Optimize MD5 Hash for .net6

Author: mythz

src/ServiceStack.Text/StreamExtensions.cs

@@ -446,27 +446,23 @@ public static Task WriteAsync(this Stream stream, byte[] bytes, CancellationToke
         public static Task WriteAsync(this Stream stream, string text, CancellationToken token = default) =>
             MemoryProvider.Instance.WriteAsync(stream, text.AsSpan(), token);
 
-        public static string ToMd5Hash(this Stream stream)
+        public static byte[] ToMd5Bytes(this Stream stream)
         {
-            var hash = System.Security.Cryptography.MD5.Create().ComputeHash(stream);
-            var sb = StringBuilderCache.Allocate();
-            foreach (byte b in hash)
+#if NET6_0_OR_GREATER
+            if (stream is MemoryStream ms)
+                return System.Security.Cryptography.MD5.HashData(ms.GetBufferAsSpan());
+#endif
+            if (stream.CanSeek)
             {
-                sb.Append(b.ToString("x2"));
+                stream.Position = 0;
             }
-            return StringBuilderCache.ReturnAndFree(sb);
+            return System.Security.Cryptography.MD5.Create().ComputeHash(stream);
         }
 
-        public static string ToMd5Hash(this byte[] bytes)
-        {
-            var hash = System.Security.Cryptography.MD5.Create().ComputeHash(bytes);
-            var sb = StringBuilderCache.Allocate();
-            foreach (byte b in hash)
-            {
-                sb.Append(b.ToString("x2"));
-            }
-            return StringBuilderCache.ReturnAndFree(sb);
-        }
+        public static string ToMd5Hash(this Stream stream) => ToMd5Bytes(stream).ToHex();
+
+        public static string ToMd5Hash(this byte[] bytes) =>
+            System.Security.Cryptography.MD5.Create().ComputeHash(bytes).ToHex();
 
         /// <summary>
         /// Returns bytes in publiclyVisible MemoryStream

tests/ServiceStack.Text.Tests/StreamTests.cs

@@ -52,5 +52,15 @@ public void Does_escape_string_when_serializing_to_Stream()
                 Assert.That(ssString, Is.EqualTo(expected));
             }
         }
+
+        [Test]
+        public void Can_create_MD5_hashes_from_Stream()
+        {
+            var md5Hash = "35f184b0e35d7f5629e79cb4bc802893";
+            var utf8Bytes = nameof(Can_create_MD5_hashes_from_Stream).ToUtf8Bytes();
+            var ms = new MemoryStream(utf8Bytes);
+            Assert.That(utf8Bytes.ToMd5Hash(), Is.EqualTo(md5Hash));
+            Assert.That(ms.ToMd5Bytes().ToHex(), Is.EqualTo(md5Hash));
+        }
     }
 }