Merge pull request #128 from Cysharp/hadashiA/update-msgpack

Add messagepack configurations

src/ZLogger.MessagePack/MessagePackEncodedText.cs

@@ -0,0 +1,71 @@
+using System;
+using System.Text;
+using MessagePack;
+
+namespace ZLogger.MessagePack;
+
+public readonly struct MessagePackEncodedText : IEquatable<MessagePackEncodedText>
+{
+    static readonly Encoding StringEncoding = new UTF8Encoding(false);
+
+    public string Value { get; private init; }
+    public ReadOnlySpan<byte> Utf8EncodedValue => utf8EncodedValue;
+
+    readonly byte[] utf8EncodedValue;
+
+    MessagePackEncodedText(string value, byte[] utf8EncodedValue)
+    {
+        Value = value;
+        this.utf8EncodedValue = utf8EncodedValue;
+    }
+
+    public static MessagePackEncodedText Encode(string stringValue, MessagePackSerializerOptions? options = null)
+    {
+        var oldSpec = options?.OldSpec ?? false;
+        var characterLength = stringValue.Length;
+        var bufferSize = StringEncoding.GetMaxByteCount(characterLength) + 5;
+
+        var useOffset = characterLength switch
+        {
+            <= MessagePackRange.MaxFixStringLength => 1,
+            <= byte.MaxValue when !oldSpec => 2,
+            <= ushort.MaxValue => 3,
+            _ => 5
+        };
+
+        Span<byte> buffer = stackalloc byte[bufferSize];
+        var byteCount = StringEncoding.GetBytes(stringValue, buffer[useOffset..]);
+        // move body and write prefix
+        if (byteCount <= MessagePackRange.MaxFixStringLength)
+        {
+            buffer[0] = (byte)(MessagePackCode.MinFixStr | byteCount);
+        }
+        else if (byteCount <= byte.MaxValue && !oldSpec)
+        {
+            buffer[0] = MessagePackCode.Str8;
+            buffer[1] = unchecked((byte)byteCount);
+        }
+        else if (byteCount <= ushort.MaxValue)
+        {
+            buffer[0] = MessagePackCode.Str16;
+            // Write big-endian
+            buffer[1] = (byte)(byteCount >> 8);
+            buffer[2] = (byte)byteCount;
+        }
+        else
+        {
+            buffer[0] = MessagePackCode.Str32;
+            buffer[1] = (byte)(byteCount >> 24);
+            buffer[2] = (byte)(byteCount >> 16);
+            buffer[3] = (byte)(byteCount >> 8);
+            buffer[4] = (byte)byteCount;
+        }
+
+        var encodedValue = buffer[..(byteCount + useOffset)].ToArray();
+        return new MessagePackEncodedText(stringValue, encodedValue);
+    }
+
+    public bool Equals(MessagePackEncodedText other) => Value == other.Value;
+    public override bool Equals(object? obj) => obj is MessagePackEncodedText other && Equals(other);
+    public override int GetHashCode() => Value.GetHashCode();
+}