Implement IUtf8SpanFormattable on Version

src/libraries/System.Private.CoreLib/src/System/Version.cs

@@ -1,10 +1,13 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
+using System.Buffers.Text;
 using System.Diagnostics;
 using System.Diagnostics.CodeAnalysis;
 using System.Globalization;
+using System.Numerics;
 using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
 
 namespace System
 {
@@ -16,7 +19,7 @@ namespace System
 
     [Serializable]
     [TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
-    public sealed class Version : ICloneable, IComparable, IComparable<Version?>, IEquatable<Version?>, ISpanFormattable
+    public sealed class Version : ICloneable, IComparable, IComparable<Version?>, IEquatable<Version?>, ISpanFormattable, IUtf8SpanFormattable
     {
         // AssemblyName depends on the order staying the same
         private readonly int _Major; // Do not rename (binary serialization)
@@ -177,10 +180,15 @@ string IFormattable.ToString(string? format, IFormatProvider? formatProvider) =>
             ToString();
 
         public bool TryFormat(Span<char> destination, out int charsWritten) =>
-            TryFormat(destination, DefaultFormatFieldCount, out charsWritten);
+            TryFormatCore(destination, DefaultFormatFieldCount, out charsWritten);
 
-        public bool TryFormat(Span<char> destination, int fieldCount, out int charsWritten)
+        public bool TryFormat(Span<char> destination, int fieldCount, out int charsWritten) =>
+            TryFormatCore(destination, fieldCount, out charsWritten);
+
+        private bool TryFormatCore<TChar>(Span<TChar> destination, int fieldCount, out int charsWritten) where TChar : unmanaged, IBinaryInteger<TChar>
         {
+            Debug.Assert(typeof(TChar) == typeof(char) || typeof(TChar) == typeof(byte));
+
             switch ((uint)fieldCount)
             {
                 case > 4:
@@ -211,7 +219,7 @@ static void ThrowArgumentException(string failureUpperBound) =>
                         return false;
                     }
 
-                    destination[0] = '.';
+                    destination[0] = TChar.CreateTruncating('.');
                     destination = destination.Slice(1);
                     totalCharsWritten++;
                 }
@@ -224,7 +232,12 @@ static void ThrowArgumentException(string failureUpperBound) =>
                     _ => _Revision
                 };
 
-                if (!((uint)value).TryFormat(destination, out int valueCharsWritten))
+                int valueCharsWritten;
+                bool formatted = typeof(TChar) == typeof(char) ?
+                    ((uint)value).TryFormat(MemoryMarshal.Cast<TChar, char>(destination), out valueCharsWritten) :
+                    Utf8Formatter.TryFormat((uint)value, MemoryMarshal.Cast<TChar, byte>(destination), out valueCharsWritten); // TODO https://github.com/dotnet/runtime/issues/84527: Use UInt32's IUtf8SpanFormattable when available
+
+                if (!formatted)
                 {
                     charsWritten = 0;
                     return false;
@@ -240,7 +253,11 @@ static void ThrowArgumentException(string failureUpperBound) =>
 
         bool ISpanFormattable.TryFormat(Span<char> destination, out int charsWritten, ReadOnlySpan<char> format, IFormatProvider? provider) =>
             // format and provider are ignored.
-            TryFormat(destination, DefaultFormatFieldCount, out charsWritten);
+            TryFormatCore(destination, DefaultFormatFieldCount, out charsWritten);
+
+        bool IUtf8SpanFormattable.TryFormat(Span<byte> utf8Destination, out int bytesWritten, ReadOnlySpan<char> format, IFormatProvider? provider) =>
+            // format and provider are ignored.
+            TryFormatCore(utf8Destination, DefaultFormatFieldCount, out bytesWritten);
 
         private int DefaultFormatFieldCount =>
             _Build == -1 ? 2 :

src/libraries/System.Runtime/ref/System.Runtime.cs

@@ -7058,7 +7058,7 @@ protected ValueType() { }
         public override int GetHashCode() { throw null; }
         public override string? ToString() { throw null; }
     }
-    public sealed partial class Version : System.ICloneable, System.IComparable, System.IComparable<System.Version?>, System.IEquatable<System.Version?>, System.IFormattable, System.ISpanFormattable
+    public sealed partial class Version : System.ICloneable, System.IComparable, System.IComparable<System.Version?>, System.IEquatable<System.Version?>, System.IFormattable, System.ISpanFormattable, System.IUtf8SpanFormattable
     {
         public Version() { }
         public Version(int major, int minor) { }
@@ -7087,6 +7087,7 @@ public Version(string version) { }
         public static System.Version Parse(string input) { throw null; }
         string System.IFormattable.ToString(string? format, System.IFormatProvider? formatProvider) { throw null; }
         bool System.ISpanFormattable.TryFormat(System.Span<char> destination, out int charsWritten, System.ReadOnlySpan<char> format, System.IFormatProvider? provider) { throw null; }
+        bool System.IUtf8SpanFormattable.TryFormat(System.Span<byte> utf8Destination, out int bytesWritten, System.ReadOnlySpan<char> format, System.IFormatProvider? provider) { throw null; }
         public override string ToString() { throw null; }
         public string ToString(int fieldCount) { throw null; }
         public bool TryFormat(System.Span<char> destination, int fieldCount, out int charsWritten) { throw null; }

src/libraries/System.Runtime/tests/System/VersionTests.cs

@@ -2,6 +2,7 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 
 using System.Collections.Generic;
+using System.Text;
 using Xunit;
 
 namespace System.Tests
@@ -405,5 +406,29 @@ public static void TryFormat_Invoke_WritesExpected(Version version, string[] exp
             AssertExtensions.Throws<ArgumentException>("fieldCount", () => version.TryFormat(dest, -1, out charsWritten)); // Index < 0
             AssertExtensions.Throws<ArgumentException>("fieldCount", () => version.TryFormat(dest, maxFieldCount + 1, out charsWritten)); // Index > version.fieldCount
         }
+
+        [Theory]
+        [MemberData(nameof(ToString_TestData))]
+        public static void IUtf8SpanFormattableTryFormat_Invoke_WritesExpected(Version version, string[] expectedFieldCounts)
+        {
+            string expected = expectedFieldCounts[^1];
+
+            // Too small
+            byte[] dest = new byte[expected.Length - 1];
+            Assert.False(((IUtf8SpanFormattable)version).TryFormat(dest, out int charsWritten, default, null));
+            Assert.Equal(0, charsWritten);
+
+            // Just right
+            dest = new byte[expected.Length];
+            Assert.True(((IUtf8SpanFormattable)version).TryFormat(dest, out charsWritten, default, null));
+            Assert.Equal(expected.Length, charsWritten);
+            Assert.Equal(expected, Encoding.UTF8.GetString(dest.AsSpan(0, charsWritten)));
+
+            // More than needed
+            dest = new byte[expected.Length + 10];
+            Assert.True(((IUtf8SpanFormattable)version).TryFormat(dest, out charsWritten, default, null));
+            Assert.Equal(expected.Length, charsWritten);
+            Assert.Equal(expected, Encoding.UTF8.GetString(dest.AsSpan(0, charsWritten)));
+        }
     }
 }