Merge pull request #876 from Akarinnnnn/fix-872

Fix #872 by reserve null title string.

.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">
 
@@ -12,9 +12,9 @@ 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/)
+- Passing more than **600+ tests** from the latest [CommonMark specs (0.31.2)](http://spec.commonmark.org/)
 - Includes all the core elements of CommonMark:
   - including **GFM fenced code blocks**.  
 - **Extensible** architecture
@@ -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="0.14.0" />
+    <PackageReference Include="BenchmarkDotNet.Diagnostics.Windows" Version="0.14.0" />
     <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="3.1.512801" />
   </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="17.12.0" />
+    <PackageReference Include="NUnit" Version="4.3.2" />
+    <PackageReference Include="NUnit3TestAdapter" Version="4.6.0" />
   </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/AutoLinks.generated.cs

@@ -533,5 +533,28 @@ namespace Markdig.Tests.Specs.AutoLinks
 
             TestParser.TestSpec("<http://foö.bar.`baz>`", "<p><a href=\"http://xn--fo-gka.bar.%60baz\">http://foö.bar.`baz</a>`</p>", "autolinks|advanced", context: "Example 25\nSection Extensions / AutoLinks / Unicode support\n");
         }
+
+        // Unicode punctuation characters are not allowed, but symbols are.
+        // Note that this does _not_ exactly match CommonMark's "Unicode punctuation character" definition.
+        [Test]
+        public void ExtensionsAutoLinksUnicodeSupport_Example026()
+        {
+            // Example 26
+            // Section: Extensions / AutoLinks / Unicode support
+            //
+            // The following Markdown:
+            //     http://☃.net?☃ // OtherSymbol
+            //     
+            //     http://🍉.net?🍉 // A UTF-16 surrogate pair, but code point is OtherSymbol
+            //     
+            //     http://‰.net?‰ // OtherPunctuation
+            //
+            // Should be rendered as:
+            //     <p><a href="http://xn--n3h.net?%E2%98%83">http://☃.net?☃</a> // OtherSymbol</p>
+            //     <p><a href="http://xn--ji8h.net?%F0%9F%8D%89">http://🍉.net?🍉</a> // A UTF-16 surrogate pair, but code point is OtherSymbol</p>
+            //     <p>http://‰.net?‰ // OtherPunctuation</p>
+
+            TestParser.TestSpec("http://☃.net?☃ // OtherSymbol\n\nhttp://🍉.net?🍉 // A UTF-16 surrogate pair, but code point is OtherSymbol\n\nhttp://‰.net?‰ // OtherPunctuation", "<p><a href=\"http://xn--n3h.net?%E2%98%83\">http://☃.net?☃</a> // OtherSymbol</p>\n<p><a href=\"http://xn--ji8h.net?%F0%9F%8D%89\">http://🍉.net?🍉</a> // A UTF-16 surrogate pair, but code point is OtherSymbol</p>\n<p>http://‰.net?‰ // OtherPunctuation</p>", "autolinks|advanced", context: "Example 26\nSection Extensions / AutoLinks / Unicode support\n");
+        }
     }
 }

src/Markdig.Tests/Specs/AutoLinks.md

@@ -303,4 +303,19 @@ This will therefore be seen as an autolink and not as code inline.
 <http://foö.bar.`baz>`
 .
 <p><a href="http://xn--fo-gka.bar.%60baz">http://foö.bar.`baz</a>`</p>
+````````````````````````````````
+
+Unicode punctuation characters are not allowed, but symbols are.
+Note that this does _not_ exactly match CommonMark's "Unicode punctuation character" definition.
+
+```````````````````````````````` example
+http://☃.net?☃ // OtherSymbol
+
+http://🍉.net?🍉 // A UTF-16 surrogate pair, but code point is OtherSymbol
+
+http://‰.net?‰ // OtherPunctuation
+.
+<p><a href="http://xn--n3h.net?%E2%98%83">http://☃.net?☃</a> // OtherSymbol</p>
+<p><a href="http://xn--ji8h.net?%F0%9F%8D%89">http://🍉.net?🍉</a> // A UTF-16 surrogate pair, but code point is OtherSymbol</p>
+<p>http://‰.net?‰ // OtherPunctuation</p>
 ````````````````````````````````

src/Markdig.Tests/Specs/CommonMark.md

@@ -1,9 +1,9 @@
 ---
 title: CommonMark Spec
 author: John MacFarlane
-version: '0.30'
-date: '2021-06-19'
-license: '[CC-BY-SA 4.0](http://creativecommons.org/licenses/by-sa/4.0/)'
+version: '0.31.2'
+date: '2024-01-28'
+license: '[CC-BY-SA 4.0](https://creativecommons.org/licenses/by-sa/4.0/)'
 ...
 
 # Introduction
@@ -14,7 +14,7 @@ Markdown is a plain text format for writing structured documents,
 based on conventions for indicating formatting in email
 and usenet posts.  It was developed by John Gruber (with
 help from Aaron Swartz) and released in 2004 in the form of a
-[syntax description](http://daringfireball.net/projects/markdown/syntax)
+[syntax description](https://daringfireball.net/projects/markdown/syntax)
 and a Perl script (`Markdown.pl`) for converting Markdown to
 HTML.  In the next decade, dozens of implementations were
 developed in many languages.  Some extended the original
@@ -34,10 +34,10 @@ As Gruber writes:
 > Markdown-formatted document should be publishable as-is, as
 > plain text, without looking like it's been marked up with tags
 > or formatting instructions.
-> (<http://daringfireball.net/projects/markdown/>)
+> (<https://daringfireball.net/projects/markdown/>)
 
 The point can be illustrated by comparing a sample of
-[AsciiDoc](http://www.methods.co.nz/asciidoc/) with
+[AsciiDoc](https://asciidoc.org/) with
 an equivalent sample of Markdown.  Here is a sample of
 AsciiDoc from the AsciiDoc manual:
 
@@ -103,7 +103,7 @@ source, not just in the processed document.
 ## Why is a spec needed?
 
 John Gruber's [canonical description of Markdown's
-syntax](http://daringfireball.net/projects/markdown/syntax)
+syntax](https://daringfireball.net/projects/markdown/syntax)
 does not specify the syntax unambiguously.  Here are some examples of
 questions it does not answer:
 
@@ -316,9 +316,9 @@ A line containing no characters, or a line containing only spaces
 
 The following definitions of character classes will be used in this spec:
 
-A [Unicode whitespace character](@) is
-any code point in the Unicode `Zs` general category, or a tab (`U+0009`),
-line feed (`U+000A`), form feed (`U+000C`), or carriage return (`U+000D`).
+A [Unicode whitespace character](@) is a character in the Unicode `Zs` general
+category, or a tab (`U+0009`), line feed (`U+000A`), form feed (`U+000C`), or
+carriage return (`U+000D`).
 
 [Unicode whitespace](@) is a sequence of one or more
 [Unicode whitespace characters].
@@ -337,9 +337,8 @@ is `!`, `"`, `#`, `$`, `%`, `&`, `'`, `(`, `)`,
 `[`, `\`, `]`, `^`, `_`, `` ` `` (U+005B–0060), 
 `{`, `|`, `}`, or `~` (U+007B–007E).
 
-A [Unicode punctuation character](@) is an [ASCII
-punctuation character] or anything in
-the general Unicode categories  `Pc`, `Pd`, `Pe`, `Pf`, `Pi`, `Po`, or `Ps`.
+A [Unicode punctuation character](@) is a character in the Unicode `P`
+(puncuation) or `S` (symbol) general categories.
 
 ## Tabs
 
@@ -579,9 +578,9 @@ raw HTML:
 
 
 ```````````````````````````````` example
-<http://example.com?find=\*>
+<https://example.com?find=\*>
 .
-<p><a href="http://example.com?find=%5C*">http://example.com?find=\*</a></p>
+<p><a href="https://example.com?find=%5C*">https://example.com?find=\*</a></p>
 ````````````````````````````````
 
 
@@ -1964,7 +1963,7 @@ has been found, the code block contains all of the lines after the
 opening code fence until the end of the containing block (or
 document).  (An alternative spec would require backtracking in the
 event that a closing code fence is not found.  But this makes parsing
-much less efficient, and there seems to be no real down side to the
+much less efficient, and there seems to be no real downside to the
 behavior described here.)
 
 A fenced code block may interrupt a paragraph, and does not require
@@ -2403,7 +2402,7 @@ followed by one of the strings (case-insensitive) `address`,
 `h1`, `h2`, `h3`, `h4`, `h5`, `h6`, `head`, `header`, `hr`,
 `html`, `iframe`, `legend`, `li`, `link`, `main`, `menu`, `menuitem`,
 `nav`, `noframes`, `ol`, `optgroup`, `option`, `p`, `param`,
-`section`, `source`, `summary`, `table`, `tbody`, `td`,
+`search`, `section`, `summary`, `table`, `tbody`, `td`,
 `tfoot`, `th`, `thead`, `title`, `tr`, `track`, `ul`, followed
 by a space, a tab, the end of the line, the string `>`, or
 the string `/>`.\
@@ -4115,7 +4114,7 @@ The following rules define [list items]:
     blocks *Bs* starting with a character other than a space or tab, and *M* is
     a list marker of width *W* followed by 1 ≤ *N* ≤ 4 spaces of indentation,
     then the result of prepending *M* and the following spaces to the first line
-    of Ls*, and indenting subsequent lines of *Ls* by *W + N* spaces, is a
+    of *Ls*, and indenting subsequent lines of *Ls* by *W + N* spaces, is a
     list item with *Bs* as its contents.  The type of the list item
     (bullet or ordered) is determined by the type of its list marker.
     If the list item is ordered, then it is also assigned a start
@@ -5350,11 +5349,11 @@ by itself should be a paragraph followed by a nested sublist.
 Since it is well established Markdown practice to allow lists to
 interrupt paragraphs inside list items, the [principle of
 uniformity] requires us to allow this outside list items as
-well.  ([reStructuredText](http://docutils.sourceforge.net/rst.html)
+well.  ([reStructuredText](https://docutils.sourceforge.net/rst.html)
 takes a different approach, requiring blank lines before lists
 even inside other list items.)
 
-In order to solve of unwanted lists in paragraphs with
+In order to solve the problem of unwanted lists in paragraphs with
 hard-wrapped numerals, we allow only lists starting with `1` to
 interrupt paragraphs.  Thus,
 
@@ -6055,18 +6054,18 @@ But this is an HTML tag:
 And this is code:
 
 ```````````````````````````````` example
-`<http://foo.bar.`baz>`
+`<https://foo.bar.`baz>`
 .
-<p><code>&lt;http://foo.bar.</code>baz&gt;`</p>
+<p><code>&lt;https://foo.bar.</code>baz&gt;`</p>
 ````````````````````````````````
 
 
 But this is an autolink:
 
 ```````````````````````````````` example
-<http://foo.bar.`baz>`
+<https://foo.bar.`baz>`
 .
-<p><a href="http://foo.bar.%60baz">http://foo.bar.`baz</a>`</p>
+<p><a href="https://foo.bar.%60baz">https://foo.bar.`baz</a>`</p>
 ````````````````````````````````
 
 
@@ -6099,7 +6098,7 @@ closing backtick strings to be equal in length:
 ## Emphasis and strong emphasis
 
 John Gruber's original [Markdown syntax
-description](http://daringfireball.net/projects/markdown/syntax#em) says:
+description](https://daringfireball.net/projects/markdown/syntax#em) says:
 
 > Markdown treats asterisks (`*`) and underscores (`_`) as indicators of
 > emphasis. Text wrapped with one `*` or `_` will be wrapped with an HTML
@@ -6201,7 +6200,7 @@ Here are some examples of delimiter runs.
 (The idea of distinguishing left-flanking and right-flanking
 delimiter runs based on the character before and the character
 after comes from Roopesh Chander's
-[vfmd](http://www.vfmd.org/vfmd-spec/specification/#procedure-for-identifying-emphasis-tags).
+[vfmd](https://web.archive.org/web/20220608143320/http://www.vfmd.org/vfmd-spec/specification/#procedure-for-identifying-emphasis-tags).
 vfmd uses the terminology "emphasis indicator string" instead of "delimiter
 run," and its rules for distinguishing left- and right-flanking runs
 are a bit more complex than the ones given here.)
@@ -6343,6 +6342,21 @@ Unicode nonbreaking spaces count as whitespace, too:
 ````````````````````````````````
 
 
+Unicode symbols count as punctuation, too:
+
+```````````````````````````````` example
+*$*alpha.
+
+*£*bravo.
+
+*€*charlie.
+.
+<p>*$*alpha.</p>
+<p>*£*bravo.</p>
+<p>*€*charlie.</p>
+````````````````````````````````
+
+
 Intraword emphasis with `*` is permitted:
 
 ```````````````````````````````` example
@@ -7428,16 +7442,16 @@ _a `_`_
 
 
 ```````````````````````````````` example
-**a<http://foo.bar/?q=**>
+**a<https://foo.bar/?q=**>
 .
-<p>**a<a href="http://foo.bar/?q=**">http://foo.bar/?q=**</a></p>
+<p>**a<a href="https://foo.bar/?q=**">https://foo.bar/?q=**</a></p>
 ````````````````````````````````
 
 
 ```````````````````````````````` example
-__a<http://foo.bar/?q=__>
+__a<https://foo.bar/?q=__>
 .
-<p>__a<a href="http://foo.bar/?q=__">http://foo.bar/?q=__</a></p>
+<p>__a<a href="https://foo.bar/?q=__">https://foo.bar/?q=__</a></p>
 ````````````````````````````````
 
 
@@ -7685,13 +7699,13 @@ A link can contain fragment identifiers and queries:
 ```````````````````````````````` example
 [link](#fragment)
 
-[link](http://example.com#fragment)
+[link](https://example.com#fragment)
 
-[link](http://example.com?foo=3#frag)
+[link](https://example.com?foo=3#frag)
 .
 <p><a href="#fragment">link</a></p>
-<p><a href="http://example.com#fragment">link</a></p>
-<p><a href="http://example.com?foo=3#frag">link</a></p>
+<p><a href="https://example.com#fragment">link</a></p>
+<p><a href="https://example.com?foo=3#frag">link</a></p>
 ````````````````````````````````
 
 
@@ -7935,9 +7949,9 @@ and autolinks over link grouping:
 
 
 ```````````````````````````````` example
-[foo<http://example.com/?search=](uri)>
+[foo<https://example.com/?search=](uri)>
 .
-<p>[foo<a href="http://example.com/?search=%5D(uri)">http://example.com/?search=](uri)</a></p>
+<p>[foo<a href="https://example.com/?search=%5D(uri)">https://example.com/?search=](uri)</a></p>
 ````````````````````````````````
 
 
@@ -8091,11 +8105,11 @@ and autolinks over link grouping:
 
 
 ```````````````````````````````` example
-[foo<http://example.com/?search=][ref]>
+[foo<https://example.com/?search=][ref]>
 
 [ref]: /uri
 .
-<p>[foo<a href="http://example.com/?search=%5D%5Bref%5D">http://example.com/?search=][ref]</a></p>
+<p>[foo<a href="https://example.com/?search=%5D%5Bref%5D">https://example.com/?search=][ref]</a></p>
 ````````````````````````````````
 
 
@@ -8295,7 +8309,7 @@ A [collapsed reference link](@)
 consists of a [link label] that [matches] a
 [link reference definition] elsewhere in the
 document, followed by the string `[]`.
-The contents of the first link label are parsed as inlines,
+The contents of the link label are parsed as inlines,
 which are used as the link's text.  The link's URI and title are
 provided by the matching reference link definition.  Thus,
 `[foo][]` is equivalent to `[foo][foo]`.
@@ -8348,7 +8362,7 @@ A [shortcut reference link](@)
 consists of a [link label] that [matches] a
 [link reference definition] elsewhere in the
 document and is not followed by `[]` or a link label.
-The contents of the first link label are parsed as inlines,
+The contents of the link label are parsed as inlines,
 which are used as the link's text.  The link's URI and title
 are provided by the matching link reference definition.
 Thus, `[foo]` is equivalent to `[foo][]`.
@@ -8435,7 +8449,7 @@ following closing bracket:
 ````````````````````````````````
 
 
-Full and compact references take precedence over shortcut
+Full and collapsed references take precedence over shortcut
 references:
 
 ```````````````````````````````` example
@@ -8771,9 +8785,9 @@ Here are some valid autolinks:
 
 
 ```````````````````````````````` example
-<http://foo.bar.baz/test?q=hello&id=22&boolean>
+<https://foo.bar.baz/test?q=hello&id=22&boolean>
 .
-<p><a href="http://foo.bar.baz/test?q=hello&amp;id=22&amp;boolean">http://foo.bar.baz/test?q=hello&amp;id=22&amp;boolean</a></p>
+<p><a href="https://foo.bar.baz/test?q=hello&amp;id=22&amp;boolean">https://foo.bar.baz/test?q=hello&amp;id=22&amp;boolean</a></p>
 ````````````````````````````````
 
 
@@ -8813,9 +8827,9 @@ with their syntax:
 
 
 ```````````````````````````````` example
-<http://../>
+<https://../>
 .
-<p><a href="http://../">http://../</a></p>
+<p><a href="https://../">https://../</a></p>
 ````````````````````````````````
 
 
@@ -8829,18 +8843,18 @@ with their syntax:
 Spaces are not allowed in autolinks:
 
 ```````````````````````````````` example
-<http://foo.bar/baz bim>
+<https://foo.bar/baz bim>
 .
-<p>&lt;http://foo.bar/baz bim&gt;</p>
+<p>&lt;https://foo.bar/baz bim&gt;</p>
 ````````````````````````````````
 
 
 Backslash-escapes do not work inside autolinks:
 
 ```````````````````````````````` example
-<http://example.com/\[\>
+<https://example.com/\[\>
 .
-<p><a href="http://example.com/%5C%5B%5C">http://example.com/\[\</a></p>
+<p><a href="https://example.com/%5C%5B%5C">https://example.com/\[\</a></p>
 ````````````````````````````````
 
 
@@ -8892,9 +8906,9 @@ These are not autolinks:
 
 
 ```````````````````````````````` example
-< http://foo.bar >
+< https://foo.bar >
 .
-<p>&lt; http://foo.bar &gt;</p>
+<p>&lt; https://foo.bar &gt;</p>
 ````````````````````````````````
 
 
@@ -8913,9 +8927,9 @@ These are not autolinks:
 
 
 ```````````````````````````````` example
-http://example.com
+https://example.com
 .
-<p>http://example.com</p>
+<p>https://example.com</p>
 ````````````````````````````````
 
 
@@ -8977,10 +8991,9 @@ A [closing tag](@) consists of the string `</`, a
 [tag name], optional spaces, tabs, and up to one line ending, and the character
 `>`.
 
-An [HTML comment](@) consists of `<!--` + *text* + `-->`,
-where *text* does not start with `>` or `->`, does not end with `-`,
-and does not contain `--`.  (See the
-[HTML5 spec](http://www.w3.org/TR/html5/syntax.html#comments).)
+An [HTML comment](@) consists of `<!-->`, `<!--->`, or  `<!--`, a string of
+characters not including the string `-->`, and `-->` (see the
+[HTML spec](https://html.spec.whatwg.org/multipage/parsing.html#markup-declaration-open-state)).
 
 A [processing instruction](@)
 consists of the string `<?`, a string
@@ -9119,30 +9132,20 @@ Illegal attributes in closing tag:
 Comments:
 
 ```````````````````````````````` example
-foo <!-- this is a
-comment - with hyphen -->
+foo <!-- this is a --
+comment - with hyphens -->
 .
-<p>foo <!-- this is a
-comment - with hyphen --></p>
+<p>foo <!-- this is a --
+comment - with hyphens --></p>
 ````````````````````````````````
 
-
-```````````````````````````````` example
-foo <!-- not a comment -- two hyphens -->
-.
-<p>foo &lt;!-- not a comment -- two hyphens --&gt;</p>
-````````````````````````````````
-
-
-Not comments:
-
 ```````````````````````````````` example
 foo <!--> foo -->
 
-foo <!-- foo--->
+foo <!---> foo -->
 .
-<p>foo &lt;!--&gt; foo --&gt;</p>
-<p>foo &lt;!-- foo---&gt;</p>
+<p>foo <!--> foo --&gt;</p>
+<p>foo <!---> foo --&gt;</p>
 ````````````````````````````````
 
 
@@ -9671,7 +9674,7 @@ through the stack for an opening `[` or `![` delimiter.
   delimiter from the stack, and return a literal text node `]`.
 
 - If we find one and it's active, then we parse ahead to see if
-  we have an inline link/image, reference link/image, compact reference
+  we have an inline link/image, reference link/image, collapsed reference
   link/image, or shortcut reference link/image.
 
   + If we don't, then we remove the opening delimiter from the

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/EmphasisExtraSpecs.generated.cs

@@ -123,6 +123,8 @@ namespace Markdig.Tests.Specs.EmphasisExtra
     public class TestExtensionsEmphasisOnHtmlEntities
     {
         // ## Emphasis on Html Entities
+        // 
+        // Note that Unicode symbols are treated as punctuation, which are not allowed to open the emphasis unless they are preceded by a space.
         [Test]
         public void ExtensionsEmphasisOnHtmlEntities_Example006()
         {
@@ -132,14 +134,14 @@ namespace Markdig.Tests.Specs.EmphasisExtra
             // The following Markdown:
             //     This is text MyBrand ^®^ and MyTrademark ^™^
             //     This is text MyBrand^®^ and MyTrademark^™^
-            //     This is text MyBrand~®~ and MyCopyright^©^
+            //     This is text MyBrand ~®~ and MyCopyright ^©^
             //
             // Should be rendered as:
             //     <p>This is text MyBrand <sup>®</sup> and MyTrademark <sup>TM</sup>
-            //     This is text MyBrand<sup>®</sup> and MyTrademark<sup>TM</sup>
-            //     This is text MyBrand<sub>®</sub> and MyCopyright<sup>©</sup></p>
+            //     This is text MyBrand^®^ and MyTrademark^TM^
+            //     This is text MyBrand <sub>®</sub> and MyCopyright <sup>©</sup></p>
 
-            TestParser.TestSpec("This is text MyBrand ^&reg;^ and MyTrademark ^&trade;^\nThis is text MyBrand^&reg;^ and MyTrademark^&trade;^\nThis is text MyBrand~&reg;~ and MyCopyright^&copy;^", "<p>This is text MyBrand <sup>®</sup> and MyTrademark <sup>TM</sup>\nThis is text MyBrand<sup>®</sup> and MyTrademark<sup>TM</sup>\nThis is text MyBrand<sub>®</sub> and MyCopyright<sup>©</sup></p>", "emphasisextras|advanced", context: "Example 6\nSection Extensions / Emphasis on Html Entities\n");
+            TestParser.TestSpec("This is text MyBrand ^&reg;^ and MyTrademark ^&trade;^\nThis is text MyBrand^&reg;^ and MyTrademark^&trade;^\nThis is text MyBrand ~&reg;~ and MyCopyright ^&copy;^", "<p>This is text MyBrand <sup>®</sup> and MyTrademark <sup>TM</sup>\nThis is text MyBrand^®^ and MyTrademark^TM^\nThis is text MyBrand <sub>®</sub> and MyCopyright <sup>©</sup></p>", "emphasisextras|advanced", context: "Example 6\nSection Extensions / Emphasis on Html Entities\n");
         }
     }
 }

src/Markdig.Tests/Specs/EmphasisExtraSpecs.md

@@ -52,16 +52,17 @@ Marked text can be used to specify that a text has been marked in a document.  T
 .
 <p><mark>Marked text</mark></p>
 ````````````````````````````````
+
 ## Emphasis on Html Entities
 
+Note that Unicode symbols are treated as punctuation, which are not allowed to open the emphasis unless they are preceded by a space.
 
 ```````````````````````````````` example
 This is text MyBrand ^&reg;^ and MyTrademark ^&trade;^
 This is text MyBrand^&reg;^ and MyTrademark^&trade;^
-This is text MyBrand~&reg;~ and MyCopyright^&copy;^
+This is text MyBrand ~&reg;~ and MyCopyright ^&copy;^
 .
 <p>This is text MyBrand <sup>®</sup> and MyTrademark <sup>TM</sup>
-This is text MyBrand<sup>®</sup> and MyTrademark<sup>TM</sup>
-This is text MyBrand<sub>®</sub> and MyCopyright<sup>©</sup></p>
+This is text MyBrand^®^ and MyTrademark^TM^
+This is text MyBrand <sub>®</sub> and MyCopyright <sup>©</sup></p>
 ````````````````````````````````
-

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

@@ -17,7 +17,7 @@ namespace Markdig.Tests.Specs.Math
         // 
         // ## Math Inline
         //  
-        // Allows to define a mathematic block embraced by `$...$`
+        // Allows to define a mathematic inline block embraced by `$...$`
         [Test]
         public void ExtensionsMathInline_Example001()
         {
@@ -25,12 +25,12 @@ namespace Markdig.Tests.Specs.Math
             // Section: Extensions / Math Inline
             //
             // The following Markdown:
-            //     This is a $math block$
+            //     This is a $math inline$
             //
             // Should be rendered as:
-            //     <p>This is a <span class="math">\(math block\)</span></p>
+            //     <p>This is a <span class="math">\(math inline\)</span></p>
 
-            TestParser.TestSpec("This is a $math block$", "<p>This is a <span class=\"math\">\\(math block\\)</span></p>", "mathematics|advanced", context: "Example 1\nSection Extensions / Math Inline\n");
+            TestParser.TestSpec("This is a $math inline$", "<p>This is a <span class=\"math\">\\(math inline\\)</span></p>", "mathematics|advanced", context: "Example 1\nSection Extensions / Math Inline\n");
         }
 
         // Or by `$$...$$` embracing it by:
@@ -41,12 +41,12 @@ namespace Markdig.Tests.Specs.Math
             // Section: Extensions / Math Inline
             //
             // The following Markdown:
-            //     This is a $$math block$$
+            //     This is a $$math inline$$
             //
             // Should be rendered as:
-            //     <p>This is a <span class="math">\(math block\)</span></p>
+            //     <p>This is a <span class="math">\(math inline\)</span></p>
 
-            TestParser.TestSpec("This is a $$math block$$", "<p>This is a <span class=\"math\">\\(math block\\)</span></p>", "mathematics|advanced", context: "Example 2\nSection Extensions / Math Inline\n");
+            TestParser.TestSpec("This is a $$math inline$$", "<p>This is a <span class=\"math\">\\(math inline\\)</span></p>", "mathematics|advanced", context: "Example 2\nSection Extensions / Math Inline\n");
         }
 
         // Newlines inside an inline math are not allowed:
@@ -58,13 +58,13 @@ namespace Markdig.Tests.Specs.Math
             //
             // The following Markdown:
             //     This is not a $$math 
-            //     block$$ and? this is a $$math block$$
+            //     inline$$ and? this is a $$math inline$$
             //
             // Should be rendered as:
             //     <p>This is not a $$math
-            //     block$$ and? this is a <span class="math">\(math block\)</span></p>
+            //     inline$$ and? this is a <span class="math">\(math inline\)</span></p>
 
-            TestParser.TestSpec("This is not a $$math \nblock$$ and? this is a $$math block$$", "<p>This is not a $$math\nblock$$ and? this is a <span class=\"math\">\\(math block\\)</span></p>", "mathematics|advanced", context: "Example 3\nSection Extensions / Math Inline\n");
+            TestParser.TestSpec("This is not a $$math \ninline$$ and? this is a $$math inline$$", "<p>This is not a $$math\ninline$$ and? this is a <span class=\"math\">\\(math inline\\)</span></p>", "mathematics|advanced", context: "Example 3\nSection Extensions / Math Inline\n");
         }
 
         [Test]
@@ -75,13 +75,13 @@ namespace Markdig.Tests.Specs.Math
             //
             // The following Markdown:
             //     This is not a $math 
-            //     block$ and? this is a $math block$
+            //     inline$ and? this is a $math inline$
             //
             // Should be rendered as:
             //     <p>This is not a $math
-            //     block$ and? this is a <span class="math">\(math block\)</span></p>
+            //     inline$ and? this is a <span class="math">\(math inline\)</span></p>
 
-            TestParser.TestSpec("This is not a $math \nblock$ and? this is a $math block$", "<p>This is not a $math\nblock$ and? this is a <span class=\"math\">\\(math block\\)</span></p>", "mathematics|advanced", context: "Example 4\nSection Extensions / Math Inline\n");
+            TestParser.TestSpec("This is not a $math \ninline$ and? this is a $math inline$", "<p>This is not a $math\ninline$ and? this is a <span class=\"math\">\\(math inline\\)</span></p>", "mathematics|advanced", context: "Example 4\nSection Extensions / Math Inline\n");
         }
 
         // An opening `$` can be followed by a space if the closing is also preceded by a space `$`:
@@ -92,12 +92,12 @@ namespace Markdig.Tests.Specs.Math
             // Section: Extensions / Math Inline
             //
             // The following Markdown:
-            //     This is a $ math block $
+            //     This is a $ math inline $
             //
             // Should be rendered as:
-            //     <p>This is a <span class="math">\(math block\)</span></p>
+            //     <p>This is a <span class="math">\(math inline\)</span></p>
 
-            TestParser.TestSpec("This is a $ math block $", "<p>This is a <span class=\"math\">\\(math block\\)</span></p>", "mathematics|advanced", context: "Example 5\nSection Extensions / Math Inline\n");
+            TestParser.TestSpec("This is a $ math inline $", "<p>This is a <span class=\"math\">\\(math inline\\)</span></p>", "mathematics|advanced", context: "Example 5\nSection Extensions / Math Inline\n");
         }
 
         [Test]
@@ -107,12 +107,12 @@ namespace Markdig.Tests.Specs.Math
             // Section: Extensions / Math Inline
             //
             // The following Markdown:
-            //     This is a $    math block     $ after
+            //     This is a $    math inline     $ after
             //
             // Should be rendered as:
-            //     <p>This is a <span class="math">\(math block\)</span> after</p>
+            //     <p>This is a <span class="math">\(math inline\)</span> after</p>
 
-            TestParser.TestSpec("This is a $    math block     $ after", "<p>This is a <span class=\"math\">\\(math block\\)</span> after</p>", "mathematics|advanced", context: "Example 6\nSection Extensions / Math Inline\n");
+            TestParser.TestSpec("This is a $    math inline     $ after", "<p>This is a <span class=\"math\">\\(math inline\\)</span> after</p>", "mathematics|advanced", context: "Example 6\nSection Extensions / Math Inline\n");
         }
 
         [Test]
@@ -122,12 +122,12 @@ namespace Markdig.Tests.Specs.Math
             // Section: Extensions / Math Inline
             //
             // The following Markdown:
-            //     This is a $$    math block     $$ after
+            //     This is a $$    math inline     $$ after
             //
             // Should be rendered as:
-            //     <p>This is a <span class="math">\(math block\)</span> after</p>
+            //     <p>This is a <span class="math">\(math inline\)</span> after</p>
 
-            TestParser.TestSpec("This is a $$    math block     $$ after", "<p>This is a <span class=\"math\">\\(math block\\)</span> after</p>", "mathematics|advanced", context: "Example 7\nSection Extensions / Math Inline\n");
+            TestParser.TestSpec("This is a $$    math inline     $$ after", "<p>This is a <span class=\"math\">\\(math inline\\)</span> after</p>", "mathematics|advanced", context: "Example 7\nSection Extensions / Math Inline\n");
         }
 
         [Test]
@@ -137,12 +137,12 @@ namespace Markdig.Tests.Specs.Math
             // Section: Extensions / Math Inline
             //
             // The following Markdown:
-            //     This is a not $ math block$ because there is not a whitespace before the closing
+            //     This is a not $ math inline$ because there is not a whitespace before the closing
             //
             // Should be rendered as:
-            //     <p>This is a not $ math block$ because there is not a whitespace before the closing</p>
+            //     <p>This is a not $ math inline$ because there is not a whitespace before the closing</p>
 
-            TestParser.TestSpec("This is a not $ math block$ because there is not a whitespace before the closing", "<p>This is a not $ math block$ because there is not a whitespace before the closing</p>", "mathematics|advanced", context: "Example 8\nSection Extensions / Math Inline\n");
+            TestParser.TestSpec("This is a not $ math inline$ because there is not a whitespace before the closing", "<p>This is a not $ math inline$ because there is not a whitespace before the closing</p>", "mathematics|advanced", context: "Example 8\nSection Extensions / Math Inline\n");
         }
 
         // For the opening `$` it requires a space or a punctuation before (but cannot be used within a word):
@@ -153,12 +153,12 @@ namespace Markdig.Tests.Specs.Math
             // Section: Extensions / Math Inline
             //
             // The following Markdown:
-            //     This is not a m$ath block$
+            //     This is not a m$ath inline$
             //
             // Should be rendered as:
-            //     <p>This is not a m$ath block$</p>
+            //     <p>This is not a m$ath inline$</p>
 
-            TestParser.TestSpec("This is not a m$ath block$", "<p>This is not a m$ath block$</p>", "mathematics|advanced", context: "Example 9\nSection Extensions / Math Inline\n");
+            TestParser.TestSpec("This is not a m$ath inline$", "<p>This is not a m$ath inline$</p>", "mathematics|advanced", context: "Example 9\nSection Extensions / Math Inline\n");
         }
 
         // For the closing `$` it requires a space after or a punctuation (but cannot be preceded by a space and cannot be used within a word):
@@ -169,12 +169,12 @@ namespace Markdig.Tests.Specs.Math
             // Section: Extensions / Math Inline
             //
             // The following Markdown:
-            //     This is not a $math bloc$k
+            //     This is not a $math inlin$e
             //
             // Should be rendered as:
-            //     <p>This is not a $math bloc$k</p>
+            //     <p>This is not a $math inlin$e</p>
 
-            TestParser.TestSpec("This is not a $math bloc$k", "<p>This is not a $math bloc$k</p>", "mathematics|advanced", context: "Example 10\nSection Extensions / Math Inline\n");
+            TestParser.TestSpec("This is not a $math inlin$e", "<p>This is not a $math inlin$e</p>", "mathematics|advanced", context: "Example 10\nSection Extensions / Math Inline\n");
         }
 
         // For the closing `$` it requires a space after or a punctuation (but cannot be preceded by a space and cannot be used within a word):
@@ -201,12 +201,12 @@ namespace Markdig.Tests.Specs.Math
             // Section: Extensions / Math Inline
             //
             // The following Markdown:
-            //     This is a $math \$ block$
+            //     This is a $math \$ inline$
             //
             // Should be rendered as:
-            //     <p>This is a <span class="math">\(math \$ block\)</span></p>
+            //     <p>This is a <span class="math">\(math \$ inline\)</span></p>
 
-            TestParser.TestSpec("This is a $math \\$ block$", "<p>This is a <span class=\"math\">\\(math \\$ block\\)</span></p>", "mathematics|advanced", context: "Example 12\nSection Extensions / Math Inline\n");
+            TestParser.TestSpec("This is a $math \\$ inline$", "<p>This is a <span class=\"math\">\\(math \\$ inline\\)</span></p>", "mathematics|advanced", context: "Example 12\nSection Extensions / Math Inline\n");
         }
 
         // At most, two `$` will be matched for the opening and closing:
@@ -217,12 +217,12 @@ namespace Markdig.Tests.Specs.Math
             // Section: Extensions / Math Inline
             //
             // The following Markdown:
-            //     This is a $$$math block$$$
+            //     This is a $$$math inline$$$
             //
             // Should be rendered as:
-            //     <p>This is a <span class="math">\($math block$\)</span></p>
+            //     <p>This is a <span class="math">\($math inline$\)</span></p>
 
-            TestParser.TestSpec("This is a $$$math block$$$", "<p>This is a <span class=\"math\">\\($math block$\\)</span></p>", "mathematics|advanced", context: "Example 13\nSection Extensions / Math Inline\n");
+            TestParser.TestSpec("This is a $$$math inline$$$", "<p>This is a <span class=\"math\">\\($math inline$\\)</span></p>", "mathematics|advanced", context: "Example 13\nSection Extensions / Math Inline\n");
         }
 
         // Regular text can come both before and after the math inline
@@ -233,15 +233,15 @@ namespace Markdig.Tests.Specs.Math
             // Section: Extensions / Math Inline
             //
             // The following Markdown:
-            //     This is a $math block$ with text on both sides.
+            //     This is a $math inline$ with text on both sides.
             //
             // Should be rendered as:
-            //     <p>This is a <span class="math">\(math block\)</span> with text on both sides.</p>
+            //     <p>This is a <span class="math">\(math inline\)</span> with text on both sides.</p>
 
-            TestParser.TestSpec("This is a $math block$ with text on both sides.", "<p>This is a <span class=\"math\">\\(math block\\)</span> with text on both sides.</p>", "mathematics|advanced", context: "Example 14\nSection Extensions / Math Inline\n");
+            TestParser.TestSpec("This is a $math inline$ with text on both sides.", "<p>This is a <span class=\"math\">\\(math inline\\)</span> with text on both sides.</p>", "mathematics|advanced", context: "Example 14\nSection Extensions / Math Inline\n");
         }
 
-        // A mathematic block takes precedence over standard emphasis `*` `_`:
+        // A mathematic inline block takes precedence over standard emphasis `*` `_`:
         [Test]
         public void ExtensionsMathInline_Example015()
         {
@@ -249,15 +249,15 @@ namespace Markdig.Tests.Specs.Math
             // Section: Extensions / Math Inline
             //
             // The following Markdown:
-            //     This is *a $math* block$
+            //     This is *a $math* inline$
             //
             // Should be rendered as:
-            //     <p>This is *a <span class="math">\(math* block\)</span></p>
+            //     <p>This is *a <span class="math">\(math* inline\)</span></p>
 
-            TestParser.TestSpec("This is *a $math* block$", "<p>This is *a <span class=\"math\">\\(math* block\\)</span></p>", "mathematics|advanced", context: "Example 15\nSection Extensions / Math Inline\n");
+            TestParser.TestSpec("This is *a $math* inline$", "<p>This is *a <span class=\"math\">\\(math* inline\\)</span></p>", "mathematics|advanced", context: "Example 15\nSection Extensions / Math Inline\n");
         }
 
-        // An opening $$ at the beginning of a line should not be interpreted as a Math block:
+        // An opening $$ at the beginning of a line should not be interpreted as a Math inline:
         [Test]
         public void ExtensionsMathInline_Example016()
         {
@@ -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

@@ -4,79 +4,79 @@ Adds support for mathematics spans:
 
 ## Math Inline
  
-Allows to define a mathematic block embraced by `$...$`
+Allows to define a mathematic inline block embraced by `$...$`
 
 ```````````````````````````````` example
-This is a $math block$
+This is a $math inline$
 .
-<p>This is a <span class="math">\(math block\)</span></p>
+<p>This is a <span class="math">\(math inline\)</span></p>
 ````````````````````````````````
 
 Or by `$$...$$` embracing it by:
 
 ```````````````````````````````` example
-This is a $$math block$$
+This is a $$math inline$$
 .
-<p>This is a <span class="math">\(math block\)</span></p>
+<p>This is a <span class="math">\(math inline\)</span></p>
 ````````````````````````````````
 
 Newlines inside an inline math are not allowed:
 
 ```````````````````````````````` example
 This is not a $$math 
-block$$ and? this is a $$math block$$
+inline$$ and? this is a $$math inline$$
 .
 <p>This is not a $$math
-block$$ and? this is a <span class="math">\(math block\)</span></p>
+inline$$ and? this is a <span class="math">\(math inline\)</span></p>
 ````````````````````````````````
 
 ```````````````````````````````` example
 This is not a $math 
-block$ and? this is a $math block$
+inline$ and? this is a $math inline$
 .
 <p>This is not a $math
-block$ and? this is a <span class="math">\(math block\)</span></p>
+inline$ and? this is a <span class="math">\(math inline\)</span></p>
 ````````````````````````````````
 An opening `$` can be followed by a space if the closing is also preceded by a space `$`:
 
 ```````````````````````````````` example
-This is a $ math block $
+This is a $ math inline $
 .
-<p>This is a <span class="math">\(math block\)</span></p>
+<p>This is a <span class="math">\(math inline\)</span></p>
 ````````````````````````````````
 
 ```````````````````````````````` example
-This is a $    math block     $ after
+This is a $    math inline     $ after
 .
-<p>This is a <span class="math">\(math block\)</span> after</p>
+<p>This is a <span class="math">\(math inline\)</span> after</p>
 ````````````````````````````````
 
 ```````````````````````````````` example
-This is a $$    math block     $$ after
+This is a $$    math inline     $$ after
 .
-<p>This is a <span class="math">\(math block\)</span> after</p>
+<p>This is a <span class="math">\(math inline\)</span> after</p>
 ````````````````````````````````
 
 ```````````````````````````````` example
-This is a not $ math block$ because there is not a whitespace before the closing
+This is a not $ math inline$ because there is not a whitespace before the closing
 .
-<p>This is a not $ math block$ because there is not a whitespace before the closing</p>
+<p>This is a not $ math inline$ because there is not a whitespace before the closing</p>
 ````````````````````````````````
 
 For the opening `$` it requires a space or a punctuation before (but cannot be used within a word):
 
 ```````````````````````````````` example
-This is not a m$ath block$
+This is not a m$ath inline$
 .
-<p>This is not a m$ath block$</p>
+<p>This is not a m$ath inline$</p>
 ````````````````````````````````
 
 For the closing `$` it requires a space after or a punctuation (but cannot be preceded by a space and cannot be used within a word):
 
 ```````````````````````````````` example
-This is not a $math bloc$k
+This is not a $math inlin$e
 .
-<p>This is not a $math bloc$k</p>
+<p>This is not a $math inlin$e</p>
 ````````````````````````````````
 
 For the closing `$` it requires a space after or a punctuation (but cannot be preceded by a space and cannot be used within a word):
@@ -90,34 +90,34 @@ This is should not match a 16$ or a $15
 A `$` can be escaped between a math inline block by using the escape `\\` 
 
 ```````````````````````````````` example
-This is a $math \$ block$
+This is a $math \$ inline$
 .
-<p>This is a <span class="math">\(math \$ block\)</span></p>
+<p>This is a <span class="math">\(math \$ inline\)</span></p>
 ````````````````````````````````
 
 At most, two `$` will be matched for the opening and closing:
 
 ```````````````````````````````` example
-This is a $$$math block$$$
+This is a $$$math inline$$$
 .
-<p>This is a <span class="math">\($math block$\)</span></p>
+<p>This is a <span class="math">\($math inline$\)</span></p>
 ````````````````````````````````
 
 Regular text can come both before and after the math inline
 
 ```````````````````````````````` example
-This is a $math block$ with text on both sides.
+This is a $math inline$ with text on both sides.
 .
-<p>This is a <span class="math">\(math block\)</span> with text on both sides.</p>
+<p>This is a <span class="math">\(math inline\)</span> with text on both sides.</p>
 ````````````````````````````````
-A mathematic block takes precedence over standard emphasis `*` `_`:
+A mathematic inline block takes precedence over standard emphasis `*` `_`:
 
 ```````````````````````````````` example
-This is *a $math* block$
+This is *a $math* inline$
 .
-<p>This is *a <span class="math">\(math* block\)</span></p>
+<p>This is *a <span class="math">\(math* inline\)</span></p>
 ````````````````````````````````
-An opening $$ at the beginning of a line should not be interpreted as a Math block:
+An opening $$ at the beginning of a line should not be interpreted as a Math inline:
 
 ```````````````````````````````` example
 $$ math $$ starting at a line
@@ -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/TestAutoLinks.cs

@@ -0,0 +1,24 @@
+using Markdig.Extensions.AutoLinks;
+
+namespace Markdig.Tests;
+
+[TestFixture]
+public class TestAutoLinks
+{
+    [Test]
+    [TestCase("https://localhost", "<p><a href=\"https://localhost\">https://localhost</a></p>")]
+    [TestCase("http://localhost", "<p><a href=\"http://localhost\">http://localhost</a></p>")]
+    [TestCase("https://l", "<p><a href=\"https://l\">https://l</a></p>")]
+    [TestCase("www.l", "<p><a href=\"http://www.l\">www.l</a></p>")]
+    [TestCase("https://localhost:5000", "<p><a href=\"https://localhost:5000\">https://localhost:5000</a></p>")]
+    [TestCase("www.l:5000", "<p><a href=\"http://www.l:5000\">www.l:5000</a></p>")]
+    public void TestLinksWithAllowDomainWithoutPeriod(string markdown, string expected)
+    {
+        var pipeline = new MarkdownPipelineBuilder()
+            .UseAutoLinks(new AutoLinkOptions { AllowDomainWithoutPeriod = true })
+            .Build();
+        var html = Markdown.ToHtml(markdown, pipeline);
+
+        Assert.That(html, Is.EqualTo(expected).IgnoreWhiteSpace);
+    }
+}

src/Markdig.Tests/TestCharHelper.cs

@@ -19,18 +19,32 @@ public class TestCharHelper
         '{', '|', '}', '~'
     };
 
-    // A Unicode punctuation character is an ASCII punctuation character or anything in the general Unicode categories
-    // Pc, Pd, Pe, Pf, Pi, Po, or Ps.
-    private static readonly HashSet<UnicodeCategory> s_punctuationCategories = new()
-    {
+    // A Unicode punctuation character is a character in the Unicode P (punctuation) or S (symbol) general categories.
+    private static readonly HashSet<UnicodeCategory> s_punctuationCategories =
+    [
         UnicodeCategory.ConnectorPunctuation,
         UnicodeCategory.DashPunctuation,
+        UnicodeCategory.OpenPunctuation,
         UnicodeCategory.ClosePunctuation,
-        UnicodeCategory.FinalQuotePunctuation,
         UnicodeCategory.InitialQuotePunctuation,
+        UnicodeCategory.FinalQuotePunctuation,
         UnicodeCategory.OtherPunctuation,
-        UnicodeCategory.OpenPunctuation
-    };
+        UnicodeCategory.MathSymbol,
+        UnicodeCategory.CurrencySymbol,
+        UnicodeCategory.ModifierSymbol,
+        UnicodeCategory.OtherSymbol,
+    ];
+
+    private static readonly HashSet<UnicodeCategory> s_punctuationWithoutSymbolsCategories =
+    [
+        UnicodeCategory.ConnectorPunctuation,
+        UnicodeCategory.DashPunctuation,
+        UnicodeCategory.OpenPunctuation,
+        UnicodeCategory.ClosePunctuation,
+        UnicodeCategory.InitialQuotePunctuation,
+        UnicodeCategory.FinalQuotePunctuation,
+        UnicodeCategory.OtherPunctuation,
+    ];
 
     private static bool ExpectedIsPunctuation(char c)
     {
@@ -39,23 +53,98 @@ public class TestCharHelper
             : s_punctuationCategories.Contains(CharUnicodeInfo.GetUnicodeCategory(c));
     }
 
+    private static bool ExpectedIsPunctuationWithoutSymbols(char c)
+    {
+        return c <= 127
+            ? s_asciiPunctuation.Contains(c)
+            : s_punctuationWithoutSymbolsCategories.Contains(CharUnicodeInfo.GetUnicodeCategory(c));
+    }
+
     private static bool ExpectedIsWhitespace(char c)
     {
         // A Unicode whitespace character is any code point in the Unicode Zs general category,
         // or a tab (U+0009), line feed (U+000A), form feed (U+000C), or carriage return (U+000D).
-        return c == '\t' || c == '\n' || c == '\u000C' || c == '\r' ||
+        return c == '\t' || c == '\n' || c == '\f' || c == '\r' ||
             CharUnicodeInfo.GetUnicodeCategory(c) == UnicodeCategory.SpaceSeparator;
     }
 
+    [Test]
+    public void IsAcrossTab()
+    {
+        Assert.False(CharHelper.IsAcrossTab(0));
+        Assert.True(CharHelper.IsAcrossTab(1));
+        Assert.True(CharHelper.IsAcrossTab(2));
+        Assert.True(CharHelper.IsAcrossTab(3));
+        Assert.False(CharHelper.IsAcrossTab(4));
+    }
+
+    [Test]
+    public void AddTab()
+    {
+        Assert.AreEqual(4, CharHelper.AddTab(0));
+        Assert.AreEqual(4, CharHelper.AddTab(1));
+        Assert.AreEqual(4, CharHelper.AddTab(2));
+        Assert.AreEqual(4, CharHelper.AddTab(3));
+        Assert.AreEqual(8, CharHelper.AddTab(4));
+        Assert.AreEqual(8, CharHelper.AddTab(5));
+    }
+
     [Test]
     public void IsWhitespace()
     {
-        for (int i = char.MinValue; i <= char.MaxValue; i++)
-        {
-            char c = (char)i;
+        Test(
+            ExpectedIsWhitespace,
+            CharHelper.IsWhitespace);
 
-            Assert.AreEqual(ExpectedIsWhitespace(c), CharHelper.IsWhitespace(c));
-        }
+        Test(
+            ExpectedIsWhitespace,
+            CharHelper.WhitespaceChars.Contains);
+    }
+
+    [Test]
+    public void IsWhiteSpaceOrZero()
+    {
+        Test(
+            c => ExpectedIsWhitespace(c) || c == 0,
+            CharHelper.IsWhiteSpaceOrZero);
+    }
+
+    [Test]
+    public void IsAsciiPunctuation()
+    {
+        Test(
+            c => char.IsAscii(c) && ExpectedIsPunctuation(c),
+            CharHelper.IsAsciiPunctuation);
+    }
+
+    [Test]
+    public void IsAsciiPunctuationOrZero()
+    {
+        Test(
+            c => char.IsAscii(c) && (ExpectedIsPunctuation(c) || c == 0),
+            CharHelper.IsAsciiPunctuationOrZero);
+    }
+
+    [Test]
+    public void IsSpaceOrPunctuationForGFMAutoLink()
+    {
+        Test(
+            c => c == 0 || ExpectedIsWhitespace(c) || ExpectedIsPunctuationWithoutSymbols(c),
+            CharHelper.IsSpaceOrPunctuationForGFMAutoLink);
+    }
+
+    [Test]
+    public void InvalidAutoLinkCharacters()
+    {
+        // 6.5 Autolinks - https://spec.commonmark.org/0.31.2/#autolinks
+        // An absolute URI, for these purposes, consists of a scheme followed by a colon (:) followed by
+        // zero or more characters other than ASCII control characters, space, <, and >.
+        //
+        // 2.1 Characters and lines
+        // An ASCII control character is a character between U+0000–1F (both including) or U+007F.
+        Test(
+            c => c != 0 && c is < (char)0x20 or ' ' or '<' or '>' or '\u007F',
+            CharHelper.InvalidAutoLinkCharacters.Contains);
     }
 
     [Test]
@@ -76,15 +165,98 @@ public class TestCharHelper
     }
 
     [Test]
-    public void IsSpaceOrPunctuation()
+    public void IsControl()
+    {
+        Test(
+            char.IsControl,
+            CharHelper.IsControl);
+    }
+
+    [Test]
+    public void IsAlpha()
+    {
+        Test(
+            c => (c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z'),
+            CharHelper.IsAlpha);
+    }
+
+    [Test]
+    public void IsAlphaUpper()
+    {
+        Test(
+            c => c >= 'A' && c <= 'Z',
+            CharHelper.IsAlphaUpper);
+    }
+
+    [Test]
+    public void IsAlphaNumeric()
+    {
+        Test(
+            c => (c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z') || (c >= '0' && c <= '9'),
+            CharHelper.IsAlphaNumeric);
+    }
+
+    [Test]
+    public void IsDigit()
+    {
+        Test(
+            c => c >= '0' && c <= '9',
+            CharHelper.IsDigit);
+    }
+
+    [Test]
+    public void IsNewLineOrLineFeed()
+    {
+        Test(
+            c => c is '\r' or '\n',
+            CharHelper.IsNewLineOrLineFeed);
+    }
+
+    [Test]
+    public void IsSpaceOrTab()
+    {
+        Test(
+            c => c is ' ' or '\t',
+            CharHelper.IsSpaceOrTab);
+    }
+
+    [Test]
+    public void IsEscapableSymbol()
+    {
+        Test(
+            "!\"#$%&'()*+,-./:;<=>?@[\\]^_`{|}~•".Contains,
+            CharHelper.IsEscapableSymbol);
+    }
+
+    [Test]
+    public void IsEmailUsernameSpecialChar()
+    {
+        Test(
+            ".!#$%&'*+/=?^_`{|}~-+.~".Contains,
+            CharHelper.IsEmailUsernameSpecialChar);
+    }
+
+    [Test]
+    public void IsEmailUsernameSpecialCharOrDigit()
+    {
+        Test(
+            c => CharHelper.IsDigit(c) || ".!#$%&'*+/=?^_`{|}~-+.~".Contains(c),
+            CharHelper.IsEmailUsernameSpecialCharOrDigit);
+    }
+
+    private static void Test(Func<char, bool> expected, Func<char, bool> actual)
     {
         for (int i = char.MinValue; i <= char.MaxValue; i++)
         {
             char c = (char)i;
 
-            bool expected = c == 0 || ExpectedIsWhitespace(c) || ExpectedIsPunctuation(c);
+            bool expectedResult = expected(c);
+            bool actualResult = actual(c);
 
-            Assert.AreEqual(expected, CharHelper.IsSpaceOrPunctuation(c));
+            if (expectedResult != actualResult)
+            {
+                Assert.AreEqual(expectedResult, actualResult, $"Char: '{c}' ({i})");
+            }
         }
     }
 }

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/TestHtmlCodeBlocks.cs

@@ -0,0 +1,35 @@
+using Markdig.Syntax;
+
+namespace Markdig.Tests;
+
+public class TestHtmlCodeBlocks
+{
+    // Start condition: line begins with the string < or </ followed by one of the strings (case-insensitive)
+    // {list of all tags}, followed by a space, a tab, the end of the line, the string >, or the string />.
+    public static string[] KnownSimpleHtmlTags =>
+    [
+        "address", "article", "aside", "base", "basefont", "blockquote", "body", "caption", "center", "col", "colgroup", "dd", "details",
+        "dialog", "dir", "div", "dl", "dt", "fieldset", "figcaption", "figure", "footer", "form", "frame", "frameset",
+        "h1", "h2", "h3", "h4", "h5", "h6", "head", "header", "hr", "html", "iframe", "legend", "li", "link",
+        "main", "menu", "menuitem", "nav", "noframes", "ol", "optgroup", "option", "p", "param",
+        "search", "section", "summary", "table", "tbody", "td", "tfoot", "th", "thead", "title", "tr", "track", "ul",
+    ];
+
+    [Theory]
+    [TestCaseSource(nameof(KnownSimpleHtmlTags))]
+    public void TestKnownTags(string tag)
+    {
+        MarkdownDocument document = Markdown.Parse(
+            $"""
+            Hello
+             <{tag} />
+            World
+            """.ReplaceLineEndings("\n"));
+
+        HtmlBlock[] htmlBlocks = document.Descendants<HtmlBlock>().ToArray();
+
+        Assert.AreEqual(1, htmlBlocks.Length);
+        Assert.AreEqual(7, htmlBlocks[0].Span.Start);
+        Assert.AreEqual(10 + tag.Length, htmlBlocks[0].Span.Length);
+    }
+}

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()
     {
@@ -96,26 +112,26 @@ public class TestLinkHelper
     }
 
     [Test]
-    public void TestUrlAndTitleEmpty()
+    public void TestUrlEmptyAndTitleNull()
     {
         //                           01234
         var text = new StringSlice(@"(<>)A");
         Assert.True(LinkHelper.TryParseInlineLink(ref text, out string link, out string title, out SourceSpan linkSpan, out SourceSpan titleSpan));
         Assert.AreEqual(string.Empty, link);
-        Assert.AreEqual(string.Empty, title);
+        Assert.AreEqual(null, title);
         Assert.AreEqual(new SourceSpan(1, 2), linkSpan);
         Assert.AreEqual(SourceSpan.Empty, titleSpan);
         Assert.AreEqual('A', text.CurrentChar);
     }
 
     [Test]
-    public void TestUrlAndTitleEmpty2()
+    public void TestUrlEmptyAndTitleNull2()
     {
         //                           012345
         var text = new StringSlice(@"( <> )A");
         Assert.True(LinkHelper.TryParseInlineLink(ref text, out string link, out string title, out SourceSpan linkSpan, out SourceSpan titleSpan));
         Assert.AreEqual(string.Empty, link);
-        Assert.AreEqual(string.Empty, title);
+        Assert.AreEqual(null, title);
         Assert.AreEqual(new SourceSpan(2, 3), linkSpan);
         Assert.AreEqual(SourceSpan.Empty, titleSpan);
         Assert.AreEqual('A', text.CurrentChar);
@@ -142,7 +158,7 @@ public class TestLinkHelper
         var text = new StringSlice(@"()A");
         Assert.True(LinkHelper.TryParseInlineLink(ref text, out string link, out string title, out SourceSpan linkSpan, out SourceSpan titleSpan));
         Assert.AreEqual(string.Empty, link);
-        Assert.AreEqual(string.Empty, title);
+        Assert.AreEqual(null, title);
         Assert.AreEqual(SourceSpan.Empty, linkSpan);
         Assert.AreEqual(SourceSpan.Empty, titleSpan);
         Assert.AreEqual('A', text.CurrentChar);
@@ -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")]
@@ -33,9 +34,19 @@ 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)",
+        "<p><video width=\"500\" height=\"281\" controls=\"\"><source type=\"video/mp4\" src=\"./video.mp4\"></source></video></p>\n")]
+    [TestCase("![static audio relative path](./audio.mp3)",
+        "<p><audio width=\"500\" controls=\"\"><source type=\"audio/mpeg\" src=\"./audio.mp3\"></source></audio></p>\n")]
+    public void TestBuiltInHostsWithRelativePaths(string markdown, string expected)
+    {
+        string html = Markdown.ToHtml(markdown, GetPipeline());
+        Assert.AreEqual(expected, html);
+    }
+    
     private class TestHostProvider : IHostProvider
     {
         public string Class { get; } = "regex";

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/TestPipeTable.cs

@@ -12,10 +12,47 @@ public sealed class TestPipeTable
     [TestCase("| S | \r\n|---|\r\n| G |\r\n\r\n| D | D |\r\n| ---| ---| \r\n| V | V |", 2)]
     public void TestTableBug(string markdown, int tableCount = 1)
     {
-        MarkdownDocument document = Markdown.Parse(markdown, new MarkdownPipelineBuilder().UseAdvancedExtensions().Build());
+        MarkdownDocument document =
+            Markdown.Parse(markdown, new MarkdownPipelineBuilder().UseAdvancedExtensions().Build());
 
         Table[] tables = document.Descendants().OfType<Table>().ToArray();
 
         Assert.AreEqual(tableCount, tables.Length);
     }
+
+    [TestCase("A | B\r\n---|---", new[] {50.0f, 50.0f})]
+    [TestCase("A | B\r\n-|---", new[] {25.0f, 75.0f})]
+    [TestCase("A | B\r\n-|---\r\nA | B\r\n---|---", new[] {25.0f, 75.0f})]
+    [TestCase("A | B\r\n---|---|---", new[] {33.33f, 33.33f, 33.33f})]
+    [TestCase("A | B\r\n---|---|---|", new[] {33.33f, 33.33f, 33.33f})]
+    public void TestColumnWidthByHeaderLines(string markdown, float[] expectedWidth)
+    {
+        var pipeline = new MarkdownPipelineBuilder()
+            .UsePipeTables(new PipeTableOptions() {InferColumnWidthsFromSeparator = true})
+            .Build();
+        var document = Markdown.Parse(markdown, pipeline);
+        var table = document.Descendants().OfType<Table>().FirstOrDefault();
+        Assert.IsNotNull(table);
+        var actualWidths = table.ColumnDefinitions.Select(x => x.Width).ToList();
+        Assert.AreEqual(actualWidths.Count, expectedWidth.Length);
+        for (int i = 0; i < expectedWidth.Length; i++)
+        {
+            Assert.AreEqual(actualWidths[i], expectedWidth[i], 0.01);
+        }
+    }
+
+    [Test]
+    public void TestColumnWidthIsNotSetWithoutConfigurationFlag()
+    {
+        var pipeline = new MarkdownPipelineBuilder()
+            .UsePipeTables(new PipeTableOptions() {InferColumnWidthsFromSeparator = false})
+            .Build();
+        var document = Markdown.Parse("| A | B | C |\r\n|---|---|---|", pipeline);
+        var table = document.Descendants().OfType<Table>().FirstOrDefault();
+        Assert.IsNotNull(table);
+        foreach (var column in table.ColumnDefinitions)
+        {
+            Assert.AreEqual(0, column.Width);
+        }
+    }
 }

src/Markdig.Tests/TestPlainText.cs

@@ -26,6 +26,14 @@ public class TestPlainText
         Assert.AreEqual(expected, actual);
     }
 
+    [Test]
+    [TestCase(/* markdownText: */ "```\nConsole.WriteLine(\"Hello, World!\");\n```", /* expected: */ "Console.WriteLine(\"Hello, World!\");\n")]
+    public void TestPlainCodeBlock(string markdownText, string expected)
+    {
+        var actual = Markdown.ToPlainText(markdownText);
+        Assert.AreEqual(expected, actual);
+    }
+
     [Test]
     [TestCase(/* markdownText: */ ":::\nfoo\n:::", /* expected: */ "foo\n", /*extensions*/ "customcontainers|advanced")]
     [TestCase(/* markdownText: */ ":::bar\nfoo\n:::", /* expected: */ "foo\n", /*extensions*/ "customcontainers+attributes|advanced")]

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;
@@ -180,4 +181,62 @@ public class TestStringSliceList
             Assert.AreEqual('\0', iterator.CurrentChar); iterator.SkipChar();
         }
     }
-}
+
+    [Test]
+    public void TestStringLineGroupCharIteratorAtCapacity()
+    {
+        string str = "ABCDEFGHI";
+        var text = new StringLineGroup(1)
+        {
+            // Will store the following line at capacity
+            new StringSlice(str, NewLine.CarriageReturnLineFeed) { Start = 0, End = 2 },
+        };
+
+        var iterator = text.ToCharIterator();
+        var chars = ToString(iterator);
+        TextAssert.AreEqual("ABC\r\n", chars.ToString());
+        TextAssert.AreEqual("ABC", text.ToString());
+    }
+
+    [Test]
+    public void TestStringLineGroupCharIteratorForcingIncreaseCapacity()
+    {
+        string str = "ABCDEFGHI";
+        var text = new StringLineGroup(1)
+        {
+            // Will store the following line at capacity
+            new StringSlice(str, NewLine.CarriageReturnLineFeed) { Start = 0, End = 2 },
+
+            // Will force increase capacity to 2 and store the line at capacity
+            new StringSlice(str, NewLine.CarriageReturnLineFeed) { Start = 3, End = 3 },
+        };
+
+        var iterator = text.ToCharIterator();
+        var chars = ToString(iterator);
+        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

@@ -75,12 +75,39 @@ 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)
         {
             return null;
         }
     }
+
+    [TestCase("---\nkey1: value1\nkey2: value2\n---\n\n# Content\n")]
+    [TestCase("---\nkey1: value1\nkey2: value2\nkey3: value3\nkey4: value4\nkey5: value5\nkey6: value6\nkey7: value7\nkey8: value8\n---\n\n# Content\n")]
+    public void FrontMatterBlockLinesCharIterator(string value)
+    {
+        var builder = new MarkdownPipelineBuilder();
+        builder.Extensions.Add(new YamlFrontMatterExtension());
+        var markdownDocument = Markdown.Parse(value, builder.Build());
+
+        var yamlBlocks = markdownDocument.Descendants<YamlFrontMatterBlock>();
+        Assert.True(yamlBlocks.Any());
+
+        foreach (var yamlBlock in yamlBlocks)
+        {
+            var iterator = yamlBlock.Lines.ToCharIterator();
+            while(iterator.CurrentChar != '\0')
+            {
+                iterator.NextChar();
+            }
+        }
+
+        // No exception parsing and iterating through YAML front matter block lines
+    }
+
 }

src/Markdig.WebApp/ApiController.cs

@@ -8,7 +8,7 @@ public class ApiController : Controller
 {
     [HttpGet()]
     [Route("")]
-    public string Empty()
+    public new string Empty()
     {
         return string.Empty;
     }

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.WebApp/Startup.cs

@@ -12,7 +12,7 @@ public class Startup
         if (env.IsEnvironment("Development"))
         {
             // This will push telemetry data through Application Insights pipeline faster, allowing you to view results immediately.
-            builder.AddApplicationInsightsSettings(developerMode: true);
+            builder.AddApplicationInsightsSettings(connectionString: null, developerMode: true);
         }
 
         builder.AddEnvironmentVariables();

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,
                     };
@@ -202,20 +203,17 @@ public class AbbreviationParser : BlockParser
         while (index <= contentNew.End)
         {
             var c = contentNew.PeekCharAbsolute(index);
-            if (!(c == '\0' || c.IsWhitespace() || c.IsAsciiPunctuation()))
-            {
-                return false;
-            }
-
-            if (c.IsAlphaNumeric())
-            {
-                return false;
-            }
 
             if (c.IsWhitespace())
             {
                 break;
             }
+
+            if (!c.IsAsciiPunctuationOrZero())
+            {
+                return false;
+            }
+
             index++;
         }
         return true;

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 +1,86 @@
+// 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;
+
+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 +1,134 @@
+// 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;
+
+namespace Markdig.Extensions.Alerts;
+
+/// <summary>
+/// An inline parser for an alert inline (e.g. `[!NOTE]`).
+/// </summary>
+/// <seealso cref="InlineParser" />
+public class AlertInlineParser : InlineParser
+{
+    private static readonly TransformedStringCache s_alertTypeClassCache = new(
+        type => $"markdown-alert-{type.ToLowerInvariant()}");
+
+    /// <summary>
+    /// Initializes a new instance of the <see cref="AlertInlineParser"/> class.
+    /// </summary>
+    public AlertInlineParser()
+    {
+        OpeningCharacters = ['['];
+    }
+
+    public override bool Match(InlineProcessor processor, ref StringSlice slice)
+    {
+        if (slice.PeekChar() != '!')
+        {
+            return false;
+        }
+
+        // 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;
+        }
+
+        StringSlice saved = slice;
+
+        slice.SkipChar(); // Skip [
+        char c = slice.NextChar(); // Skip !
+
+        int start = slice.Start;
+        int 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.SkipChar(); // Skip \n
+                        }
+                    }
+                }
+                else if (c == '\n')
+                {
+                    slice.SkipChar(); // 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,
+        };
+
+        HtmlAttributes attributes = alertBlock.GetAttributes();
+        attributes.AddClass("markdown-alert");
+        attributes.AddClass(s_alertTypeClassCache.Get(alertType.AsSpan()));
+
+        // 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 +18,12 @@ 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;
+    private readonly ProcessInlineDelegate _processInlinesBegin;
+    private readonly ProcessInlineDelegate _processInlinesEnd;
 
     /// <summary>
     /// Initializes a new instance of the <see cref="AutoIdentifierExtension"/> class.
@@ -29,7 +31,9 @@ public class AutoIdentifierExtension : IMarkdownExtension
     /// <param name="options">The options.</param>
     public AutoIdentifierExtension(AutoIdentifierOptions options)
     {
-        this.options = options;
+        _options = options;
+        _processInlinesBegin = DocumentOnProcessInlinesBegin;
+        _processInlinesEnd = HeadingBlock_ProcessInlinesEnd;
     }
 
     public void Setup(MarkdownPipelineBuilder pipeline)
@@ -68,7 +72,7 @@ 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];
 
@@ -85,19 +89,19 @@ public class AutoIdentifierExtension : IMarkdownExtension
             {
                 dictionary = new Dictionary<string, HeadingLinkReferenceDefinition>();
                 doc.SetData(this, dictionary);
-                doc.ProcessInlinesBegin += DocumentOnProcessInlinesBegin;
+                doc.ProcessInlinesBegin += _processInlinesBegin;
             }
             dictionary[text] = linkRef;
         }
 
         // Then we register after inline have been processed to actually generate the proper #id
-        headingBlock.ProcessInlinesEnd += HeadingBlock_ProcessInlinesEnd;
+        headingBlock.ProcessInlinesEnd += _processInlinesEnd;
     }
 
     private void DocumentOnProcessInlinesBegin(InlineProcessor processor, Inline? inline)
     {
         var doc = processor.Document;
-        doc.ProcessInlinesBegin -= DocumentOnProcessInlinesBegin;
+        doc.ProcessInlinesBegin -= _processInlinesBegin;
         var dictionary = (Dictionary<string, HeadingLinkReferenceDefinition>)doc.GetData(this)!;
         foreach (var keyPair in dictionary)
         {
@@ -117,7 +121,7 @@ public class AutoIdentifierExtension : IMarkdownExtension
     /// Callback when there is a reference to found to a heading.
     /// Note that reference are only working if they are declared after.
     /// </summary>
-    private Inline CreateLinkInlineForHeading(InlineProcessor inlineState, LinkReferenceDefinition linkRef, Inline? child)
+    private static Inline CreateLinkInlineForHeading(InlineProcessor inlineState, LinkReferenceDefinition linkRef, Inline? child)
     {
         var headingRef = (HeadingLinkReferenceDefinition) linkRef;
         return new LinkInline()
@@ -157,16 +161,17 @@ 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 +202,7 @@ 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 +214,9 @@ 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/AutoLinkOptions.cs

@@ -22,4 +22,9 @@ public class AutoLinkOptions
     /// Should a www link be prefixed with https:// instead of http:// (false by default)
     /// </summary>
     public bool UseHttpsForWWWLinks { get; set; }
+
+    /// <summary>
+    /// Should auto-linking allow a domain with no period, e.g. https://localhost (false by default)
+    /// </summary>
+    public bool AllowDomainWithoutPeriod { get; set; }
 }

src/Markdig/Extensions/AutoLinks/AutoLinkParser.cs

@@ -6,6 +6,8 @@ using Markdig.Helpers;
 using Markdig.Parsers;
 using Markdig.Renderers.Html;
 using Markdig.Syntax.Inlines;
+using System.Buffers;
+using System.Diagnostics;
 
 namespace Markdig.Extensions.AutoLinks;
 
@@ -22,195 +24,180 @@ 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();
+        _validPreviousCharacters = SearchValues.Create(options.ValidPreviousCharacters);
     }
 
     public readonly AutoLinkOptions Options;
 
-    private readonly ListOfCharCache _listOfCharCache;
+    private readonly SearchValues<char> _validPreviousCharacters;
 
+    // This is a particularly expensive parser as it gets called for many common letters.
     public override bool Match(InlineProcessor processor, ref StringSlice slice)
     {
         // Previous char must be a whitespace or a punctuation
         var previousChar = slice.PeekCharExtra(-1);
-        if (!previousChar.IsWhiteSpaceOrZero() && Options.ValidPreviousCharacters.IndexOf(previousChar) == -1)
+        if (!previousChar.IsWhiteSpaceOrZero() && !_validPreviousCharacters.Contains(previousChar))
         {
             return false;
         }
 
+        ReadOnlySpan<char> span = slice.AsSpan();
+
+        Debug.Assert(span[0] is 'h' or 'f' or 'm' or 't' or 'w');
+
+        // Precheck URL
+        bool mayBeValid = span.Length >= 4 && span[0] switch
+        {
+            'h' => span.StartsWith("https://", StringComparison.Ordinal) || span.StartsWith("http://", StringComparison.Ordinal),
+            'w' => span.StartsWith("www.", StringComparison.Ordinal), // We won't match http:/www. or /www.xxx
+            'f' => span.StartsWith("ftp://", StringComparison.Ordinal),
+            'm' => span.StartsWith("mailto:", StringComparison.Ordinal),
+            _ => span.StartsWith("tel:", StringComparison.Ordinal),
+        };
+
+        return mayBeValid && MatchCore(processor, ref slice);
+    }
+
+    private bool MatchCore(InlineProcessor processor, ref StringSlice slice)
+    {
+        char c = slice.CurrentChar;
         var startPosition = slice.Start;
+
+        // We don't bother disposing the builder as it'll realistically never grow beyond the initial stack size.
+        var pendingEmphasis = new ValueStringBuilder(stackalloc char[32]);
+
+        // Check that an autolink is possible in the current context
+        if (!IsAutoLinkValidInCurrentContext(processor, ref pendingEmphasis))
+        {
+            return false;
+        }
+
+        // Parse URL
+        if (!LinkHelper.TryParseUrl(ref slice, out string? link, out _, true))
+        {
+            return false;
+        }
+
+        // If we have any pending emphasis, remove any pending emphasis characters from the end of the link
+        if (pendingEmphasis.Length > 0)
+        {
+            for (int i = link.Length - 1; i >= 0; i--)
+            {
+                if (pendingEmphasis.AsSpan().Contains(link[i]))
+                {
+                    slice.Start--;
+                }
+                else
+                {
+                    if (i < link.Length - 1)
+                    {
+                        link = link.Substring(0, i + 1);
+                    }
+                    break;
+                }
+            }
+        }
+
         int domainOffset = 0;
 
-        var c = slice.CurrentChar;
-        // Precheck URL
+        // Post-check URL
         switch (c)
         {
             case 'h':
-                if (slice.MatchLowercase("ttp://", 1))
+                if (string.Equals(link, "http://", StringComparison.Ordinal) ||
+                    string.Equals(link, "https://", StringComparison.Ordinal))
                 {
-                    domainOffset = 7; // http://
+                    return false;
                 }
-                else if (slice.MatchLowercase("ttps://", 1))
-                {
-                    domainOffset = 8; // https://
-                }
-                else return false;
+                domainOffset = link[4] == 's' ? 8 : 7; // https:// or http://
                 break;
+
+            case 'w':
+                domainOffset = 4; // www.
+                break;
+
             case 'f':
-                if (!slice.MatchLowercase("tp://", 1))
+                if (string.Equals(link, "ftp://", StringComparison.Ordinal))
                 {
                     return false;
                 }
                 domainOffset = 6; // ftp://
                 break;
-            case 'm':
-                if (!slice.MatchLowercase("ailto:", 1))
-                {
-                    return false;
-                }
-                break;
+
             case 't':
-                if (!slice.MatchLowercase("el:", 1))
+                if (string.Equals(link, "tel", StringComparison.Ordinal))
                 {
                     return false;
                 }
-                domainOffset = 4;
                 break;
-            case 'w':
-                if (!slice.MatchLowercase("ww.", 1)) // We won't match http:/www. or /www.xxx
+
+            case 'm':
+                int atIndex = link.IndexOf('@');
+                if (atIndex == -1 ||
+                    atIndex == 7) // mailto:@ - no email part
                 {
                     return false;
                 }
-                domainOffset = 4; // www.
+                domainOffset = atIndex + 1;
                 break;
         }
 
-        List<char> pendingEmphasis = _listOfCharCache.Get();
-        try
+        // Do not need to check if a telephone number is a valid domain
+        if (c != 't' && !LinkHelper.IsValidDomain(link, domainOffset, Options.AllowDomainWithoutPeriod))
         {
-            // Check that an autolink is possible in the current context
-            if (!IsAutoLinkValidInCurrentContext(processor, pendingEmphasis))
-            {
-                return false;
-            }
-
-            // Parse URL
-            if (!LinkHelper.TryParseUrl(ref slice, out string? link, out _, true))
-            {
-                return false;
-            }
-
-
-            // If we have any pending emphasis, remove any pending emphasis characters from the end of the link
-            if (pendingEmphasis.Count > 0)
-            {
-                for (int i = link.Length - 1; i >= 0; i--)
-                {
-                    if (pendingEmphasis.Contains(link[i]))
-                    {
-                        slice.Start--;
-                    }
-                    else
-                    {
-                        if (i < link.Length - 1)
-                        {
-                            link = link.Substring(0, i + 1);
-                        }
-                        break;
-                    }
-                }
-            }
-
-            // Post-check URL
-            switch (c)
-            {
-                case 'h':
-                    if (string.Equals(link, "http://", StringComparison.OrdinalIgnoreCase) ||
-                        string.Equals(link, "https://", StringComparison.OrdinalIgnoreCase))
-                    {
-                        return false;
-                    }
-                    break;
-                case 'f':
-                    if (string.Equals(link, "ftp://", StringComparison.OrdinalIgnoreCase))
-                    {
-                        return false;
-                    }
-                    break;
-                case 't':
-                    if (string.Equals(link, "tel", StringComparison.OrdinalIgnoreCase))
-                    {
-                        return false;
-                    }
-                    break;
-                case 'm':
-                    int atIndex = link.IndexOf('@');
-                    if (atIndex == -1 ||
-                        atIndex == 7) // mailto:@ - no email part
-                    {
-                        return false;
-                    }
-                    domainOffset = atIndex + 1;
-                    break;
-            }
-
-            // Do not need to check if a telephone number is a valid domain
-            if (c != 't' && !LinkHelper.IsValidDomain(link, domainOffset))
-            {
-                return false;
-            }
-
-            var inline = new LinkInline()
-            {
-                Span =
-                {
-                    Start = processor.GetSourcePosition(startPosition, out int line, out int column),
-                },
-                Line = line,
-                Column = column,
-                Url = c == 'w' ? ((Options.UseHttpsForWWWLinks ? "https://" : "http://") + link) : link,
-                IsClosed = true,
-                IsAutoLink = true,
-            };
-
-            var skipFromBeginning = c == 'm' ? 7 : 0; // For mailto: skip "mailto:" for content
-            skipFromBeginning = c == 't' ? 4 : skipFromBeginning; // See above but for tel:
-
-            inline.Span.End = inline.Span.Start + link.Length - 1;
-            inline.UrlSpan = inline.Span;
-            inline.AppendChild(new LiteralInline()
-            {
-                Span = inline.Span,
-                Line = line,
-                Column = column,
-                Content = new StringSlice(slice.Text, startPosition + skipFromBeginning, startPosition + link.Length - 1),
-                IsClosed = true
-            });
-            processor.Inline = inline;
-
-            if (Options.OpenInNewWindow)
-            {
-                inline.GetAttributes().AddPropertyIfNotExist("target", "_blank");
-            }
-
-            return true;
+            return false;
         }
-        finally
+
+        var inline = new LinkInline()
         {
-            _listOfCharCache.Release(pendingEmphasis);
+            Span =
+            {
+                Start = processor.GetSourcePosition(startPosition, out int line, out int column),
+            },
+            Line = line,
+            Column = column,
+            Url = c == 'w' ? ((Options.UseHttpsForWWWLinks ? "https://" : "http://") + link) : link,
+            IsClosed = true,
+            IsAutoLink = true,
+        };
+
+        int skipFromBeginning = c switch
+        {
+            'm' => 7, // For mailto: skip "mailto:" for content
+            't' => 4, // Same but for tel:
+            _ => 0
+        };
+
+        inline.Span.End = inline.Span.Start + link.Length - 1;
+        inline.UrlSpan = inline.Span;
+        inline.AppendChild(new LiteralInline()
+        {
+            Span = inline.Span,
+            Line = line,
+            Column = column,
+            Content = new StringSlice(slice.Text, startPosition + skipFromBeginning, startPosition + link.Length - 1),
+            IsClosed = true
+        });
+        processor.Inline = inline;
+
+        if (Options.OpenInNewWindow)
+        {
+            inline.GetAttributes().AddPropertyIfNotExist("target", "_blank");
         }
+
+        return true;
     }
 
-    private bool IsAutoLinkValidInCurrentContext(InlineProcessor processor, List<char> pendingEmphasis)
+    private static bool IsAutoLinkValidInCurrentContext(InlineProcessor processor, ref ValueStringBuilder pendingEmphasis)
     {
         // Case where there is a pending HtmlInline <a>
         var currentInline = processor.Inline;
@@ -257,9 +244,9 @@ public class AutoLinkParser : InlineParser
                 // Record all pending characters for emphasis
                 if (currentInline is EmphasisDelimiterInline emphasisDelimiter)
                 {
-                    if (!pendingEmphasis.Contains(emphasisDelimiter.DelimiterChar))
+                    if (!pendingEmphasis.AsSpan().Contains(emphasisDelimiter.DelimiterChar))
                     {
-                        pendingEmphasis.Add(emphasisDelimiter.DelimiterChar);
+                        pendingEmphasis.Append(emphasisDelimiter.DelimiterChar);
                     }
                 }
             }
@@ -268,12 +255,4 @@ public class AutoLinkParser : InlineParser
 
         return countBrackets <= 0;
     }
-
-    private sealed class ListOfCharCache : DefaultObjectCache<List<char>>
-    {
-        protected override void Reset(List<char> instance)
-        {
-            instance.Clear();
-        }
-    }
 }

src/Markdig/Extensions/Bootstrap/BootstrapExtension.cs

@@ -1,7 +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)
@@ -124,7 +124,7 @@ public class GenericAttributesParser : InlineParser
                 var start = line.Start;
                 // Get all non-whitespace characters following a #
                 // But stop if we found a } or \0
-                while (c != '}' && c != '\0' && !c.IsWhitespace())
+                while (c != '}' && !c.IsWhiteSpaceOrZero())
                 {
                     c = line.NextChar();
                 }
@@ -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/Globalization/GlobalizationExtension.cs

@@ -105,7 +105,7 @@ public class GlobalizationExtension : IMarkdownExtension
             }
 
             int rune = c;
-            if (CharHelper.IsHighSurrogate(c) && i < slice.End && CharHelper.IsLowSurrogate(slice[i + 1]))
+            if (char.IsHighSurrogate(c) && i < slice.End && char.IsLowSurrogate(slice[i + 1]))
             {
                 Debug.Assert(char.IsSurrogatePair(c, slice[i + 1]));
                 rune = char.ConvertToUtf32(c, slice[i + 1]);

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)
         {
@@ -59,19 +55,19 @@ public class HostProviderBuilder
         return new DelegateProvider(hostPrefix, handler, allowFullScreen, iframeClass);
     }
 
-    internal static Dictionary<string, IHostProvider> KnownHosts { get; }
-        = new Dictionary<string, IHostProvider>(StringComparer.OrdinalIgnoreCase)
-        {
-            ["YouTube"] = Create("www.youtube.com", YouTube, iframeClass: "youtube"),
-            ["YouTubeShortened"] = Create("youtu.be", YouTubeShortened, iframeClass: "youtube"),
-            ["Vimeo"] = Create("vimeo.com", Vimeo, iframeClass: "vimeo"),
-            ["Yandex"] = Create("music.yandex.ru", Yandex, allowFullScreen: false, iframeClass: "yandex"),
-            ["Odnoklassniki"] = Create("ok.ru", Odnoklassniki, iframeClass: "odnoklassniki"),
-        };
+    internal static readonly IHostProvider[] KnownHosts =
+    [
+        Create("www.youtube.com", YouTubeShort, iframeClass: "youtubeshort"),
+        Create("www.youtube.com", YouTube, iframeClass: "youtube"),
+        Create("youtu.be", YouTubeShortened, iframeClass: "youtube"),
+        Create("vimeo.com", Vimeo, iframeClass: "vimeo"),
+        Create("music.yandex.ru", Yandex, allowFullScreen: false, iframeClass: "yandex"),
+        Create("ok.ru", Odnoklassniki, iframeClass: "odnoklassniki"),
+    ];
 
     #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 +92,19 @@ 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/MediaLinks/MediaLinkExtension.cs

@@ -50,27 +50,32 @@ public class MediaLinkExtension : IMarkdownExtension
             return false;
         }
 
+        var url = linkInline.Url;
         bool isSchemaRelative = false;
-        // Only process absolute Uri
-        if (!Uri.TryCreate(linkInline.Url, UriKind.RelativeOrAbsolute, out Uri? uri) || !uri.IsAbsoluteUri)
+
+        // force // schema to an absolute url
+        if (url.StartsWith("//", StringComparison.Ordinal))
         {
-            // see https://tools.ietf.org/html/rfc3986#section-4.2
-            // since relative uri doesn't support many properties, "http" is used as a placeholder here.
-            if (linkInline.Url.StartsWith("//", StringComparison.Ordinal) && Uri.TryCreate("http:" + linkInline.Url, UriKind.Absolute, out uri))
+            url = "https:" + url;
+            isSchemaRelative = true;
+        }
+
+        // Make sure we have a valid absolute/relative url
+        if (!Uri.TryCreate(url, UriKind.RelativeOrAbsolute, out Uri? uri)) // || !uri.IsAbsoluteUri)
+        {
+            return false;
+        }
+        
+        // iFrame has to be absolute path
+        if (uri.IsAbsoluteUri)
+        {
+            if (TryRenderIframeFromKnownProviders(uri, isSchemaRelative, renderer, linkInline))
             {
-                isSchemaRelative = true;
-            }
-            else
-            {
-                return false;
+                return true;
             }
         }
 
-        if (TryRenderIframeFromKnownProviders(uri, isSchemaRelative, renderer, linkInline))
-        {
-            return true;
-        }
-
+        // audio/video has can have relative path
         if (TryGuessAudioVideoFile(uri, isSchemaRelative, renderer, linkInline))
         {
             return true;
@@ -93,7 +98,10 @@ public class MediaLinkExtension : IMarkdownExtension
 
     private bool TryGuessAudioVideoFile(Uri uri, bool isSchemaRelative, HtmlRenderer renderer, LinkInline linkInline)
     {
-        var path = uri.GetComponents(UriComponents.Path, UriFormat.Unescaped);
+        string path = uri.IsAbsoluteUri
+            ? uri.GetComponents(UriComponents.Path, UriFormat.Unescaped)
+            : uri.ToString();
+        
         // Otherwise try to detect if we have an audio/video from the file extension
         var lastDot = path.LastIndexOf('.');
         if (lastDot >= 0 &&

src/Markdig/Extensions/MediaLinks/MediaOptions.cs

@@ -81,7 +81,7 @@ public class MediaOptions
             {".au", "audio/basic"},
             {".wav", "audio/x-wav"},
         };
-        Hosts = new List<IHostProvider>(HostProviderBuilder.KnownHosts.Values);
+        Hosts = new List<IHostProvider>(HostProviderBuilder.KnownHosts);
     }
 
     public string Width { get; set; }

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)
@@ -43,7 +43,7 @@ public class GridTableParser : BlockParser
             }
 
             // Parse a column alignment
-            if (!TableHelper.ParseColumnHeader(ref line, '-', out TableColumnAlign? columnAlign))
+            if (!TableHelper.ParseColumnHeader(ref line, '-', out TableColumnAlign? columnAlign, out _))
             {
                 return BlockState.None;
             }
@@ -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/PipeTableOptions.cs

@@ -33,4 +33,11 @@ public class PipeTableOptions
     /// in all other rows (default behavior).
     /// </summary>
     public bool UseHeaderForColumnCount { get; set; }
+
+
+    /// <summary>
+    /// Gets or sets a value indicating whether column widths should be inferred based on the number of dashes
+    /// in the header separator row. Each column's width will be proportional to the dash count in its respective column.
+    /// </summary>
+    public bool InferColumnWidthsFromSeparator { get; set; }
 }

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
@@ -462,9 +481,10 @@ public class PipeTableParser : InlineParser, IPostInlineProcessor
         return false;
     }
 
-    private static bool ParseHeaderString(Inline? inline, out TableColumnAlign? align)
+    private static bool ParseHeaderString(Inline? inline, out TableColumnAlign? align, out int delimiterCount)
     {
         align = 0;
+        delimiterCount = 0;
         var literal = inline as LiteralInline;
         if (literal is null)
         {
@@ -473,7 +493,7 @@ public class PipeTableParser : InlineParser, IPostInlineProcessor
 
         // Work on a copy of the slice
         var line = literal.Content;
-        if (TableHelper.ParseColumnHeader(ref line, '-', out align))
+        if (TableHelper.ParseColumnHeader(ref line, '-', out align, out delimiterCount))
         {
             if (line.CurrentChar != '\0')
             {
@@ -488,7 +508,8 @@ public class PipeTableParser : InlineParser, IPostInlineProcessor
     private List<TableColumnDefinition>? FindHeaderRow(List<Inline> delimiters)
     {
         bool isValidRow = false;
-        List<TableColumnDefinition>? aligns = null;
+        int totalDelimiterCount = 0;
+        List<TableColumnDefinition>? columnDefinitions = null;
         for (int i = 0; i < delimiters.Count; i++)
         {
             if (!IsLine(delimiters[i]))
@@ -510,18 +531,19 @@ public class PipeTableParser : InlineParser, IPostInlineProcessor
 
                 // Check the left side of a `|` delimiter
                 TableColumnAlign? align = null;
+                int delimiterCount = 0;
                 if (delimiter.PreviousSibling != null &&
                     !(delimiter.PreviousSibling is LiteralInline li && li.Content.IsEmptyOrWhitespace()) && // ignore parsed whitespace
-                    !ParseHeaderString(delimiter.PreviousSibling, out align))
+                    !ParseHeaderString(delimiter.PreviousSibling, out align, out delimiterCount))
                 {
                     break;
                 }
 
                 // Create aligns until we may have a header row
 
-                aligns ??= new List<TableColumnDefinition>();
-                
-                aligns.Add(new TableColumnDefinition() { Alignment =  align });
+                columnDefinitions ??= new List<TableColumnDefinition>();
+                totalDelimiterCount += delimiterCount;
+                columnDefinitions.Add(new TableColumnDefinition() { Alignment =  align, Width = delimiterCount});
 
                 // If this is the last delimiter, we need to check the right side of the `|` delimiter
                 if (nextDelimiter is null)
@@ -537,13 +559,13 @@ public class PipeTableParser : InlineParser, IPostInlineProcessor
                         break;
                     }
 
-                    if (!ParseHeaderString(nextSibling, out align))
+                    if (!ParseHeaderString(nextSibling, out align, out delimiterCount))
                     {
                         break;
                     }
-
+                    totalDelimiterCount += delimiterCount;
                     isValidRow = true;
-                    aligns.Add(new TableColumnDefinition() { Alignment = align });
+                    columnDefinitions.Add(new TableColumnDefinition() { Alignment = align, Width = delimiterCount});
                     break;
                 }
 
@@ -557,7 +579,27 @@ public class PipeTableParser : InlineParser, IPostInlineProcessor
             break;
         }
 
-        return isValidRow ? aligns : null;
+        // calculate the width of the columns in percent based on the delimiter count
+        if (!isValidRow || columnDefinitions == null)
+        {
+            return null;
+        }
+
+        if (Options.InferColumnWidthsFromSeparator)
+        {
+            foreach (var columnDefinition in columnDefinitions)
+            {
+                columnDefinition.Width = (columnDefinition.Width * 100) / totalDelimiterCount;
+            }
+        }
+        else
+        {
+            foreach (var columnDefinition in columnDefinitions)
+            {
+                columnDefinition.Width = 0;
+            }
+        }
+        return columnDefinitions;
     }
 
     private static bool IsLine(Inline inline)
@@ -632,10 +674,10 @@ 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/Tables/TableHelper.cs

@@ -17,12 +17,13 @@ public static class TableHelper
     /// <param name="slice">The text slice.</param>
     /// <param name="delimiterChar">The delimiter character (either `-` or `=`).</param>
     /// <param name="align">The alignment of the column.</param>
+    /// <param name="delimiterCount">The number of delimiters.</param>
     /// <returns>
     ///   <c>true</c> if parsing was successful
     /// </returns>
-    public static bool ParseColumnHeader(ref StringSlice slice, char delimiterChar, out TableColumnAlign? align)
+    public static bool ParseColumnHeader(ref StringSlice slice, char delimiterChar, out TableColumnAlign? align, out int delimiterCount)
     {
-        return ParseColumnHeaderDetect(ref slice, ref delimiterChar, out align);
+        return ParseColumnHeaderDetect(ref slice, ref delimiterChar, out align, out delimiterCount);
     }
 
     /// <summary>
@@ -37,7 +38,7 @@ public static class TableHelper
     public static bool ParseColumnHeaderAuto(ref StringSlice slice, out char delimiterChar, out TableColumnAlign? align)
     {
         delimiterChar = '\0';
-        return ParseColumnHeaderDetect(ref slice, ref delimiterChar, out align);
+        return ParseColumnHeaderDetect(ref slice, ref delimiterChar, out align, out _);
     }
 
     /// <summary>
@@ -49,10 +50,10 @@ public static class TableHelper
     /// <returns>
     ///   <c>true</c> if parsing was successful
     /// </returns>
-    public static bool ParseColumnHeaderDetect(ref StringSlice slice, ref char delimiterChar, out TableColumnAlign? align)
+    public static bool ParseColumnHeaderDetect(ref StringSlice slice, ref char delimiterChar, out TableColumnAlign? align, out int delimiterCount)
     {
         align = null;
-
+        delimiterCount = 0;
         slice.TrimStart();
         var c = slice.CurrentChar;
         bool hasLeft = false;
@@ -80,7 +81,8 @@ public static class TableHelper
         }
 
         // We expect at least one `-` delimiter char
-        if (slice.CountAndSkipChar(delimiterChar) == 0)
+        delimiterCount = slice.CountAndSkipChar(delimiterChar);
+        if (delimiterCount == 0)
         {
             return false;
         }

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>
@@ -71,7 +71,7 @@ public class YamlFrontMatterParser : BlockParser
 
         // If three dashes (optionally followed by whitespace)
         // this is a YAML front matter block
-        if (count == 3 && (c == '\0' || c.IsWhitespace()) && line.TrimEnd())
+        if (count == 3 && c.IsWhiteSpaceOrZero() && line.TrimEnd())
         {
             bool hasFullYamlFrontMatter = false;
             // We make sure that there is a closing frontmatter somewhere in the document
@@ -146,7 +146,7 @@ public class YamlFrontMatterParser : BlockParser
 
             // If we have a closing fence, close it and discard the current line
             // The line must contain only fence characters and optional following whitespace.
-            if (count == 3 && !processor.IsCodeIndent && (c == '\0' || c.IsWhitespace()) && line.TrimEnd())
+            if (count == 3 && !processor.IsCodeIndent && c.IsWhiteSpaceOrZero() && line.TrimEnd())
             {
                 block.UpdateSpanEnd(line.Start - 1);
 

src/Markdig/Globals.cs

@@ -1,2 +1,3 @@
 global using System;
+global using System.Collections.Frozen;
 global using System.Collections.Generic;

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

@@ -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.Diagnostics;
 using System.Globalization;
 using System.Runtime.CompilerServices;
@@ -19,26 +20,65 @@ public static class CharHelper
 
     public const string ReplacementCharString = "\uFFFD";
 
-    private const char HighSurrogateStart = '\ud800';
-    private const char HighSurrogateEnd = '\udbff';
-    private const char LowSurrogateStart = '\udc00';
-    private const char LowSurrogateEnd = '\udfff';
+    private const string EmailUsernameSpecialChars = ".!#$%&'*+/=?^_`{|}~-+.~";
 
-    // We don't support LCDM
-    private static readonly Dictionary<char, int> romanMap = new Dictionary<char, int>(6) {
-        { 'i', 1 }, { 'v', 5 }, { 'x', 10 },
-        { 'I', 1 }, { 'V', 5 }, { 'X', 10 }
-    };
+    // 2.1 Characters and lines
+    // A Unicode whitespace character is any code point in the Unicode Zs general category,
+    // or a tab (U+0009), line feed (U+000A), form feed (U+000C), or carriage return (U+000D).
+    // CharUnicodeInfo.GetUnicodeCategory(c) == UnicodeCategory.SpaceSeparator;
+    private const string AsciiWhitespaceChars = "\t\n\f\r ";
+    internal const string WhitespaceChars = AsciiWhitespaceChars + "\u00A0\u1680\u2000\u2001\u2002\u2003\u2004\u2005\u2006\u2007\u2008\u2009\u200A\u202F\u205F\u3000";
 
-    private static readonly char[] punctuationExceptions = { '−', '-', '†', '‡' };
+    // 2.1 Characters and lines
+    // An ASCII punctuation character is
+    // !, ", #, $, %, &, ', (, ), *, +, ,, -, ., / (U+0021–2F),
+    // :, ;, <, =, >, ?, @ (U+003A–0040),
+    // [, \, ], ^, _, ` (U+005B–0060),
+    // {, |, }, or ~ (U+007B–007E).
+    private const string AsciiPunctuationChars = "!\"#$%&'()*+,-./:;<=>?@[\\]^_`{|}~";
+
+    // Unicode P (punctuation) categories.
+    private const int UnicodePunctuationCategoryMask =
+        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;
+
+    private const int UnicodePunctuationOrSpaceCategoryMask =
+        UnicodePunctuationCategoryMask |
+        1 << (int)UnicodeCategory.SpaceSeparator;
+
+    // 2.1 Characters and lines
+    // A Unicode punctuation character is a character in the Unicode P (punctuation) or S (symbol) general categories.
+    private const int CommonMarkPunctuationCategoryMask =
+        UnicodePunctuationCategoryMask |
+        1 << (int)UnicodeCategory.MathSymbol |
+        1 << (int)UnicodeCategory.CurrencySymbol |
+        1 << (int)UnicodeCategory.ModifierSymbol |
+        1 << (int)UnicodeCategory.OtherSymbol;
+
+    // We're not currently using these SearchValues instances for vectorized IndexOfAny-like searches, but for their efficient single Contains(char) checks.
+    private static readonly SearchValues<char> s_emailUsernameSpecialChar = SearchValues.Create(EmailUsernameSpecialChars);
+    private static readonly SearchValues<char> s_emailUsernameSpecialCharOrDigit = SearchValues.Create(EmailUsernameSpecialChars + "0123456789");
+    private static readonly SearchValues<char> s_asciiPunctuationChars = SearchValues.Create(AsciiPunctuationChars);
+    private static readonly SearchValues<char> s_asciiPunctuationCharsOrZero = SearchValues.Create(AsciiPunctuationChars + '\0');
+    private static readonly SearchValues<char> s_asciiPunctuationOrWhitespaceCharsOrZero = SearchValues.Create(AsciiPunctuationChars + AsciiWhitespaceChars + '\0');
+    private static readonly SearchValues<char> s_escapableSymbolChars = SearchValues.Create("!\"#$%&'()*+,-./:;<=>?@[\\]^_`{|}~•");
+
+    [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
@@ -99,8 +139,8 @@ public static class CharHelper
         int result = 0;
         for (int i = 0; i < text.Length; i++)
         {
-            var candidate = romanMap[text[i]];
-            if ((uint)(i + 1) < text.Length && candidate < romanMap[text[i + 1]])
+            int candidate = RomanToArabic(text[i]);
+            if ((uint)(i + 1) < text.Length && candidate < RomanToArabic(text[i + 1]))
             {
                 result -= candidate;
             }
@@ -110,6 +150,20 @@ public static class CharHelper
             }
         }
         return result;
+
+        // We don't support LCDM
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        static int RomanToArabic(char c)
+        {
+            Debug.Assert(IsRomanLetterPartial(c));
+
+            return (c | 0x20) switch
+            {
+                'i' => 1,
+                'v' => 5,
+                _ => 10
+            };
+        }
     }
 
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
@@ -126,72 +180,67 @@ 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)
     {
         // 2.1 Characters and lines
         // A Unicode whitespace character is any code point in the Unicode Zs general category,
         // or a tab (U+0009), line feed (U+000A), form feed (U+000C), or carriage return (U+000D).
-        if (c <= ' ')
+        if (c < '\u00A0')
         {
-            const long Mask =
-                (1L << ' ') |
-                (1L << '\t') |
-                (1L << '\n') |
-                (1L << '\f') |
-                (1L << '\r');
-
-            return (Mask & (1L << c)) != 0;
+            // Matches any of "\t\n\f\r ". See comments in HexConverter.IsHexChar for how these checks work:
+            // https://github.com/dotnet/runtime/blob/a2e1d21bb4faf914363968b812c990329ba92d8e/src/libraries/Common/src/System/HexConverter.cs#L392-L415
+            // https://gist.github.com/MihaZupan/b93ba180c2b5fbaaed993db2ade76b49
+            ulong shift = 30399299632234496UL << c;
+            ulong mask = (ulong)c - 64;
+            return (long)(shift & mask) < 0;
         }
 
-        return c >= '\u00A0' && IsWhitespaceRare(c);
+        return IsWhitespaceRare(c);
+    }
 
-        static bool IsWhitespaceRare(char c)
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static bool IsWhiteSpaceOrZero(this char c)
+    {
+        if (c < '\u00A0')
         {
-            // return CharUnicodeInfo.GetUnicodeCategory(c) == UnicodeCategory.SpaceSeparator;
+            // Matches any of "\0\t\n\f\r ".
+            ulong shift = 9253771336487010304UL << c;
+            ulong mask = (ulong)c - 64;
+            return (long)(shift & mask) < 0;
+        }
 
-            if (c < 5760)
-            {
-                return c == '\u00A0';
-            }
-            else
-            {
-                return c <= 12288 &&
-                    (c == 5760 || IsInInclusiveRange(c, 8192, 8202) || c == 8239 || c == 8287 || c == 12288);
-            }
+        return IsWhitespaceRare(c);
+    }
+
+    private static bool IsWhitespaceRare(char c)
+    {
+        Debug.Assert(c >= '\u00A0');
+
+        // return CharUnicodeInfo.GetUnicodeCategory(c) == UnicodeCategory.SpaceSeparator;
+
+        if (c < 5760)
+        {
+            return c == '\u00A0';
+        }
+        else
+        {
+            return c <= 12288 &&
+                (c == 5760 || IsInInclusiveRange(c, 8192, 8202) || c == 8239 || c == 8287 || c == 12288);
         }
     }
 
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
     public static bool IsControl(this char c)
     {
-        return c < ' ' || char.IsControl(c);
+        return char.IsControl(c);
     }
 
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
     public static bool IsEscapableSymbol(this char c)
     {
         // char.IsSymbol also works with Unicode symbols that cannot be escaped based on the specification.
-        return (c > ' ' && c < '0') || (c > '9' && c < 'A') || (c > 'Z' && c < 'a') || (c > 'z' && c < 127) || c == '•';
-    }
-
-    //[MethodImpl(MethodImplOptions.AggressiveInlining)]
-    public static bool IsWhiteSpaceOrZero(this char c)
-    {
-        return IsZero(c) || IsWhitespace(c);
+        return s_escapableSymbolChars.Contains(c);
     }
 
     // Check if a char is a space or a punctuation
@@ -205,48 +254,46 @@ public static class CharHelper
         else if (c <= 127)
         {
             space = c == '\0';
-            punctuation = c == '\0' || IsAsciiPunctuation(c);
+            punctuation = IsAsciiPunctuationOrZero(c);
         }
         else
         {
-            // A Unicode punctuation character is an ASCII punctuation character
-            // or anything in the general Unicode categories Pc, Pd, Pe, Pf, Pi, Po, or Ps.
             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 = (CommonMarkPunctuationCategoryMask & (1 << (int)CharUnicodeInfo.GetUnicodeCategory(c))) != 0;
         }
     }
 
-    // Same as CheckUnicodeCategory
-    internal static bool IsSpaceOrPunctuation(this char c)
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    internal static bool IsSpaceOrPunctuationForGFMAutoLink(char c)
     {
-        if (IsWhitespace(c))
+        // Github Flavored Markdown's allowed set of domain characters differs from CommonMark's "punctuation" definition.
+        // CommonMark also counts symbols as punctuation, but GitHub will render e.g. http://☃.net as an autolink, despite
+        // the snowman emoji falling under the OtherSymbol (So) category.
+        if (c <= 127)
         {
-            return true;
-        }
-        else if (c <= 127)
-        {
-            return c == '\0' || IsAsciiPunctuation(c);
+            return s_asciiPunctuationOrWhitespaceCharsOrZero.Contains(c);
         }
         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;
+            return NonAscii(c);
+
+            static bool NonAscii(char c) =>
+                (UnicodePunctuationOrSpaceCategoryMask & (1 << (int)CharUnicodeInfo.GetUnicodeCategory(c))) != 0;
         }
     }
 
+    // 6.5 Autolinks - https://spec.commonmark.org/0.31.2/#autolinks
+    // An absolute URI, for these purposes, consists of a scheme followed by a colon (:) followed by
+    // zero or more characters other than ASCII control characters, space, <, and >.
+    //
+    // 2.1 Characters and lines
+    // An ASCII control character is a character between U+0000–1F (both including) or U+007F.
+    internal static readonly SearchValues<char> InvalidAutoLinkCharacters = SearchValues.Create(
+        // 0 is excluded because it can be slightly more expensive for SearchValues to handle, and we've already removed it from the input text.
+        "\u0001\u0002\u0003\u0004\u0005\u0006\u0007\u0008\u0009\u000A\u000B\u000C\u000D\u000E\u000F" +
+        "\u0010\u0011\u0012\u0013\u0014\u0015\u0016\u0017\u0018\u0019\u001A\u001B\u001C\u001D\u001E\u001F" +
+        " <>\u007F");
+
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
     public static bool IsNewLineOrLineFeed(this char c)
     {
@@ -286,7 +333,7 @@ public static class CharHelper
     {
         // 2.3 Insecure characters
         // For security reasons, the Unicode character U+0000 must be replaced with the REPLACEMENT CHARACTER (U+FFFD).
-        return c == '\0' ? '\ufffd' : c;
+        return c == '\0' ? ReplacementChar : c;
     }
 
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
@@ -313,46 +360,33 @@ public static class CharHelper
         return (uint)(c - '0') <= ('9' - '0');
     }
 
-    public static bool IsAsciiPunctuation(this char c)
-    {
-        // 2.1 Characters and lines 
-        // An ASCII punctuation character is
-        // !, ", #, $, %, &, ', (, ), *, +, ,, -, ., / (U+0021–2F),
-        // :, ;, <, =, >, ?, @ (U+003A–0040),
-        // [, \, ], ^, _, ` (U+005B–0060),
-        // {, |, }, or ~ (U+007B–007E).
-        return c <= 127 && (
-            IsInInclusiveRange(c, 33, 47) ||
-            IsInInclusiveRange(c, 58, 64) ||
-            IsInInclusiveRange(c, 91, 96) ||
-            IsInInclusiveRange(c, 123, 126));
-    }
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    internal static bool IsAsciiPunctuationOrZero(this char c) =>
+        s_asciiPunctuationCharsOrZero.Contains(c);
 
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
-    public static bool IsEmailUsernameSpecialChar(char c)
-    {
-        return ".!#$%&'*+/=?^_`{|}~-+.~".IndexOf(c) >= 0;
-    }
+    public static bool IsAsciiPunctuation(this char c) =>
+        s_asciiPunctuationChars.Contains(c);
 
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
-    public static bool IsHighSurrogate(char c)
-    {
-        return IsInInclusiveRange(c, HighSurrogateStart, HighSurrogateEnd);
-    }
+    public static bool IsEmailUsernameSpecialChar(char c) =>
+        s_emailUsernameSpecialChar.Contains(c);
 
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
-    public static bool IsLowSurrogate(char c)
-    {
-        return IsInInclusiveRange(c, LowSurrogateStart, LowSurrogateEnd);
-    }
+    internal static bool IsEmailUsernameSpecialCharOrDigit(char c) =>
+        s_emailUsernameSpecialCharOrDigit.Contains(c);
 
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
-    private static bool IsInInclusiveRange(char c, char min, char max)
-        => (uint)(c - min) <= (uint)(max - min);
+    public static bool IsHighSurrogate(char c) =>
+        char.IsHighSurrogate(c);
 
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
-    internal static bool IsInInclusiveRange(int value, uint min, uint max)
-        => ((uint)value - min) <= (max - min);
+    public static bool IsLowSurrogate(char c) =>
+        char.IsLowSurrogate(c);
+
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    internal static bool IsInInclusiveRange(int value, uint min, uint max) =>
+        ((uint)value - min) <= (max - min);
 
     public static bool IsRightToLeft(int c)
     {
@@ -729,11 +763,11 @@ 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/CharNormalizer.cs

@@ -20,7 +20,7 @@ public static class CharNormalizer
     }
 
     // This table was generated by the app UnicodeNormDApp
-    private static readonly Dictionary<char, string> CodeToAscii = new(1269)
+    private static readonly FrozenDictionary<char, string> CodeToAscii = new Dictionary<char, string>(1269)
     {
         {'Ḋ', "D"},
         {'Ḍ', "D"},
@@ -1291,5 +1291,5 @@ public static class CharNormalizer
         {'｜', "|"},
         {'｝', "}"},
         {'～', "~"},
-    };
+    }.ToFrozenDictionary();
 }

src/Markdig/Helpers/CharacterMap.cs

@@ -2,14 +2,9 @@
 // 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 +14,9 @@ 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 FrozenDictionary<uint, T>? _nonAsciiMap;
 
     /// <summary>
     /// Initializes a new instance of the <see cref="CharacterMap{T}"/> class.
@@ -35,64 +26,44 @@ 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];
+        Dictionary<uint, T>? nonAsciiMap = null;
 
         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 ??= [];
+
+                if (!nonAsciiMap.ContainsKey(openingChar))
+                {
+                    nonAsciiMap[openingChar] = state.Value;
+                }
             }
         }
 
-#if NETCOREAPP3_1_OR_GREATER
-        if (nonAsciiMap is null)
+        _values = SearchValues.Create(OpeningCharacters);
+
+        if (nonAsciiMap is not 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();
+            _nonAsciiMap = nonAsciiMap.ToFrozenDictionary();
         }
-#endif
     }
 
     /// <summary>
@@ -110,7 +81,7 @@ 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 +89,12 @@ 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 +102,20 @@ 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

@@ -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.Diagnostics;
 using System.Diagnostics.CodeAnalysis;
 using System.Runtime.CompilerServices;
 
@@ -12,8 +13,8 @@ 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()
@@ -393,40 +394,52 @@ public static class HtmlHelper
 
     private static bool TryParseHtmlTagHtmlComment(ref StringSlice text, ref ValueStringBuilder builder)
     {
+        // https://spec.commonmark.org/0.31.2/#raw-html
+        // An HTML comment consists of <!-->, <!--->, or
+        // <!--, a string of characters not including the string -->, and -->.
+
+        // The caller already checked <!-
+        Debug.Assert(text.CurrentChar == '-' && text.PeekCharExtra(-1) == '!' && text.PeekCharExtra(-2) == '<');
+
         var c = text.NextChar();
         if (c != '-')
         {
             return false;
         }
-        builder.Append('-');
-        builder.Append('-');
-        if (text.PeekChar() == '>')
+
+        c = text.NextChar();
+
+        if (c == '>')
+        {
+            // <!--> is considered valid.
+            builder.Append("-->");
+            text.SkipChar();
+            return true;
+        }
+
+        if (c == '-' && text.PeekChar() == '>')
+        {
+            // <!---> is also considered valid.
+            builder.Append("--->");
+            text.SkipChar();
+            text.SkipChar();
+            return true;
+        }
+
+        ReadOnlySpan<char> slice = text.AsSpan();
+
+        const string EndOfComment = "-->";
+
+        int endOfComment = slice.IndexOf(EndOfComment, StringComparison.Ordinal);
+        if (endOfComment < 0)
         {
             return false;
         }
 
-        var countHyphen = 0;
-        while (true)
-        {
-            c = text.NextChar();
-            if (c == '\0')
-            {
-                return false;
-            }
-
-            if (countHyphen == 2)
-            {
-                if (c == '>')
-                {
-                    builder.Append('>');
-                    text.SkipChar();
-                    return true;
-                }
-                return false;
-            }
-            countHyphen = c == '-' ? countHyphen + 1 : 0;
-            builder.Append(c);
-        }
+        builder.Append("--");
+        builder.Append(slice.Slice(0, endOfComment + EndOfComment.Length));
+        text.Start += endOfComment + EndOfComment.Length;
+        return true;
     }
 
     private static bool TryParseHtmlTagProcessingInstruction(ref StringSlice text, ref ValueStringBuilder builder)

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

@@ -2,6 +2,8 @@
 // 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.Diagnostics.CodeAnalysis;
 using System.Runtime.CompilerServices;
 using Markdig.Syntax;
@@ -19,6 +21,11 @@ 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 +102,24 @@ 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();
@@ -152,7 +168,7 @@ public static class LinkHelper
         if (!c.IsAlpha())
         {
             // We may have an email char?
-            if (c.IsDigit() || CharHelper.IsEmailUsernameSpecialChar(c))
+            if (CharHelper.IsEmailUsernameSpecialCharOrDigit(c))
             {
                 state = -1;
             }
@@ -272,40 +288,34 @@ public static class LinkHelper
         }
         else
         {
-            // scan an uri            
-            // An absolute URI, for these purposes, consists of a scheme followed by a colon (:) 
-            // followed by zero or more characters other than ASCII whitespace and control characters, <, and >. 
+            // 6.5 Autolinks - https://spec.commonmark.org/0.31.2/#autolinks
+            // An absolute URI, for these purposes, consists of a scheme followed by a colon (:) followed by
+            // zero or more characters other than ASCII control characters, space, <, and >.
             // If the URI includes these characters, they must be percent-encoded (e.g. %20 for a space).
+            //
+            // 2.1 Characters and lines
+            // An ASCII control character is a character between U+0000–1F (both including) or U+007F.
 
-            while (true)
+            text.SkipChar();
+            ReadOnlySpan<char> slice = text.AsSpan();
+
+            Debug.Assert(!slice.Contains('\0'));
+
+            // This set of invalid characters includes '>'.
+            int end = slice.IndexOfAny(CharHelper.InvalidAutoLinkCharacters);
+
+            if ((uint)end < (uint)slice.Length && slice[end] == '>')
             {
-                c = text.NextChar();
-                if (c == '\0')
-                {
-                    break;
-                }
-
-                if (c == '>')
-                {
-                    text.SkipChar();
-                    link = builder.ToString();
-                    return true;
-                }
-
-                // Chars valid for both scheme and email
-                if (c <= 127)
-                {
-                    if (c > ' ' && c != '>')
-                    {
-                        builder.Append(c);
-                    }
-                    else break;
-                }
-                else if (!c.IsSpaceOrPunctuation())
-                {
-                    builder.Append(c);
-                }
-                else break;
+                // We've found '>' and all characters before it are valid.
+#if NET
+                link = string.Concat(builder.AsSpan(), slice.Slice(0, end));
+                builder.Dispose();
+#else
+                builder.Append(slice.Slice(0, end));
+                link = builder.ToString();
+#endif
+                text.Start += end + 1; // +1 to skip '>'
+                return true;
             }
         }
 
@@ -401,7 +411,7 @@ public static class LinkHelper
         {
             // Skip ')'
             text.SkipChar();
-            title ??= string.Empty;
+            // not to normalize nulls into empty strings, since LinkInline.Title property is nullable.
         }
 
         return isValid;
@@ -531,87 +541,70 @@ 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 +620,70 @@ 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 +720,15 @@ 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 +739,6 @@ public static class LinkHelper
                     break;
                 }
 
-                hasEscape = false;
-
                 buffer.Append(c);
 
             } while (c != '\0');
@@ -800,20 +777,21 @@ 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 +869,15 @@ 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 +888,6 @@ public static class LinkHelper
                     break;
                 }
 
-                hasEscape = false;
-
                 buffer.Append(c);
 
             } while (c != '\0');
@@ -947,20 +926,21 @@ 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))
@@ -1022,7 +1002,7 @@ public static class LinkHelper
         return c == '\0' || c.IsSpaceOrTab() || c.IsControl() || (isAutoLink && c == '<'); // TODO: specs unclear. space is strict or relaxed? (includes tabs?)
     }
 
-    public static bool IsValidDomain(string link, int prefixLength)
+    public static bool IsValidDomain(string link, int prefixLength, bool allowDomainWithoutPeriod = false)
     {
         // https://github.github.com/gfm/#extended-www-autolink
         // A valid domain consists of alphanumeric characters, underscores (_), hyphens (-) and periods (.).
@@ -1035,22 +1015,22 @@ public static class LinkHelper
         bool segmentHasCharacters = false;
         int lastUnderscoreSegment = -1;
 
-        for (int i = prefixLength; i < link.Length; i++)
+        for (int i = prefixLength; (uint)i < (uint)link.Length; i++)
         {
             char c = link[i];
 
-            if (c == '.') // New segment
-            {
-                if (!segmentHasCharacters)
-                    return false;
-
-                segmentCount++;
-                segmentHasCharacters = false;
-                continue;
-            }
-
             if (!c.IsAlphaNumeric())
             {
+                if (c == '.') // New segment
+                {
+                    if (!segmentHasCharacters)
+                        return false;
+
+                    segmentCount++;
+                    segmentHasCharacters = false;
+                    continue;
+                }
+
                 if (c == '/' || c == '?' || c == '#' || c == ':') // End of domain name
                     break;
 
@@ -1058,7 +1038,7 @@ public static class LinkHelper
                 {
                     lastUnderscoreSegment = segmentCount;
                 }
-                else if (c != '-' && c.IsSpaceOrPunctuation())
+                else if (c != '-' && CharHelper.IsSpaceOrPunctuationForGFMAutoLink(c))
                 {
                     // An invalid character has been found
                     return false;
@@ -1068,7 +1048,7 @@ public static class LinkHelper
             segmentHasCharacters = true;
         }
 
-        return segmentCount != 1 && // At least one dot was present
+        return (segmentCount != 1 || allowDomainWithoutPeriod) && // At least one dot was present
             segmentHasCharacters && // Last segment has valid characters
             segmentCount - lastUnderscoreSegment >= 2; // No underscores are present in the last two segments of the domain
     }
@@ -1145,7 +1125,7 @@ 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 +1265,7 @@ 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
@@ -1585,4 +1565,4 @@ public static class LinkHelper
         label = buffer.ToString();
         return true;
     }
-}
+}

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()
@@ -334,9 +357,12 @@ public struct StringLineGroup : IEnumerable
             goto Return;
 
         MoveToNewLine:
-            SliceIndex++;
-            _offset = -1;
-            _currentSlice = _lines.Lines[SliceIndex];
+            if (SliceIndex < _lines.Lines.Length - 1)
+            {
+                SliceIndex++;
+                _offset = -1;
+                _currentSlice = _lines.Lines[SliceIndex];
+            }
 
         Return:
             return CurrentChar;
@@ -420,25 +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

@@ -231,7 +231,7 @@ public struct StringSlice : ICharIterator
     }
 
     /// <summary>
-    /// Peeks a character at the specified offset from the current begining of the slice
+    /// Peeks a character at the specified offset from the current beginning of the slice
     /// without using the range <see cref="Start"/> or <see cref="End"/>, returns `\0` if outside the <see cref="Text"/>.
     /// </summary>
     /// <param name="offset">The offset.</param>
@@ -291,7 +291,7 @@ public struct StringSlice : ICharIterator
             var c = Text[i];
             if (c.IsWhitespace())
             {
-                if (c == '\0' || c == '\n' || (c == '\r' && i + 1 <= End && Text[i + 1] != '\n'))
+                if (c == '\n' || (c == '\r' && i + 1 <= End && Text[i + 1] != '\n'))
                 {
                     return true;
                 }
@@ -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

@@ -5,16 +5,16 @@
     <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>
+    <PackageReleaseNotes>https://github.com/xoofx/markdig/blob/master/changelog.md</PackageReleaseNotes>
     <PackageLicenseExpression>BSD-2-Clause</PackageLicenseExpression>
     <PackageReadmeFile>readme.md</PackageReadmeFile>
     <PackageIcon>markdig.png</PackageIcon>
-    <PackageProjectUrl>https://github.com/lunet-io/markdig</PackageProjectUrl>
+    <PackageProjectUrl>https://github.com/xoofx/markdig</PackageProjectUrl>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
-    <LangVersion>10</LangVersion>
+    <LangVersion>preview</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="4.6.0" />
   </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

@@ -2,8 +2,8 @@
 // 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.CodeAnalysis;
 using System.IO;
-using System.Linq;
 using System.Reflection;
 
 using Markdig.Helpers;
@@ -17,21 +17,15 @@ namespace Markdig;
 /// <summary>
 /// Provides methods for parsing a Markdown string to a syntax tree and converting it to other formats.
 /// </summary>
-public static partial class Markdown
+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;
+    [field: MaybeNull]
+    public static string Version => field ??= typeof(Markdown).Assembly.GetCustomAttribute<AssemblyFileVersionAttribute>()?.Version ?? "Unknown";
 
     internal static readonly MarkdownPipeline DefaultPipeline = new MarkdownPipelineBuilder().Build();
-    private static readonly MarkdownPipeline _defaultTrackTriviaPipeline = new MarkdownPipelineBuilder().EnableTrackTrivia().Build();
+
+    [field: MaybeNull]
+    private static MarkdownPipeline DefaultTrackTriviaPipeline => field ??= new MarkdownPipelineBuilder().EnableTrackTrivia().Build();
 
     private static MarkdownPipeline GetPipeline(MarkdownPipeline? pipeline, string markdown)
     {
@@ -96,8 +90,8 @@ public static partial class Markdown
     /// <param name="markdown">A Markdown text.</param>
     /// <param name="pipeline">The pipeline used for the conversion.</param>
     /// <param name="context">A parser context used for the parsing.</param>
-    /// <returns>The result of the conversion</returns>
-    /// <exception cref="ArgumentNullException">if markdown variable is null</exception>
+    /// <returns>The HTML string.</returns>
+    /// <exception cref="ArgumentNullException">If <paramref name="markdown"/> is null.</exception>
     public static string ToHtml(string markdown, MarkdownPipeline? pipeline = null, MarkdownParserContext? context = null)
     {
         if (markdown is null) ThrowHelper.ArgumentNullException_markdown();
@@ -114,8 +108,8 @@ public static partial class Markdown
     /// </summary>
     /// <param name="document">A Markdown document.</param>
     /// <param name="pipeline">The pipeline used for the conversion.</param>
-    /// <returns>The result of the conversion</returns>
-    /// <exception cref="ArgumentNullException">if markdown document variable is null</exception>
+    /// <returns>The HTML string.</returns>
+    /// <exception cref="ArgumentNullException">If <paramref name="document"/> is null.</exception>
     public static string ToHtml(this MarkdownDocument document, MarkdownPipeline? pipeline = null)
     {
         if (document is null) ThrowHelper.ArgumentNullException(nameof(document));
@@ -137,8 +131,8 @@ public static partial class Markdown
     /// <param name="document">A Markdown document.</param>
     /// <param name="writer">The destination <see cref="TextWriter"/> that will receive the result of the conversion.</param>
     /// <param name="pipeline">The pipeline used for the conversion.</param>
-    /// <returns>The result of the conversion</returns>
-    /// <exception cref="ArgumentNullException">if markdown document variable is null</exception>
+    /// <returns>The HTML string.</returns>
+    /// <exception cref="ArgumentNullException">If <paramref name="document"/> is null.</exception>
     public static void ToHtml(this MarkdownDocument document, TextWriter writer, MarkdownPipeline? pipeline = null)
     {
         if (document is null) ThrowHelper.ArgumentNullException(nameof(document));
@@ -171,11 +165,7 @@ public static partial class Markdown
 
         var document = MarkdownParser.Parse(markdown, pipeline, context);
 
-        using var rentedRenderer = pipeline.RentHtmlRenderer(writer);
-        HtmlRenderer renderer = rentedRenderer.Instance;
-
-        renderer.Render(document);
-        writer.Flush();
+        ToHtml(document, writer, pipeline);
 
         return document;
     }
@@ -212,7 +202,7 @@ public static partial class Markdown
     {
         if (markdown is null) ThrowHelper.ArgumentNullException_markdown();
 
-        MarkdownPipeline? pipeline = trackTrivia ? _defaultTrackTriviaPipeline : null;
+        MarkdownPipeline? pipeline = trackTrivia ? DefaultTrackTriviaPipeline : null;
 
         return Parse(markdown, pipeline);
     }
@@ -268,7 +258,7 @@ public static partial class Markdown
     }
 
     /// <summary>
-    /// Converts a Markdown string to HTML.
+    /// Converts a Markdown string to Plain text by using a <see cref="StringWriter"/> .
     /// </summary>
     /// <param name="markdown">A Markdown text.</param>
     /// <param name="pipeline">The pipeline used for the conversion.</param>

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()
         {
@@ -131,7 +127,7 @@ public sealed class MarkdownPipeline
         }
     }
 
-    internal readonly struct RentedHtmlRenderer : IDisposable
+    internal readonly ref struct RentedHtmlRenderer : IDisposable
     {
         private readonly HtmlRendererCache _cache;
         public readonly HtmlRenderer Instance;

src/Markdig/MarkdownPipelineBuilder.cs

@@ -16,7 +16,7 @@ namespace Markdig;
 /// <remarks>NOTE: A pipeline is not thread-safe.</remarks>
 public class MarkdownPipelineBuilder
 {
-    private MarkdownPipeline? pipeline;
+    private MarkdownPipeline? _pipeline;
 
     /// <summary>
     /// Initializes a new instance of the <see cref="MarkdownPipeline" /> class.
@@ -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>();
     }
@@ -95,9 +95,9 @@ public class MarkdownPipelineBuilder
     /// <exception cref="InvalidOperationException">An extension cannot be null</exception>
     public MarkdownPipeline Build()
     {
-        if (pipeline != null)
+        if (_pipeline != null)
         {
-            return pipeline;
+            return _pipeline;
         }
 
         // TODO: Review the whole initialization process for extensions
@@ -115,7 +115,7 @@ public class MarkdownPipelineBuilder
             extension.Setup(this);
         }
 
-        pipeline = new MarkdownPipeline(
+        _pipeline = new MarkdownPipeline(
             new OrderedList<IMarkdownExtension>(Extensions),
             new BlockParserList(BlockParsers),
             new InlineParserList(InlineParsers),
@@ -125,6 +125,6 @@ public class MarkdownPipelineBuilder
             PreciseSourceLocation = PreciseSourceLocation,
             TrackTrivia = TrackTrivia,
         };
-        return pipeline;
+        return _pipeline;
     }
 }

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.IsWhiteSpaceOrZero() &&
+            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)
@@ -139,9 +139,7 @@ public class HtmlBlockParser : BlockParser
             c = line.NextChar();
         }
 
-        if (
-            !(c == '>' || (!hasLeadingClose && c == '/' && line.PeekChar() == '>') || c.IsWhitespace() ||
-              c == '\0'))
+        if (!(c == '>' || (!hasLeadingClose && c == '/' && line.PeekChar() == '>') || c.IsWhiteSpaceOrZero()))
         {
             return BlockState.None;
         }
@@ -297,7 +295,7 @@ public class HtmlBlockParser : BlockParser
         return BlockState.Continue;
     }
 
-    private static readonly CompactPrefixTree<int> HtmlTags = new(66, 94, 83)
+    private static readonly CompactPrefixTree<int> HtmlTags = new(67, 96, 86)
     {
         { "address", 0 },
         { "article", 1 },
@@ -364,6 +362,7 @@ public class HtmlBlockParser : BlockParser
         { "title", 62 },
         { "tr", 63 },
         { "track", 64 },
-        { "ul", 65 }
+        { "ul", 65 },
+        { "search", 66 },
     };
 }

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();
     }
 }