GetBytes(string).Length -> GetByteCount(string) + stackalloc in ReadString (#181)

Author: sungam3r

RabbitMQ.Stream.Client/AMQP/AmqpWireFormattingRead.cs

@@ -177,16 +177,16 @@ internal static int ReadString(ref SequenceReader<byte> reader, out string value
                     reader.TryCopyTo(tempSpan);
                     reader.Advance(lenC);
                     value = Encoding.UTF8.GetString(tempSpan);
-                    return offset + s_encoding.GetBytes(value).Length;
+                    return offset + s_encoding.GetByteCount(value);
 
                 case FormatCode.Sym32:
                 case FormatCode.Str32:
                     offset += WireFormatting.ReadInt32(ref reader, out var len);
-                    Span<byte> tempSpan32 = new byte[len];
+                    Span<byte> tempSpan32 = len <= 64 ? stackalloc byte[len] : new byte[len];
                     reader.TryCopyTo(tempSpan32);
                     reader.Advance(len);
                     value = Encoding.UTF8.GetString(tempSpan32);
-                    return offset + s_encoding.GetBytes(value).Length;
+                    return offset + s_encoding.GetByteCount(value);
             }
 
             throw new AMQP.AmqpParseException($"ReadString invalid type {type}");

RabbitMQ.Stream.Client/AMQP/AmqpWireFormattingWrite.cs

@@ -36,7 +36,7 @@ public static int WriteAny(Span<byte> seq, object value)
 
         private static int WriteString(Span<byte> seq, string value)
         {
-            var len = s_encoding.GetBytes(value).Length;
+            var len = s_encoding.GetByteCount(value);
             var offset = 0;
             // Str8
             if (len <= byte.MaxValue)