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Use ReadOnlyMemory<byte> for binary data to eliminate UTF-16 transcoding #1070

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Use ReadOnlyMemory<byte> for binary data to eliminate UTF-16 transcoding #1070

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7dca602
Initial plan
Copilot Dec 5, 2025
4287694
Update protocol types to use ReadOnlyMemory<byte> for binary data
Copilot Dec 5, 2025
8e6fcf0
Fix test files to work with new binary data representation
Copilot Dec 5, 2025
e405dfc
Add cache invalidation when Blob/Data properties are set
Copilot Dec 5, 2025
ebe3eef
Apply performance optimizations using MemoryMarshal.TryGetArray
Copilot Dec 8, 2025
1d76c11
Use GetBytes overload with offset and count parameters
Copilot Dec 8, 2025
39213fb
Use Base64.DecodeFromUtf8 to avoid string intermediate during decoding
Copilot Dec 9, 2025
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6 changes: 4 additions & 2 deletions src/ModelContextProtocol.Core/Protocol/BlobResourceContents.cs
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Original file line number Diff line number Diff line change
@@ -1,3 +1,4 @@
using System.Runtime.InteropServices;
using System.Text.Json.Serialization;

namespace ModelContextProtocol.Protocol;
Expand Down Expand Up @@ -56,10 +57,11 @@ public ReadOnlyMemory<byte> Data
{
if (_decodedData is null)
{
#if NET6_0_OR_GREATER
#if NET
_decodedData = Convert.FromBase64String(System.Text.Encoding.UTF8.GetString(Blob.Span));
#else
_decodedData = Convert.FromBase64String(System.Text.Encoding.UTF8.GetString(Blob.ToArray()));
byte[] array = MemoryMarshal.TryGetArray(Blob, out ArraySegment<byte> segment) && segment.Offset == 0 && segment.Count == segment.Array!.Length ? segment.Array : Blob.ToArray();
_decodedData = Convert.FromBase64String(System.Text.Encoding.UTF8.GetString(array));
#endif
}
return _decodedData;
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11 changes: 7 additions & 4 deletions src/ModelContextProtocol.Core/Protocol/ContentBlock.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -2,6 +2,7 @@
using System.ComponentModel;
using System.Diagnostics;
using System.Diagnostics.CodeAnalysis;
using System.Runtime.InteropServices;
using System.Text.Json;
using System.Text.Json.Nodes;
using System.Text.Json.Serialization;
Expand Down Expand Up @@ -419,10 +420,11 @@ public ReadOnlyMemory<byte> DecodedData
{
if (_decodedData is null)
{
#if NET6_0_OR_GREATER
#if NET
_decodedData = Convert.FromBase64String(System.Text.Encoding.UTF8.GetString(Data.Span));
#else
_decodedData = Convert.FromBase64String(System.Text.Encoding.UTF8.GetString(Data.ToArray()));
byte[] array = MemoryMarshal.TryGetArray(Data, out ArraySegment<byte> segment) && segment.Offset == 0 && segment.Count == segment.Array!.Length ? segment.Array : Data.ToArray();
_decodedData = Convert.FromBase64String(System.Text.Encoding.UTF8.GetString(array));
#endif
}
return _decodedData;
Expand Down Expand Up @@ -479,10 +481,11 @@ public ReadOnlyMemory<byte> DecodedData
{
if (_decodedData is null)
{
#if NET6_0_OR_GREATER
#if NET
_decodedData = Convert.FromBase64String(System.Text.Encoding.UTF8.GetString(Data.Span));
#else
_decodedData = Convert.FromBase64String(System.Text.Encoding.UTF8.GetString(Data.ToArray()));
byte[] array = MemoryMarshal.TryGetArray(Data, out ArraySegment<byte> segment) && segment.Offset == 0 && segment.Count == segment.Array!.Length ? segment.Array : Data.ToArray();
_decodedData = Convert.FromBase64String(System.Text.Encoding.UTF8.GetString(array));
#endif
}
return _decodedData;
Expand Down
14 changes: 12 additions & 2 deletions src/ModelContextProtocol.Core/Server/AIFunctionMcpServerResource.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -7,6 +7,7 @@
using System.Globalization;
using System.Reflection;
using System.Runtime.CompilerServices;
using System.Runtime.InteropServices;
using System.Text;
using System.Text.Json;
using System.Text.Json.Nodes;
Expand Down Expand Up @@ -391,7 +392,14 @@ public override async ValueTask<ReadResourceResult> ReadAsync(

DataContent dc => new()
{
Contents = [new BlobResourceContents { Uri = request.Params!.Uri, MimeType = dc.MediaType, Blob = System.Text.Encoding.UTF8.GetBytes(dc.Base64Data.ToString()) }],
Contents = [new BlobResourceContents
{
Uri = request.Params!.Uri,
MimeType = dc.MediaType,
Blob = MemoryMarshal.TryGetArray(dc.Base64Data, out ArraySegment<char> segment) && segment.Offset == 0 && segment.Count == segment.Array!.Length
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@stephentoub stephentoub Dec 8, 2025

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@copilot, these two don't need to Offset and Count, as the actual offset and length can be passed as arguments to GetBytes

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Copilot AI Dec 8, 2025

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Updated to use the GetBytes(char[], int, int) overload to pass offset and count directly in commit 1d76c11

? System.Text.Encoding.UTF8.GetBytes(segment.Array)
: System.Text.Encoding.UTF8.GetBytes(dc.Base64Data.ToString())
}],
},

string text => new()
Expand Down Expand Up @@ -420,7 +428,9 @@ public override async ValueTask<ReadResourceResult> ReadAsync(
{
Uri = request.Params!.Uri,
MimeType = dc.MediaType,
Blob = System.Text.Encoding.UTF8.GetBytes(dc.Base64Data.ToString())
Blob = MemoryMarshal.TryGetArray(dc.Base64Data, out ArraySegment<char> segment) && segment.Offset == 0 && segment.Count == segment.Array!.Length
? System.Text.Encoding.UTF8.GetBytes(segment.Array)
: System.Text.Encoding.UTF8.GetBytes(dc.Base64Data.ToString())
},

_ => throw new InvalidOperationException($"Unsupported AIContent type '{ac.GetType()}' returned from resource function."),
Expand Down