From bd823ba8182b3409048c98d3e394ac913a853027 Mon Sep 17 00:00:00 2001
From: Oliver Booth <me@olivr.me>
Date: Sun, 27 Aug 2023 01:26:37 +0100
Subject: [PATCH] perf: stackalloc single char span, instead of using ToString,
 for .NET 7

This removes the allocations caused by ToString(). Unfortunately, the ReadOnlySpan<char> overload is only available from .NET 7, and so this is a conditional performance gain. Shame.
---
 CHANGELOG.md                    | 1 +
 X10D/src/Text/CharExtensions.cs | 8 +++++++-
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 5f31c88..77ec199 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -38,6 +38,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 BigEndian/LittleEndian methods.
 - X10D: `Stream.GetHash<>` and `Stream.TryWriteHash<>` now throw ArgumentException in lieu of
 TypeInitializationException.
+- X10D: `char.IsEmoji` no longer allocates for .NET 7.
 
 ### Removed
 
diff --git a/X10D/src/Text/CharExtensions.cs b/X10D/src/Text/CharExtensions.cs
index 2a3eef8..06ca0f7 100644
--- a/X10D/src/Text/CharExtensions.cs
+++ b/X10D/src/Text/CharExtensions.cs
@@ -18,7 +18,13 @@ public static class CharExtensions
     [MethodImpl(CompilerResources.MethodImplOptions)]
     public static bool IsEmoji(this char value)
     {
-        return value.ToString().IsEmoji();
+#if NET7_0_OR_GREATER
+        Span<char> chars = stackalloc char[1];
+        chars[0] = value;
+        return EmojiRegex.Value.IsMatch(chars);
+#else
+        return EmojiRegex.Value.IsMatch(value.ToString());
+#endif
     }
 
     /// <summary>