Address code review feedback: rename Data to DecodedData, use span-based encoding, remove System.Text qualifiers

Co-authored-by: ericstj <8918108+ericstj@users.noreply.github.com>

Author: Copilot

samples/EverythingServer/Resources/SimpleResourceType.cs

@@ -1,6 +1,7 @@
 using ModelContextProtocol.Protocol;
 using ModelContextProtocol.Server;
 using System.ComponentModel;
+using System.Text;
 
 namespace EverythingServer.Resources;
 
@@ -31,7 +32,7 @@ public static ResourceContents TemplateResource(RequestContext<ReadResourceReque
             } :
             new BlobResourceContents
             {
-                Blob = System.Text.Encoding.UTF8.GetBytes(resource.Description!),
+                Blob = Encoding.UTF8.GetBytes(resource.Description!),
                 MimeType = resource.MimeType,
                 Uri = resource.Uri,
             };

samples/EverythingServer/Tools/AnnotatedMessageTool.cs

@@ -1,6 +1,7 @@
 using ModelContextProtocol.Protocol;
 using ModelContextProtocol.Server;
 using System.ComponentModel;
+using System.Text;
 
 namespace EverythingServer.Tools;
 
@@ -41,7 +42,7 @@ public static IEnumerable<ContentBlock> AnnotatedMessage(MessageType messageType
         {
             contents.Add(new ImageContentBlock
             {
-                Data = System.Text.Encoding.UTF8.GetBytes(TinyImageTool.MCP_TINY_IMAGE.Split(",").Last()),
+                Data = Encoding.UTF8.GetBytes(TinyImageTool.MCP_TINY_IMAGE.Split(",").Last()),
                 MimeType = "image/png",
                 Annotations = new() { Audience = [Role.User], Priority = 0.5f }
             });

src/Common/Polyfills/System/Text/EncodingExtensions.cs

@@ -0,0 +1,50 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+#if !NET
+
+namespace System.Text;
+
+internal static class EncodingExtensions
+{
+    /// <summary>
+    /// Gets the number of bytes required to encode the specified characters.
+    /// </summary>
+    public static int GetByteCount(this Encoding encoding, ReadOnlySpan<char> chars)
+    {
+        if (chars.IsEmpty)
+        {
+            return 0;
+        }
+
+        unsafe
+        {
+            fixed (char* charsPtr = chars)
+            {
+                return encoding.GetByteCount(charsPtr, chars.Length);
+            }
+        }
+    }
+
+    /// <summary>
+    /// Encodes the specified characters into the specified byte span.
+    /// </summary>
+    public static int GetBytes(this Encoding encoding, ReadOnlySpan<char> chars, Span<byte> bytes)
+    {
+        if (chars.IsEmpty)
+        {
+            return 0;
+        }
+
+        unsafe
+        {
+            fixed (char* charsPtr = chars)
+            fixed (byte* bytesPtr = bytes)
+            {
+                return encoding.GetBytes(charsPtr, chars.Length, bytesPtr, bytes.Length);
+            }
+        }
+    }
+}
+
+#endif

src/ModelContextProtocol.Core/AIContentExtensions.cs

@@ -1,9 +1,7 @@
 using Microsoft.Extensions.AI;
 using ModelContextProtocol.Client;
 using ModelContextProtocol.Protocol;
-#if !NET
-using System.Runtime.InteropServices;
-#endif
+using System.Text;
 using System.Text.Json;
 using System.Text.Json.Nodes;
 
@@ -324,7 +322,7 @@ public static AIContent ToAIContent(this ResourceContents content)
 
         AIContent ac = content switch
         {
-            BlobResourceContents blobResource => new DataContent(blobResource.Data, blobResource.MimeType ?? "application/octet-stream"),
+            BlobResourceContents blobResource => new DataContent(blobResource.DecodedData, blobResource.MimeType ?? "application/octet-stream"),
             TextResourceContents textResource => new TextContent(textResource.Text),
             _ => throw new NotSupportedException($"Resource type '{content.GetType().Name}' is not supported.")
         };
@@ -449,20 +447,12 @@ public static ContentBlock ToContentBlock(this AIContent content, JsonSerializer
 
         return contentBlock;
 
-        unsafe byte[] GetUtf8Bytes(ReadOnlySpan<char> utf16)
+        static byte[] GetUtf8Bytes(ReadOnlySpan<char> utf16)
         {
-            // gets UTF-8 bytes from UTF-16 chars without intermediate string allocations
-            fixed (char* pChars = utf16)
-            {
-                var byteCount = System.Text.Encoding.UTF8.GetByteCount(pChars, utf16.Length);
-                var bytes = new byte[byteCount];
-                
-                fixed (byte* pBytes = bytes)
-                {
-                    System.Text.Encoding.UTF8.GetBytes(pChars, utf16.Length, pBytes, byteCount);
-                }
-                return bytes;
-            }
+            // Get UTF-8 bytes from UTF-16 chars without intermediate string allocations
+            byte[] bytes = new byte[Encoding.UTF8.GetByteCount(utf16)];
+            Encoding.UTF8.GetBytes(utf16, bytes);
+            return bytes;
         }
     }
 

src/ModelContextProtocol.Core/Protocol/BlobResourceContents.cs

@@ -47,6 +47,7 @@ public static BlobResourceContents FromData(ReadOnlyMemory<byte> data, string ur
         byte[] buffer = new byte[maxLength];
         if (Base64.EncodeToUtf8(data.Span, buffer, out _, out int bytesWritten) == OperationStatus.Done)
         {
+            Debug.Assert(bytesWritten == buffer.Length, "Base64 encoding should always produce exact length for non-padded input");
             blob = buffer.AsMemory(0, bytesWritten);
         }
         else
@@ -67,7 +68,7 @@ public static BlobResourceContents FromData(ReadOnlyMemory<byte> data, string ur
     /// Gets or sets the base64-encoded UTF-8 bytes representing the binary data of the item.
     /// </summary>
     /// <remarks>
-    /// This is a zero-copy representation of the wire payload of this item. Setting this value will invalidate any cached value of <see cref="Data"/>.
+    /// This is a zero-copy representation of the wire payload of this item. Setting this value will invalidate any cached value of <see cref="DecodedData"/>.
     /// </remarks>
     [JsonPropertyName("blob")]
     public required ReadOnlyMemory<byte> Blob
@@ -94,7 +95,7 @@ public required ReadOnlyMemory<byte> Blob
     /// </para>
     /// </remarks>
     [JsonIgnore]
-    public ReadOnlyMemory<byte> Data
+    public ReadOnlyMemory<byte> DecodedData
     {
         get
         {
@@ -121,7 +122,7 @@ private string DebuggerDisplay
     {
         get
         {
-            string lengthDisplay = _decodedData is null ? DebuggerDisplayHelper.GetBase64LengthDisplay(Blob) : $"{Data.Length} bytes";
+            string lengthDisplay = _decodedData is null ? DebuggerDisplayHelper.GetBase64LengthDisplay(Blob) : $"{DecodedData.Length} bytes";
             string mimeInfo = MimeType is not null ? $", MimeType = {MimeType}" : "";
             return $"Uri = \"{Uri}\"{mimeInfo}, Length = {lengthDisplay}";
         }

src/ModelContextProtocol/ModelContextProtocol.csproj

@@ -7,6 +7,7 @@
     <PackageId>ModelContextProtocol</PackageId>
     <Description>.NET SDK for the Model Context Protocol (MCP) with hosting and dependency injection extensions.</Description>
     <PackageReadmeFile>README.md</PackageReadmeFile>
+    <AllowUnsafeBlocks>True</AllowUnsafeBlocks>
     <!-- Suppress the experimental tasks warning -->
     <NoWarn>$(NoWarn);MCPEXP001</NoWarn>
   </PropertyGroup>

tests/Directory.Build.props

@@ -2,6 +2,7 @@
   <Import Project="$([MSBuild]::GetPathOfFileAbove('Directory.Build.props', '$(MSBuildThisFileDirectory)..'))" />
 
   <PropertyGroup>
+    <AllowUnsafeBlocks>True</AllowUnsafeBlocks>
     <!-- Suppress the experimental tasks warning in test projects -->
     <NoWarn>$(NoWarn);MCPEXP001</NoWarn>
   </PropertyGroup>