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Make Blob.FromStream GC safe #3473

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Make Blob.FromStream GC safe #3473

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e7b3d4d
Make Blob.FromStream GC safe
jeremy-visionaid Jan 28, 2026
085f2ee
Handle non-seekable streams in Blob.FromStream
jeremy-visionaid Jan 29, 2026
484b017
Improve CreateFromStreamIsGCSafe
jeremy-visionaid Jan 29, 2026
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30 changes: 23 additions & 7 deletions binding/HarfBuzzSharp/Blob.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -2,6 +2,7 @@

using System;
using System.IO;
using System.Runtime.InteropServices;

namespace HarfBuzzSharp
{
Expand Down Expand Up @@ -70,14 +71,29 @@ public static Blob FromFile (string fileName)

public static unsafe Blob FromStream (Stream stream)
{
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// TODO: check to see if we can avoid the second copy (the ToArray)

using var ms = new MemoryStream ();
stream.CopyTo (ms);
var data = ms.ToArray ();
if (stream == null)
throw new ArgumentNullException (nameof (stream));

// For non-seekable streams, buffer into memory first
if (!stream.CanSeek) {
using var ms = new MemoryStream ();
stream.CopyTo (ms);
ms.Position = 0;
return FromStream (ms);
}

fixed (byte* dataPtr = data) {
return new Blob ((IntPtr)dataPtr, data.Length, MemoryMode.ReadOnly, () => ms.Dispose ());
var length = (int)(stream.Length - stream.Position);
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if (length == 0)
return Empty;

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var dataPtr = Marshal.AllocCoTaskMem (length);
try {
using var ums = new UnmanagedMemoryStream ((byte*)dataPtr, length, length, FileAccess.ReadWrite);
stream.CopyTo (ums);
return new Blob (dataPtr, length, MemoryMode.ReadOnly, () => Marshal.FreeCoTaskMem (dataPtr));
} catch {
Marshal.FreeCoTaskMem (dataPtr);
throw;
}
}

Expand Down
23 changes: 19 additions & 4 deletions tests/Tests/HarfBuzzSharp/HBBlobTest.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -20,10 +20,25 @@ public void ShouldCreateFromFileName()
[SkippableFact]
public void ShouldCreateFromStream()
{
using (var blob = Blob.FromStream(File.Open(Path.Combine(PathToFonts, "Funkster.ttf"), FileMode.Open, FileAccess.Read)))
{
Assert.Equal(236808, blob.Length);
}
using var stream = File.Open(Path.Combine(PathToFonts, "Funkster.ttf"), FileMode.Open, FileAccess.Read);
using var blob = Blob.FromStream(stream);
Assert.Equal(236808, blob.Length);
}

[SkippableFact]
public void CreateFromStreamIsGCSafe()
{
using var stream = File.Open(Path.Combine(PathToFonts, "Funkster.ttf"), FileMode.Open, FileAccess.Read);
var originalData = new byte[stream.Length];
stream.Read(originalData, 0, (int)stream.Length);
stream.Position = 0;

using var blob = Blob.FromStream(stream);
GC.Collect();
GC.WaitForPendingFinalizers();
GC.Collect();

Assert.Equal(originalData, blob.AsSpan().ToArray());
}

[SkippableFact]
Expand Down