Bump to 0.18.1

Merge pull request #387 from MihaZupan/descendants-api
Add missing Descendants<T> api
2026-02-10 21:40:00 +00:00 · 2020-01-21 08:30:32 +01:00 · 2020-01-21 08:24:13 +01:00 · 2020-01-21 08:23:48 +01:00 · 2020-01-21 01:31:44 +01:00 · 2020-01-21 01:03:47 +01:00
65 changed files with 3555 additions and 2643 deletions
--- a/.github/FUNDING.yml
+++ b/.github/FUNDING.yml
@@ -0,0 +1,12 @@
+# These are supported funding model platforms
+
+github: [xoofx]
+patreon: # Replace with a single Patreon username
+open_collective: # Replace with a single Open Collective username
+ko_fi: # Replace with a single Ko-fi username
+tidelift: # Replace with a single Tidelift platform-name/package-name e.g., npm/babel
+community_bridge: # Replace with a single Community Bridge project-name e.g., cloud-foundry
+liberapay: # Replace with a single Liberapay username
+issuehunt: # Replace with a single IssueHunt username
+otechie: # Replace with a single Otechie username
+custom: # Replace with up to 4 custom sponsorship URLs e.g., ['link1', 'link2']
--- a/appveyor.yml
+++ b/appveyor.yml
@@ -1,5 +1,5 @@
 version: 10.0.{build}
-image: Visual Studio 2017
+image: Visual Studio 2019
 configuration: Release
 environment:
  COVERALLS_REPO_TOKEN:
--- a/changelog.md
+++ b/changelog.md
@@ -1,5 +1,18 @@
 # Changelog

+## 0.18.1 (21 Jan 2020)
+- Re-allow emojis and smileys customization, that was broken in [PR #308](https://github.com/lunet-io/markdig/pull/308) ([PR #386](https://github.com/lunet-io/markdig/pull/386))
+- Add `IHostProvider` for medialink customization (#337), support protocol-less url (#135) ([(PR #341)](https://github.com/lunet-io/markdig/pull/341))
+- Add missing Descendants<T> overload ([(PR #387)](https://github.com/lunet-io/markdig/pull/387))
+
+## 0.18.0 (24 Oct 2019)
+- Ignore backslashes in GFM AutoLinks ([(PR #357)](https://github.com/lunet-io/markdig/pull/357))
+- Fix SmartyPants quote matching ([(PR #360)](https://github.com/lunet-io/markdig/pull/360))
+- Fix generic attributes with values of length 1 ([(PR #361)](https://github.com/lunet-io/markdig/pull/361))
+- Fix link text balanced bracket matching ([(PR #375)](https://github.com/lunet-io/markdig/pull/375))
+- Improve overall performance and substantially reduce allocations ([(PR #377)](https://github.com/lunet-io/markdig/pull/377))
+
+
 ## 0.17.1 (04 July 2019)
 - Fix regression when escaping HTML characters ([(PR #340)](https://github.com/lunet-io/markdig/pull/340))
 - Update Emoji Dictionary ([(PR #346)](https://github.com/lunet-io/markdig/pull/346))
--- a/src/Markdig.Tests/MiscTests.cs
+++ b/src/Markdig.Tests/MiscTests.cs
@@ -1,5 +1,6 @@
 using System;
 using System.IO;
+using System.Linq;
 using System.Text.RegularExpressions;
 using Markdig.Extensions.AutoLinks;
 using NUnit.Framework;
@@ -8,6 +9,55 @@ namespace Markdig.Tests
 {
    public class MiscTests
    {
+        [TestCase("link [foo [bar]]")] // https://spec.commonmark.org/0.29/#example-508
+        [TestCase("link [foo][bar]")]
+        [TestCase("link [][foo][bar][]")]
+        [TestCase("link [][foo][bar][[]]")]
+        [TestCase("link [foo] [bar]")]
+        [TestCase("link [[foo] [] [bar] [[abc]def]]")]
+        [TestCase("[]")]
+        [TestCase("[ ]")]
+        [TestCase("[bar][]")]
+        [TestCase("[bar][ foo]")]
+        [TestCase("[bar][foo ][]")]
+        [TestCase("[bar][fo[ ]o ][][]")]
+        [TestCase("[a]b[c[d[e]f]g]h")]
+        [TestCase("a[b[c[d]e]f[g]h]i foo [j]k[l[m]n]o")]
+        [TestCase("a[b[c[d]e]f[g]h]i[] [][foo][bar][] foo [j]k[l[m]n]o")]
+        [TestCase("a[b[c[d]e]f[g]h]i foo [j]k[l[m]n]o[][]")]
+        public void LinkTextMayContainBalancedBrackets(string linkText)
+        {
+            string markdown = $"[{linkText}](/uri)";
+            string expected = $@"<p><a href=""/uri"">{linkText}</a></p>";
+
+            TestParser.TestSpec(markdown, expected);
+
+            // Make the link text unbalanced
+            foreach (var bracketIndex in linkText
+                .Select((c, i) => new Tuple<char, int>(c, i))
+                .Where(t => t.Item1 == '[' || t.Item1 == ']')
+                .Select(t => t.Item2))
+            {
+                string brokenLinkText = linkText.Remove(bracketIndex, 1);
+
+                markdown = $"[{brokenLinkText}](/uri)";
+                expected = $@"<p><a href=""/uri"">{brokenLinkText}</a></p>";
+
+                string actual = Markdown.ToHtml(markdown);
+                Assert.AreNotEqual(expected, actual);
+            }
+        }
+
+        [Test]
+        public void IsIssue356Corrected()
+        {
+            string input = @"https://foo.bar/path/\#m4mv5W0GYKZpGvfA.97";
+            string expected = @"<p><a href=""https://foo.bar/path/%5C#m4mv5W0GYKZpGvfA.97"">https://foo.bar/path/\#m4mv5W0GYKZpGvfA.97</a></p>";
+
+            TestParser.TestSpec($"<{input}>", expected);
+            TestParser.TestSpec(input, expected, "autolinks|advanced");
+        }
+
        [Test]
        public void TestAltTextIsCorrectlyEscaped()
        {
--- a/src/Markdig.Tests/Specs/AbbreviationSpecs.generated.cs
+++ b/src/Markdig.Tests/Specs/AbbreviationSpecs.generated.cs
@@ -1,4 +1,4 @@
-// Generated: 2019-04-05 16:06:14
+// Generated: 2019-05-15 02:46:55

 // --------------------------------
 //           Abbreviations
--- a/src/Markdig.Tests/Specs/EmojiSpecs.generated.cs
+++ b/src/Markdig.Tests/Specs/EmojiSpecs.generated.cs
@@ -1,4 +1,4 @@
-// Generated: 2019-04-15 05:20:50
+// Generated: 2020-01-13 21:08:58

 // --------------------------------
 //               Emoji
@@ -18,7 +18,7 @@ namespace Markdig.Tests.Specs.Emoji
        // 
        // ## Emoji
        // 
-        // Emoji and smiley can be converted to their respective unicode characters:
+        // Emoji shortcodes and smileys can be converted to their respective unicode characters:
        [Test]
        public void ExtensionsEmoji_Example001()
        {
@@ -52,7 +52,7 @@ namespace Markdig.Tests.Specs.Emoji
            TestParser.TestSpec("These are not:) an emoji with a:) x:angry:x", "<p>These are not:) an emoji with a:) x:angry:x</p>", "emojis|advanced+emojis");
        }

-        // Emoji can be followed by close punctuation (or any other characters):
+        // Emojis can be followed by close punctuation (or any other characters):
        [Test]
        public void ExtensionsEmoji_Example003()
        {
@@ -69,7 +69,7 @@ namespace Markdig.Tests.Specs.Emoji
            TestParser.TestSpec("We all need :), it makes us :muscle:. (and :ok_hand:).", "<p>We all need 😃, it makes us 💪. (and 👌).</p>", "emojis|advanced+emojis");
        }

-        // Sentences can end with Emoji:
+        // Sentences can end with emojis:
        [Test]
        public void ExtensionsEmoji_Example004()
        {
--- a/src/Markdig.Tests/Specs/EmojiSpecs.md
+++ b/src/Markdig.Tests/Specs/EmojiSpecs.md
@@ -4,7 +4,7 @@ This section describes the different extensions supported:

 ## Emoji

-Emoji and smiley can be converted to their respective unicode characters:
+Emoji shortcodes and smileys can be converted to their respective unicode characters:

 ```````````````````````````````` example
 This is a test with a :) and a :angry: smiley
@@ -20,7 +20,7 @@ These are not:) an emoji with a:) x:angry:x
 <p>These are not:) an emoji with a:) x:angry:x</p>
 ````````````````````````````````

-Emoji can be followed by close punctuation (or any other characters):
+Emojis can be followed by close punctuation (or any other characters):

 ```````````````````````````````` example
 We all need :), it makes us :muscle:. (and :ok_hand:).
@@ -28,7 +28,7 @@ We all need :), it makes us :muscle:. (and :ok_hand:).
 <p>We all need 😃, it makes us 💪. (and 👌).</p>
 ````````````````````````````````

-Sentences can end with Emoji:
+Sentences can end with emojis:

 ```````````````````````````````` example
 This is a sentence :ok_hand:
--- a/src/Markdig.Tests/Specs/GenericAttributesSpecs.generated.cs
+++ b/src/Markdig.Tests/Specs/GenericAttributesSpecs.generated.cs
@@ -1,4 +1,4 @@
-// Generated: 2019-04-05 16:06:14
+// Generated: 2019-08-01 13:57:17

 // --------------------------------
 //        Generic Attributes
@@ -79,5 +79,28 @@ namespace Markdig.Tests.Specs.GenericAttributes
            Console.WriteLine("Example 2\nSection Extensions / Generic Attributes\n");
            TestParser.TestSpec("{#fenced-id .fenced-class}\n~~~\nThis is a fenced with attached attributes\n~~~ ", "<pre><code id=\"fenced-id\" class=\"fenced-class\">This is a fenced with attached attributes\n</code></pre>", "attributes|advanced");
        }
+
+        // Attribute values can be one character long
+        [Test]
+        public void ExtensionsGenericAttributes_Example003()
+        {
+            // Example 3
+            // Section: Extensions / Generic Attributes
+            //
+            // The following Markdown:
+            //     [Foo](url){data-x=1}
+            //     
+            //     [Foo](url){data-x='1'}
+            //     
+            //     [Foo](url){data-x=11}
+            //
+            // Should be rendered as:
+            //     <p><a href="url" data-x="1">Foo</a></p>
+            //     <p><a href="url" data-x="1">Foo</a></p>
+            //     <p><a href="url" data-x="11">Foo</a></p>
+
+            Console.WriteLine("Example 3\nSection Extensions / Generic Attributes\n");
+            TestParser.TestSpec("[Foo](url){data-x=1}\n\n[Foo](url){data-x='1'}\n\n[Foo](url){data-x=11}", "<p><a href=\"url\" data-x=\"1\">Foo</a></p>\n<p><a href=\"url\" data-x=\"1\">Foo</a></p>\n<p><a href=\"url\" data-x=\"11\">Foo</a></p>", "attributes|advanced");
+        }
    }
 }
--- a/src/Markdig.Tests/Specs/GenericAttributesSpecs.md
+++ b/src/Markdig.Tests/Specs/GenericAttributesSpecs.md
@@ -47,3 +47,17 @@ This is a fenced with attached attributes
 <pre><code id="fenced-id" class="fenced-class">This is a fenced with attached attributes
 </code></pre>
 ````````````````````````````````
+
+Attribute values can be one character long
+
+```````````````````````````````` example
+[Foo](url){data-x=1}
+
+[Foo](url){data-x='1'}
+
+[Foo](url){data-x=11}
+.
+<p><a href="url" data-x="1">Foo</a></p>
+<p><a href="url" data-x="1">Foo</a></p>
+<p><a href="url" data-x="11">Foo</a></p>
+````````````````````````````````
--- a/src/Markdig.Tests/Specs/MediaSpecs.generated.cs
+++ b/src/Markdig.Tests/Specs/MediaSpecs.generated.cs
@@ -1,4 +1,4 @@
-// Generated: 2019-04-29 18:40:06
+// Generated: 2019-05-15 02:46:20

 // --------------------------------
 //               Media
@@ -47,19 +47,19 @@ namespace Markdig.Tests.Specs.Media
            //     ![ok.ru](https://ok.ru/video/26870090463)
            //
            // Should be rendered as:
-            //     <p><iframe src="https://www.youtube.com/embed/mswPy5bt3TQ" width="500" height="281" frameborder="0" allowfullscreen=""></iframe></p>
-            //     <p><iframe src="https://www.youtube.com/embed/mswPy5bt3TQ?start=100" width="500" height="281" frameborder="0" allowfullscreen=""></iframe></p>
-            //     <p><iframe src="https://www.youtube.com/embed/mswPy5bt3TQ" width="500" height="281" frameborder="0" allowfullscreen=""></iframe></p>
-            //     <p><iframe src="https://www.youtube.com/embed/mswPy5bt3TQ?start=100" width="500" height="281" frameborder="0" allowfullscreen=""></iframe></p>
-            //     <p><iframe src="https://www.youtube.com/embed/mswPy5bt3TQ?start=100&amp;rel=0" width="500" height="281" frameborder="0" allowfullscreen=""></iframe></p>
-            //     <p><iframe src="https://www.youtube.com/embed?listType=playlist&amp;list=PLC77007E23FF423C6" width="500" height="281" frameborder="0" allowfullscreen=""></iframe></p>
-            //     <p><iframe src="https://player.vimeo.com/video/8607834" width="500" height="281" frameborder="0" allowfullscreen=""></iframe></p>
+            //     <p><iframe src="https://www.youtube.com/embed/mswPy5bt3TQ" width="500" height="281" class="youtube" frameborder="0" allowfullscreen=""></iframe></p>
+            //     <p><iframe src="https://www.youtube.com/embed/mswPy5bt3TQ?start=100" width="500" height="281" class="youtube" frameborder="0" allowfullscreen=""></iframe></p>
+            //     <p><iframe src="https://www.youtube.com/embed/mswPy5bt3TQ" width="500" height="281" class="youtube" frameborder="0" allowfullscreen=""></iframe></p>
+            //     <p><iframe src="https://www.youtube.com/embed/mswPy5bt3TQ?start=100" width="500" height="281" class="youtube" frameborder="0" allowfullscreen=""></iframe></p>
+            //     <p><iframe src="https://www.youtube.com/embed/mswPy5bt3TQ?start=100&amp;rel=0" width="500" height="281" class="youtube" frameborder="0" allowfullscreen=""></iframe></p>
+            //     <p><iframe src="https://www.youtube.com/embed?listType=playlist&amp;list=PLC77007E23FF423C6" width="500" height="281" class="youtube" frameborder="0" allowfullscreen=""></iframe></p>
+            //     <p><iframe src="https://player.vimeo.com/video/8607834" width="500" height="281" class="vimeo" frameborder="0" allowfullscreen=""></iframe></p>
            //     <p><video width="500" height="281" controls=""><source type="video/mp4" src="https://sample.com/video.mp4"></source></video></p>
-            //     <p><iframe src="https://music.yandex.ru/iframe/#track/4402274/411845/" width="500" height="281" frameborder="0"></iframe></p>
-            //     <p><iframe src="https://ok.ru/videoembed/26870090463" width="500" height="281" frameborder="0" allowfullscreen=""></iframe></p>
+            //     <p><iframe src="https://music.yandex.ru/iframe/#track/4402274/411845/" width="500" height="281" class="yandex" frameborder="0"></iframe></p>
+            //     <p><iframe src="https://ok.ru/videoembed/26870090463" width="500" height="281" class="odnoklassniki" frameborder="0" allowfullscreen=""></iframe></p>

            Console.WriteLine("Example 1\nSection Extensions / Media links\n");
-            TestParser.TestSpec("![youtube.com](https://www.youtube.com/watch?v=mswPy5bt3TQ)\n\n![youtube.com with t](https://www.youtube.com/watch?v=mswPy5bt3TQ&t=100)\n\n![youtu.be](https://youtu.be/mswPy5bt3TQ)\n\n![youtu.be with t](https://youtu.be/mswPy5bt3TQ?t=100)\n\n![youtube.com/embed 1](https://www.youtube.com/embed/mswPy5bt3TQ?start=100&rel=0)\n \n![youtube.com/embed 2](https://www.youtube.com/embed?listType=playlist&list=PLC77007E23FF423C6)\n\n![vimeo](https://vimeo.com/8607834)\n\n![static mp4](https://sample.com/video.mp4)\n\n![yandex.ru](https://music.yandex.ru/album/411845/track/4402274)\n\n![ok.ru](https://ok.ru/video/26870090463)", "<p><iframe src=\"https://www.youtube.com/embed/mswPy5bt3TQ\" width=\"500\" height=\"281\" frameborder=\"0\" allowfullscreen=\"\"></iframe></p>\n<p><iframe src=\"https://www.youtube.com/embed/mswPy5bt3TQ?start=100\" width=\"500\" height=\"281\" frameborder=\"0\" allowfullscreen=\"\"></iframe></p>\n<p><iframe src=\"https://www.youtube.com/embed/mswPy5bt3TQ\" width=\"500\" height=\"281\" frameborder=\"0\" allowfullscreen=\"\"></iframe></p>\n<p><iframe src=\"https://www.youtube.com/embed/mswPy5bt3TQ?start=100\" width=\"500\" height=\"281\" frameborder=\"0\" allowfullscreen=\"\"></iframe></p>\n<p><iframe src=\"https://www.youtube.com/embed/mswPy5bt3TQ?start=100&amp;rel=0\" width=\"500\" height=\"281\" frameborder=\"0\" allowfullscreen=\"\"></iframe></p>\n<p><iframe src=\"https://www.youtube.com/embed?listType=playlist&amp;list=PLC77007E23FF423C6\" width=\"500\" height=\"281\" frameborder=\"0\" allowfullscreen=\"\"></iframe></p>\n<p><iframe src=\"https://player.vimeo.com/video/8607834\" width=\"500\" height=\"281\" frameborder=\"0\" allowfullscreen=\"\"></iframe></p>\n<p><video width=\"500\" height=\"281\" controls=\"\"><source type=\"video/mp4\" src=\"https://sample.com/video.mp4\"></source></video></p>\n<p><iframe src=\"https://music.yandex.ru/iframe/#track/4402274/411845/\" width=\"500\" height=\"281\" frameborder=\"0\"></iframe></p>\n<p><iframe src=\"https://ok.ru/videoembed/26870090463\" width=\"500\" height=\"281\" frameborder=\"0\" allowfullscreen=\"\"></iframe></p>", "medialinks|advanced+medialinks");
+            TestParser.TestSpec("![youtube.com](https://www.youtube.com/watch?v=mswPy5bt3TQ)\n\n![youtube.com with t](https://www.youtube.com/watch?v=mswPy5bt3TQ&t=100)\n\n![youtu.be](https://youtu.be/mswPy5bt3TQ)\n\n![youtu.be with t](https://youtu.be/mswPy5bt3TQ?t=100)\n\n![youtube.com/embed 1](https://www.youtube.com/embed/mswPy5bt3TQ?start=100&rel=0)\n \n![youtube.com/embed 2](https://www.youtube.com/embed?listType=playlist&list=PLC77007E23FF423C6)\n\n![vimeo](https://vimeo.com/8607834)\n\n![static mp4](https://sample.com/video.mp4)\n\n![yandex.ru](https://music.yandex.ru/album/411845/track/4402274)\n\n![ok.ru](https://ok.ru/video/26870090463)", "<p><iframe src=\"https://www.youtube.com/embed/mswPy5bt3TQ\" width=\"500\" height=\"281\" class=\"youtube\" frameborder=\"0\" allowfullscreen=\"\"></iframe></p>\n<p><iframe src=\"https://www.youtube.com/embed/mswPy5bt3TQ?start=100\" width=\"500\" height=\"281\" class=\"youtube\" frameborder=\"0\" allowfullscreen=\"\"></iframe></p>\n<p><iframe src=\"https://www.youtube.com/embed/mswPy5bt3TQ\" width=\"500\" height=\"281\" class=\"youtube\" frameborder=\"0\" allowfullscreen=\"\"></iframe></p>\n<p><iframe src=\"https://www.youtube.com/embed/mswPy5bt3TQ?start=100\" width=\"500\" height=\"281\" class=\"youtube\" frameborder=\"0\" allowfullscreen=\"\"></iframe></p>\n<p><iframe src=\"https://www.youtube.com/embed/mswPy5bt3TQ?start=100&amp;rel=0\" width=\"500\" height=\"281\" class=\"youtube\" frameborder=\"0\" allowfullscreen=\"\"></iframe></p>\n<p><iframe src=\"https://www.youtube.com/embed?listType=playlist&amp;list=PLC77007E23FF423C6\" width=\"500\" height=\"281\" class=\"youtube\" frameborder=\"0\" allowfullscreen=\"\"></iframe></p>\n<p><iframe src=\"https://player.vimeo.com/video/8607834\" width=\"500\" height=\"281\" class=\"vimeo\" frameborder=\"0\" allowfullscreen=\"\"></iframe></p>\n<p><video width=\"500\" height=\"281\" controls=\"\"><source type=\"video/mp4\" src=\"https://sample.com/video.mp4\"></source></video></p>\n<p><iframe src=\"https://music.yandex.ru/iframe/#track/4402274/411845/\" width=\"500\" height=\"281\" class=\"yandex\" frameborder=\"0\"></iframe></p>\n<p><iframe src=\"https://ok.ru/videoembed/26870090463\" width=\"500\" height=\"281\" class=\"odnoklassniki\" frameborder=\"0\" allowfullscreen=\"\"></iframe></p>", "medialinks|advanced+medialinks");
        }
    }
 }
--- a/src/Markdig.Tests/Specs/MediaSpecs.md
+++ b/src/Markdig.Tests/Specs/MediaSpecs.md
@@ -27,14 +27,14 @@ Allows to embed audio/video links to popular website:

 ![ok.ru](https://ok.ru/video/26870090463)
 .
-<p><iframe src="https://www.youtube.com/embed/mswPy5bt3TQ" width="500" height="281" frameborder="0" allowfullscreen=""></iframe></p>
-<p><iframe src="https://www.youtube.com/embed/mswPy5bt3TQ?start=100" width="500" height="281" frameborder="0" allowfullscreen=""></iframe></p>
-<p><iframe src="https://www.youtube.com/embed/mswPy5bt3TQ" width="500" height="281" frameborder="0" allowfullscreen=""></iframe></p>
-<p><iframe src="https://www.youtube.com/embed/mswPy5bt3TQ?start=100" width="500" height="281" frameborder="0" allowfullscreen=""></iframe></p>
-<p><iframe src="https://www.youtube.com/embed/mswPy5bt3TQ?start=100&amp;rel=0" width="500" height="281" frameborder="0" allowfullscreen=""></iframe></p>
-<p><iframe src="https://www.youtube.com/embed?listType=playlist&amp;list=PLC77007E23FF423C6" width="500" height="281" frameborder="0" allowfullscreen=""></iframe></p>
-<p><iframe src="https://player.vimeo.com/video/8607834" width="500" height="281" frameborder="0" allowfullscreen=""></iframe></p>
+<p><iframe src="https://www.youtube.com/embed/mswPy5bt3TQ" width="500" height="281" class="youtube" frameborder="0" allowfullscreen=""></iframe></p>
+<p><iframe src="https://www.youtube.com/embed/mswPy5bt3TQ?start=100" width="500" height="281" class="youtube" frameborder="0" allowfullscreen=""></iframe></p>
+<p><iframe src="https://www.youtube.com/embed/mswPy5bt3TQ" width="500" height="281" class="youtube" frameborder="0" allowfullscreen=""></iframe></p>
+<p><iframe src="https://www.youtube.com/embed/mswPy5bt3TQ?start=100" width="500" height="281" class="youtube" frameborder="0" allowfullscreen=""></iframe></p>
+<p><iframe src="https://www.youtube.com/embed/mswPy5bt3TQ?start=100&amp;rel=0" width="500" height="281" class="youtube" frameborder="0" allowfullscreen=""></iframe></p>
+<p><iframe src="https://www.youtube.com/embed?listType=playlist&amp;list=PLC77007E23FF423C6" width="500" height="281" class="youtube" frameborder="0" allowfullscreen=""></iframe></p>
+<p><iframe src="https://player.vimeo.com/video/8607834" width="500" height="281" class="vimeo" frameborder="0" allowfullscreen=""></iframe></p>
 <p><video width="500" height="281" controls=""><source type="video/mp4" src="https://sample.com/video.mp4"></source></video></p>
-<p><iframe src="https://music.yandex.ru/iframe/#track/4402274/411845/" width="500" height="281" frameborder="0"></iframe></p>
-<p><iframe src="https://ok.ru/videoembed/26870090463" width="500" height="281" frameborder="0" allowfullscreen=""></iframe></p>
+<p><iframe src="https://music.yandex.ru/iframe/#track/4402274/411845/" width="500" height="281" class="yandex" frameborder="0"></iframe></p>
+<p><iframe src="https://ok.ru/videoembed/26870090463" width="500" height="281" class="odnoklassniki" frameborder="0" allowfullscreen=""></iframe></p>
 ````````````````````````````````
--- a/src/Markdig.Tests/Specs/SmartyPantsSpecs.generated.cs
+++ b/src/Markdig.Tests/Specs/SmartyPantsSpecs.generated.cs
@@ -1,4 +1,4 @@
-// Generated: 2019-04-05 16:06:14
+// Generated: 2019-08-01 12:33:23

 // --------------------------------
 //           Smarty Pants
@@ -140,13 +140,13 @@ namespace Markdig.Tests.Specs.SmartyPants
            // Section: Extensions / SmartyPants Quotes
            //
            // The following Markdown:
-            //     This is a 'text <<with' a another text>>
+            //     This is 'a "text 'with" a another text'
            //
            // Should be rendered as:
-            //     <p>This is a &lsquo;text &lt;&lt;with&rsquo; a another text&gt;&gt;</p>
+            //     <p>This is &lsquo;a &ldquo;text 'with&rdquo; a another text&rsquo;</p>

            Console.WriteLine("Example 8\nSection Extensions / SmartyPants Quotes\n");
-            TestParser.TestSpec("This is a 'text <<with' a another text>>", "<p>This is a &lsquo;text &lt;&lt;with&rsquo; a another text&gt;&gt;</p>", "pipetables+smartypants|advanced+smartypants");
+            TestParser.TestSpec("This is 'a \"text 'with\" a another text'", "<p>This is &lsquo;a &ldquo;text 'with&rdquo; a another text&rsquo;</p>", "pipetables+smartypants|advanced+smartypants");
        }

        [Test]
@@ -156,20 +156,36 @@ namespace Markdig.Tests.Specs.SmartyPants
            // Section: Extensions / SmartyPants Quotes
            //
            // The following Markdown:
+            //     This is a 'text <<with' a another text>>
+            //
+            // Should be rendered as:
+            //     <p>This is a &lsquo;text &lt;&lt;with&rsquo; a another text&gt;&gt;</p>
+
+            Console.WriteLine("Example 9\nSection Extensions / SmartyPants Quotes\n");
+            TestParser.TestSpec("This is a 'text <<with' a another text>>", "<p>This is a &lsquo;text &lt;&lt;with&rsquo; a another text&gt;&gt;</p>", "pipetables+smartypants|advanced+smartypants");
+        }
+
+        [Test]
+        public void ExtensionsSmartyPantsQuotes_Example010()
+        {
+            // Example 10
+            // Section: Extensions / SmartyPants Quotes
+            //
+            // The following Markdown:
            //     This is a <<text 'with>> a another text'
            //
            // Should be rendered as:
            //     <p>This is a &laquo;text 'with&raquo; a another text'</p>

-            Console.WriteLine("Example 9\nSection Extensions / SmartyPants Quotes\n");
+            Console.WriteLine("Example 10\nSection Extensions / SmartyPants Quotes\n");
            TestParser.TestSpec("This is a <<text 'with>> a another text'", "<p>This is a &laquo;text 'with&raquo; a another text'</p>", "pipetables+smartypants|advanced+smartypants");
        }

        // Quotes requires to have the same rules than emphasis `_` regarding left/right frankling rules:
        [Test]
-        public void ExtensionsSmartyPantsQuotes_Example010()
+        public void ExtensionsSmartyPantsQuotes_Example011()
        {
-            // Example 10
+            // Example 11
            // Section: Extensions / SmartyPants Quotes
            //
            // The following Markdown:
@@ -178,24 +194,8 @@ namespace Markdig.Tests.Specs.SmartyPants
            // Should be rendered as:
            //     <p>It's not quotes'</p>

-            Console.WriteLine("Example 10\nSection Extensions / SmartyPants Quotes\n");
-            TestParser.TestSpec("It's not quotes'", "<p>It's not quotes'</p>", "pipetables+smartypants|advanced+smartypants");
-        }
-
-        [Test]
-        public void ExtensionsSmartyPantsQuotes_Example011()
-        {
-            // Example 11
-            // Section: Extensions / SmartyPants Quotes
-            //
-            // The following Markdown:
-            //     They are ' not matching quotes '
-            //
-            // Should be rendered as:
-            //     <p>They are ' not matching quotes '</p>
-
            Console.WriteLine("Example 11\nSection Extensions / SmartyPants Quotes\n");
-            TestParser.TestSpec("They are ' not matching quotes '", "<p>They are ' not matching quotes '</p>", "pipetables+smartypants|advanced+smartypants");
+            TestParser.TestSpec("It's not quotes'", "<p>It's not quotes'</p>", "pipetables+smartypants|advanced+smartypants");
        }

        [Test]
@@ -205,20 +205,36 @@ namespace Markdig.Tests.Specs.SmartyPants
            // Section: Extensions / SmartyPants Quotes
            //
            // The following Markdown:
+            //     They are ' not matching quotes '
+            //
+            // Should be rendered as:
+            //     <p>They are ' not matching quotes '</p>
+
+            Console.WriteLine("Example 12\nSection Extensions / SmartyPants Quotes\n");
+            TestParser.TestSpec("They are ' not matching quotes '", "<p>They are ' not matching quotes '</p>", "pipetables+smartypants|advanced+smartypants");
+        }
+
+        [Test]
+        public void ExtensionsSmartyPantsQuotes_Example013()
+        {
+            // Example 13
+            // Section: Extensions / SmartyPants Quotes
+            //
+            // The following Markdown:
            //     They are' not matching 'quotes
            //
            // Should be rendered as:
            //     <p>They are' not matching 'quotes</p>

-            Console.WriteLine("Example 12\nSection Extensions / SmartyPants Quotes\n");
+            Console.WriteLine("Example 13\nSection Extensions / SmartyPants Quotes\n");
            TestParser.TestSpec("They are' not matching 'quotes", "<p>They are' not matching 'quotes</p>", "pipetables+smartypants|advanced+smartypants");
        }

        // An emphasis starting inside left/right quotes will span over the right quote:
        [Test]
-        public void ExtensionsSmartyPantsQuotes_Example013()
+        public void ExtensionsSmartyPantsQuotes_Example014()
        {
-            // Example 13
+            // Example 14
            // Section: Extensions / SmartyPants Quotes
            //
            // The following Markdown:
@@ -227,9 +243,26 @@ namespace Markdig.Tests.Specs.SmartyPants
            // Should be rendered as:
            //     <p>This is &ldquo;a <em>text&rdquo; with an emphasis</em></p>

-            Console.WriteLine("Example 13\nSection Extensions / SmartyPants Quotes\n");
+            Console.WriteLine("Example 14\nSection Extensions / SmartyPants Quotes\n");
            TestParser.TestSpec("This is \"a *text\" with an emphasis*", "<p>This is &ldquo;a <em>text&rdquo; with an emphasis</em></p>", "pipetables+smartypants|advanced+smartypants");
        }
+
+        // Multiple sets of quotes can be used
+        [Test]
+        public void ExtensionsSmartyPantsQuotes_Example015()
+        {
+            // Example 15
+            // Section: Extensions / SmartyPants Quotes
+            //
+            // The following Markdown:
+            //     "aaa" "bbb" "ccc" "ddd"
+            //
+            // Should be rendered as:
+            //     <p>&ldquo;aaa&rdquo; &ldquo;bbb&rdquo; &ldquo;ccc&rdquo; &ldquo;ddd&rdquo;</p>
+
+            Console.WriteLine("Example 15\nSection Extensions / SmartyPants Quotes\n");
+            TestParser.TestSpec("\"aaa\" \"bbb\" \"ccc\" \"ddd\"", "<p>&ldquo;aaa&rdquo; &ldquo;bbb&rdquo; &ldquo;ccc&rdquo; &ldquo;ddd&rdquo;</p>", "pipetables+smartypants|advanced+smartypants");
+        }
    }

    [TestFixture]
@@ -237,9 +270,9 @@ namespace Markdig.Tests.Specs.SmartyPants
    {
        // ## SmartyPants Separators
        [Test]
-        public void ExtensionsSmartyPantsSeparators_Example014()
+        public void ExtensionsSmartyPantsSeparators_Example016()
        {
-            // Example 14
+            // Example 16
            // Section: Extensions / SmartyPants Separators
            //
            // The following Markdown:
@@ -248,14 +281,14 @@ namespace Markdig.Tests.Specs.SmartyPants
            // Should be rendered as:
            //     <p>This is a &ndash; text</p>

-            Console.WriteLine("Example 14\nSection Extensions / SmartyPants Separators\n");
+            Console.WriteLine("Example 16\nSection Extensions / SmartyPants Separators\n");
            TestParser.TestSpec("This is a -- text", "<p>This is a &ndash; text</p>", "pipetables+smartypants|advanced+smartypants");
        }

        [Test]
-        public void ExtensionsSmartyPantsSeparators_Example015()
+        public void ExtensionsSmartyPantsSeparators_Example017()
        {
-            // Example 15
+            // Example 17
            // Section: Extensions / SmartyPants Separators
            //
            // The following Markdown:
@@ -264,14 +297,14 @@ namespace Markdig.Tests.Specs.SmartyPants
            // Should be rendered as:
            //     <p>This is a &mdash; text</p>

-            Console.WriteLine("Example 15\nSection Extensions / SmartyPants Separators\n");
+            Console.WriteLine("Example 17\nSection Extensions / SmartyPants Separators\n");
            TestParser.TestSpec("This is a --- text", "<p>This is a &mdash; text</p>", "pipetables+smartypants|advanced+smartypants");
        }

        [Test]
-        public void ExtensionsSmartyPantsSeparators_Example016()
+        public void ExtensionsSmartyPantsSeparators_Example018()
        {
-            // Example 16
+            // Example 18
            // Section: Extensions / SmartyPants Separators
            //
            // The following Markdown:
@@ -280,15 +313,15 @@ namespace Markdig.Tests.Specs.SmartyPants
            // Should be rendered as:
            //     <p>This is a en ellipsis&hellip;</p>

-            Console.WriteLine("Example 16\nSection Extensions / SmartyPants Separators\n");
+            Console.WriteLine("Example 18\nSection Extensions / SmartyPants Separators\n");
            TestParser.TestSpec("This is a en ellipsis...", "<p>This is a en ellipsis&hellip;</p>", "pipetables+smartypants|advanced+smartypants");
        }

        // Check that a smartypants are not breaking pipetable parsing:
        [Test]
-        public void ExtensionsSmartyPantsSeparators_Example017()
+        public void ExtensionsSmartyPantsSeparators_Example019()
        {
-            // Example 17
+            // Example 19
            // Section: Extensions / SmartyPants Separators
            //
            // The following Markdown:
@@ -312,15 +345,15 @@ namespace Markdig.Tests.Specs.SmartyPants
            //     </tbody>
            //     </table>

-            Console.WriteLine("Example 17\nSection Extensions / SmartyPants Separators\n");
+            Console.WriteLine("Example 19\nSection Extensions / SmartyPants Separators\n");
            TestParser.TestSpec("a  | b\n-- | --\n0  | 1", "<table>\n<thead>\n<tr>\n<th>a</th>\n<th>b</th>\n</tr>\n</thead>\n<tbody>\n<tr>\n<td>0</td>\n<td>1</td>\n</tr>\n</tbody>\n</table>", "pipetables+smartypants|advanced+smartypants");
        }

        // Check quotes and dash:
        [Test]
-        public void ExtensionsSmartyPantsSeparators_Example018()
+        public void ExtensionsSmartyPantsSeparators_Example020()
        {
-            // Example 18
+            // Example 20
            // Section: Extensions / SmartyPants Separators
            //
            // The following Markdown:
@@ -329,7 +362,7 @@ namespace Markdig.Tests.Specs.SmartyPants
            // Should be rendered as:
            //     <p>A &ldquo;quote&rdquo; with a &mdash;</p>

-            Console.WriteLine("Example 18\nSection Extensions / SmartyPants Separators\n");
+            Console.WriteLine("Example 20\nSection Extensions / SmartyPants Separators\n");
            TestParser.TestSpec("A \"quote\" with a ---", "<p>A &ldquo;quote&rdquo; with a &mdash;</p>", "pipetables+smartypants|advanced+smartypants");
        }
    }
--- a/src/Markdig.Tests/Specs/SmartyPantsSpecs.md
+++ b/src/Markdig.Tests/Specs/SmartyPantsSpecs.md
@@ -52,6 +52,12 @@ This is a "text 'with" a another text'
 <p>This is a &ldquo;text 'with&rdquo; a another text'</p>
 ````````````````````````````````

+```````````````````````````````` example
+This is 'a "text 'with" a another text'
+.
+<p>This is &lsquo;a &ldquo;text 'with&rdquo; a another text&rsquo;</p>
+````````````````````````````````
+
 ```````````````````````````````` example
 This is a 'text <<with' a another text>>
 .
@@ -91,6 +97,14 @@ This is "a *text" with an emphasis*
 <p>This is &ldquo;a <em>text&rdquo; with an emphasis</em></p>
 ````````````````````````````````

+Multiple sets of quotes can be used
+
+```````````````````````````````` example
+"aaa" "bbb" "ccc" "ddd"
+.
+<p>&ldquo;aaa&rdquo; &ldquo;bbb&rdquo; &ldquo;ccc&rdquo; &ldquo;ddd&rdquo;</p>
+````````````````````````````````
+
 ## SmartyPants Separators

 ```````````````````````````````` example
--- a/src/Markdig.Tests/TestCustomEmojis.cs
+++ b/src/Markdig.Tests/TestCustomEmojis.cs
@@ -0,0 +1,99 @@
+using System.Collections.Generic;
+using Markdig.Extensions.Emoji;
+using NUnit.Framework;
+
+namespace Markdig.Tests
+{
+    [TestFixture]
+    public class TestCustomEmojis
+    {
+        [Test]
+        [TestCase(":smiley:", "<p>♥</p>\n")]
+        [TestCase(":confused:", "<p>:confused:</p>\n")] // default emoji does not work
+        [TestCase(":/", "<p>:/</p>\n")] // default smiley does not work
+        public void TestCustomEmoji(string input, string expected)
+        {
+            var emojiToUnicode = new Dictionary<string, string>();
+            var smileyToEmoji = new Dictionary<string, string>();
+
+            emojiToUnicode[":smiley:"] = "♥";
+
+            var customMapping = new EmojiMapping(emojiToUnicode, smileyToEmoji);
+
+            var pipeline = new MarkdownPipelineBuilder()
+                .UseEmojiAndSmiley(customEmojiMapping: customMapping)
+                .Build();
+
+            var actual = Markdown.ToHtml(input, pipeline);
+            Assert.AreEqual(expected, actual);
+        }
+
+        [Test]
+        [TestCase(":testheart:", "<p>♥</p>\n")]
+        [TestCase("hello", "<p>♥</p>\n")]
+        [TestCase(":confused:", "<p>:confused:</p>\n")] // default emoji does not work
+        [TestCase(":/", "<p>:/</p>\n")] // default smiley does not work
+        public void TestCustomSmiley(string input, string expected)
+        {
+            var emojiToUnicode = new Dictionary<string, string>();
+            var smileyToEmoji = new Dictionary<string, string>();
+
+            emojiToUnicode[":testheart:"] = "♥";
+            smileyToEmoji["hello"] = ":testheart:";
+
+            var customMapping = new EmojiMapping(emojiToUnicode, smileyToEmoji);
+
+            var pipeline = new MarkdownPipelineBuilder()
+                .UseEmojiAndSmiley(customEmojiMapping: customMapping)
+                .Build();
+
+            var actual = Markdown.ToHtml(input, pipeline);
+            Assert.AreEqual(expected, actual);
+        }
+
+        [Test]
+        [TestCase(":smiley:", "<p>♥</p>\n")]
+        [TestCase(":)", "<p>♥</p>\n")]
+        [TestCase(":confused:", "<p>😕</p>\n")] // default emoji still works
+        [TestCase(":/", "<p>😕</p>\n")] // default smiley still works
+        public void TestOverrideDefaultWithCustomEmoji(string input, string expected)
+        {
+            var emojiToUnicode = EmojiMapping.GetDefaultEmojiShortcodeToUnicode();
+            var smileyToEmoji = EmojiMapping.GetDefaultSmileyToEmojiShortcode();
+
+            emojiToUnicode[":smiley:"] = "♥";
+
+            var customMapping = new EmojiMapping(emojiToUnicode, smileyToEmoji);
+
+            var pipeline = new MarkdownPipelineBuilder()
+                .UseEmojiAndSmiley(customEmojiMapping: customMapping)
+                .Build();
+
+            var actual = Markdown.ToHtml(input, pipeline);
+            Assert.AreEqual(expected, actual);
+        }
+
+        [Test]
+        [TestCase(":testheart:", "<p>♥</p>\n")]
+        [TestCase("hello", "<p>♥</p>\n")]
+        [TestCase(":confused:", "<p>😕</p>\n")] // default emoji still works
+        [TestCase(":/", "<p>😕</p>\n")] // default smiley still works
+        public void TestOverrideDefaultWithCustomSmiley(string input, string expected)
+        {
+            var emojiToUnicode = EmojiMapping.GetDefaultEmojiShortcodeToUnicode();
+            var smileyToEmoji = EmojiMapping.GetDefaultSmileyToEmojiShortcode();
+
+            emojiToUnicode[":testheart:"] = "♥";
+            smileyToEmoji["hello"] = ":testheart:";
+
+            var customMapping = new EmojiMapping(emojiToUnicode, smileyToEmoji);
+
+            var pipeline = new MarkdownPipelineBuilder()
+                .UseEmojiAndSmiley(customEmojiMapping: customMapping)
+                .Build();
+
+            var actual = Markdown.ToHtml(input, pipeline);
+            Assert.AreEqual(expected, actual);
+        }
+    }
+}
--- a/src/Markdig.Tests/TestDescendantsOrder.cs
+++ b/src/Markdig.Tests/TestDescendantsOrder.cs
@@ -3,6 +3,7 @@ using Markdig.Syntax;
 using Markdig.Syntax.Inlines;
 using System.Linq;
 using System.Collections.Generic;
+using Markdig.Helpers;

 namespace Markdig.Tests
 {
@@ -12,24 +13,91 @@ namespace Markdig.Tests
        [Test]
        public void TestSchemas()
        {
-            foreach (var markdown in TestParser.SpecsMarkdown)
+            foreach (var syntaxTree in TestParser.SpecsSyntaxTrees)
            {
-                AssertSameDescendantsOrder(markdown);
+                AssertIEnumerablesAreEqual(
+                    Descendants_Legacy(syntaxTree),
+                    syntaxTree.Descendants());
+
+                AssertIEnumerablesAreEqual(
+                    syntaxTree.Descendants().OfType<ParagraphBlock>(),
+                    syntaxTree.Descendants<ParagraphBlock>());
+
+                AssertIEnumerablesAreEqual(
+                    syntaxTree.Descendants().OfType<ParagraphBlock>(),
+                    (syntaxTree as ContainerBlock).Descendants<ParagraphBlock>());
+
+                AssertIEnumerablesAreEqual(
+                    syntaxTree.Descendants().OfType<LiteralInline>(),
+                    syntaxTree.Descendants<LiteralInline>());
+
+                foreach (LiteralInline literalInline in syntaxTree.Descendants<LiteralInline>())
+                {
+                    Assert.AreSame(ArrayHelper<ListBlock>.Empty, literalInline.Descendants<ListBlock>());
+                    Assert.AreSame(ArrayHelper<ParagraphBlock>.Empty, literalInline.Descendants<ParagraphBlock>());
+                    Assert.AreSame(ArrayHelper<ContainerInline>.Empty, literalInline.Descendants<ContainerInline>());
+                }
+
+                foreach (ContainerInline containerInline in syntaxTree.Descendants<ContainerInline>())
+                {
+                    AssertIEnumerablesAreEqual(
+                        containerInline.FindDescendants<LiteralInline>(),
+                        containerInline.Descendants<LiteralInline>());
+
+                    AssertIEnumerablesAreEqual(
+                        containerInline.FindDescendants<LiteralInline>(),
+                        (containerInline as MarkdownObject).Descendants<LiteralInline>());
+
+                    if (containerInline.FirstChild is null)
+                    {
+                        Assert.AreSame(ArrayHelper<LiteralInline>.Empty, containerInline.Descendants<LiteralInline>());
+                        Assert.AreSame(ArrayHelper<LiteralInline>.Empty, containerInline.FindDescendants<LiteralInline>());
+                        Assert.AreSame(ArrayHelper<LiteralInline>.Empty, (containerInline as MarkdownObject).Descendants<LiteralInline>());
+                    }
+
+                    Assert.AreSame(ArrayHelper<ListBlock>.Empty, containerInline.Descendants<ListBlock>());
+                    Assert.AreSame(ArrayHelper<ParagraphBlock>.Empty, containerInline.Descendants<ParagraphBlock>());
+                }
+
+                foreach (ParagraphBlock paragraphBlock in syntaxTree.Descendants<ParagraphBlock>())
+                {
+                    AssertIEnumerablesAreEqual(
+                        (paragraphBlock as MarkdownObject).Descendants<LiteralInline>(),
+                        paragraphBlock.Descendants<LiteralInline>());
+
+                    Assert.AreSame(ArrayHelper<ParagraphBlock>.Empty, paragraphBlock.Descendants<ParagraphBlock>());
+                }
+
+                foreach (ContainerBlock containerBlock in syntaxTree.Descendants<ContainerBlock>())
+                {
+                    AssertIEnumerablesAreEqual(
+                        containerBlock.Descendants<LiteralInline>(),
+                        (containerBlock as MarkdownObject).Descendants<LiteralInline>());
+
+                    AssertIEnumerablesAreEqual(
+                        containerBlock.Descendants<ParagraphBlock>(),
+                        (containerBlock as MarkdownObject).Descendants<ParagraphBlock>());
+
+                    if (containerBlock.Count == 0)
+                    {
+                        Assert.AreSame(ArrayHelper<LiteralInline>.Empty, containerBlock.Descendants<LiteralInline>());
+                        Assert.AreSame(ArrayHelper<LiteralInline>.Empty, (containerBlock as Block).Descendants<LiteralInline>());
+                        Assert.AreSame(ArrayHelper<LiteralInline>.Empty, (containerBlock as MarkdownObject).Descendants<LiteralInline>());
+                    }
+                }
            }
        }

-        private void AssertSameDescendantsOrder(string markdown)
+        private static void AssertIEnumerablesAreEqual<T>(IEnumerable<T> first, IEnumerable<T> second)
        {
-            var syntaxTree = Markdown.Parse(markdown, new MarkdownPipelineBuilder().UseAdvancedExtensions().Build());
+            var firstList = new List<T>(first);
+            var secondList = new List<T>(second);

-            var descendants_legacy = Descendants_Legacy(syntaxTree).ToList();
-            var descendants_new = syntaxTree.Descendants().ToList();
+            Assert.AreEqual(firstList.Count, secondList.Count);

-            Assert.AreEqual(descendants_legacy.Count, descendants_new.Count);
-
-            for (int i = 0; i < descendants_legacy.Count; i++)
+            for (int i = 0; i < firstList.Count; i++)
            {
-                Assert.AreSame(descendants_legacy[i], descendants_new[i]);
+                Assert.AreSame(firstList[i], secondList[i]);
            }
        }

--- a/src/Markdig.Tests/TestMediaLinks.cs
+++ b/src/Markdig.Tests/TestMediaLinks.cs
@@ -0,0 +1,87 @@
+using Markdig.Extensions.MediaLinks;
+using NUnit.Framework;
+using System;
+using System.Text.RegularExpressions;
+
+namespace Markdig.Tests
+{
+    [TestFixture]
+    public class TestMediaLinks
+    {
+        private MarkdownPipeline GetPipeline(MediaOptions options = null)
+        {
+            return new MarkdownPipelineBuilder()
+                 .UseMediaLinks(options)
+                 .Build();
+        }
+
+        [Test]
+        [TestCase("![static mp4](https://sample.com/video.mp4)", "<p><video width=\"500\" height=\"281\" controls=\"\"><source type=\"video/mp4\" src=\"https://sample.com/video.mp4\"></source></video></p>\n")]
+        [TestCase("![static mp4](//sample.com/video.mp4)", "<p><video width=\"500\" height=\"281\" controls=\"\"><source type=\"video/mp4\" src=\"//sample.com/video.mp4\"></source></video></p>\n")]
+        [TestCase(@"![youtube.com](https://www.youtube.com/watch?v=mswPy5bt3TQ)", "<p><iframe src=\"https://www.youtube.com/embed/mswPy5bt3TQ\" width=\"500\" height=\"281\" class=\"youtube\" frameborder=\"0\" allowfullscreen=\"\"></iframe></p>\n")]
+        [TestCase("![yandex.ru](https://music.yandex.ru/album/411845/track/4402274)", "<p><iframe src=\"https://music.yandex.ru/iframe/#track/4402274/411845/\" width=\"500\" height=\"281\" class=\"yandex\" frameborder=\"0\"></iframe></p>\n")]
+        [TestCase("![vimeo](https://vimeo.com/8607834)", "<p><iframe src=\"https://player.vimeo.com/video/8607834\" width=\"500\" height=\"281\" class=\"vimeo\" frameborder=\"0\" allowfullscreen=\"\"></iframe></p>\n")]
+        [TestCase("![ok.ru](https://ok.ru/video/26870090463)", "<p><iframe src=\"https://ok.ru/videoembed/26870090463\" width=\"500\" height=\"281\" class=\"odnoklassniki\" frameborder=\"0\" allowfullscreen=\"\"></iframe></p>\n")]
+        [TestCase("![ok.ru](//ok.ru/video/26870090463)", "<p><iframe src=\"https://ok.ru/videoembed/26870090463\" width=\"500\" height=\"281\" class=\"odnoklassniki\" frameborder=\"0\" allowfullscreen=\"\"></iframe></p>\n")]
+        public void TestBuiltInHosts(string markdown, string expected)
+        {
+            string html = Markdown.ToHtml(markdown, GetPipeline());
+            Assert.AreEqual(html, expected);
+        }
+
+        private class TestHostProvider : IHostProvider
+        {
+            public string Class { get; } = "regex";
+            public bool AllowFullScreen { get; }
+
+            public bool TryHandle(Uri mediaUri, bool isSchemaRelative, out string iframeUrl)
+            {
+                iframeUrl = null;
+                var uri = isSchemaRelative ? "//" + mediaUri.GetComponents(UriComponents.AbsoluteUri & ~UriComponents.Scheme, UriFormat.UriEscaped) : mediaUri.ToString();
+                if (!matcher.IsMatch(uri))
+                    return false;
+                iframeUrl = matcher.Replace(uri, replacement);
+                return true;
+            }
+
+            private Regex matcher;
+            private string replacement;
+
+            public TestHostProvider(string provider, string replace)
+            {
+                matcher = new Regex(provider);
+                replacement = replace;
+            }
+        }
+
+        [Test]
+        [TestCase("![p1](https://sample.com/video.mp4)", "<p><iframe src=\"https://example.com/video.mp4\" width=\"500\" height=\"281\" class=\"regex\" frameborder=\"0\"></iframe></p>\n", @"^https?://sample.com/(.+)$", @"https://example.com/$1")]
+        [TestCase("![p1](//sample.com/video.mp4)", "<p><iframe src=\"https://example.com/video.mp4\" width=\"500\" height=\"281\" class=\"regex\" frameborder=\"0\"></iframe></p>\n", @"^//sample.com/(.+)$", @"https://example.com/$1")]
+        [TestCase("![p1](https://sample.com/video.mp4)", "<p><iframe src=\"https://example.com/video.mp4?token=aaabbb\" width=\"500\" height=\"281\" class=\"regex\" frameborder=\"0\"></iframe></p>\n", @"^https?://sample.com/(.+)$", @"https://example.com/$1?token=aaabbb")]
+        public void TestCustomHostProvider(string markdown, string expected, string provider, string replace)
+        {
+            string html = Markdown.ToHtml(markdown, GetPipeline(new MediaOptions
+            {
+                Hosts =
+                {
+                    new TestHostProvider(provider, replace),
+                }
+            }));
+            Assert.AreEqual(html, expected);
+        }
+
+        [Test]
+        [TestCase("![static mp4](//sample.com/video.mp4)", "<p><video width=\"500\" height=\"281\" controls=\"\"><source type=\"video/mp4\" src=\"//sample.com/video.mp4\"></source></video></p>\n", "")]
+        [TestCase(@"![youtube.com](https://www.youtube.com/watch?v=mswPy5bt3TQ)", "<p><iframe src=\"https://www.youtube.com/embed/mswPy5bt3TQ\" width=\"500\" height=\"281\" class=\"youtube\" frameborder=\"0\" allowfullscreen=\"\"></iframe></p>\n", "")]
+        [TestCase("![static mp4](//sample.com/video.mp4)", "<p><video width=\"500\" height=\"281\" controls=\"\" class=\"k\"><source type=\"video/mp4\" src=\"//sample.com/video.mp4\"></source></video></p>\n", "k")]
+        [TestCase(@"![youtube.com](https://www.youtube.com/watch?v=mswPy5bt3TQ)", "<p><iframe src=\"https://www.youtube.com/embed/mswPy5bt3TQ\" width=\"500\" height=\"281\" class=\"k youtube\" frameborder=\"0\" allowfullscreen=\"\"></iframe></p>\n", "k")]
+        public void TestCustomClass(string markdown, string expected, string klass)
+        {
+            string html = Markdown.ToHtml(markdown, GetPipeline(new MediaOptions
+            {
+                Class = klass,
+            }));
+            Assert.AreEqual(html, expected);
+        }
+    }
+}
--- a/src/Markdig.Tests/TestParser.cs
+++ b/src/Markdig.Tests/TestParser.cs
@@ -8,6 +8,7 @@ using System.Linq;
 using System.Text;
 using System.Text.RegularExpressions;
 using Markdig.Extensions.JiraLinks;
+using Markdig.Syntax;
 using NUnit.Framework;

 namespace Markdig.Tests
@@ -33,9 +34,9 @@ namespace Markdig.Tests

                // If file creation times aren't preserved by git, add some leeway
                // If specs have come from git, assume that they were regenerated since CI would fail otherwise
-                testTime = testTime.AddSeconds(2);
+                testTime = testTime.AddMinutes(3);

-                // This might not catch a changed spec every time, but should most of the time. Otherwise CI will catch it
+                // This might not catch a changed spec every time, but should at least sometimes. Otherwise CI will catch it

                // This could also trigger, if a user has modified the spec file but reverted the change - can't think of a good workaround
                Assert.Less(specTime, testTime,
@@ -151,6 +152,11 @@ namespace Markdig.Tests
        /// Contains the markdown source for specification files (order is the same as in <see cref="SpecsFilePaths"/>)
        /// </summary>
        public static readonly string[] SpecsMarkdown;
+        /// <summary>
+        /// Contains the markdown syntax tree for specification files (order is the same as in <see cref="SpecsFilePaths"/>)
+        /// </summary>
+        public static readonly MarkdownDocument[] SpecsSyntaxTrees;
+
        static TestParser()
        {
            SpecsFilePaths = Directory.GetDirectories(TestsDirectory)
@@ -161,10 +167,16 @@ namespace Markdig.Tests
                .ToArray();

            SpecsMarkdown = new string[SpecsFilePaths.Length];
+            SpecsSyntaxTrees = new MarkdownDocument[SpecsFilePaths.Length];
+
+            var pipeline = new MarkdownPipelineBuilder()
+                .UseAdvancedExtensions()
+                .Build();

            for (int i = 0; i < SpecsFilePaths.Length; i++)
            {
-                SpecsMarkdown[i] = File.ReadAllText(SpecsFilePaths[i]);
+                string markdown = SpecsMarkdown[i] = File.ReadAllText(SpecsFilePaths[i]);
+                SpecsSyntaxTrees[i] = Markdown.Parse(markdown, pipeline);
            }
        }
    }
--- a/src/Markdig.Tests/TestPlayParser.cs
+++ b/src/Markdig.Tests/TestPlayParser.cs
@@ -57,7 +57,7 @@ Later in a text we are using HTML and it becomes an abbr tag HTML
 > some other text";
            var doc = Markdown.Parse(text);

-            Assert.True(doc.Descendants().OfType<LiteralInline>().All(x => !x.Content.IsEmpty),
+            Assert.True(doc.Descendants<LiteralInline>().All(x => !x.Content.IsEmpty),
                "There should not have any empty literals");
        }

--- a/src/Markdig.Tests/TestSourcePosition.cs
+++ b/src/Markdig.Tests/TestSourcePosition.cs
@@ -6,8 +6,7 @@ using System;
 using System.Collections.Generic;
 using System.Linq;
 using System.Text;
-using Markdig.Extensions.Footnotes;
-using Markdig.Helpers;
+using Markdig.Extensions.Footnotes;
 using Markdig.Renderers.Html;
 using Markdig.Syntax;
 using Markdig.Syntax.Inlines;
@@ -147,7 +146,7 @@ literal      ( 0, 6)  6-7
        public void TestFootnoteLinkReferenceDefinition()
        {
            //                             01 2 345678
-            var footnote = Markdown.Parse("0\n\n [^1]:", new MarkdownPipelineBuilder().UsePreciseSourceLocation().UseFootnotes().Build()).Descendants().OfType<FootnoteLinkReferenceDefinition>().FirstOrDefault();
+            var footnote = Markdown.Parse("0\n\n [^1]:", new MarkdownPipelineBuilder().UsePreciseSourceLocation().UseFootnotes().Build()).Descendants<FootnoteLinkReferenceDefinition>().FirstOrDefault();
            Assert.NotNull(footnote);

            Assert.AreEqual(2, footnote.Line);
@@ -160,7 +159,7 @@ literal      ( 0, 6)  6-7
        {
            //                         0         1
            //                         0123456789012345
-            var link = Markdown.Parse("[234]: /56 'yo' ", new MarkdownPipelineBuilder().UsePreciseSourceLocation().Build()).Descendants().OfType<LinkReferenceDefinition>().FirstOrDefault();
+            var link = Markdown.Parse("[234]: /56 'yo' ", new MarkdownPipelineBuilder().UsePreciseSourceLocation().Build()).Descendants<LinkReferenceDefinition>().FirstOrDefault();
            Assert.NotNull(link);

            Assert.AreEqual(0, link.Line);
@@ -175,7 +174,7 @@ literal      ( 0, 6)  6-7
        {
            //                         0          1
            //                         01 2 34567890123456789
-            var link = Markdown.Parse("0\n\n [234]: /56 'yo' ", new MarkdownPipelineBuilder().UsePreciseSourceLocation().Build()).Descendants().OfType<LinkReferenceDefinition>().FirstOrDefault();
+            var link = Markdown.Parse("0\n\n [234]: /56 'yo' ", new MarkdownPipelineBuilder().UsePreciseSourceLocation().Build()).Descendants<LinkReferenceDefinition>().FirstOrDefault();
            Assert.NotNull(link);

            Assert.AreEqual(2, link.Line);
@@ -213,7 +212,7 @@ literal      ( 0, 4)  4-5
        {
            //                         0           1
            //                         01 2 3456789012345
-            var link = Markdown.Parse("0\n\n01 [234](/56)", new MarkdownPipelineBuilder().UsePreciseSourceLocation().Build()).Descendants().OfType<LinkInline>().FirstOrDefault();
+            var link = Markdown.Parse("0\n\n01 [234](/56)", new MarkdownPipelineBuilder().UsePreciseSourceLocation().Build()).Descendants<LinkInline>().FirstOrDefault();
            Assert.NotNull(link);

            Assert.AreEqual(new SourceSpan(7, 9), link.LabelSpan);
@@ -226,7 +225,7 @@ literal      ( 0, 4)  4-5
        {
            //                         0           1
            //                         01 2 34567890123456789
-            var link = Markdown.Parse("0\n\n01 [234](/56 'yo')", new MarkdownPipelineBuilder().UsePreciseSourceLocation().Build()).Descendants().OfType<LinkInline>().FirstOrDefault();
+            var link = Markdown.Parse("0\n\n01 [234](/56 'yo')", new MarkdownPipelineBuilder().UsePreciseSourceLocation().Build()).Descendants<LinkInline>().FirstOrDefault();
            Assert.NotNull(link);

            Assert.AreEqual(new SourceSpan(7, 9), link.LabelSpan);
@@ -240,7 +239,7 @@ literal      ( 0, 4)  4-5
        {
            //                         0           1
            //                         01 2 3456789012345
-            var link = Markdown.Parse("0\n\n01![234](/56)", new MarkdownPipelineBuilder().UsePreciseSourceLocation().Build()).Descendants().OfType<LinkInline>().FirstOrDefault();
+            var link = Markdown.Parse("0\n\n01![234](/56)", new MarkdownPipelineBuilder().UsePreciseSourceLocation().Build()).Descendants<LinkInline>().FirstOrDefault();
            Assert.NotNull(link);

            Assert.AreEqual(new SourceSpan(5, 15), link.Span);
@@ -408,7 +407,7 @@ literal      ( 1, 2)  6-6
 6. Bar
 987123. FooBar";
            test = test.Replace("\r\n", "\n");
-            var list = Markdown.Parse(test, new MarkdownPipelineBuilder().UsePreciseSourceLocation().Build()).Descendants().OfType<ListBlock>().FirstOrDefault();
+            var list = Markdown.Parse(test, new MarkdownPipelineBuilder().UsePreciseSourceLocation().Build()).Descendants<ListBlock>().FirstOrDefault();
            Assert.NotNull(list);

            Assert.AreEqual(1, list.Line);
--- a/src/Markdig.Tests/TestStringSliceList.cs
+++ b/src/Markdig.Tests/TestStringSliceList.cs
@@ -1,4 +1,4 @@
-using NUnit.Framework;
+using NUnit.Framework;
 using System.Collections.Generic;
 using System.Text;
 using Markdig.Helpers;
@@ -81,8 +81,18 @@ namespace Markdig.Tests
        public void TestSkipWhitespaces()
        {
            var text = new StringLineGroup("             ABC").ToCharIterator();
-            Assert.True(text.TrimStart());
+            Assert.False(text.TrimStart());
            Assert.AreEqual('A', text.CurrentChar);
+
+            text = new StringLineGroup("        ").ToCharIterator();
+            Assert.True(text.TrimStart());
+            Assert.AreEqual('\0', text.CurrentChar);
+
+            var slice = new StringSlice("             ABC");
+            Assert.False(slice.TrimStart());
+
+            slice = new StringSlice("        ");
+            Assert.True(slice.TrimStart());
        }

        [Test]
--- a/src/Markdig/Extensions/AutoIdentifiers/AutoIdentifierExtension.cs
+++ b/src/Markdig/Extensions/AutoIdentifiers/AutoIdentifierExtension.cs
@@ -22,6 +22,7 @@ namespace Markdig.Extensions.AutoIdentifiers
    {
        private const string AutoIdentifierKey = "AutoIdentifier";
        private readonly AutoIdentifierOptions options;
+        private readonly StripRendererCache rendererCache = new StripRendererCache();

        /// <summary>
        /// Initializes a new instance of the <see cref="AutoIdentifierExtension"/> class.
@@ -159,17 +160,11 @@ namespace Markdig.Extensions.AutoIdentifiers
            }

            // Use internally a HtmlRenderer to strip links from a heading
-            var headingWriter = new StringWriter();
-            var stripRenderer = new HtmlRenderer(headingWriter)
-            {
-                // Set to false both to avoid having any HTML tags in the output
-                EnableHtmlForInline = false,
-                EnableHtmlEscape = false
-            };
+            var stripRenderer = rendererCache.Get();

            stripRenderer.Render(headingBlock.Inline);
-            var headingText = headingWriter.ToString();
-            headingWriter.GetStringBuilder().Length = 0;
+            var headingText = stripRenderer.Writer.ToString();
+            rendererCache.Release(stripRenderer);

            // Urilize the link
            headingText = (options & AutoIdentifierOptions.GitHub) != 0
@@ -195,5 +190,25 @@ namespace Markdig.Extensions.AutoIdentifiers

            attributes.Id = headingId;
        }
+
+        private sealed class StripRendererCache : ObjectCache<HtmlRenderer>
+        {
+            protected override HtmlRenderer NewInstance()
+            {
+                var headingWriter = new StringWriter();
+                var stripRenderer = new HtmlRenderer(headingWriter)
+                {
+                    // Set to false both to avoid having any HTML tags in the output
+                    EnableHtmlForInline = false,
+                    EnableHtmlEscape = false
+                };
+                return stripRenderer;
+            }
+
+            protected override void Reset(HtmlRenderer instance)
+            {
+                instance.Reset();
+            }
+        }
    }
 }
--- a/src/Markdig/Extensions/AutoLinks/AutoLinkParser.cs
+++ b/src/Markdig/Extensions/AutoLinks/AutoLinkParser.cs
@@ -14,7 +14,7 @@ namespace Markdig.Extensions.AutoLinks
    /// <summary>
    /// The inline parser used to for autolinks.
    /// </summary>
-    /// <seealso cref="Markdig.Parsers.InlineParser" />
+    /// <seealso cref="InlineParser" />
    public class AutoLinkParser : InlineParser
    {
        /// <summary>
@@ -30,10 +30,14 @@ namespace Markdig.Extensions.AutoLinks
                'f', // for ftp://
                'm', // for mailto:
                'w', // for www.
-            };
-        }
-
-        public readonly AutoLinkOptions Options;
+            };
+
+            _listOfCharCache = new ListOfCharCache();
+        }
+
+        public readonly AutoLinkOptions Options;
+
+        private readonly ListOfCharCache _listOfCharCache;

        public override bool Match(InlineProcessor processor, ref StringSlice slice)
        {
@@ -44,159 +48,162 @@ namespace Markdig.Extensions.AutoLinks
                return false;
            }

-            List<char> pendingEmphasis;
-            // Check that an autolink is possible in the current context
-            if (!IsAutoLinkValidInCurrentContext(processor, out pendingEmphasis))
-            {
-                return false;
-            }
-
-            var startPosition = slice.Start;
-            int domainOffset = 0;
-
-            var c = slice.CurrentChar;
-            // Precheck URL
-            switch (c)
-            {
-                case 'h':
-                    if (slice.MatchLowercase("ttp://", 1))
-                    {
-                        domainOffset = 7; // http://
-                    }
-                    else if (slice.MatchLowercase("ttps://", 1))
-                    {
-                        domainOffset = 8; // https://
-                    }
-                    else return false;
-                    break;
-                case 'f':
-                    if (!slice.MatchLowercase("tp://", 1))
-                    {
-                        return false;
-                    }
-                    domainOffset = 6; // ftp://
-                    break;
-                case 'm':
-                    if (!slice.MatchLowercase("ailto:", 1))
-                    {
-                        return false;
-                    }
-                    break;
-
-                case 'w':
-                    if (!slice.MatchLowercase("ww.", 1)) // We won't match http:/www. or /www.xxx
-                    {
-                        return false;
-                    }
-                    domainOffset = 4; // www.
-                    break;
-            }
-
-            // Parse URL
-            string link;
-            if (!LinkHelper.TryParseUrl(ref slice, out link, true))
-            {
-                return false;
-            }
-
-
-            // If we have any pending emphasis, remove any pending emphasis characters from the end of the link
-            if (pendingEmphasis != null)
-            {
-                for (int i = link.Length - 1; i >= 0; i--)
-                {
-                    if (pendingEmphasis.Contains(link[i]))
-                    {
-                        slice.Start--;
-                    }
-                    else
-                    {
-                        if (i < link.Length - 1)
-                        {
-                            link = link.Substring(0, i + 1);
-                        }
-                        break;
-                    }
-                }
-            }
-
-            // Post-check URL
-            switch (c)
-            {
-                case 'h':
-                    if (string.Equals(link, "http://", StringComparison.OrdinalIgnoreCase) ||
-                        string.Equals(link, "https://", StringComparison.OrdinalIgnoreCase))
-                    {
-                        return false;
-                    }
-                    break;
-                case 'f':
-                    if (string.Equals(link, "ftp://", StringComparison.OrdinalIgnoreCase))
-                    {
-                        return false;
-                    }
-                    break;
-                case 'm':
-                    int atIndex = link.IndexOf('@');
-                    if (atIndex == -1 ||
-                        atIndex == 7) // mailto:@ - no email part
-                    {
-                        return false;
-                    }
-                    domainOffset = atIndex + 1;
-                    break;
-            }
-
-            if (!LinkHelper.IsValidDomain(link, domainOffset))
+            List<char> pendingEmphasis = _listOfCharCache.Get();
+            try
            {
-                return false;
+                // Check that an autolink is possible in the current context
+                if (!IsAutoLinkValidInCurrentContext(processor, pendingEmphasis))
+                {
+                    return false;
+                }
+
+                var startPosition = slice.Start;
+                int domainOffset = 0;
+
+                var c = slice.CurrentChar;
+                // Precheck URL
+                switch (c)
+                {
+                    case 'h':
+                        if (slice.MatchLowercase("ttp://", 1))
+                        {
+                            domainOffset = 7; // http://
+                        }
+                        else if (slice.MatchLowercase("ttps://", 1))
+                        {
+                            domainOffset = 8; // https://
+                        }
+                        else return false;
+                        break;
+                    case 'f':
+                        if (!slice.MatchLowercase("tp://", 1))
+                        {
+                            return false;
+                        }
+                        domainOffset = 6; // ftp://
+                        break;
+                    case 'm':
+                        if (!slice.MatchLowercase("ailto:", 1))
+                        {
+                            return false;
+                        }
+                        break;
+
+                    case 'w':
+                        if (!slice.MatchLowercase("ww.", 1)) // We won't match http:/www. or /www.xxx
+                        {
+                            return false;
+                        }
+                        domainOffset = 4; // www.
+                        break;
+                }
+
+                // Parse URL
+                if (!LinkHelper.TryParseUrl(ref slice, out string link, true))
+                {
+                    return false;
+                }
+
+
+                // If we have any pending emphasis, remove any pending emphasis characters from the end of the link
+                if (pendingEmphasis.Count > 0)
+                {
+                    for (int i = link.Length - 1; i >= 0; i--)
+                    {
+                        if (pendingEmphasis.Contains(link[i]))
+                        {
+                            slice.Start--;
+                        }
+                        else
+                        {
+                            if (i < link.Length - 1)
+                            {
+                                link = link.Substring(0, i + 1);
+                            }
+                            break;
+                        }
+                    }
+                }
+
+                // Post-check URL
+                switch (c)
+                {
+                    case 'h':
+                        if (string.Equals(link, "http://", StringComparison.OrdinalIgnoreCase) ||
+                            string.Equals(link, "https://", StringComparison.OrdinalIgnoreCase))
+                        {
+                            return false;
+                        }
+                        break;
+                    case 'f':
+                        if (string.Equals(link, "ftp://", StringComparison.OrdinalIgnoreCase))
+                        {
+                            return false;
+                        }
+                        break;
+                    case 'm':
+                        int atIndex = link.IndexOf('@');
+                        if (atIndex == -1 ||
+                            atIndex == 7) // mailto:@ - no email part
+                        {
+                            return false;
+                        }
+                        domainOffset = atIndex + 1;
+                        break;
+                }
+
+                if (!LinkHelper.IsValidDomain(link, domainOffset))
+                {
+                    return false;
+                }
+
+                var inline = new LinkInline()
+                {
+                    Span =
+                    {
+                        Start = processor.GetSourcePosition(startPosition, out int line, out int column),
+                    },
+                    Line = line,
+                    Column = column,
+                    Url = c == 'w' ? ((Options.UseHttpsForWWWLinks ? "https://" : "http://") + link) : link,
+                    IsClosed = true,
+                    IsAutoLink = true,
+                };
+
+                var skipFromBeginning = c == 'm' ? 7 : 0; // For mailto: skip "mailto:" for content
+
+                inline.Span.End = inline.Span.Start + link.Length - 1;
+                inline.UrlSpan = inline.Span;
+                inline.AppendChild(new LiteralInline()
+                {
+                    Span = inline.Span,
+                    Line = line,
+                    Column = column,
+                    Content = new StringSlice(slice.Text, startPosition + skipFromBeginning, startPosition + link.Length - 1),
+                    IsClosed = true
+                });
+                processor.Inline = inline;
+
+                if (Options.OpenInNewWindow)
+                {
+                    inline.GetAttributes().AddPropertyIfNotExist("target", "blank");
+                }
+
+                return true;
            }
-
-            var inline = new LinkInline()
-            {
-                Span =
-                {
-                    Start = processor.GetSourcePosition(startPosition, out int line, out int column),
-                },
-                Line = line,
-                Column = column,
-                Url = c == 'w' ? ((Options.UseHttpsForWWWLinks ? "https://" : "http://") + link) : link,
-                IsClosed = true,
-                IsAutoLink = true,
-            };
-
-            var skipFromBeginning = c == 'm' ? 7 : 0; // For mailto: skip "mailto:" for content
-
-            inline.Span.End = inline.Span.Start + link.Length - 1;
-            inline.UrlSpan = inline.Span;
-            inline.AppendChild(new LiteralInline()
-            {
-                Span = inline.Span,
-                Line = line,
-                Column = column,
-                Content = new StringSlice(slice.Text, startPosition + skipFromBeginning, startPosition + link.Length - 1),
-                IsClosed = true
-            });
-            processor.Inline = inline;
-
-            if (Options.OpenInNewWindow)
+            finally
            {
-                inline.GetAttributes().AddPropertyIfNotExist("target", "blank");
+                _listOfCharCache.Release(pendingEmphasis);
            }
-
-            return true;
        }

-        private bool IsAutoLinkValidInCurrentContext(InlineProcessor processor, out List<char> pendingEmphasis)
+        private bool IsAutoLinkValidInCurrentContext(InlineProcessor processor, List<char> pendingEmphasis)
        {
-            pendingEmphasis = null;
-
            // Case where there is a pending HtmlInline <a>
            var currentInline = processor.Inline;
            while (currentInline != null)
            {
-                var htmlInline = currentInline as HtmlInline;
-                if (htmlInline != null)
+                if (currentInline is HtmlInline htmlInline)
                {
                    // If we have a </a> we don't expect nested <a>
                    if (htmlInline.Tag.StartsWith("</a", StringComparison.OrdinalIgnoreCase))
@@ -211,7 +218,7 @@ namespace Markdig.Extensions.AutoLinks
                    }
                }

-                // Check previous sibling and parents in the tree 
+                // Check previous sibling and parents in the tree
                currentInline = currentInline.PreviousSibling ?? currentInline.Parent;
            }

@@ -221,8 +228,7 @@ namespace Markdig.Extensions.AutoLinks
            int countBrackets = 0;
            while (currentInline != null)
            {
-                var linkDelimiterInline = currentInline as LinkDelimiterInline;
-                if (linkDelimiterInline != null && linkDelimiterInline.IsActive)
+                if (currentInline is LinkDelimiterInline linkDelimiterInline && linkDelimiterInline.IsActive)
                {
                    if (linkDelimiterInline.Type == DelimiterType.Open)
                    {
@@ -236,14 +242,8 @@ namespace Markdig.Extensions.AutoLinks
                else
                {
                    // Record all pending characters for emphasis
-                    var emphasisDelimiter = currentInline as EmphasisDelimiterInline;
-                    if (emphasisDelimiter != null)
+                    if (currentInline is EmphasisDelimiterInline emphasisDelimiter)
                    {
-                        if (pendingEmphasis == null)
-                        {
-                            // Not optimized for GC, but we don't expect this case much
-                            pendingEmphasis = new List<char>();
-                        }
                        if (!pendingEmphasis.Contains(emphasisDelimiter.DelimiterChar))
                        {
                            pendingEmphasis.Add(emphasisDelimiter.DelimiterChar);
@@ -254,6 +254,14 @@ namespace Markdig.Extensions.AutoLinks
            }

            return countBrackets <= 0;
+        }
+
+        private sealed class ListOfCharCache : DefaultObjectCache<List<char>>
+        {
+            protected override void Reset(List<char> instance)
+            {
+                instance.Clear();
+            }
        }
    }
 }
--- a/src/Markdig/Extensions/Bootstrap/BootstrapExtension.cs
+++ b/src/Markdig/Extensions/Bootstrap/BootstrapExtension.cs
@@ -1,4 +1,4 @@
-// Copyright (c) Alexandre Mutel. All rights reserved.
+// Copyright (c) Alexandre Mutel. All rights reserved.
 // This file is licensed under the BSD-Clause 2 license. 
 // See the license.txt file in the project root for more information.

@@ -51,8 +51,7 @@ namespace Markdig.Extensions.Bootstrap
                }
                else if (node is Inline)
                {
-                    var link = node as LinkInline;
-                    if (link != null && link.IsImage)
+                    if (node is LinkInline link && link.IsImage)
                    {
                        link.GetAttributes().AddClass("img-fluid");
                    }
--- a/src/Markdig/Extensions/Emoji/EmojiExtension.cs
+++ b/src/Markdig/Extensions/Emoji/EmojiExtension.cs
@@ -7,24 +7,24 @@ using Markdig.Renderers;
 namespace Markdig.Extensions.Emoji
 {
    /// <summary>
-    /// Extension to allow emoji and smiley replacement.
+    /// Extension to allow emoji shortcodes and smileys replacement.
    /// </summary>
    /// <seealso cref="Markdig.IMarkdownExtension" />
    public class EmojiExtension : IMarkdownExtension
    {
-        public EmojiExtension(bool enableSmiley = true)
-        {
-            EnableSmiley = enableSmiley;
+        public EmojiExtension(EmojiMapping emojiMapping)
+        {
+            EmojiMapping = emojiMapping;
        }
-
-        public bool EnableSmiley { get; set; }
-
+
+        public EmojiMapping EmojiMapping { get; }
+
        public void Setup(MarkdownPipelineBuilder pipeline)
        {
            if (!pipeline.InlineParsers.Contains<EmojiParser>())
            {
                // Insert the parser before any other parsers
-                pipeline.InlineParsers.Insert(0, new EmojiParser(EnableSmiley));
+                pipeline.InlineParsers.Insert(0, new EmojiParser(EmojiMapping));
            }
        }

--- a/src/Markdig/Extensions/Emoji/EmojiInline.cs
+++ b/src/Markdig/Extensions/Emoji/EmojiInline.cs
@@ -1,4 +1,4 @@
-// Copyright (c) Alexandre Mutel. All rights reserved.
+// Copyright (c) Alexandre Mutel. All rights reserved.
 // This file is licensed under the BSD-Clause 2 license. 
 // See the license.txt file in the project root for more information.

@@ -8,7 +8,7 @@ using Markdig.Syntax.Inlines;
 namespace Markdig.Extensions.Emoji
 {
    /// <summary>
-    /// An emoji inline 
+    /// An emoji inline.
    /// </summary>
    /// <seealso cref="Markdig.Syntax.Inlines.Inline" />
    public class EmojiInline : LiteralInline
@@ -32,7 +32,7 @@ namespace Markdig.Extensions.Emoji
        }

        /// <summary>
-        /// Gets or sets the original match string (either an emoji or a text smiley)
+        /// Gets or sets the original match string (either an emoji shortcode or a text smiley)
        /// </summary>
        public string Match { get; set; }
    }
--- a/src/Markdig/Extensions/Emoji/EmojiMapping.cs
+++ b/src/Markdig/Extensions/Emoji/EmojiMapping.cs
--- a/src/Markdig/Extensions/Emoji/EmojiParser.cs
+++ b/src/Markdig/Extensions/Emoji/EmojiParser.cs
--- a/src/Markdig/Extensions/GenericAttributes/GenericAttributesExtension.cs
+++ b/src/Markdig/Extensions/GenericAttributes/GenericAttributesExtension.cs
@@ -1,4 +1,4 @@
-// Copyright (c) Alexandre Mutel. All rights reserved.
+// Copyright (c) Alexandre Mutel. All rights reserved.
 // This file is licensed under the BSD-Clause 2 license. 
 // See the license.txt file in the project root for more information.

@@ -16,7 +16,7 @@ namespace Markdig.Extensions.GenericAttributes
    /// Extension that allows to attach HTML attributes to the previous <see cref="Inline"/> or current <see cref="Block"/>.
    /// This extension should be enabled last after enabling other extensions.
    /// </summary>
-    /// <seealso cref="Markdig.IMarkdownExtension" />
+    /// <seealso cref="IMarkdownExtension" />
    public class GenericAttributesExtension : IMarkdownExtension
    {
        public void Setup(MarkdownPipelineBuilder pipeline)
@@ -29,8 +29,7 @@ namespace Markdig.Extensions.GenericAttributes
            // Plug into all IAttributesParseable
            foreach (var parser in pipeline.BlockParsers)
            {
-                var attributesParseable = parser as IAttributesParseable;
-                if (attributesParseable != null)
+                if (parser is IAttributesParseable attributesParseable)
                {
                    attributesParseable.TryParseAttributes = TryProcessAttributesForHeading;
                }
@@ -53,8 +52,7 @@ namespace Markdig.Extensions.GenericAttributes
                    var copy = line;
                    copy.Start = indexOfAttributes;
                    var startOfAttributes = copy.Start;
-                    HtmlAttributes attributes;
-                    if (GenericAttributesParser.TryParse(ref copy, out attributes))
+                    if (GenericAttributesParser.TryParse(ref copy, out HtmlAttributes attributes))
                    {
                        var htmlAttributes = block.GetAttributes();
                        attributes.CopyTo(htmlAttributes);
--- a/src/Markdig/Extensions/GenericAttributes/GenericAttributesParser.cs
+++ b/src/Markdig/Extensions/GenericAttributes/GenericAttributesParser.cs
@@ -14,7 +14,7 @@ namespace Markdig.Extensions.GenericAttributes
    /// <summary>
    /// An inline parser used to parse a HTML attributes that can be attached to the previous <see cref="Inline"/> or current <see cref="Block"/>.
    /// </summary>
-    /// <seealso cref="Markdig.Parsers.InlineParser" />
+    /// <seealso cref="InlineParser" />
    public class GenericAttributesParser : InlineParser
    {
        /// <summary>
@@ -27,9 +27,8 @@ namespace Markdig.Extensions.GenericAttributes

        public override bool Match(InlineProcessor processor, ref StringSlice slice)
        {
-            HtmlAttributes attributes;
            var startPosition = slice.Start;
-            if (TryParse(ref slice, out attributes))
+            if (TryParse(ref slice, out HtmlAttributes attributes))
            {
                var inline = processor.Inline;

@@ -50,8 +49,10 @@ namespace Markdig.Extensions.GenericAttributes

                // If the current block is a Paragraph, but only the HtmlAttributes is used,
                // Try to attach the attributes to the following block
-                var paragraph = objectToAttach as ParagraphBlock;
-                if (paragraph != null && paragraph.Inline.FirstChild == null && processor.Inline == null && slice.IsEmptyOrWhitespace())
+                if (objectToAttach is ParagraphBlock paragraph &&
+                    paragraph.Inline.FirstChild == null &&
+                    processor.Inline == null &&
+                    slice.IsEmptyOrWhitespace())
                {
                    var parent = paragraph.Parent;
                    var indexOfParagraph = parent.IndexOf(paragraph);
@@ -67,9 +68,7 @@ namespace Markdig.Extensions.GenericAttributes
                attributes.CopyTo(currentHtmlAttributes, true, false);

                // Update the position of the attributes
-                int line;
-                int column;
-                currentHtmlAttributes.Span.Start = processor.GetSourcePosition(startPosition, out line, out column);
+                currentHtmlAttributes.Span.Start = processor.GetSourcePosition(startPosition, out int line, out int column);
                currentHtmlAttributes.Line = line;
                currentHtmlAttributes.Column = column;
                currentHtmlAttributes.Span.End = currentHtmlAttributes.Span.Start + slice.Start - startPosition - 1;
@@ -223,6 +222,7 @@ namespace Markdig.Extensions.GenericAttributes
                    {
                        // Parse until we match a space or a special html character
                        startValue = line.Start;
+                        bool valid = false;
                        while (true)
                        {
                            if (c == '\0')
@@ -234,9 +234,10 @@ namespace Markdig.Extensions.GenericAttributes
                                break;
                            }
                            c = line.NextChar();
+                            valid = true;
                        }
                        endValue = line.Start - 1;
-                        if (endValue == startValue)
+                        if (!valid)
                        {
                            break;
                        }
--- a/src/Markdig/Extensions/Globalization/GlobalizationExtension.cs
+++ b/src/Markdig/Extensions/Globalization/GlobalizationExtension.cs
@@ -38,7 +38,7 @@ namespace Markdig.Extensions.Globalization
                    var attributes = node.GetAttributes();
                    attributes.AddPropertyIfNotExist("dir", "rtl");

-                    if (node is Table table)
+                    if (node is Table)
                    {
                        attributes.AddPropertyIfNotExist("align", "right");
                    }
@@ -71,19 +71,16 @@ namespace Markdig.Extensions.Globalization
            }
            else if (item is LiteralInline literal)
            {
-                return StartsWithRtlCharacter(literal.ToString());
+                return StartsWithRtlCharacter(literal.Content);
            }

-            foreach (var descendant in item.Descendants())
+            foreach (var paragraph in item.Descendants<ParagraphBlock>())
            {
-                if (descendant is ParagraphBlock p)
+                foreach (var inline in paragraph.Inline)
                {
-                    foreach (var i in p.Inline)
+                    if (inline is LiteralInline literal)
                    {
-                        if (i is LiteralInline l)
-                        {
-                            return StartsWithRtlCharacter(l.ToString());
-                        }
+                        return StartsWithRtlCharacter(literal.Content);
                    }
                }
            }
@@ -91,9 +88,9 @@ namespace Markdig.Extensions.Globalization
            return false;
        }

-        private bool StartsWithRtlCharacter(string text)
+        private bool StartsWithRtlCharacter(StringSlice slice)
        {
-            foreach (var c in CharHelper.ToUtf32(text))
+            foreach (var c in CharHelper.ToUtf32(slice))
            {
                if (CharHelper.IsRightToLeft(c))
                    return true;
--- a/src/Markdig/Extensions/MediaLinks/HostProviderBuilder.cs
+++ b/src/Markdig/Extensions/MediaLinks/HostProviderBuilder.cs
@@ -0,0 +1,137 @@
+// Copyright (c) Alexandre Mutel. All rights reserved.
+// This file is licensed under the BSD-Clause 2 license.
+// See the license.txt file in the project root for more information.
+
+using System;
+using System.Collections.Generic;
+using System.Linq;
+
+namespace Markdig.Extensions.MediaLinks
+{
+    public class HostProviderBuilder
+    {
+        private sealed class DelegateProvider : IHostProvider
+        {
+            public string HostPrefix { get; set; }
+            public Func<Uri, string> Delegate { get; set; }
+            public bool AllowFullScreen { get; set; } = true;
+            public string Class { get; set; }
+
+            public bool TryHandle(Uri mediaUri, bool isSchemaRelative, out string iframeUrl)
+            {
+                if (!mediaUri.Host.StartsWith(HostPrefix, StringComparison.OrdinalIgnoreCase))
+                {
+                    iframeUrl = null;
+                    return false;
+                }
+                iframeUrl = Delegate(mediaUri);
+                return !string.IsNullOrEmpty(iframeUrl);
+            }
+        }
+
+        /// <summary>
+        /// Create a <see cref="IHostProvider"/> with delegate handler.
+        /// </summary>
+        /// <param name="hostPrefix">Prefix of host that can be handled.</param>
+        /// <param name="handler">Handler that generate iframe url, if uri cannot be handled, it can return <see langword="null"/>.</param>
+        /// <param name="allowFullScreen">Should the generated iframe has allowfullscreen attribute.</param>
+        /// <param name="iframeClass">"class" attribute of generated iframe.</param>
+        /// <returns>A <see cref="IHostProvider"/> with delegate handler.</returns>
+        public static IHostProvider Create(string hostPrefix, Func<Uri, string> handler, bool allowFullScreen = true, string iframeClass = null)
+        {
+            if (string.IsNullOrEmpty(hostPrefix))
+                throw new ArgumentException("hostPrefix is null or empty.", nameof(hostPrefix));
+            if (handler == null)
+                throw new ArgumentNullException(nameof(handler));
+            return new DelegateProvider { HostPrefix = hostPrefix, Delegate = handler, AllowFullScreen = allowFullScreen, Class = iframeClass };
+        }
+
+        internal static Dictionary<string, IHostProvider> KnownHosts { get; }
+            = new Dictionary<string, IHostProvider>(StringComparer.OrdinalIgnoreCase)
+            {
+                ["YouTube"] = Create("www.youtube.com", YouTube, iframeClass: "youtube"),
+                ["YouTubeShortened"] = Create("youtu.be", YouTubeShortened, iframeClass: "youtube"),
+                ["Vimeo"] = Create("vimeo.com", Vimeo, iframeClass: "vimeo"),
+                ["Yandex"] = Create("music.yandex.ru", Yandex, allowFullScreen: false, iframeClass: "yandex"),
+                ["Odnoklassniki"] = Create("ok.ru", Odnoklassniki, iframeClass: "odnoklassniki"),
+            };
+
+        #region Known providers
+
+        private static readonly string[] SplitAnd = { "&" };
+        private static string[] SplitQuery(Uri uri)
+        {
+            var query = uri.Query.Substring(uri.Query.IndexOf('?') + 1);
+            return query.Split(SplitAnd, StringSplitOptions.RemoveEmptyEntries);
+        }
+
+        private static string YouTube(Uri uri)
+        {
+            string uriPath = uri.AbsolutePath;
+            if (string.Equals(uriPath, "/embed", StringComparison.OrdinalIgnoreCase) || uriPath.StartsWith("/embed/", StringComparison.OrdinalIgnoreCase))
+            {
+                return uri.ToString();
+            }
+            if (!string.Equals(uriPath, "/watch", StringComparison.OrdinalIgnoreCase) && !uriPath.StartsWith("/watch/", StringComparison.OrdinalIgnoreCase))
+            {
+                return null;
+            }
+            var queryParams = SplitQuery(uri);
+            return BuildYouTubeIframeUrl(
+                queryParams.FirstOrDefault(p => p.StartsWith("v="))?.Substring(2),
+                queryParams.FirstOrDefault(p => p.StartsWith("t="))?.Substring(2)
+            );
+        }
+
+        private static string YouTubeShortened(Uri uri)
+        {
+            return BuildYouTubeIframeUrl(
+                uri.AbsolutePath.Substring(1),
+                SplitQuery(uri).FirstOrDefault(p => p.StartsWith("t="))?.Substring(2)
+            );
+        }
+
+        private static string BuildYouTubeIframeUrl(string videoId, string startTime)
+        {
+            if (string.IsNullOrEmpty(videoId))
+            {
+                return null;
+            }
+            string url = $"https://www.youtube.com/embed/{videoId}";
+            return string.IsNullOrEmpty(startTime) ? url : $"{url}?start={startTime}";
+        }
+
+        private static string Vimeo(Uri uri)
+        {
+            var items = uri.GetComponents(UriComponents.Path, UriFormat.Unescaped).Split('/');
+            return items.Length > 0 ? $"https://player.vimeo.com/video/{ items[items.Length - 1] }" : null;
+        }
+
+        private static string Odnoklassniki(Uri uri)
+        {
+            var items = uri.GetComponents(UriComponents.Path, UriFormat.Unescaped).Split('/');
+            return items.Length > 0 ? $"https://ok.ru/videoembed/{ items[items.Length - 1] }" : null;
+        }
+
+        private static string Yandex(Uri uri)
+        {
+            var items = uri.GetComponents(UriComponents.Path, UriFormat.Unescaped).Split('/');
+            var albumKeyword
+                = items.Skip(0).FirstOrDefault();
+            var albumId
+                = items.Skip(1).FirstOrDefault();
+            var trackKeyword
+                = items.Skip(2).FirstOrDefault();
+            var trackId
+                = items.Skip(3).FirstOrDefault();
+
+            if (albumKeyword != "album" || albumId == null || trackKeyword != "track" || trackId == null)
+            {
+                return null;
+            }
+
+            return $"https://music.yandex.ru/iframe/#track/{trackId}/{albumId}/";
+        }
+        #endregion
+    }
+}
--- a/src/Markdig/Extensions/MediaLinks/IHostProvider.cs
+++ b/src/Markdig/Extensions/MediaLinks/IHostProvider.cs
@@ -0,0 +1,36 @@
+// Copyright (c) Alexandre Mutel. All rights reserved.
+// This file is licensed under the BSD-Clause 2 license.
+// See the license.txt file in the project root for more information.
+
+using System;
+
+namespace Markdig.Extensions.MediaLinks
+{
+    /// <summary>
+    /// Provides url for media links.
+    /// </summary>
+    public interface IHostProvider
+    {
+        /// <summary>
+        /// "class" attribute of generated iframe.
+        /// </summary>
+        string Class { get; }
+
+        /// <summary>
+        /// Generate url for iframe.
+        /// </summary>
+        /// <param name="mediaUri">Input media uri.</param>
+        /// <param name="isSchemaRelative"><see langword="true"/> if <paramref name="mediaUri"/> is a schema relative uri, i.e. uri starts with "//".</param>
+        /// <param name="iframeUrl">Generated url for iframe.</param>
+        /// <seealso href="https://tools.ietf.org/html/rfc3986#section-4.2"/>
+        bool TryHandle(Uri mediaUri, bool isSchemaRelative, out string iframeUrl);
+
+        /// <summary>
+        /// Should the generated iframe has allowfullscreen attribute.
+        /// </summary>
+        /// <remarks>
+        /// Should be false for audio embedding.
+        /// </remarks>
+        bool AllowFullScreen { get; }
+    }
+}
--- a/src/Markdig/Extensions/MediaLinks/MediaLinkExtension.cs
+++ b/src/Markdig/Extensions/MediaLinks/MediaLinkExtension.cs
@@ -3,7 +3,6 @@
 // See the license.txt file in the project root for more information.

 using System;
-using System.Collections.Generic;
 using System.Linq;
 using Markdig.Renderers;
 using Markdig.Renderers.Html;
@@ -55,18 +54,28 @@ namespace Markdig.Extensions.MediaLinks
            }

            Uri uri;
+            bool isSchemaRelative = false;
            // Only process absolute Uri
            if (!Uri.TryCreate(linkInline.Url, UriKind.RelativeOrAbsolute, out uri) || !uri.IsAbsoluteUri)
            {
-                return false;
+                // see https://tools.ietf.org/html/rfc3986#section-4.2
+                // since relative uri doesn't support many properties, "http" is used as a placeholder here.
+                if (linkInline.Url.StartsWith("//") && Uri.TryCreate("http:" + linkInline.Url, UriKind.Absolute, out uri))
+                {
+                    isSchemaRelative = true;
+                }
+                else
+                {
+                    return false;
+                }
            }

-            if (TryRenderIframeFromKnownProviders(uri, renderer, linkInline))
+            if (TryRenderIframeFromKnownProviders(uri, isSchemaRelative, renderer, linkInline))
            {
                return true;
            }

-            if (TryGuessAudioVideoFile(uri, renderer, linkInline))
+            if (TryGuessAudioVideoFile(uri, isSchemaRelative, renderer, linkInline))
            {
                return true;
            }
@@ -86,7 +95,7 @@ namespace Markdig.Extensions.MediaLinks
            return htmlAttributes;
        }

-        private bool TryGuessAudioVideoFile(Uri uri, HtmlRenderer renderer, LinkInline linkInline)
+        private bool TryGuessAudioVideoFile(Uri uri, bool isSchemaRelative, HtmlRenderer renderer, LinkInline linkInline)
        {
            var path = uri.GetComponents(UriComponents.Path, UriFormat.Unescaped);
            // Otherwise try to detect if we have an audio/video from the file extension
@@ -106,6 +115,10 @@ namespace Markdig.Extensions.MediaLinks
                    htmlAttributes.AddPropertyIfNotExist("height", Options.Height);
                }
                htmlAttributes.AddPropertyIfNotExist("controls", null);
+
+                if (!string.IsNullOrEmpty(Options.Class))
+                    htmlAttributes.AddPropertyIfNotExist("class", Options.Class);
+
                renderer.WriteAttributes(htmlAttributes);

                renderer.Write($"><source type=\"{mimeType}\" src=\"{linkInline.Url}\"></source></{tagType}>");
@@ -115,38 +128,18 @@ namespace Markdig.Extensions.MediaLinks
            return false;
        }

-        #region Known providers
-
-        private class KnownProvider
+        private bool TryRenderIframeFromKnownProviders(Uri uri, bool isSchemaRelative, HtmlRenderer renderer, LinkInline linkInline)
        {
-            public string HostPrefix { get; set; }
-            public Func<Uri, string> Delegate { get; set; }
-            public bool AllowFullScreen { get; set; } = true; //Should be false for audio embedding
-        }

-        private static readonly List<KnownProvider> KnownHosts = new List<KnownProvider>()
-        {
-            new KnownProvider {HostPrefix = "www.youtube.com", Delegate = YouTube},
-            new KnownProvider {HostPrefix = "youtu.be", Delegate = YouTubeShortened},
-            new KnownProvider {HostPrefix = "vimeo.com", Delegate = Vimeo},
-            new KnownProvider {HostPrefix = "music.yandex.ru", Delegate = Yandex, AllowFullScreen = false},
-            new KnownProvider {HostPrefix = "ok.ru", Delegate = Odnoklassniki},
-        };
-
-
-        private bool TryRenderIframeFromKnownProviders(Uri uri, HtmlRenderer renderer, LinkInline linkInline)
-        {
-            var foundProvider =
-                KnownHosts
-                    .Where(pair => uri.Host.StartsWith(pair.HostPrefix, StringComparison.OrdinalIgnoreCase))  // when host is match
-                    .Select(provider =>
-                        new
-                        {
-                            provider.AllowFullScreen,
-                            Result = provider.Delegate(uri) // try to call delegate to get iframeUrl
-                        }
-                        )
-                    .FirstOrDefault(provider => provider.Result != null);                                   // use first success
+            IHostProvider foundProvider = null;
+            string iframeUrl = null;
+            foreach (var provider in Options.Hosts)
+            {
+                if (!provider.TryHandle(uri, isSchemaRelative, out iframeUrl))
+                    continue;
+                foundProvider = provider;
+                break;
+            }

            if (foundProvider == null)
            {
@@ -155,17 +148,20 @@ namespace Markdig.Extensions.MediaLinks

            var htmlAttributes = GetHtmlAttributes(linkInline);
            renderer.Write("<iframe src=\"");
-            renderer.WriteEscapeUrl(foundProvider.Result);
+            renderer.WriteEscapeUrl(iframeUrl);
            renderer.Write("\"");

-            if(!string.IsNullOrEmpty(Options.Width))
+            if (!string.IsNullOrEmpty(Options.Width))
                htmlAttributes.AddPropertyIfNotExist("width", Options.Width);

            if (!string.IsNullOrEmpty(Options.Height))
                htmlAttributes.AddPropertyIfNotExist("height", Options.Height);

-            if (!string.IsNullOrEmpty(Options.Class))
-                htmlAttributes.AddPropertyIfNotExist("class", Options.Class);
+            if (!string.IsNullOrEmpty(Options.Class) || !string.IsNullOrEmpty(foundProvider.Class))
+                htmlAttributes.AddPropertyIfNotExist("class",
+                    (!string.IsNullOrEmpty(Options.Class) && !string.IsNullOrEmpty(foundProvider.Class))
+                    ? Options.Class + " " + foundProvider.Class
+                    : Options.Class + foundProvider.Class);

            htmlAttributes.AddPropertyIfNotExist("frameborder", "0");
            if (foundProvider.AllowFullScreen)
@@ -177,81 +173,5 @@ namespace Markdig.Extensions.MediaLinks

            return true;
        }
-
-        private static readonly string[] SplitAnd = {"&"};
-        private static string[] SplitQuery(Uri uri)
-        {
-            var query = uri.Query.Substring(uri.Query.IndexOf('?') + 1);
-            return query.Split(SplitAnd, StringSplitOptions.RemoveEmptyEntries);
-        }
-
-        private static string YouTube(Uri uri)
-        {
-            string uriPath = uri.AbsolutePath;
-            if (string.Equals(uriPath, "/embed", StringComparison.OrdinalIgnoreCase) || uriPath.StartsWith("/embed/", StringComparison.OrdinalIgnoreCase))
-            {
-                return uri.ToString();
-            }
-            if (!string.Equals(uriPath, "/watch", StringComparison.OrdinalIgnoreCase) && !uriPath.StartsWith("/watch/", StringComparison.OrdinalIgnoreCase))
-            {
-                return null;
-            }
-            var queryParams = SplitQuery(uri);
-            return BuildYouTubeIframeUrl(
-                queryParams.FirstOrDefault(p => p.StartsWith("v="))?.Substring(2),
-                queryParams.FirstOrDefault(p => p.StartsWith("t="))?.Substring(2)
-            );
-        }
-
-        private static string YouTubeShortened(Uri uri)
-        {
-            return BuildYouTubeIframeUrl(
-                uri.AbsolutePath.Substring(1),
-                SplitQuery(uri).FirstOrDefault(p => p.StartsWith("t="))?.Substring(2)
-            );
-        }
-
-        private static string BuildYouTubeIframeUrl(string videoId, string startTime)
-        {
-            if (string.IsNullOrEmpty(videoId))
-            {
-                return null;
-            }
-            string url = $"https://www.youtube.com/embed/{videoId}";
-            return string.IsNullOrEmpty(startTime) ? url : $"{url}?start={startTime}";
-        }
-
-        private static string Vimeo(Uri uri)
-        {
-            var items = uri.GetComponents(UriComponents.Path, UriFormat.Unescaped).Split('/');
-            return items.Length > 0 ? $"https://player.vimeo.com/video/{items[items.Length - 1]}" : null;
-        }
-
-        private static string Odnoklassniki(Uri uri)
-        {
-            var items = uri.GetComponents(UriComponents.Path, UriFormat.Unescaped).Split('/');
-            return items.Length > 0 ? $"https://ok.ru/videoembed/{items[items.Length - 1]}" : null;
-        }
-
-        private static string Yandex(Uri uri)
-        {
-            var items = uri.GetComponents(UriComponents.Path, UriFormat.Unescaped).Split('/');
-            var albumKeyword
-                = items.Skip(0).FirstOrDefault();
-            var albumId
-                = items.Skip(1).FirstOrDefault();
-            var trackKeyword
-                = items.Skip(2).FirstOrDefault();
-            var trackId
-                = items.Skip(3).FirstOrDefault();
-
-            if (albumKeyword != "album" || albumId == null || trackKeyword != "track" || trackId == null)
-            {
-                return null;
-            }
-
-            return $"https://music.yandex.ru/iframe/#track/{trackId}/{albumId}/";
-        }
-        #endregion
    }
 }
--- a/src/Markdig/Extensions/MediaLinks/MediaOptions.cs
+++ b/src/Markdig/Extensions/MediaLinks/MediaOptions.cs
@@ -76,12 +76,14 @@ namespace Markdig.Extensions.MediaLinks
                {".ecelp7470", "audio/vnd.nuera.ecelp7470"},
                {".ecelp9600", "audio/vnd.nuera.ecelp9600"},
                {".oga", "audio/ogg"},
+                {".ogg", "audio/ogg"},
                {".weba", "audio/webm"},
                {".ram", "audio/x-pn-realaudio"},
                {".rmp", "audio/x-pn-realaudio-plugin"},
                {".au", "audio/basic"},
                {".wav", "audio/x-wav"},
            };
+            Hosts = new List<IHostProvider>(HostProviderBuilder.KnownHosts.Values);
        }

        public string Width { get; set; }
@@ -91,5 +93,7 @@ namespace Markdig.Extensions.MediaLinks
        public string Class { get; set; }

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

        protected override void Write(HtmlRenderer renderer, SmartyPant obj)
        {
-            string text;
-            if (!options.Mapping.TryGetValue(obj.Type, out text))
+            if (!options.Mapping.TryGetValue(obj.Type, out string text))
            {
                DefaultOptions.Mapping.TryGetValue(obj.Type, out text);
            }
--- a/src/Markdig/Extensions/SmartyPants/SmartyPant.cs
+++ b/src/Markdig/Extensions/SmartyPants/SmartyPant.cs
@@ -1,4 +1,4 @@
-// Copyright (c) Alexandre Mutel. All rights reserved.
+// Copyright (c) Alexandre Mutel. All rights reserved.
 // This file is licensed under the BSD-Clause 2 license. 
 // See the license.txt file in the project root for more information.
 using System.Diagnostics;
@@ -45,5 +45,15 @@ namespace Markdig.Extensions.SmartyPants
            }
            return OpeningCharacter != 0 ? OpeningCharacter.ToString() : string.Empty;
        }
+
+        public LiteralInline AsLiteralInline()
+        {
+            return new LiteralInline(ToString())
+            {
+                Span = Span,
+                Line = Line,
+                Column = Column,
+            };
+        }
    }
 }
--- a/src/Markdig/Extensions/SmartyPants/SmartyPantsExtension.cs
+++ b/src/Markdig/Extensions/SmartyPants/SmartyPantsExtension.cs
@@ -1,4 +1,4 @@
-// Copyright (c) Alexandre Mutel. All rights reserved.
+// Copyright (c) Alexandre Mutel. All rights reserved.
 // This file is licensed under the BSD-Clause 2 license. 
 // See the license.txt file in the project root for more information.

@@ -37,8 +37,7 @@ namespace Markdig.Extensions.SmartyPants

        public void Setup(MarkdownPipeline pipeline, IMarkdownRenderer renderer)
        {
-            var htmlRenderer = renderer as HtmlRenderer;
-            if (htmlRenderer != null)
+            if (renderer is HtmlRenderer htmlRenderer)
            {
                if (!htmlRenderer.ObjectRenderers.Contains<HtmlSmartyPantRenderer>())
                {
--- a/src/Markdig/Extensions/SmartyPants/SmartyPantsInlineParser.cs
+++ b/src/Markdig/Extensions/SmartyPants/SmartyPantsInlineParser.cs
@@ -49,7 +49,7 @@ namespace Markdig.Extensions.SmartyPants
            {
                case '\'':
                    type = SmartyPantType.Quote; // We will resolve them at the end of parsing all inlines
-                    if (slice.PeekChar(1) == '\'')
+                    if (slice.PeekChar() == '\'')
                    {
                        slice.NextChar();
                        type = SmartyPantType.DoubleQuote; // We will resolve them at the end of parsing all inlines
@@ -95,9 +95,7 @@ namespace Markdig.Extensions.SmartyPants
            // Skip char
            c = slice.NextChar();

-            bool canOpen;
-            bool canClose;
-            CharHelper.CheckOpenCloseDelimiter(pc, c, false, out canOpen, out canClose);
+            CharHelper.CheckOpenCloseDelimiter(pc, c, false, out bool canOpen, out bool canClose);

            bool postProcess = false;

@@ -156,11 +154,9 @@ namespace Markdig.Extensions.SmartyPants
            }

            // Create the SmartyPant inline
-            int line;
-            int column;
            var pant = new SmartyPant()
            {
-                Span = {Start = processor.GetSourcePosition(startingPosition, out line, out column)},
+                Span = { Start = processor.GetSourcePosition(startingPosition, out int line, out int column) },
                Line = line,
                Column = column,
                OpeningCharacter = openingChar,
@@ -195,96 +191,90 @@ namespace Markdig.Extensions.SmartyPants
            return quotePants;
        }

+        private readonly struct Opener
+        {
+            public readonly int Type;
+            public readonly int Index;
+
+            public Opener(int type, int index)
+            {
+                Type = type;
+                Index = index;
+            }
+        }
+
        private void BlockOnProcessInlinesEnd(InlineProcessor processor, Inline inline)
        {
            processor.Block.ProcessInlinesEnd -= BlockOnProcessInlinesEnd;

            var pants = (ListSmartyPants) processor.ParserStates[Index];

-            // We only change quote into left or right quotes if we find proper balancing
-            var previousIndices = new int[3] {-1, -1, -1};
+            Stack<Opener> openers = new Stack<Opener>(4);

            for (int i = 0; i < pants.Count; i++)
            {
                var quote = pants[i];
+                var quoteType = quote.Type;

-                int currentTypeIndex = -1;
-                SmartyPantType expectedLeftQuote = 0;
-                SmartyPantType expectedRightQuote = 0;
+                int type;
+                bool isLeft;

-                if (quote.Type == SmartyPantType.LeftQuote || quote.Type == SmartyPantType.RightQuote)
+                if (quoteType == SmartyPantType.LeftQuote || quoteType == SmartyPantType.RightQuote)
                {
-                    currentTypeIndex = 0;
-                    expectedLeftQuote = SmartyPantType.LeftQuote;
-                    expectedRightQuote = SmartyPantType.RightQuote;
+                    type = 0;
+                    isLeft = quoteType == SmartyPantType.LeftQuote;
                }
-                else if (quote.Type == SmartyPantType.LeftDoubleQuote || quote.Type == SmartyPantType.RightDoubleQuote)
+                else if (quoteType == SmartyPantType.LeftDoubleQuote || quoteType == SmartyPantType.RightDoubleQuote)
                {
-                    currentTypeIndex = 1;
-                    expectedLeftQuote = SmartyPantType.LeftDoubleQuote;
-                    expectedRightQuote = SmartyPantType.RightDoubleQuote;
+                    type = 1;
+                    isLeft = quoteType == SmartyPantType.LeftDoubleQuote;
                }
-                else if (quote.Type == SmartyPantType.LeftAngleQuote || quote.Type == SmartyPantType.RightAngleQuote)
+                else if (quoteType == SmartyPantType.LeftAngleQuote || quoteType == SmartyPantType.RightAngleQuote)
                {
-                    currentTypeIndex = 2;
-                    expectedLeftQuote = SmartyPantType.LeftAngleQuote;
-                    expectedRightQuote = SmartyPantType.RightAngleQuote;
-                }
-
-                if (currentTypeIndex < 0)
-                {
-                    continue;
-                }
-
-                int previousIndex = previousIndices[currentTypeIndex];
-                var previousQuote = previousIndex >= 0 ? pants[previousIndex] : null;
-                if (previousQuote == null)
-                {
-                    if (quote.Type == expectedLeftQuote)
-                    {
-                        previousIndices[currentTypeIndex] = i;
-                    }
+                    type = 2;
+                    isLeft = quoteType == SmartyPantType.LeftAngleQuote;
                }
                else
                {
-                    if (quote.Type == expectedRightQuote)
-                    {
-                        // Replace all intermediate unmatched left or right SmartyPants to their literal equivalent
-                        pants.RemoveAt(i);
-                        i--;
-                        for (int j = i; j > previousIndex; j--)
-                        {
-                            var toReplace = pants[j];
-                            pants.RemoveAt(j);
-                            toReplace.ReplaceBy(new LiteralInline(toReplace.ToString())
-                            {
-                                Span = toReplace.Span,
-                                Line = toReplace.Line,
-                                Column = toReplace.Column,
-                            });
-                            i--;
-                        }
+                    quote.ReplaceBy(quote.AsLiteralInline());
+                    continue;
+                }

-                        // If we matched, we remove left/right quotes from the list
-                        pants.RemoveAt(previousIndex);
-                        previousIndices[currentTypeIndex] = -1;
-                    }
-                    else
+                if (isLeft)
+                {
+                    openers.Push(new Opener(type, i));
+                }
+                else
+                {
+                    bool found = false;
+
+                    while (openers.Count > 0)
                    {
-                        previousIndices[currentTypeIndex] = i;
+                        Opener opener = openers.Pop();
+                        var previousQuote = pants[opener.Index];
+
+                        if (opener.Type == type)
+                        {
+                            found = true;
+                            break;
+                        }
+                        else
+                        {
+                            previousQuote.ReplaceBy(previousQuote.AsLiteralInline());
+                        }
+                    }
+
+                    if (!found)
+                    {
+                        quote.ReplaceBy(quote.AsLiteralInline());
                    }
                }
            }

-            // If we have any quotes lefts, replace them by there literal equivalent
-            foreach (var quote in pants)
+            foreach (var opener in openers)
            {
-                quote.ReplaceBy(new LiteralInline(quote.ToString())
-                {
-                    Span = quote.Span,
-                    Line = quote.Line,
-                    Column = quote.Column,
-                });
+                var quote = pants[opener.Index];
+                quote.ReplaceBy(quote.AsLiteralInline());
            }

            pants.Clear();
@@ -294,8 +284,7 @@ namespace Markdig.Extensions.SmartyPants
            bool isFinalProcessing)
        {
            // Don't try to process anything if there are no dash
-            var quotePants = state.ParserStates[Index] as ListSmartyPants;
-            if (quotePants == null || !quotePants.HasDash)
+            if (!(state.ParserStates[Index] is ListSmartyPants quotePants) || !quotePants.HasDash)
            {
                return true;
            }
@@ -309,10 +298,8 @@ namespace Markdig.Extensions.SmartyPants
                {
                    var next = child.NextSibling;

-                    if (child is LiteralInline)
+                    if (child is LiteralInline literal)
                    {
-                        var literal = (LiteralInline) child;
-
                        var startIndex = 0;

                        var indexOfDash = literal.Content.IndexOf("--", startIndex);
@@ -372,7 +359,7 @@ namespace Markdig.Extensions.SmartyPants
        }


-        private class ListSmartyPants : List<SmartyPant>
+        private sealed class ListSmartyPants : List<SmartyPant>
        {
            public bool HasDash { get; set; }
        }
--- a/src/Markdig/Extensions/Tables/GridTableParser.cs
+++ b/src/Markdig/Extensions/Tables/GridTableParser.cs
@@ -1,4 +1,4 @@
-
+
 // Copyright (c) Alexandre Mutel. All rights reserved.
 // This file is licensed under the BSD-Clause 2 license. 
 // See the license.txt file in the project root for more information.
@@ -138,7 +138,7 @@ namespace Markdig.Extensions.Tables
        private static void SetRowSpanState(List<GridTableState.ColumnSlice> columns, StringSlice line, out bool isHeaderRow, out bool hasRowSpan)
        {
            var lineStart = line.Start;
-            isHeaderRow = line.PeekChar(1) == '=' || line.PeekChar(2) == '=';
+            isHeaderRow = line.PeekChar() == '=' || line.PeekChar(2) == '=';
            hasRowSpan = false;
            foreach (var columnSlice in columns)
            {
--- a/src/Markdig/Extensions/Tables/GridTableState.cs
+++ b/src/Markdig/Extensions/Tables/GridTableState.cs
@@ -10,7 +10,7 @@ namespace Markdig.Extensions.Tables
    /// <summary>
    /// Internal state used by the <see cref="GridTableParser"/>
    /// </summary>
-    internal class GridTableState
+    internal sealed class GridTableState
    {
        public int Start { get; set; }

--- a/src/Markdig/Helpers/CharHelper.cs
+++ b/src/Markdig/Helpers/CharHelper.cs
@@ -36,7 +36,8 @@ using System;
 using System.Globalization;
 using System.Collections.Generic;
 using System.Runtime.CompilerServices;
-
+using System.Diagnostics;
+
 namespace Markdig.Helpers
 {
    /// <summary>
@@ -130,9 +131,9 @@ namespace Markdig.Helpers
            int result = 0;
            for (int i = 0; i < text.Length; i++)
            {
-                var character = Char.ToUpperInvariant(text[i]);
+                var character = char.ToUpperInvariant(text[i]);
                var candidate = romanMap[character];
-                if (i + 1 < text.Length && candidate < romanMap[Char.ToUpperInvariant(text[i + 1])])
+                if (i + 1 < text.Length && candidate < romanMap[char.ToUpperInvariant(text[i + 1])])
                {
                    result -= candidate;
                }
@@ -147,7 +148,9 @@ namespace Markdig.Helpers
        [MethodImpl(MethodImplOptionPortable.AggressiveInlining)]
        public static int AddTab(int column)
        {
-            return ((column + TabSize) / TabSize) * TabSize;
+            // return ((column + TabSize) / TabSize) * TabSize;
+            Debug.Assert(TabSize == 4, "Change the AddTab implementation if TabSize is no longer a power of 2");
+            return TabSize + (column & ~(TabSize - 1));
        }

        [MethodImpl(MethodImplOptionPortable.AggressiveInlining)]
@@ -174,13 +177,13 @@ namespace Markdig.Helpers
        {
            // 2.1 Characters and lines 
            // A whitespace character is a space(U + 0020), tab(U + 0009), newline(U + 000A), line tabulation (U + 000B), form feed (U + 000C), or carriage return (U + 000D).
-            return c == ' ' || c == '\t' || c == '\n' || c == '\v' || c == '\f' || c == '\r';
+            return c <= ' ' && (c == ' ' || c == '\t' || c == '\n' || c == '\v' || c == '\f' || c == '\r');
        }

        [MethodImpl(MethodImplOptionPortable.AggressiveInlining)]
        public static bool IsControl(this char c)
        {
-            return c < ' ' || Char.IsControl(c);
+            return c < ' ' || char.IsControl(c);
        }

        [MethodImpl(MethodImplOptionPortable.AggressiveInlining)]
@@ -193,7 +196,7 @@ namespace Markdig.Helpers
        //[MethodImpl(MethodImplOptionPortable.AggressiveInlining)]
        public static bool IsWhiteSpaceOrZero(this char c)
        {
-            return IsWhitespace(c) || IsZero(c);
+            return IsZero(c) || IsWhitespace(c);
        }

        // Note that we are not considering the character & as a punctuation in HTML
@@ -294,14 +297,14 @@ namespace Markdig.Helpers

        [MethodImpl(MethodImplOptionPortable.AggressiveInlining)]
        public static bool IsAlphaUpper(this char c)
-        {
-            return c >= 'A' && c <= 'Z';
+        {
+            return (uint)(c - 'A') <= ('Z' - 'A');
        }

        [MethodImpl(MethodImplOptionPortable.AggressiveInlining)]
        public static bool IsAlpha(this char c)
-        {
-            return (c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z');
+        {
+            return (uint)((c - 'A') & ~0x20) <= ('Z' - 'A');
        }

        [MethodImpl(MethodImplOptionPortable.AggressiveInlining)]
@@ -313,7 +316,7 @@ namespace Markdig.Helpers
        [MethodImpl(MethodImplOptionPortable.AggressiveInlining)]
        public static bool IsDigit(this char c)
        {
-            return c >= '0' && c <= '9';
+            return (uint)(c - '0') <= ('9' - '0');
        }

        public static bool IsAsciiPunctuation(this char c)
@@ -367,16 +370,20 @@ namespace Markdig.Helpers

        [MethodImpl(MethodImplOptionPortable.AggressiveInlining)]
        public static bool IsHighSurrogate(char c)
-        {
-            return ((c >= HighSurrogateStart) && (c <= HighSurrogateEnd));
+        {
+            return IsInInclusiveRange(c, HighSurrogateStart, HighSurrogateEnd);
        }

        [MethodImpl(MethodImplOptionPortable.AggressiveInlining)]
        public static bool IsLowSurrogate(char c)
        {
-            return ((c >= LowSurrogateStart) && (c <= LowSurrogateEnd));
+            return IsInInclusiveRange(c, LowSurrogateStart, LowSurrogateEnd);
        }

+        [MethodImpl(MethodImplOptionPortable.AggressiveInlining)]
+        private static bool IsInInclusiveRange(char c, char min, char max)
+            => (uint) (c - min) <= (uint) (max - min);
+
        public static int ConvertToUtf32(char highSurrogate, char lowSurrogate)
        {
            if (!IsHighSurrogate(highSurrogate))
@@ -390,13 +397,14 @@ namespace Markdig.Helpers
            return (((highSurrogate - HighSurrogateStart) * 0x400) + (lowSurrogate - LowSurrogateStart) + UnicodePlane01Start);
        }

-        public static IEnumerable<int> ToUtf32(string text)
+        public static IEnumerable<int> ToUtf32(StringSlice text)
        {
-            for (int i = 0; i < text.Length; i++)
+            for (int i = text.Start; i <= text.End; i++)
            {
-                if (IsHighSurrogate(text[i]) && i < text.Length - 1 && IsLowSurrogate(text[i + 1]))
-                {
-                    yield return ConvertToUtf32(text[i], text[i + 1]);
+                if (IsHighSurrogate(text[i]) && i < text.End && IsLowSurrogate(text[i + 1]))
+                {
+                    Debug.Assert(char.IsSurrogatePair(text[i], text[i + 1]));
+                    yield return char.ConvertToUtf32(text[i], text[i + 1]);
                }
                else
                {
--- a/src/Markdig/Helpers/CompactPrefixTree.cs
+++ b/src/Markdig/Helpers/CompactPrefixTree.cs
@@ -25,7 +25,7 @@ namespace Markdig.Helpers
    /// <para>Something between a Trie and a full Radix tree, but stored linearly in memory</para>
    /// </summary>
    /// <typeparam name="TValue">The value associated with the key</typeparam>
-    internal class CompactPrefixTree<TValue>
+    internal sealed class CompactPrefixTree<TValue>
 //#if !LEGACY
 //        : IReadOnlyDictionary<string, TValue>, IReadOnlyList<KeyValuePair<string, TValue>>
 //#endif
--- a/src/Markdig/Helpers/CustomArrayPool.cs
+++ b/src/Markdig/Helpers/CustomArrayPool.cs
@@ -0,0 +1,86 @@
+using System.Threading;
+
+namespace Markdig.Helpers
+{
+    internal sealed class CustomArrayPool<T>
+    {
+        private sealed class Bucket
+        {
+            private readonly T[][] _buffers;
+
+            private int _index;
+            private int _lock;
+
+            public Bucket(int numberOfBuffers)
+            {
+                _buffers = new T[numberOfBuffers][];
+            }
+
+            public T[] Rent()
+            {
+                T[][] buffers = _buffers;
+                T[] buffer = null;
+                if (Interlocked.CompareExchange(ref _lock, 1, 0) == 0)
+                {
+                    int index = _index;
+                    if ((uint)index < (uint)buffers.Length)
+                    {
+                        buffer = buffers[index];
+                        buffers[index] = null;
+                        _index = index + 1;
+                    }
+                    Interlocked.Decrement(ref _lock);
+                }
+                return buffer;
+            }
+
+            public void Return(T[] array)
+            {
+                var buffers = _buffers;
+                if (Interlocked.CompareExchange(ref _lock, 1, 0) == 0)
+                {
+                    int index = _index - 1;
+                    if ((uint)index < (uint)buffers.Length)
+                    {
+                        buffers[index] = array;
+                        _index = index;
+                    }
+                    Interlocked.Decrement(ref _lock);
+                }
+            }
+        }
+
+        private readonly Bucket _bucket4, _bucket8, _bucket16, _bucket32;
+
+        public CustomArrayPool(int size4, int size8, int size16, int size32)
+        {
+            _bucket4 = new Bucket(size4);
+            _bucket8 = new Bucket(size8);
+            _bucket16 = new Bucket(size16);
+            _bucket32 = new Bucket(size32);
+        }
+
+        private Bucket SelectBucket(int length)
+        {
+            switch (length)
+            {
+                case 4: return _bucket4;
+                case 8: return _bucket8;
+                case 16: return _bucket16;
+                case 32: return _bucket32;
+
+                default: return null;
+            }
+        }
+
+        public T[] Rent(int length)
+        {
+            return SelectBucket(length)?.Rent() ?? new T[length];
+        }
+
+        public void Return(T[] array)
+        {
+            SelectBucket(array.Length)?.Return(array);
+        }
+    }
+}
--- a/src/Markdig/Helpers/HtmlHelper.cs
+++ b/src/Markdig/Helpers/HtmlHelper.cs
@@ -373,7 +373,7 @@ namespace Markdig.Helpers
            }
            builder.Append('-');
            builder.Append('-');
-            if (text.PeekChar(1) == '>')
+            if (text.PeekChar() == '>')
            {
                return false;
            }
--- a/src/Markdig/Helpers/LinkHelper.cs
+++ b/src/Markdig/Helpers/LinkHelper.cs
@@ -597,20 +597,23 @@ namespace Markdig.Helpers
                        }
                    }

-                    if (hasEscape && !c.IsAsciiPunctuation())
+                    if (!isAutoLink)
                    {
-                        buffer.Append('\\');
-                    }
+                        if (hasEscape && !c.IsAsciiPunctuation())
+                        {
+                            buffer.Append('\\');
+                        }

-                    // If we have an escape
-                    if (c == '\\')
-                    {
-                        hasEscape = true;
-                        c = text.NextChar();
-                        continue;
-                    }
+                        // If we have an escape
+                        if (c == '\\')
+                        {
+                            hasEscape = true;
+                            c = text.NextChar();
+                            continue;
+                        }

-                    hasEscape = false;
+                        hasEscape = false;
+                    }

                    if (IsEndOfUri(c, isAutoLink))
                    {
@@ -622,10 +625,7 @@ namespace Markdig.Helpers
                    {
                        if (c == '&')
                        {
-                            int entityNameStart;
-                            int entityNameLength;
-                            int entityValue;
-                            if (HtmlHelper.ScanEntity(text, out entityValue, out entityNameStart, out entityNameLength) > 0)
+                            if (HtmlHelper.ScanEntity(text, out _, out _, out _) > 0)
                            {
                                isValid = true;
                                break;
--- a/src/Markdig/Helpers/StringBuilderExtensions.cs
+++ b/src/Markdig/Helpers/StringBuilderExtensions.cs
@@ -6,7 +6,7 @@ using System.Text;
 namespace Markdig.Helpers
 {
    /// <summary>
-    /// Extensions for StringBuilder with <see cref="StringSlice"/>
+    /// Extensions for StringBuilder
    /// </summary>
    public static class StringBuilderExtensions
    {
@@ -19,5 +19,12 @@ namespace Markdig.Helpers
        {
            return builder.Append(slice.Text, slice.Start, slice.Length);
        }
+
+        internal static string GetStringAndReset(this StringBuilder builder)
+        {
+            string text = builder.ToString();
+            builder.Length = 0;
+            return text;
+        }
    }
 }
--- a/src/Markdig/Helpers/StringLine.cs
+++ b/src/Markdig/Helpers/StringLine.cs
@@ -77,7 +77,7 @@ namespace Markdig.Helpers
            return line.Slice;
        }

-        public override string ToString()
+        public readonly override string ToString()
        {
            return Slice.ToString();
        }
--- a/src/Markdig/Helpers/StringLineGroup.cs
+++ b/src/Markdig/Helpers/StringLineGroup.cs
@@ -5,26 +5,28 @@
 using System;
 using System.Collections;
 using System.Collections.Generic;
-using System.Diagnostics;
 using System.Runtime.CompilerServices;
-using Markdig.Extensions.Tables;

 namespace Markdig.Helpers
 {
    /// <summary>
    /// A group of <see cref="StringLine"/>.
    /// </summary>
-    /// <seealso cref="System.Collections.IEnumerable" />
+    /// <seealso cref="IEnumerable" />
    public struct StringLineGroup : IEnumerable
    {
+        // Feel free to change these numbers if you see a positive change
+        private static readonly CustomArrayPool<StringLine> _pool
+            = new CustomArrayPool<StringLine>(512, 386, 128, 64);
+
        /// <summary>
        /// Initializes a new instance of the <see cref="StringLineGroup"/> class.
        /// </summary>
        /// <param name="capacity"></param>
-        public StringLineGroup(int capacity)
+        public StringLineGroup(int capacity, bool willRelease = false)
        {
            if (capacity <= 0) throw new ArgumentOutOfRangeException(nameof(capacity));
-            Lines = new StringLine[capacity];
+            Lines = _pool.Rent(willRelease ? Math.Max(8, capacity) : capacity);
            Count = 0;
        }

@@ -100,7 +102,7 @@ namespace Markdig.Helpers
            Lines[Count++] = new StringLine(ref slice);
        }

-        public override string ToString()
+        public readonly override string ToString()
        {
            return ToSlice().ToString();
        }
@@ -110,7 +112,7 @@ namespace Markdig.Helpers
        /// </summary>
        /// <param name="lineOffsets">The position of the `\n` line offsets from the beginning of the returned slice.</param>
        /// <returns>A single slice concatenating the lines of this instance</returns>
-        public StringSlice ToSlice(List<LineOffset> lineOffsets = null)
+        public readonly StringSlice ToSlice(List<LineOffset> lineOffsets = null)
        {
            // Optimization case when no lines
            if (Count == 0)
@@ -128,6 +130,11 @@ namespace Markdig.Helpers
                return Lines[0];
            }

+            if (lineOffsets != null && lineOffsets.Capacity < lineOffsets.Count + Count)
+            {
+                lineOffsets.Capacity = Math.Max(lineOffsets.Count + Count, lineOffsets.Capacity * 2);
+            }
+
            // Else use a builder
            var builder = StringBuilderCache.Local();
            int previousStartOfLine = 0;
@@ -151,16 +158,14 @@ namespace Markdig.Helpers
            {
                lineOffsets.Add(new LineOffset(Lines[Count - 1].Position, Lines[Count - 1].Column, Lines[Count - 1].Slice.Start - Lines[Count - 1].Position, previousStartOfLine, builder.Length));
            }
-            var str = builder.ToString();
-            builder.Length = 0;
-            return new StringSlice(str);
+            return new StringSlice(builder.GetStringAndReset());
        }

        /// <summary>
        /// Converts this instance into a <see cref="ICharIterator"/>.
        /// </summary>
        /// <returns></returns>
-        public Iterator ToCharIterator()
+        public readonly Iterator ToCharIterator()
        {
            return new Iterator(this);
        }
@@ -183,14 +188,24 @@ namespace Markdig.Helpers

        private void IncreaseCapacity()
        {
-            var newItems = new StringLine[Lines.Length * 2];
+            var newItems = _pool.Rent(Lines.Length * 2);
            if (Count > 0)
            {
                Array.Copy(Lines, 0, newItems, 0, Count);
+                Array.Clear(Lines, 0, Count);
            }
+            _pool.Return(Lines);
            Lines = newItems;
        }

+        internal void Release()
+        {
+            Array.Clear(Lines, 0, Count);
+            _pool.Return(Lines);
+            Lines = null;
+            Count = -1;
+        }
+
        /// <summary>
        /// The iterator used to iterate other the lines.
        /// </summary>
@@ -207,7 +222,7 @@ namespace Markdig.Helpers
                _offset = -1;
                SliceIndex = 0;
                CurrentChar = '\0';
-                End = -2; 
+                End = -2;
                for (int i = 0; i < lines.Count; i++)
                {
                    End += lines.Lines[i].Slice.Length + 1; // Add chars
@@ -221,7 +236,7 @@ namespace Markdig.Helpers

            public int End { get; private set; }

-            public bool IsEmpty => Start > End;
+            public readonly bool IsEmpty => Start > End;

            public int SliceIndex { get; private set; }

@@ -277,7 +292,7 @@ namespace Markdig.Helpers
                return CurrentChar;
            }

-            public char PeekChar(int offset = 1)
+            public readonly char PeekChar(int offset = 1)
            {
                if (offset < 0) throw new ArgumentOutOfRangeException("Negative offset are not supported for StringLineGroup", nameof(offset));

@@ -298,17 +313,15 @@ namespace Markdig.Helpers
            public bool TrimStart()
            {
                var c = CurrentChar;
-                bool hasSpaces = false;
                while (c.IsWhitespace())
                {
-                    hasSpaces = true;
                    c = NextChar();
                }
-                return hasSpaces;
+                return IsEmpty;
            }
        }

-        public struct LineOffset
+        public readonly struct LineOffset
        {
            public LineOffset(int linePosition, int column, int offset, int start, int end)
            {
--- a/src/Markdig/Helpers/StringSlice.cs
+++ b/src/Markdig/Helpers/StringSlice.cs
@@ -38,8 +38,7 @@ namespace Markdig.Helpers
        /// <exception cref="System.ArgumentNullException"></exception>
        public StringSlice(string text, int start, int end)
        {
-            if (text == null) throw new ArgumentNullException(nameof(text));
-            Text = text;
+            Text = text ?? throw new ArgumentNullException(nameof(text));
            Start = start;
            End = end;
        }
@@ -62,24 +61,40 @@ namespace Markdig.Helpers
        /// <summary>
        /// Gets the length.
        /// </summary>
-        public int Length => End - Start + 1;
+        public readonly int Length => End - Start + 1;

        /// <summary>
        /// Gets the current character.
        /// </summary>
-        public char CurrentChar => Start <= End ? this[Start] : '\0';
+        public readonly char CurrentChar
+        {
+            get
+            {
+                int start = Start;
+                return start <= End ? Text[start] : '\0';
+            }
+        }

        /// <summary>
        /// Gets a value indicating whether this instance is empty.
        /// </summary>
-        public bool IsEmpty => Start > End;
+        public readonly bool IsEmpty
+        {
+            [MethodImpl(MethodImplOptionPortable.AggressiveInlining)]
+            get => Start > End;
+        }

        /// <summary>
        /// Gets the <see cref="System.Char"/> at the specified index.
        /// </summary>
        /// <param name="index">The index.</param>
        /// <returns>A character in the slice at the specified index (not from <see cref="Start"/> but from the begining of the slice)</returns>
-        public char this[int index] => Text[index];
+        public readonly char this[int index]
+        {
+            [MethodImpl(MethodImplOptionPortable.AggressiveInlining)]
+            get => Text[index];
+        }
+

        /// <summary>
        /// Goes to the next character, incrementing the <see cref="Start" /> position.
@@ -90,13 +105,27 @@ namespace Markdig.Helpers
        [MethodImpl(MethodImplOptionPortable.AggressiveInlining)]
        public char NextChar()
        {
-            Start++;
-            if (Start > End)
+            int start = Start;
+            if (start >= End)
            {
                Start = End + 1;
                return '\0';
            }
-            return Text[Start];
+            start++;
+            Start = start;
+            return Text[start];
+        }
+
+        /// <summary>
+        /// Peeks a character at the offset of 1 from the current <see cref="Start"/> position
+        /// inside the range <see cref="Start"/> and <see cref="End"/>, returns `\0` if outside this range.
+        /// </summary>
+        /// <returns>The character at offset, returns `\0` if none.</returns>
+        [MethodImpl(MethodImplOptionPortable.AggressiveInlining)]
+        public readonly char PeekChar()
+        {
+            int index = Start + 1;
+            return index <= End ? Text[index] : '\0';
        }

        /// <summary>
@@ -106,10 +135,10 @@ namespace Markdig.Helpers
        /// <param name="offset">The offset.</param>
        /// <returns>The character at offset, returns `\0` if none.</returns>
        [MethodImpl(MethodImplOptionPortable.AggressiveInlining)]
-        public char PeekChar(int offset = 1)
+        public readonly char PeekChar(int offset)
        {
            var index = Start + offset;
-            return index >= Start && index <= End ? Text[index] : (char) 0;
+            return index >= Start && index <= End ? Text[index] : '\0';
        }

        /// <summary>
@@ -117,9 +146,10 @@ namespace Markdig.Helpers
        /// </summary>
        /// <returns>The character at offset, returns `\0` if none.</returns>
        [MethodImpl(MethodImplOptionPortable.AggressiveInlining)]
-        public char PeekCharAbsolute(int index)
+        public readonly char PeekCharAbsolute(int index)
        {
-            return index >= 0 && index < Text.Length ? Text[index] : (char)0;
+            string text = Text;
+            return (uint)index < (uint)text.Length ? text[index] : '\0';
        }

        /// <summary>
@@ -129,10 +159,11 @@ namespace Markdig.Helpers
        /// <param name="offset">The offset.</param>
        /// <returns>The character at offset, returns `\0` if none.</returns>
        [MethodImpl(MethodImplOptionPortable.AggressiveInlining)]
-        public char PeekCharExtra(int offset)
+        public readonly char PeekCharExtra(int offset)
        {
            var index = Start + offset;
-            return index >= 0 && index < Text.Length ? Text[index] : (char)0;
+            var text = Text;
+            return (uint)index < (uint)text.Length ? text[index] : '\0';
        }

        /// <summary>
@@ -141,7 +172,7 @@ namespace Markdig.Helpers
        /// <param name="text">The text.</param>
        /// <param name="offset">The offset.</param>
        /// <returns><c>true</c> if the text matches; <c>false</c> otherwise</returns>
-        public bool Match(string text, int offset = 0)
+        public readonly bool Match(string text, int offset = 0)
        {
            return Match(text, End, offset);
        }
@@ -153,19 +184,22 @@ namespace Markdig.Helpers
        /// <param name="end">The end.</param>
        /// <param name="offset">The offset.</param>
        /// <returns><c>true</c> if the text matches; <c>false</c> otherwise</returns>
-        public bool Match(string text, int end, int offset)
+        public readonly bool Match(string text, int end, int offset)
        {
            var index = Start + offset;
-            int i = 0;
-            for (; index <= end && i < text.Length; i++, index++)
+
+            if (end - index + 1 < text.Length)
+                return false;
+
+            string sliceText = Text;
+            for (int i = 0; i < text.Length; i++, index++)
            {
-                if (text[i] != Text[index])
+                if (text[i] != sliceText[index])
                {
                    return false;
                }
            }
-
-            return i == text.Length;
+            return true;
        }

        /// <summary>
@@ -196,7 +230,7 @@ namespace Markdig.Helpers
        /// <param name="text">The text.</param>
        /// <param name="offset">The offset.</param>
        /// <returns><c>true</c> if the text matches; <c>false</c> otherwise</returns>
-        public bool MatchLowercase(string text, int offset = 0)
+        public readonly bool MatchLowercase(string text, int offset = 0)
        {
            return MatchLowercase(text, End, offset);
        }
@@ -208,19 +242,22 @@ namespace Markdig.Helpers
        /// <param name="end">The end.</param>
        /// <param name="offset">The offset.</param>
        /// <returns><c>true</c> if the text matches; <c>false</c> otherwise</returns>
-        public bool MatchLowercase(string text, int end, int offset)
+        public readonly bool MatchLowercase(string text, int end, int offset)
        {
            var index = Start + offset;
-            int i = 0;
-            for (; index <= end && i < text.Length; i++, index++)
+
+            if (end - index + 1 < text.Length)
+                return false;
+
+            string sliceText = Text;
+            for (int i = 0; i < text.Length; i++, index++)
            {
-                if (text[i] != char.ToLowerInvariant(Text[index]))
+                if (text[i] != char.ToLowerInvariant(sliceText[index]))
                {
                    return false;
                }
            }
-
-            return i == text.Length;
+            return true;
        }

        /// <summary>
@@ -230,46 +267,41 @@ namespace Markdig.Helpers
        /// <param name="offset">The offset.</param>
        /// <param name="ignoreCase">true if ignore case</param>
        /// <returns><c>true</c> if the text was found; <c>false</c> otherwise</returns>
-        public int IndexOf(string text, int offset = 0, bool ignoreCase = false)
+        public readonly int IndexOf(string text, int offset = 0, bool ignoreCase = false)
        {
-            var end = End - text.Length + 1;
-            if (ignoreCase)
-            {
-                for (int i = Start + offset; i <= end; i++)
-                {
-                    if (MatchLowercase(text, End, i - Start))
-                    {
-                        return i; ;
-                    }
-                }
-            }
-            else
-            {
-                for (int i = Start + offset; i <= end; i++)
-                {
-                    if (Match(text, End, i - Start))
-                    {
-                        return i; ;
-                    }
-                }
-            }
-            return -1;
+            offset += Start;
+            int length = End - offset + 1;
+
+            if (length <= 0)
+                return -1;
+
+#if NETCORE
+            var span = Text.AsSpan(offset, length);
+            int index = ignoreCase ? span.IndexOf(text, StringComparison.OrdinalIgnoreCase) : span.IndexOf(text);
+            return index == -1 ? index : index + offset;
+#else
+            return Text.IndexOf(text, offset, length, ignoreCase ? StringComparison.OrdinalIgnoreCase : StringComparison.Ordinal);
+#endif
        }

        /// <summary>
        /// Searches for the specified character within this slice.
        /// </summary>
        /// <returns>A value >= 0 if the character was found, otherwise &lt; 0</returns>
-        public int IndexOf(char c)
+        public readonly int IndexOf(char c)
        {
-            for (int i = Start; i <= End; i++)
-            {
-                if (Text[i] == c)
-                {
-                    return i;
-                }
-            }
-            return -1;
+            int start = Start;
+            int length = End - start + 1;
+
+            if (length <= 0)
+                return -1;
+
+#if NETCORE
+            int index = Text.AsSpan(start, length).IndexOf(c);
+            return index == -1 ? index : index + start;
+#else
+            return Text.IndexOf(c, start, length);
+#endif
        }

        /// <summary>
@@ -281,7 +313,6 @@ namespace Markdig.Helpers
        public bool TrimStart()
        {
            // Strip leading spaces
-            var start = Start;
            for (; Start <= End; Start++)
            {
                if (!Text[Start].IsWhitespace())
@@ -289,7 +320,7 @@ namespace Markdig.Helpers
                    break;
                }
            }
-            return start != Start;
+            return IsEmpty;
        }

        /// <summary>
@@ -336,31 +367,29 @@ namespace Markdig.Helpers
        }

        /// <summary>
-        /// Returns a <see cref="System.String" /> that represents this instance.
+        /// Returns a <see cref="string" /> that represents this instance.
        /// </summary>
        /// <returns>
-        /// A <see cref="System.String" /> that represents this instance.
+        /// A <see cref="string" /> that represents this instance.
        /// </returns>
-        public override string ToString()
+        public readonly override string ToString()
        {
-            if (Text != null && Start <= End)
-            {
-                var length = Length;
-                if (Start == 0 && Text.Length == length)
-                {
-                    return Text;
-                }
+            string text = Text;
+            int start = Start;
+            int length = End - start + 1;

-                return Text.Substring(Start, length);
+            if (text is null || length <= 0)
+            {
+                return string.Empty;
            }
-            return string.Empty;
+            return text.Substring(start, length);
        }

        /// <summary>
        /// Determines whether this slice is empty or made only of whitespaces.
        /// </summary>
        /// <returns><c>true</c> if this slice is empty or made only of whitespaces; <c>false</c> otherwise</returns>
-        public bool IsEmptyOrWhitespace()
+        public readonly bool IsEmptyOrWhitespace()
        {
            for (int i = Start; i <= End; i++)
            {
--- a/src/Markdig/Markdig.targets
+++ b/src/Markdig/Markdig.targets
@@ -4,7 +4,7 @@
    <Description>A fast, powerful, CommonMark compliant, extensible Markdown processor for .NET with 20+ builtin extensions (pipetables, footnotes, definition lists... etc.)</Description>
    <Copyright>Alexandre Mutel</Copyright>
    <NeutralLanguage>en-US</NeutralLanguage>
-    <VersionPrefix>0.17.1</VersionPrefix>
+    <VersionPrefix>0.18.1</VersionPrefix>
    <Authors>Alexandre Mutel</Authors>
    <TargetFrameworks>net35;net40;netstandard2.0;uap10.0;netcoreapp2.1</TargetFrameworks>
    <PackageTags>Markdown CommonMark md html md2html</PackageTags>
@@ -13,7 +13,7 @@
    <PackageIconUrl>https://raw.githubusercontent.com/lunet-io/markdig/master/img/markdig.png</PackageIconUrl>
    <PackageProjectUrl>https://github.com/lunet-io/markdig</PackageProjectUrl>
    <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
-    <LangVersion>7.3</LangVersion>
+    <LangVersion>8.0</LangVersion>
  </PropertyGroup>

  <PropertyGroup Condition=" '$(TargetFramework)' == 'netcoreapp2.1' ">
--- a/src/Markdig/Markdown.cs
+++ b/src/Markdig/Markdown.cs
@@ -73,9 +73,18 @@ namespace Markdig
        public static string ToHtml(string markdown, MarkdownPipeline pipeline = null)
        {
            if (markdown == null) throw new ArgumentNullException(nameof(markdown));
-            var writer = new StringWriter();
-            ToHtml(markdown, writer, pipeline);
-            return writer.ToString();
+            pipeline = pipeline ?? new MarkdownPipelineBuilder().Build();
+            pipeline = CheckForSelfPipeline(pipeline, markdown);
+
+            var renderer = pipeline.GetCacheableHtmlRenderer();
+
+            var document = Parse(markdown, pipeline);
+            renderer.Render(document);
+            renderer.Writer.Flush();
+
+            string html = renderer.Writer.ToString();
+            pipeline.ReleaseCacheableHtmlRenderer(renderer);
+            return html;
        }

        /// <summary>
--- a/src/Markdig/MarkdownExtensions.cs
+++ b/src/Markdig/MarkdownExtensions.cs
@@ -92,8 +92,8 @@ namespace Markdig
                .UseDiagrams()
                .UseAutoLinks()
                .UseGenericAttributes(); // Must be last as it is one parser that is modifying other parsers
-        }
-        
+        }
+
        /// <summary>
        /// Uses this extension to enable autolinks from text `http://`, `https://`, `ftp://`, `mailto:`, `www.xxx.yyy`
        /// </summary>
@@ -421,20 +421,35 @@ namespace Markdig
        }

        /// <summary>
-        /// Uses the emoji and smiley extension.
+        /// Uses the emojis and smileys extension.
        /// </summary>
        /// <param name="pipeline">The pipeline.</param>
-        /// <param name="enableSmiley">Enable smiley in addition to Emoji, <c>true</c> by default.</param>
+        /// <param name="enableSmileys">Enable smileys in addition to emoji shortcodes, <c>true</c> by default.</param>
        /// <returns>The modified pipeline</returns>
-        public static MarkdownPipelineBuilder UseEmojiAndSmiley(this MarkdownPipelineBuilder pipeline, bool enableSmiley = true)
+        public static MarkdownPipelineBuilder UseEmojiAndSmiley(this MarkdownPipelineBuilder pipeline, bool enableSmileys = true)
        {
            if (!pipeline.Extensions.Contains<EmojiExtension>())
            {
-                pipeline.Extensions.Add(new EmojiExtension(enableSmiley));
+                var emojiMapping = enableSmileys ? EmojiMapping.DefaultEmojisAndSmileysMapping : EmojiMapping.DefaultEmojisOnlyMapping;
+                pipeline.Extensions.Add(new EmojiExtension(emojiMapping));
            }
            return pipeline;
        }

+        /// <summary>
+        /// Uses the emojis and smileys extension.
+        /// </summary>
+        /// <param name="pipeline">The pipeline.</param>
+        /// <param name="customEmojiMapping">Enable customization of the emojis and smileys mapping.</param>
+        /// <returns>The modified pipeline</returns>
+        public static MarkdownPipelineBuilder UseEmojiAndSmiley(this MarkdownPipelineBuilder pipeline, EmojiMapping customEmojiMapping)
+        {
+            if (!pipeline.Extensions.Contains<EmojiExtension>())
+            {
+                pipeline.Extensions.Add(new EmojiExtension(customEmojiMapping));
+            }
+            return pipeline;
+        }
        /// <summary>
        /// Add rel=nofollow to all links rendered to HTML.
        /// </summary>
--- a/src/Markdig/MarkdownPipeline.cs
+++ b/src/Markdig/MarkdownPipeline.cs
@@ -1,4 +1,4 @@
-// Copyright (c) Alexandre Mutel. All rights reserved.
+// Copyright (c) Alexandre Mutel. All rights reserved.
 // This file is licensed under the BSD-Clause 2 license. 
 // See the license.txt file in the project root for more information.
 using System;
@@ -63,5 +63,42 @@ namespace Markdig
                extension.Setup(this, renderer);
            }
        }
+
+
+        private HtmlRendererCache _rendererCache = null;
+
+        internal HtmlRenderer GetCacheableHtmlRenderer()
+        {
+            if (_rendererCache is null)
+            {
+                _rendererCache = new HtmlRendererCache
+                {
+                    OnNewInstanceCreated = Setup
+                };
+            }
+            return _rendererCache.Get();
+        }
+        internal void ReleaseCacheableHtmlRenderer(HtmlRenderer renderer)
+        {
+            _rendererCache.Release(renderer);
+        }
+
+        private sealed class HtmlRendererCache : ObjectCache<HtmlRenderer>
+        {
+            public Action<HtmlRenderer> OnNewInstanceCreated;
+
+            protected override HtmlRenderer NewInstance()
+            {
+                var writer = new StringWriter();
+                var renderer = new HtmlRenderer(writer);
+                OnNewInstanceCreated(renderer);
+                return renderer;
+            }
+
+            protected override void Reset(HtmlRenderer instance)
+            {
+                instance.Reset();
+            }
+        }
    }
 }
--- a/src/Markdig/Parsers/BlockProcessor.cs
+++ b/src/Markdig/Parsers/BlockProcessor.cs
@@ -500,6 +500,11 @@ namespace Markdig.Parsers
                if (!block.Parser.Close(this, block))
                {
                    block.Parent?.Remove(block);
+
+                    if (block is LeafBlock leaf)
+                    {
+                        leaf.Lines.Release();
+                    }
                }
                else
                {
@@ -873,7 +878,7 @@ namespace Markdig.Parsers
            NewBlocks.Clear();
        }

-        private class BlockParserStateCache : ObjectCache<BlockProcessor>
+        private sealed class BlockParserStateCache : ObjectCache<BlockProcessor>
        {
            private readonly BlockProcessor root;

--- a/src/Markdig/Parsers/FencedBlockParserBase.cs
+++ b/src/Markdig/Parsers/FencedBlockParserBase.cs
@@ -124,7 +124,9 @@ namespace Markdig.Parsers
            }
            else
            {
-                infoString = line.ToString().Trim();
+                var lineCopy = line;
+                lineCopy.Trim();
+                infoString = lineCopy.ToString();
            }

            fenced.Info = HtmlHelper.Unescape(infoString);
--- a/src/Markdig/Parsers/HtmlBlockParser.cs
+++ b/src/Markdig/Parsers/HtmlBlockParser.cs
@@ -100,7 +100,7 @@ namespace Markdig.Parsers
            if (c == '!')
            {
                c = line.NextChar();
-                if (c == '-' && line.PeekChar(1) == '-')
+                if (c == '-' && line.PeekChar() == '-')
                {
                    return CreateHtmlBlock(state, HtmlBlockType.Comment, startColumn, startPosition); // group 2
                }
@@ -140,7 +140,7 @@ namespace Markdig.Parsers
            }

            if (
-                !(c == '>' || (!hasLeadingClose && c == '/' && line.PeekChar(1) == '>') || c.IsWhitespace() ||
+                !(c == '>' || (!hasLeadingClose && c == '/' && line.PeekChar() == '>') || c.IsWhitespace() ||
                  c == '\0'))
            {
                return BlockState.None;
--- a/src/Markdig/Parsers/InlineProcessor.cs
+++ b/src/Markdig/Parsers/InlineProcessor.cs
@@ -192,7 +192,7 @@ namespace Markdig.Parsers
            previousLineIndexForSliceOffset = 0;
            lineOffsets.Clear();
            var text = leafBlock.Lines.ToSlice(lineOffsets);
-            leafBlock.Lines = new StringLineGroup();
+            leafBlock.Lines.Release();

            int previousStart = -1;

--- a/src/Markdig/Parsers/Inlines/LinkInlineParser.cs
+++ b/src/Markdig/Parsers/Inlines/LinkInlineParser.cs
@@ -28,9 +28,7 @@ namespace Markdig.Parsers.Inlines

            var c = slice.CurrentChar;

-            int line;
-            int column;
-            var startPosition = processor.GetSourcePosition(slice.Start, out line, out column);
+            var startPosition = processor.GetSourcePosition(slice.Start, out int line, out int column);

            bool isImage = false;
            if (c == '!')
@@ -49,11 +47,9 @@ namespace Markdig.Parsers.Inlines
                    // If this is not an image, we may have a reference link shortcut
                    // so we try to resolve it here
                    var saved = slice;
-                    string label;

-                    SourceSpan labelSpan;
                    // If the label is followed by either a ( or a [, this is not a shortcut
-                    if (LinkHelper.TryParseLabel(ref slice, out label, out labelSpan))
+                    if (LinkHelper.TryParseLabel(ref slice, out string label, out SourceSpan labelSpan))
                    {
                        if (!processor.Document.ContainsLinkReferenceDefinition(label))
                        {
@@ -97,230 +93,208 @@ namespace Markdig.Parsers.Inlines

        private bool ProcessLinkReference(InlineProcessor state, string label, bool isShortcut, SourceSpan labelSpan, LinkDelimiterInline parent, int endPosition)
        {
-            bool isValidLink = false;
-            LinkReferenceDefinition linkRef;
-            if (state.Document.TryGetLinkReferenceDefinition(label, out linkRef))
+            if (!state.Document.TryGetLinkReferenceDefinition(label, out LinkReferenceDefinition linkRef))
            {
-                Inline link = null;
-                // Try to use a callback directly defined on the LinkReferenceDefinition
-                if (linkRef.CreateLinkInline != null)
-                {
-                    link = linkRef.CreateLinkInline(state, linkRef, parent.FirstChild);
-                }
+                return false;
+            }

-                // Create a default link if the callback was not found
-                if (link == null)
+            Inline link = null;
+            // Try to use a callback directly defined on the LinkReferenceDefinition
+            if (linkRef.CreateLinkInline != null)
+            {
+                link = linkRef.CreateLinkInline(state, linkRef, parent.FirstChild);
+            }
+
+            // Create a default link if the callback was not found
+            if (link == null)
+            {
+                // Inline Link
+                link = new LinkInline()
                {
-                    // Inline Link
-                    link = new LinkInline()
+                    Url = HtmlHelper.Unescape(linkRef.Url),
+                    Title = HtmlHelper.Unescape(linkRef.Title),
+                    Label = label,
+                    LabelSpan = labelSpan,
+                    UrlSpan = linkRef.UrlSpan,
+                    IsImage = parent.IsImage,
+                    IsShortcut = isShortcut,
+                    Reference = linkRef,
+                    Span = new SourceSpan(parent.Span.Start, endPosition),
+                    Line = parent.Line,
+                    Column = parent.Column,
+                };
+            }
+
+            if (link is ContainerInline containerLink)
+            {
+                var child = parent.FirstChild;
+                if (child == null)
+                {
+                    child = new LiteralInline()
                    {
-                        Url = HtmlHelper.Unescape(linkRef.Url),
-                        Title = HtmlHelper.Unescape(linkRef.Title),
-                        Label = label,
-                        LabelSpan = labelSpan,
-                        UrlSpan = linkRef.UrlSpan,
-                        IsImage = parent.IsImage,
-                        IsShortcut = isShortcut,
-                        Reference = linkRef,
-                        Span = new SourceSpan(parent.Span.Start, endPosition),
+                        Content = StringSlice.Empty,
+                        IsClosed = true,
+                        // Not exact but we leave it like this
+                        Span = parent.Span,
                        Line = parent.Line,
                        Column = parent.Column,
                    };
+                    containerLink.AppendChild(child);
                }
-
-                var containerLink = link as ContainerInline;
-                if (containerLink != null)
+                else
                {
-                    var child = parent.FirstChild;
-                    if (child == null)
+                    // Insert all child into the link
+                    while (child != null)
                    {
-                        child = new LiteralInline()
-                        {
-                            Content = StringSlice.Empty,
-                            IsClosed = true,
-                            // Not exact but we leave it like this
-                            Span = parent.Span,
-                            Line = parent.Line,
-                            Column = parent.Column,
-                        };
+                        var next = child.NextSibling;
+                        child.Remove();
                        containerLink.AppendChild(child);
-                    }
-                    else
-                    {
-                        // Insert all child into the link
-                        while (child != null)
-                        {
-                            var next = child.NextSibling;
-                            child.Remove();
-                            containerLink.AppendChild(child);
-                            child = next;
-                        }
+                        child = next;
                    }
                }
-
-                link.IsClosed = true;
-
-                // Process emphasis delimiters
-                state.PostProcessInlines(0, link, null, false);
-
-                state.Inline = link;
-                isValidLink = true;
            }
-            //else
-            //{
-            //    // Else output a literal, leave it opened as we may have literals after
-            //    // that could be append to this one
-            //    var literal = new LiteralInline()
-            //    {
-            //        ContentBuilder = processor.StringBuilders.Get().Append('[').Append(label).Append(']')
-            //    };
-            //    processor.Inline = literal;
-            //}
-            return isValidLink;
+
+            link.IsClosed = true;
+
+            // Process emphasis delimiters
+            state.PostProcessInlines(0, link, null, false);
+
+            state.Inline = link;
+
+            return true;
        }

        private bool TryProcessLinkOrImage(InlineProcessor inlineState, ref StringSlice text)
        {
-            LinkDelimiterInline openParent = null;
-            foreach (var parent in inlineState.Inline.FindParentOfType<LinkDelimiterInline>())
+            LinkDelimiterInline openParent = inlineState.Inline.FirstParentOfType<LinkDelimiterInline>();
+
+            if (openParent is null)
            {
-                openParent = parent;
-                break;
-            }
-
-            if (openParent != null)
-            {
-                // If we do find one, but it’s not active,
-                // we remove the inactive delimiter from the stack,
-                // and return a literal text node ].
-                if (!openParent.IsActive)
-                {
-                    inlineState.Inline = new LiteralInline()
-                    {
-                        Content = new StringSlice("["),
-                        Span = openParent.Span,
-                        Line = openParent.Line,
-                        Column = openParent.Column,
-                    };
-                    openParent.ReplaceBy(inlineState.Inline);
-                    return false;
-                }
-
-                // 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 link/image,
-                // or shortcut reference link/image
-                var parentDelimiter = openParent.Parent;
-                var savedText = text;
-                switch (text.CurrentChar)
-                {
-                    case '(':
-                        string url;
-                        string title;
-                        SourceSpan linkSpan;
-                        SourceSpan titleSpan;
-                        if (LinkHelper.TryParseInlineLink(ref text, out url, out title, out linkSpan, out titleSpan))
-                        {
-                            // Inline Link
-                            var link = new LinkInline()
-                            {
-                                Url = HtmlHelper.Unescape(url),
-                                Title = HtmlHelper.Unescape(title),
-                                IsImage = openParent.IsImage,
-                                LabelSpan = openParent.LabelSpan,
-                                UrlSpan = inlineState.GetSourcePositionFromLocalSpan(linkSpan),
-                                TitleSpan = inlineState.GetSourcePositionFromLocalSpan(titleSpan),
-                                Span = new SourceSpan(openParent.Span.Start, inlineState.GetSourcePosition(text.Start -1)),
-                                Line = openParent.Line,
-                                Column = openParent.Column,
-                            };
-
-                            openParent.ReplaceBy(link);
-                            // Notifies processor as we are creating an inline locally
-                            inlineState.Inline = link;
-
-                            // Process emphasis delimiters
-                            inlineState.PostProcessInlines(0, link, null, false);
-
-                            // If we have a link (and not an image),
-                            // we also set all [ delimiters before the opening delimiter to inactive.
-                            // (This will prevent us from getting links within links.)
-                            if (!openParent.IsImage)
-                            {
-                                MarkParentAsInactive(parentDelimiter);
-                            }
-
-                            link.IsClosed = true;
-
-                            return true;
-                        }
-
-                        text = savedText;
-                        goto default;
-                    default:
-                        var labelSpan = SourceSpan.Empty;
-                        string label = null;
-                        bool isLabelSpanLocal = true;
-
-                        bool isShortcut = false;
-                        // Handle Collapsed links
-                        if (text.CurrentChar == '[')
-                        {
-                            if (text.PeekChar(1) == ']')
-                            {
-                                label = openParent.Label;
-                                labelSpan = openParent.LabelSpan;
-                                isLabelSpanLocal = false;
-                                text.NextChar(); // Skip [
-                                text.NextChar(); // Skip ]
-                            }
-                        }
-                        else
-                        {
-                            label = openParent.Label;
-                            isShortcut = true;
-                        }
-
-                        if (label != null || LinkHelper.TryParseLabel(ref text, true, out label, out labelSpan))
-                        {
-                            if (isLabelSpanLocal)
-                            {
-                                labelSpan = inlineState.GetSourcePositionFromLocalSpan(labelSpan);
-                            }
-
-                            if (ProcessLinkReference(inlineState, label, isShortcut, labelSpan, openParent, inlineState.GetSourcePosition(text.Start - 1)))
-                            {
-                                // Remove the open parent
-                                openParent.Remove();
-                                if (!openParent.IsImage)
-                                {
-                                    MarkParentAsInactive(parentDelimiter);
-                                }
-                            }
-                            else
-                            {
-                                return false;
-                            }
-                            return true;
-                        }
-                        break;
-                }
-
-                // We have a nested [ ]
-                // firstParent.Remove();
-                // The opening [ will be transformed to a literal followed by all the children of the [
-
-                var literal = new LiteralInline()
-                {
-                    Span = openParent.Span,
-                    Content = new StringSlice(openParent.IsImage ? "![" : "[")
-                };
-
-                inlineState.Inline = openParent.ReplaceBy(literal);
                return false;
            }

+            // If we do find one, but it’s not active,
+            // we remove the inactive delimiter from the stack,
+            // and return a literal text node ].
+            if (!openParent.IsActive)
+            {
+                inlineState.Inline = new LiteralInline()
+                {
+                    Content = new StringSlice("["),
+                    Span = openParent.Span,
+                    Line = openParent.Line,
+                    Column = openParent.Column,
+                };
+                openParent.ReplaceBy(inlineState.Inline);
+                return false;
+            }
+
+            // 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 link/image,
+            // or shortcut reference link/image
+            var parentDelimiter = openParent.Parent;
+            var savedText = text;
+
+            if (text.CurrentChar == '(')
+            {
+                if (LinkHelper.TryParseInlineLink(ref text, out string url, out string title, out SourceSpan linkSpan, out SourceSpan titleSpan))
+                {
+                    // Inline Link
+                    var link = new LinkInline()
+                    {
+                        Url = HtmlHelper.Unescape(url),
+                        Title = HtmlHelper.Unescape(title),
+                        IsImage = openParent.IsImage,
+                        LabelSpan = openParent.LabelSpan,
+                        UrlSpan = inlineState.GetSourcePositionFromLocalSpan(linkSpan),
+                        TitleSpan = inlineState.GetSourcePositionFromLocalSpan(titleSpan),
+                        Span = new SourceSpan(openParent.Span.Start, inlineState.GetSourcePosition(text.Start - 1)),
+                        Line = openParent.Line,
+                        Column = openParent.Column,
+                    };
+
+                    openParent.ReplaceBy(link);
+                    // Notifies processor as we are creating an inline locally
+                    inlineState.Inline = link;
+
+                    // Process emphasis delimiters
+                    inlineState.PostProcessInlines(0, link, null, false);
+
+                    // If we have a link (and not an image),
+                    // we also set all [ delimiters before the opening delimiter to inactive.
+                    // (This will prevent us from getting links within links.)
+                    if (!openParent.IsImage)
+                    {
+                        MarkParentAsInactive(parentDelimiter);
+                    }
+
+                    link.IsClosed = true;
+
+                    return true;
+                }
+
+                text = savedText;
+            }
+
+            var labelSpan = SourceSpan.Empty;
+            string label = null;
+            bool isLabelSpanLocal = true;
+
+            bool isShortcut = false;
+            // Handle Collapsed links
+            if (text.CurrentChar == '[')
+            {
+                if (text.PeekChar() == ']')
+                {
+                    label = openParent.Label;
+                    labelSpan = openParent.LabelSpan;
+                    isLabelSpanLocal = false;
+                    text.NextChar(); // Skip [
+                    text.NextChar(); // Skip ]
+                }
+            }
+            else
+            {
+                label = openParent.Label;
+                isShortcut = true;
+            }
+
+            if (label != null || LinkHelper.TryParseLabel(ref text, true, out label, out labelSpan))
+            {
+                if (isLabelSpanLocal)
+                {
+                    labelSpan = inlineState.GetSourcePositionFromLocalSpan(labelSpan);
+                }
+
+                if (ProcessLinkReference(inlineState, label, isShortcut, labelSpan, openParent, inlineState.GetSourcePosition(text.Start - 1)))
+                {
+                    // Remove the open parent
+                    openParent.Remove();
+                    if (!openParent.IsImage)
+                    {
+                        MarkParentAsInactive(parentDelimiter);
+                    }
+                    return true;
+                }
+                else if (text.CurrentChar != ']' && text.CurrentChar != '[')
+                {
+                    return false;
+                }
+            }
+
+            // We have a nested [ ]
+            // firstParent.Remove();
+            // The opening [ will be transformed to a literal followed by all the children of the [
+
+            var literal = new LiteralInline()
+            {
+                Span = openParent.Span,
+                Content = new StringSlice(openParent.IsImage ? "![" : "[")
+            };
+
+            inlineState.Inline = openParent.ReplaceBy(literal);
            return false;
        }

--- a/src/Markdig/Parsers/MarkdownParser.cs
+++ b/src/Markdig/Parsers/MarkdownParser.cs
@@ -28,6 +28,8 @@ namespace Markdig.Parsers
        private readonly ProcessDocumentDelegate documentProcessed;
        private readonly bool preciseSourceLocation;

+        private readonly int roughLineCountEstimate;
+
        private LineReader lineReader;

        /// <summary>
@@ -42,6 +44,8 @@ namespace Markdig.Parsers
        {
            if (text == null) throw new ArgumentNullException(nameof(text));
            if (pipeline == null) throw new ArgumentNullException(nameof(pipeline));
+
+            roughLineCountEstimate = text.Length / 40;
            text = FixupZero(text);
            lineReader = new LineReader(text);
            preciseSourceLocation = pipeline.PreciseSourceLocation;
@@ -82,13 +86,16 @@ namespace Markdig.Parsers
        }

        /// <summary>
-        /// Parses the current <see cref="Reader"/> into a Markdown <see cref="MarkdownDocument"/>.
+        /// Parses the current <see cref="lineReader"/> into a Markdown <see cref="MarkdownDocument"/>.
        /// </summary>
        /// <returns>A document instance</returns>
        private MarkdownDocument Parse()
        {
            if (preciseSourceLocation)
-                document.LineStartIndexes = new List<int>();
+            {
+                // Save some List resizing allocations
+                document.LineStartIndexes = new List<int>(Math.Min(512, roughLineCountEstimate));
+            }

            ProcessBlocks();
            ProcessInlines();
@@ -127,7 +134,7 @@ namespace Markdig.Parsers
            return text.Replace('\0', CharHelper.ZeroSafeChar);
        }

-        private class ContainerItemCache : DefaultObjectCache<ContainerItem>
+        private sealed class ContainerItemCache : DefaultObjectCache<ContainerItem>
        {
            protected override void Reset(ContainerItem instance)
            {
--- a/src/Markdig/Renderers/TextRendererBase.cs
+++ b/src/Markdig/Renderers/TextRendererBase.cs
@@ -70,7 +70,9 @@ namespace Markdig.Renderers
    public abstract class TextRendererBase<T> : TextRendererBase where T : TextRendererBase<T>
    {
        private bool previousWasLine;
+#if !NETCORE
        private char[] buffer;
+#endif
        private readonly List<string> indents;

        /// <summary>
@@ -79,12 +81,29 @@ namespace Markdig.Renderers
        /// <param name="writer">The writer.</param>
        protected TextRendererBase(TextWriter writer) : base(writer)
        {
+#if !NETCORE
            buffer = new char[1024];
+#endif
            // We assume that we are starting as if we had previously a newline
            previousWasLine = true;
            indents = new List<string>();
        }

+        internal void Reset()
+        {
+            if (Writer is StringWriter stringWriter)
+            {
+                stringWriter.GetStringBuilder().Length = 0;
+            }
+            else
+            {
+                throw new InvalidOperationException("Cannot reset this TextWriter instance");
+            }
+
+            previousWasLine = true;
+            indents.Clear();
+        }
+
        /// <summary>
        /// Ensures a newline.
        /// </summary>
@@ -193,6 +212,10 @@ namespace Markdig.Renderers

            WriteIndent();
            previousWasLine = false;
+
+#if NETCORE
+            Writer.Write(content.AsSpan(offset, length));
+#else
            if (offset == 0 && content.Length == length)
            {
                Writer.Write(content);
@@ -210,6 +233,7 @@ namespace Markdig.Renderers
                    Writer.Write(buffer, 0, length);
                }
            }
+#endif
            return (T) this;
        }

--- a/src/Markdig/Syntax/ContainerBlock.cs
+++ b/src/Markdig/Syntax/ContainerBlock.cs
@@ -189,12 +189,17 @@ namespace Markdig.Syntax
        {
            get
            {
-                if (index < 0 || index >= Count) throw new ArgumentOutOfRangeException(nameof(index));
-                return children[index];
+                var array = children;
+                if ((uint)index >= (uint)array.Length || index >= Count)
+                {
+                    ThrowHelper.ThrowIndexOutOfRangeException();
+                    return null;
+                }
+                return array[index];
            }
            set
            {
-                if (index < 0 || index >= Count) throw new ArgumentOutOfRangeException(nameof(index));
+                if ((uint)index >= (uint)Count) ThrowHelper.ThrowIndexOutOfRangeException();
                children[index] = value;
            }
        }
--- a/src/Markdig/Syntax/Inlines/ContainerInline.cs
+++ b/src/Markdig/Syntax/Inlines/ContainerInline.cs
@@ -1,9 +1,11 @@
 // Copyright (c) Alexandre Mutel. All rights reserved.
 // This file is licensed under the BSD-Clause 2 license.
 // See the license.txt file in the project root for more information.
+using Markdig.Helpers;
 using System;
 using System.Collections;
 using System.Collections.Generic;
+using System.Diagnostics;
 using System.IO;

 namespace Markdig.Syntax.Inlines
@@ -94,8 +96,20 @@ namespace Markdig.Syntax.Inlines
        /// <returns>An enumeration of T</returns>
        public IEnumerable<T> FindDescendants<T>() where T : Inline
        {
-            // Fast-path an empty container to avoid allocating a Stack
-            if (LastChild == null) yield break;
+            if (FirstChild is null)
+            {
+                return ArrayHelper<T>.Empty;
+            }
+            else
+            {
+                return FindDescendantsInternal<T>();
+            }
+        }
+        internal IEnumerable<T> FindDescendantsInternal<T>() where T : MarkdownObject
+        {
+#if !UAP
+            Debug.Assert(typeof(T).IsSubclassOf(typeof(Inline)));
+#endif

            Stack<Inline> stack = new Stack<Inline>();

--- a/src/Markdig/Syntax/Inlines/Inline.cs
+++ b/src/Markdig/Syntax/Inlines/Inline.cs
@@ -215,15 +215,28 @@ namespace Markdig.Syntax.Inlines
            var inline = this;
            while (inline != null)
            {
-                var delimiter = inline as T;
-                if (delimiter != null)
+                if (inline is T inlineOfT)
                {
-                    yield return delimiter;
+                    yield return inlineOfT;
                }
                inline = inline.Parent;
            }
        }

+        internal T FirstParentOfType<T>() where T : Inline
+        {
+            var inline = this;
+            while (inline != null)
+            {
+                if (inline is T inlineOfT)
+                {
+                    return inlineOfT;
+                }
+                inline = inline.Parent;
+            }
+            return null;
+        }
+
        public Inline FindBestParent()
        {
            var current = this;
--- a/src/Markdig/Syntax/LeafBlock.cs
+++ b/src/Markdig/Syntax/LeafBlock.cs
@@ -1,4 +1,4 @@
-// Copyright (c) Alexandre Mutel. All rights reserved.
+// Copyright (c) Alexandre Mutel. All rights reserved.
 // This file is licensed under the BSD-Clause 2 license.
 // See the license.txt file in the project root for more information.
 using System.Diagnostics;
@@ -51,7 +51,7 @@ namespace Markdig.Syntax
        {
            if (Lines.Lines == null)
            {
-                Lines = new StringLineGroup(4);
+                Lines = new StringLineGroup(4, ProcessInlines);
            }

            var stringLine = new StringLine(ref slice, line, column, sourceLinePosition);
@@ -64,12 +64,9 @@ namespace Markdig.Syntax
            {
                // We need to expand tabs to spaces
                var builder = StringBuilderCache.Local();
-                for (int i = column; i < CharHelper.AddTab(column); i++)
-                {
-                    builder.Append(' ');
-                }
+                builder.Append(' ', CharHelper.AddTab(column) - column);
                builder.Append(slice.Text, slice.Start + 1, slice.Length - 1);
-                stringLine.Slice = new StringSlice(builder.ToString());
+                stringLine.Slice = new StringSlice(builder.GetStringAndReset());
                Lines.Add(ref stringLine);
            }
        }
--- a/src/Markdig/Syntax/MarkdownObjectExtensions.cs
+++ b/src/Markdig/Syntax/MarkdownObjectExtensions.cs
@@ -3,6 +3,8 @@
 // See the license.txt file in the project root for more information.

 using System.Collections.Generic;
+using System.Diagnostics;
+using Markdig.Helpers;
 using Markdig.Syntax.Inlines;

 namespace Markdig.Syntax
@@ -20,10 +22,6 @@ namespace Markdig.Syntax
        /// <returns>An iteration over the descendant elements</returns>
        public static IEnumerable<MarkdownObject> Descendants(this MarkdownObject markdownObject)
        {
-            // Fast-path an object with no children to avoid allocating Stack objects
-            if (!(markdownObject is ContainerBlock) && !(markdownObject is ContainerInline)) yield break;
-
-            // TODO: A single Stack<(MarkdownObject block, bool push)> when ValueTuples are available
            Stack<MarkdownObject> stack = new Stack<MarkdownObject>();
            Stack<bool> pushStack = new Stack<bool>();

@@ -66,7 +64,51 @@ namespace Markdig.Syntax
        }

        /// <summary>
-        /// Iterates over the descendant elements for the specified markdown <see cref="Inline" /> element and filters by the type {T}.
+        /// Iterates over the descendant elements for the specified markdown element, including <see cref="Block"/> and <see cref="Inline"/> and filters by the type <typeparamref name="T"/>.
+        /// <para>The descendant elements are returned in DFS-like order.</para>
+        /// </summary>
+        /// <typeparam name="T">Type to use for filtering the descendants</typeparam>
+        /// <param name="markdownObject">The markdown object.</param>
+        /// <returns>An iteration over the descendant elements</returns>
+        public static IEnumerable<T> Descendants<T>(this MarkdownObject markdownObject) where T : MarkdownObject
+        {
+#if UAP
+            foreach (MarkdownObject descendant in markdownObject.Descendants())
+            {
+                if (descendant is T descendantT)
+                {
+                    yield return descendantT;
+                }
+            }
+#else
+            if (typeof(T).IsSubclassOf(typeof(Block)))
+            {
+                if (markdownObject is ContainerBlock containerBlock && containerBlock.Count > 0)
+                {
+                    return BlockDescendantsInternal<T>(containerBlock);
+                }
+            }
+            else // typeof(T).IsSubclassOf(typeof(Inline)))
+            {
+                if (markdownObject is ContainerBlock containerBlock)
+                {
+                    if (containerBlock.Count > 0)
+                    {
+                        return InlineDescendantsInternal<T>(containerBlock);
+                    }
+                }
+                else if (markdownObject is ContainerInline containerInline && containerInline.FirstChild != null)
+                {
+                    return containerInline.FindDescendantsInternal<T>();
+                }
+            }
+
+            return ArrayHelper<T>.Empty;
+#endif
+        }
+
+        /// <summary>
+        /// Iterates over the descendant elements for the specified markdown <see cref="Inline" /> element and filters by the type <typeparamref name="T"/>.
        /// </summary>
        /// <typeparam name="T">Type to use for filtering the descendants</typeparam>
        /// <param name="inline">The inline markdown object.</param>
@@ -77,7 +119,7 @@ namespace Markdig.Syntax
            => inline.FindDescendants<T>();

        /// <summary>
-        /// Iterates over the descendant elements for the specified markdown <see cref="Block" /> element and filters by the type {T}.
+        /// Iterates over the descendant elements for the specified markdown <see cref="Block" /> element and filters by the type <typeparamref name="T"/>.
        /// </summary>
        /// <typeparam name="T">Type to use for filtering the descendants</typeparam>
        /// <param name="block">The markdown object.</param>
@@ -86,8 +128,21 @@ namespace Markdig.Syntax
        /// </returns>
        public static IEnumerable<T> Descendants<T>(this ContainerBlock block) where T : Block
        {
-            // Fast-path an empty container to avoid allocating a Stack
-            if (block.Count == 0) yield break;
+            if (block != null && block.Count > 0)
+            {
+                return BlockDescendantsInternal<T>(block);
+            }
+            else
+            {
+                return ArrayHelper<T>.Empty;
+            }
+        }
+
+        private static IEnumerable<T> BlockDescendantsInternal<T>(ContainerBlock block) where T : MarkdownObject
+        {
+#if !UAP
+            Debug.Assert(typeof(T).IsSubclassOf(typeof(Block)));
+#endif

            Stack<Block> stack = new Stack<Block>();

@@ -115,5 +170,20 @@ namespace Markdig.Syntax
                }
            }
        }
+
+        private static IEnumerable<T> InlineDescendantsInternal<T>(ContainerBlock block) where T : MarkdownObject
+        {
+#if !UAP
+            Debug.Assert(typeof(T).IsSubclassOf(typeof(Inline)));
+#endif
+
+            foreach (MarkdownObject descendant in block.Descendants())
+            {
+                if (descendant is T descendantT)
+                {
+                    yield return descendantT;
+                }
+            }
+        }
    }
 }
Author	SHA1	Message	Date
Alexandre Mutel	dd6418d108	Bump to 0.18.1	2020-01-21 08:30:32 +01:00
Alexandre Mutel	7875e4bce9	Merge pull request #387 from MihaZupan/descendants-api Add missing Descendants<T> api	2020-01-21 08:24:13 +01:00
Alexandre Mutel	2e1b1a1fdc	Merge pull request #386 from mlaily/emoji-customization Emojis and smileys customization	2020-01-21 08:23:48 +01:00
MihaZupan	fa2b157c1a	Improve some CharHelper methods	2020-01-21 01:31:44 +01:00
MihaZupan	e4e6406546	Add missing Descendants<T> overload	2020-01-21 01:03:47 +01:00
Melvyn Laïly	1cff10270a	Set the default emoji dictionaries capacity in their ctor	2020-01-16 09:12:05 +01:00
Melvyn Laïly	87023184cb	Clarify emoji terminology (emoji "shortcode")	2020-01-16 09:12:04 +01:00
Melvyn Laïly	aecdf2192e	Improve the emoji extension (code review remarks)	2020-01-16 09:12:04 +01:00
Melvyn Laïly	0a36382126	Update changelog	2020-01-16 09:12:04 +01:00
Melvyn Laïly	0057b368ec	Add unit tests for custom emojis and smileys	2020-01-16 09:11:04 +01:00
Melvyn Laïly	3033284096	Re-allow emojis and smileys customization (this feature was broken in #308)	2020-01-16 09:11:03 +01:00
Alexandre Mutel	9b1b791b18	Merge pull request #341 from OpportunityLiu/master Add customizable media link; handle protocol-less media	2020-01-15 13:27:06 +01:00
Opportunity	2b7d205701	Merge branch 'master' into master	2020-01-15 19:35:17 +08:00
Opportunity	89b28659b1	Update src/Markdig/Extensions/MediaLinks/HostProviderBuilder.cs Co-Authored-By: Alexandre Mutel <alexandre_mutel@live.com>	2020-01-15 19:32:37 +08:00
Alexandre Mutel	446b1bcc0d	Bump to 0.18.0	2019-10-24 21:08:11 +02:00
Alexandre Mutel	ec7a4a6902	Create FUNDING.yml	2019-10-24 07:10:27 +02:00
Alexandre Mutel	07a77142f4	Merge pull request #377 from MihaZupan/allocation-reductions 10% time and 50% memory improvement	2019-10-15 23:06:31 +02:00
MihaZupan	3606f234b8	Update changelog	2019-10-15 15:09:34 +02:00
MihaZupan	616eed62bd	Use try/finally instead of goto release in AutoLinkParser	2019-10-15 15:07:45 +02:00
MihaZupan	99f55e9ddc	Resolve merge conflict	2019-10-15 14:58:03 +02:00
Alexandre Mutel	f8ab1cccc5	Merge pull request #375 from MihaZupan/balanced-link-brackets Balanced link brackets	2019-10-15 13:46:31 +02:00
MihaZupan	f24067cd16	Update AppVeyor build image	2019-10-14 19:11:28 +02:00
MihaZupan	9af96ba2b4	Minor CharHelper optimizations	2019-10-14 19:03:15 +02:00
MihaZupan	c99f7dd96a	Mark some struct methods as readonly	2019-10-14 18:39:40 +02:00
MihaZupan	bf28cbd33f	Optimize ContainerBlock this[] accessor	2019-10-14 18:32:24 +02:00
MihaZupan	2040e23545	Correctly return IsEmpty for ICharIterator.TrimStart	2019-10-14 18:31:51 +02:00
MihaZupan	2761e36b6b	Optimize StringSlice primitives	2019-10-14 18:28:32 +02:00
MihaZupan	891334134c	Mark Readonly structs as Readonly	2019-10-14 13:38:21 +02:00
MihaZupan	0987fab6f2	Seal internal types	2019-10-14 13:33:24 +02:00
MihaZupan	ed5eea5e27	Cache List<char> in AutoLinkParser	2019-10-14 13:26:09 +02:00
MihaZupan	f73cbe4e76	Resize LineOffsets to sufficient Capacity before adding items	2019-10-14 13:11:07 +02:00
MihaZupan	aefad219cf	Cache StringLine[]s in StringLineGroup with a custom ArrayPool	2019-10-14 13:04:27 +02:00
MihaZupan	76c3e88c58	Estimate LineCount from text Length to minimize List resizes	2019-10-14 12:58:03 +02:00
MihaZupan	afe4308e91	Cache HtmlRenderer on Pipeline for ToHtml(string, Pipeline)	2019-10-13 18:03:13 +02:00
MihaZupan	606556b692	Use Write(Span) on NetCore	2019-10-13 15:44:36 +02:00
MihaZupan	253be5c362	Cache HtmlRenderers in AutoIdentifier Extension	2019-10-13 15:17:33 +02:00
MihaZupan	33037d1034	Update changelog	2019-10-08 17:29:49 +02:00
MihaZupan	f16ee828db	Fix link text balanced bracket matching	2019-10-08 17:27:50 +02:00
MihaZupan	a76305f39b	Add tests for balanced brackets in link text For issue #371	2019-10-08 17:26:16 +02:00
MihaZupan	f52a41e167	Cleanup LinkInline parsing code No functional changes, readability only Switch with a single case => if statement Pattern matching, inline out variable declarations ...	2019-10-08 16:22:53 +02:00
Opportunity	4d172bf905	Merge branch 'master' into master	2019-10-01 21:31:02 +08:00
Opportunity	890b2cda2a	Update MediaLinkExtension.cs	2019-09-30 21:09:44 +08:00
Alexandre Mutel	c818670919	Merge pull request #360 from MihaZupan/smarty-pants Fix SmartyPants quote matching	2019-09-25 22:15:36 +02:00
Alexandre Mutel	a78a0b7016	Merge pull request #361 from MihaZupan/generic-attributes Fix GenericAttributes matching of single-char values	2019-09-25 22:15:22 +02:00
Miha Zupan	6a0c9aeb47	Fix GenericAttributes matching of single-char values	2019-08-01 16:14:51 +02:00
Miha Zupan	b1cfcf2431	Add GenericAttributes test for #182	2019-08-01 16:13:37 +02:00
Miha Zupan	b411522a23	Increase EnsureSpecsAreUpToDate time leeway to 3min	2019-08-01 16:12:44 +02:00
Miha Zupan	1d2977d47b	Fix SmartyPants quote matching	2019-08-01 15:28:20 +02:00
Miha Zupan	ee8c87c357	Add SmartyPants tests for #183	2019-08-01 15:26:04 +02:00
Alexandre Mutel	25959174d5	Merge pull request #357 from MihaZupan/master Ignore backticks in GFM AutoLinks	2019-07-17 09:25:33 +02:00
Miha Zupan	033ddaf6a8	Ignore backticks in GFM AutoLinks	2019-07-16 10:21:52 +02:00
OpportunityLiu	8886b48634	add tests	2019-05-16 15:58:02 +08:00
OpportunityLiu	64cd8ec262	customize iframe class of each provider	2019-05-15 10:48:12 +08:00
OpportunityLiu	a1e19912a9	update changelog	2019-05-14 17:32:09 +08:00
OpportunityLiu	ca51967fb1	fix #135	2019-05-14 17:31:03 +08:00
OpportunityLiu	bb3a4f372c	add change log	2019-05-14 16:07:14 +08:00
OpportunityLiu	1d6a464c5d	add unit test	2019-05-14 15:59:05 +08:00
OpportunityLiu	0fe5c17a93	Add customizable media link	2019-05-14 15:30:15 +08:00