosition(endPosition)),
                     Line = line,
                     Column = column,
                 };

src/Markdig/Parsers/MarkdownParser.cs

@@ -53,34 +53,11 @@ public static class MarkdownParser
         {
             blockProcessor.Open(document);
 
-            ProcessBlocks(blockProcessor, new LineReader(text));
+            ProcessBlocks(blockProcessor, text);
 
             if (pipeline.TrackTrivia)
             {
-                Block? lastBlock = blockProcessor.LastBlock;
-                if (lastBlock is null && document.Count == 0)
-                {
-                    // this means we have unassigned characters
-                    var noBlocksFoundBlock = new EmptyBlock(null);
-                    List<StringSlice> linesBefore = blockProcessor.UseLinesBefore();
-                    noBlocksFoundBlock.LinesAfter = new List<StringSlice>();
-                    if (linesBefore != null)
-                    {
-                        noBlocksFoundBlock.LinesAfter.AddRange(linesBefore);
-                    }
-
-                    document.Add(noBlocksFoundBlock);
-                }
-                else if (lastBlock != null && blockProcessor.LinesBefore != null)
-                {
-                    // this means we're out of lines, but still have unassigned empty lines.
-                    // thus, we'll assign the empty unsassigned lines to the last block
-                    // of the document.
-                    var rootMostContainerBlock = Block.FindRootMostContainerParent(lastBlock);
-                    rootMostContainerBlock.LinesAfter ??= new List<StringSlice>();
-                    var linesBefore = blockProcessor.UseLinesBefore();
-                    rootMostContainerBlock.LinesAfter.AddRange(linesBefore);
-                }
+                ProcessBlocksTrivia(blockProcessor, document);
             }
 
             // At this point the LineIndex is the same as the number of lines in the document
@@ -117,12 +94,15 @@ public static class MarkdownParser
         return text.Replace('\0', CharHelper.ReplacementChar);
     }
 
-    private static void ProcessBlocks(BlockProcessor blockProcessor, LineReader lineReader)
+    [MethodImpl(MethodImplOptions.NoInlining)]
+    private static void ProcessBlocks(BlockProcessor blockProcessor, string text)
     {
+        var lineReader = new LineReader(text);
+
         while (true)
         {
-            // Get the precise position of the begining of the line
-            var lineText = lineReader.ReadLine();
+            // Get the precise position of the beginning of the line
+            StringSlice lineText = lineReader.ReadLine();
 
             // If this is the end of file and the last line is empty
             if (lineText.Text is null)
@@ -132,9 +112,39 @@ public static class MarkdownParser
 
             blockProcessor.ProcessLine(lineText);
         }
+
         blockProcessor.CloseAll(true);
     }
 
+    private static void ProcessBlocksTrivia(BlockProcessor blockProcessor, MarkdownDocument document)
+    {
+        Block? lastBlock = blockProcessor.LastBlock;
+        if (lastBlock is null && document.Count == 0)
+        {
+            // this means we have unassigned characters
+            var noBlocksFoundBlock = new EmptyBlock(null);
+            List<StringSlice> linesBefore = blockProcessor.UseLinesBefore();
+            noBlocksFoundBlock.LinesAfter = [];
+            if (linesBefore != null)
+            {
+                noBlocksFoundBlock.LinesAfter.AddRange(linesBefore);
+            }
+
+            document.Add(noBlocksFoundBlock);
+        }
+        else if (lastBlock != null && blockProcessor.LinesBefore != null)
+        {
+            // this means we're out of lines, but still have unassigned empty lines.
+            // thus, we'll assign the empty unsassigned lines to the last block
+            // of the document.
+            var rootMostContainerBlock = Block.FindRootMostContainerParent(lastBlock);
+            rootMostContainerBlock.LinesAfter ??= [];
+            var linesBefore = blockProcessor.UseLinesBefore();
+            rootMostContainerBlock.LinesAfter.AddRange(linesBefore);
+        }
+    }
+
+    [MethodImpl(MethodImplOptions.NoInlining)]
     private static void ProcessInlines(InlineProcessor inlineProcessor, MarkdownDocument document)
     {
         // "stackless" processor
@@ -160,6 +170,40 @@ public static class MarkdownParser
                     if (leafBlock.ProcessInlines)
                     {
                         inlineProcessor.ProcessInlineLeaf(leafBlock);
+
+                        // Experimental code to handle a replacement of a parent container
+                        // Not satisfied with this code, so we are keeping it internal for now
+                        if (inlineProcessor.PreviousContainerToReplace != null)
+                        {
+                            if (container == inlineProcessor.PreviousContainerToReplace)
+                            {
+                                item = new ContainerItem(inlineProcessor.NewContainerToReplace!) { Index = item.Index };
+                                container = item.Container;
+                            }
+                            else
+                            {
+                                bool parentBlockFound = false;
+                                for (int i = blockCount - 2; i >= 0; i--)
+                                {
+                                    ref var parentBlock = ref blocks[i];
+                                    if (parentBlock.Container == inlineProcessor.PreviousContainerToReplace)
+                                    {
+                                        parentBlock = new ContainerItem(inlineProcessor.NewContainerToReplace!) { Index = parentBlock.Index };
+                                        parentBlockFound = true;
+                                        break;
+                                    }
+                                }
+
+                                if (!parentBlockFound)
+                                {
+                                    throw new InvalidOperationException("Cannot find the parent block to replace");
+                                }
+                            }
+
+                            inlineProcessor.PreviousContainerToReplace = null;
+                            inlineProcessor.NewContainerToReplace = null;
+                        }
+
                         if (leafBlock.RemoveAfterProcessInlines)
                         {
                             container.RemoveAt(item.Index);
@@ -200,16 +244,10 @@ public static class MarkdownParser
         }
     }
 
-    private struct ContainerItem
+    private struct ContainerItem(ContainerBlock container)
     {
-        public ContainerItem(ContainerBlock container)
-        {
-            Container = container;
-            Index = 0;
-        }
+        public readonly ContainerBlock Container = container;
 
-        public readonly ContainerBlock Container;
-
-        public int Index;
+        public int Index = 0;
     }
 }

src/Markdig/Parsers/OrderedListItemParser.cs

@@ -15,7 +15,7 @@ public abstract class OrderedListItemParser : ListItemParser
     /// </summary>
     protected OrderedListItemParser()
     {
-        OrderedDelimiters = new[] { '.', ')' };
+        OrderedDelimiters = ['.', ')'];
     }
 
     /// <summary>

src/Markdig/Parsers/ParagraphBlockParser.cs

@@ -171,13 +171,9 @@ public class ParagraphBlockParser : BlockParser
         {
             count = line.CountAndSkipChar(headingChar);
 
-            if (line.IsEmpty)
-            {
-                return headingChar;
-            }
-
-            while (line.NextChar().IsSpaceOrTab())
+            while (line.CurrentChar.IsSpaceOrTab())
             {
+                line.NextChar();
             }
 
             if (line.IsEmpty)

src/Markdig/Parsers/QuoteBlockParser.cs

@@ -18,7 +18,7 @@ public class QuoteBlockParser : BlockParser
     /// </summary>
     public QuoteBlockParser()
     {
-        OpeningCharacters = new[] {'>'};
+        OpeningCharacters = ['>'];
     }
 
     public override BlockState TryOpen(BlockProcessor processor)

src/Markdig/Parsers/ThematicBreakParser.cs

@@ -16,14 +16,14 @@ public class ThematicBreakParser : BlockParser
     /// <summary>
     /// A singleton instance used by other parsers.
     /// </summary>
-    public static readonly ThematicBreakParser Default = new ThematicBreakParser();
+    public static readonly ThematicBreakParser Default = new();
 
     /// <summary>
     /// Initializes a new instance of the <see cref="ThematicBreakParser"/> class.
     /// </summary>
     public ThematicBreakParser()
     {
-        OpeningCharacters = new[] {'-', '_', '*'};
+        OpeningCharacters = ['-', '_', '*'];
     }
 
     public override BlockState TryOpen(BlockProcessor processor)

src/Markdig/Parsers/UnorderedListItemParser.cs

@@ -15,7 +15,7 @@ public class UnorderedListItemParser : ListItemParser
     /// </summary>
     public UnorderedListItemParser()
     {
-        OpeningCharacters = new [] {'-', '+', '*'};
+        OpeningCharacters = ['-', '+', '*'];
     }
 
     public override bool TryParse(BlockProcessor state, char pendingBulletType, out ListInfo result)

src/Markdig/Polyfills/Ascii.cs

@@ -0,0 +1,30 @@
+// 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.
+
+#if !NET8_0_OR_GREATER
+
+namespace System.Text;
+
+internal static class Ascii
+{
+    public static bool IsValid(this string value)
+    {
+        return IsValid(value.AsSpan());
+    }
+
+    public static bool IsValid(this ReadOnlySpan<char> value)
+    {
+        for (int i = 0; i < value.Length; i++)
+        {
+            if (value[i] > 127)
+            {
+                return false;
+            }
+        }
+
+        return true;
+    }
+}
+
+#endif

src/Markdig/Polyfills/EncodingExtensions.cs

@@ -0,0 +1,24 @@
+// 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.
+
+#if !NETSTANDARD2_1_OR_GREATER
+
+using System.Runtime.InteropServices;
+
+namespace System.Text;
+
+internal static class EncodingExtensions
+{
+    public static unsafe int GetBytes(this Encoding encoding, ReadOnlySpan<char> chars, Span<byte> bytes)
+    {
+        fixed (char* charsPtr = &MemoryMarshal.GetReference(chars))
+        {
+            fixed (byte* bytesPtr = &MemoryMarshal.GetReference(bytes))
+            {
+                return encoding.GetBytes(charsPtr, chars.Length, bytesPtr, bytes.Length);
+            }
+        }
+    }
+}
+#endif

src/Markdig/Polyfills/IndexOfHelpers.cs

@@ -0,0 +1,53 @@
+// 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.
+
+#if !NET8_0_OR_GREATER
+
+namespace System;
+
+internal static class IndexOfHelpers
+{
+    public static bool ContainsAnyExcept(this ReadOnlySpan<char> span, char value0, char value1, char value2)
+    {
+        for (int i = 0; i < span.Length; i++)
+        {
+            char c = span[i];
+            if (c != value0 && c != value1 && c != value2)
+            {
+                return true;
+            }
+        }
+
+        return false;
+    }
+
+#if !NETSTANDARD2_1_OR_GREATER
+    public static int IndexOfAny(this ReadOnlySpan<char> span, string values)
+    {
+        for (int i = 0; i < span.Length; i++)
+        {
+            char c = span[i];
+
+            foreach (char v in values)
+            {
+                if (c == v)
+                {
+                    return i;
+                }
+            }
+        }
+
+        return -1;
+    }
+#endif
+
+#if !NET6_0_OR_GREATER
+    public static bool Contains<T>(this ReadOnlySpan<T> span, T value) where T : IEquatable<T>
+    {
+        return span.IndexOf(value) >= 0;
+    }
+#endif
+}
+
+#endif

src/Markdig/Polyfills/NullableAttributes.cs

@@ -23,7 +23,7 @@ internal sealed class AllowNullAttribute : Attribute { }
 #if !NET5_0_OR_GREATER
 internal sealed class MemberNotNullAttribute : Attribute
 {
-    public MemberNotNullAttribute(string member) => Members = new[] { member };
+    public MemberNotNullAttribute(string member) => Members = [member];
 
     public MemberNotNullAttribute(params string[] members) => Members = members;
 

src/Markdig/Polyfills/SearchValues.cs

@@ -0,0 +1,137 @@
+// 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.
+
+#if !NET8_0_OR_GREATER
+
+using System.Diagnostics;
+using System.Runtime.CompilerServices;
+
+namespace System.Buffers;
+
+internal static class SearchValues
+{
+    public static SearchValues<char> Create(string values) =>
+        Create(values.AsSpan());
+
+    public static SearchValues<char> Create(ReadOnlySpan<char> values) =>
+        new PreNet8CompatSearchValues(values);
+
+    public static int IndexOfAny(this ReadOnlySpan<char> span, SearchValues<char> values) =>
+        values.IndexOfAny(span);
+
+    public static int IndexOfAnyExcept(this ReadOnlySpan<char> span, SearchValues<char> values) =>
+        values.IndexOfAnyExcept(span);
+}
+
+internal abstract class SearchValues<T>
+{
+    public abstract int IndexOfAny(ReadOnlySpan<char> span);
+
+    public abstract int IndexOfAnyExcept(ReadOnlySpan<char> span);
+}
+
+internal sealed class PreNet8CompatSearchValues : SearchValues<char>
+{
+    private readonly BoolVector128 _ascii;
+    private readonly HashSet<char>? _nonAscii;
+
+    public PreNet8CompatSearchValues(ReadOnlySpan<char> values)
+    {
+        foreach (char c in values)
+        {
+            if (c < 128)
+            {
+                _ascii.Set(c);
+            }
+            else
+            {
+                _nonAscii ??= new HashSet<char>();
+                _nonAscii.Add(c);
+            }
+        }
+    }
+
+    public override int IndexOfAny(ReadOnlySpan<char> span)
+    {
+        if (_nonAscii is null)
+        {
+            for (int i = 0; i < span.Length; i++)
+            {
+                char c = span[i];
+
+                if (c < 128 && _ascii[c])
+                {
+                    return i;
+                }
+            }
+        }
+        else
+        {
+            for (int i = 0; i < span.Length; i++)
+            {
+                char c = span[i];
+
+                if (c < 128 ? _ascii[c] : _nonAscii.Contains(c))
+                {
+                    return i;
+                }
+            }
+        }
+
+        return -1;
+    }
+
+    public override int IndexOfAnyExcept(ReadOnlySpan<char> span)
+    {
+        if (_nonAscii is null)
+        {
+            for (int i = 0; i < span.Length; i++)
+            {
+                char c = span[i];
+
+                if (c >= 128 || !_ascii[c])
+                {
+                    return i;
+                }
+            }
+        }
+        else
+        {
+            for (int i = 0; i < span.Length; i++)
+            {
+                char c = span[i];
+
+                if (c < 128 ? !_ascii[c] : !_nonAscii.Contains(c))
+                {
+                    return i;
+                }
+            }
+        }
+
+        return -1;
+    }
+
+    private 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];
+            }
+        }
+    }
+}
+
+#endif

src/Markdig/Renderers/Html/CodeBlockRenderer.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 Markdig.Parsers;
@@ -13,8 +13,6 @@ namespace Markdig.Renderers.Html;
 /// <seealso cref="HtmlObjectRenderer{CodeBlock}" />
 public class CodeBlockRenderer : HtmlObjectRenderer<CodeBlock>
 {
-    private HashSet<string>? _blocksAsDiv;
-
     /// <summary>
     /// Initializes a new instance of the <see cref="CodeBlockRenderer"/> class.
     /// </summary>
@@ -25,23 +23,32 @@ public class CodeBlockRenderer : HtmlObjectRenderer<CodeBlock>
     /// <summary>
     /// Gets a map of fenced code block infos that should be rendered as div blocks instead of pre/code blocks.
     /// </summary>
-    public HashSet<string> BlocksAsDiv => _blocksAsDiv ??= new HashSet<string>(StringComparer.OrdinalIgnoreCase);
+    public HashSet<string> BlocksAsDiv { get; } = new HashSet<string>(StringComparer.OrdinalIgnoreCase);
+
+    /// <summary>
+    /// Gets a map of custom block mapping to render as custom blocks instead of pre/code blocks.
+    /// For example defining {"mermaid", "pre"} will render a block with info `mermaid` as a `pre` block but without the code HTML element.
+    /// </summary>
+    public Dictionary<string, string> BlockMapping { get; } = new Dictionary<string, string>(StringComparer.OrdinalIgnoreCase);
 
     protected override void Write(HtmlRenderer renderer, CodeBlock obj)
     {
         renderer.EnsureLine();
 
-        if (_blocksAsDiv is not null && (obj as FencedCodeBlock)?.Info is string info && _blocksAsDiv.Contains(info))
+        if ((obj as FencedCodeBlock)?.Info is string info && (BlocksAsDiv.Contains(info) || BlockMapping.ContainsKey(info)))
         {
             var infoPrefix = (obj.Parser as FencedCodeBlockParser)?.InfoPrefix ??
                              FencedCodeBlockParser.DefaultInfoPrefix;
 
+            var htmlBlock = BlockMapping.TryGetValue(info, out var blockType) ? blockType : "div";
+
             // We are replacing the HTML attribute `language-mylang` by `mylang` only for a div block
             // NOTE that we are allocating a closure here
 
             if (renderer.EnableHtmlForBlock)
             {
-                renderer.Write("<div")
+                renderer.WriteRaw('<');
+                renderer.Write(htmlBlock)
                         .WriteAttributes(obj.TryGetAttributes(),
                             cls => cls.StartsWith(infoPrefix, StringComparison.Ordinal) ? cls.Substring(infoPrefix.Length) : cls)
                         .WriteRaw('>');
@@ -51,7 +58,7 @@ public class CodeBlockRenderer : HtmlObjectRenderer<CodeBlock>
 
             if (renderer.EnableHtmlForBlock)
             {
-                renderer.WriteLine("</div>");
+                renderer.Write("</").Write(htmlBlock).WriteLine(">");
             }
         }
         else

src/Markdig/Renderers/Html/HeadingRenderer.cs

@@ -12,14 +12,14 @@ namespace Markdig.Renderers.Html;
 /// <seealso cref="HtmlObjectRenderer{HeadingBlock}" />
 public class HeadingRenderer : HtmlObjectRenderer<HeadingBlock>
 {
-    private static readonly string[] HeadingTexts = {
+    private static readonly string[] HeadingTexts = [
         "h1",
         "h2",
         "h3",
         "h4",
         "h5",
         "h6",
-    };
+    ];
 
     protected override void Write(HtmlRenderer renderer, HeadingBlock obj)
     {

src/Markdig/Renderers/HtmlRenderer.cs

@@ -2,6 +2,7 @@
 // This file is licensed under the BSD-Clause 2 license. 
 // See the license.txt file in the project root for more information.
 
+using System.Buffers;
 using System.Globalization;
 using System.IO;
 using System.Runtime.CompilerServices;
@@ -20,7 +21,10 @@ namespace Markdig.Renderers;
 /// <seealso cref="TextRendererBase{HtmlRenderer}" />
 public class HtmlRenderer : TextRendererBase<HtmlRenderer>
 {
-    private static readonly char[] s_writeEscapeIndexOfAnyChars = new[] { '<', '>', '&', '"' };
+    private static readonly IdnMapping s_idnMapping = new();
+
+    private static readonly SearchValues<char> s_asciiNonEscapeChars =
+        SearchValues.Create("!#$%()*+,-./0123456789:;=?@ABCDEFGHIJKLMNOPQRSTUVWXYZ_abcdefghijklmnopqrstuvwxyz");
 
     /// <summary>
     /// Initializes a new instance of the <see cref="HtmlRenderer"/> class.
@@ -140,6 +144,8 @@ public class HtmlRenderer : TextRendererBase<HtmlRenderer>
         return this;
     }
 
+    private static readonly SearchValues<char> s_escapedChars = SearchValues.Create("<>&\"");
+
     /// <summary>
     /// Writes the content escaped for HTML.
     /// </summary>
@@ -149,73 +155,38 @@ public class HtmlRenderer : TextRendererBase<HtmlRenderer>
     {
         if (!content.IsEmpty)
         {
-            int nextIndex = content.IndexOfAny(s_writeEscapeIndexOfAnyChars);
-            if (nextIndex == -1)
+            WriteIndent();
+
+            while (true)
             {
-                Write(content);
-            }
-            else
-            {
-                WriteEscapeSlow(content, softEscape);
+                int indexOfCharToEscape = softEscape
+                    ? content.IndexOfAny('<', '&')
+                    : content.IndexOfAny(s_escapedChars);
+
+                if ((uint)indexOfCharToEscape >= (uint)content.Length)
+                {
+                    WriteRaw(content);
+                    return;
+                }
+
+                WriteRaw(content.Slice(0, indexOfCharToEscape));
+
+                if (EnableHtmlEscape)
+                {
+                    WriteRaw(content[indexOfCharToEscape] switch
+                    {
+                        '<' => "&lt;",
+                        '>' => "&gt;",
+                        '&' => "&amp;",
+                        _ => "&quot;",
+                    });
+                }
+
+                content = content.Slice(indexOfCharToEscape + 1);
             }
         }
     }
 
-    private void WriteEscapeSlow(ReadOnlySpan<char> content, bool softEscape = false)
-    {
-        WriteIndent();
-
-        int previousOffset = 0;
-        for (int i = 0; i < content.Length; i++)
-        {
-            switch (content[i])
-            {
-                case '<':
-                    WriteRaw(content.Slice(previousOffset, i - previousOffset));
-                    if (EnableHtmlEscape)
-                    {
-                        WriteRaw("&lt;");
-                    }
-                    previousOffset = i + 1;
-                    break;
-                case '>':
-                    if (!softEscape)
-                    {
-                        WriteRaw(content.Slice(previousOffset, i - previousOffset));
-                        if (EnableHtmlEscape)
-                        {
-                            WriteRaw("&gt;");
-                        }
-                        previousOffset = i + 1;
-                    }
-                    break;
-                case '&':
-                    WriteRaw(content.Slice(previousOffset, i - previousOffset));
-                    if (EnableHtmlEscape)
-                    {
-                        WriteRaw("&amp;");
-                    }
-                    previousOffset = i + 1;
-                    break;
-                case '"':
-                    if (!softEscape)
-                    {
-                        WriteRaw(content.Slice(previousOffset, i - previousOffset));
-                        if (EnableHtmlEscape)
-                        {
-                            WriteRaw("&quot;");
-                        }
-                        previousOffset = i + 1;
-                    }
-                    break;
-            }
-        }
-
-        WriteRaw(content.Slice(previousOffset));
-    }
-
-    private static readonly IdnMapping IdnMapping = new IdnMapping();
-
     /// <summary>
     /// Writes the URL escaped for HTML.
     /// </summary>
@@ -239,120 +210,107 @@ public class HtmlRenderer : TextRendererBase<HtmlRenderer>
             content = LinkRewriter(content);
         }
 
-        // a://c.d = 7 chars
-        int schemeOffset = content.Length < 7 ? -1 : content.IndexOf("://", StringComparison.Ordinal);
-        if (schemeOffset != -1) // This is an absolute URL
+        if (!Ascii.IsValid(content))
         {
-            schemeOffset += 3; // skip ://
-            WriteEscapeUrl(content, 0, schemeOffset);
-
-            bool idnaEncodeDomain = false;
-            int endOfDomain = schemeOffset;
-            for (; endOfDomain < content.Length; endOfDomain++)
+            int schemeOffset = content.IndexOf("://", StringComparison.Ordinal);
+            if (schemeOffset > 0) // This is an absolute URL
             {
-                char c = content[endOfDomain];
-                if (c == '/' || c == '?' || c == '#' || c == ':') // End of domain part
-                {
-                    break;
-                }
-                if (c > 127)
-                {
-                    idnaEncodeDomain = true;
-                }
-            }
+                schemeOffset += 3; // skip ://
 
-            if (idnaEncodeDomain)
-            {
-                string domainName;
+                int domainLength = content.AsSpan(schemeOffset).IndexOfAny("/?#:");
+                if (domainLength < 0)
+                {
+                    domainLength = content.Length - schemeOffset;
+                }
+
+                string? domainName = null;
 
                 try
                 {
-                    domainName = IdnMapping.GetAscii(content, schemeOffset, endOfDomain - schemeOffset);
+                    domainName = s_idnMapping.GetAscii(content, schemeOffset, domainLength);
                 }
-                catch
+                catch { }
+
+                if (domainName is not null)
                 {
-                    // Not a valid IDN, fallback to non-punycode encoding
-                    WriteEscapeUrl(content, schemeOffset, content.Length);
+                    WriteEscapeUrlCore(content.AsSpan(0, schemeOffset));
+                    WriteEscapeUrlCore(domainName.AsSpan());
+                    WriteEscapeUrlCore(content.AsSpan(schemeOffset + domainLength));
                     return this;
                 }
 
-                // Escape the characters (see Commonmark example 327 and think of it with a non-ascii symbol)
-                int previousPosition = 0;
-                for (int i = 0; i < domainName.Length; i++)
-                {
-                    var escape = HtmlHelper.EscapeUrlCharacter(domainName[i]);
-                    if (escape != null)
-                    {
-                        Write(domainName, previousPosition, i - previousPosition);
-                        previousPosition = i + 1;
-                        Write(escape);
-                    }
-                }
-                Write(domainName, previousPosition, domainName.Length - previousPosition);
-                WriteEscapeUrl(content, endOfDomain, content.Length);
+                // Not a valid IDN, fallback to non-punycode encoding
             }
-            else
-            {
-                WriteEscapeUrl(content, schemeOffset, content.Length);
-            }
-        }
-        else // This is a relative URL
-        {
-            WriteEscapeUrl(content, 0, content.Length);
         }
 
+        WriteEscapeUrlCore(content.AsSpan());
         return this;
     }
 
-    private void WriteEscapeUrl(string content, int start, int length)
+    private void WriteEscapeUrlCore(ReadOnlySpan<char> content)
     {
-        int previousPosition = start;
-        for (var i = previousPosition; i < length; i++)
+        WriteIndent();
+
+        while (true)
         {
-            var c = content[i];
+            int i = content.IndexOfAnyExcept(s_asciiNonEscapeChars);
+
+            if ((uint)i >= (uint)content.Length)
+            {
+                WriteRaw(content);
+                break;
+            }
+
+            WriteRaw(content.Slice(0, i));
+
+            char c = content[i];
 
             if (c < 128)
             {
-                var escape = HtmlHelper.EscapeUrlCharacter(c);
-                if (escape != null)
-                {
-                    Write(content, previousPosition, i - previousPosition);
-                    previousPosition = i + 1;
-                    Write(escape);
-                }
+                WriteRaw(HtmlHelper.EscapeUrlCharacter(c));
+            }
+            else if (UseNonAsciiNoEscape)
+            {
+                // Special case for Edge/IE workaround for MarkdownEditor, don't escape non-ASCII chars to make image links working
+                WriteRaw(c);
             }
             else
             {
-                Write(content, previousPosition, i - previousPosition);
-                previousPosition = i + 1;
-
-                // Special case for Edge/IE workaround for MarkdownEditor, don't escape non-ASCII chars to make image links working
-                if (UseNonAsciiNoEscape)
-                {
-                    Write(c);
-                }
-                else
-                {
-                    byte[] bytes;
-                    if (c >= '\ud800' && c <= '\udfff' && previousPosition < length)
-                    {
-                        bytes = Encoding.UTF8.GetBytes(new[] { c, content[previousPosition] });
-                        // Skip next char as it is decoded above
-                        i++;
-                        previousPosition = i + 1;
-                    }
-                    else
-                    {
-                        bytes = Encoding.UTF8.GetBytes(new[] { c });
-                    }
-                    for (var j = 0; j < bytes.Length; j++)
-                    {
-                        Write($"%{bytes[j]:X2}");
-                    }
-                }
+                i = WriteEscapedUtf8Bytes(this, content, c, i);
             }
+
+            content = content.Slice(i + 1);
+        }
+
+        static int WriteEscapedUtf8Bytes(HtmlRenderer renderer, ReadOnlySpan<char> content, char c, int i)
+        {
+            scoped ReadOnlySpan<char> chars;
+
+            if (CharHelper.IsHighSurrogate(c) && (uint)(i + 1) < (uint)content.Length)
+            {
+                chars = stackalloc char[] { c, content[i + 1] };
+                i++;
+            }
+            else
+            {
+                chars = stackalloc char[] { c };
+            }
+
+            Span<byte> utf8Buffer = stackalloc byte[4];
+            int utf8Length = Encoding.UTF8.GetBytes(chars, utf8Buffer);
+            utf8Buffer = utf8Buffer.Slice(0, utf8Length);
+
+            Span<char> escapedBuffer = stackalloc char[3];
+            escapedBuffer[0] = '%';
+
+            foreach (byte b in utf8Buffer)
+            {
+                HexConverter.ToCharsBuffer(b, escapedBuffer, startingIndex: 1);
+                renderer.WriteRaw(escapedBuffer);
+            }
+
+            return i;
         }
-        Write(content, previousPosition, length - previousPosition);
     }
 
     /// <summary>

src/Markdig/Renderers/MarkdownObjectRenderer.cs

@@ -28,15 +28,15 @@ public abstract class MarkdownObjectRenderer<TRenderer, TObject> : IMarkdownObje
 
     public virtual void Write(RendererBase renderer, MarkdownObject obj)
     {
-        var htmlRenderer = (TRenderer)renderer;
+        var typedRenderer = (TRenderer)renderer;
         var typedObj = (TObject)obj;
 
-        if (_tryWriters is not null && TryWrite(htmlRenderer, typedObj))
+        if (_tryWriters is not null && TryWrite(typedRenderer, typedObj))
         {
             return;
         }
 
-        Write(htmlRenderer, typedObj);
+        Write(typedRenderer, typedObj);
     }
 
     private bool TryWrite(TRenderer renderer, TObject obj)