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Eliminate allocation in StreamAsIStream.Read #6632

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Merged
merged 1 commit into from
Jan 29, 2024
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Eliminate allocation in StreamAsIStream.Read #6632

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14 changes: 8 additions & 6 deletions src/Microsoft.DotNet.Wpf/src/PresentationCore/System/Windows/Media/StreamAsIStream.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -10,6 +10,7 @@
using System;
using MS.Internal;
using MS.Win32;
using System.Buffers;
using System.Reflection;
using System.Collections;
using System.Diagnostics;
Expand All @@ -28,7 +29,7 @@ namespace System.Windows.Media
internal struct StreamDescriptor
{
internal delegate void Dispose(ref StreamDescriptor pSD);
internal delegate int Read(ref StreamDescriptor pSD, [MarshalAs(UnmanagedType.LPArray, SizeParamIndex = 2), Out]byte[] buffer, uint cb, out uint cbRead);
internal delegate int Read(ref StreamDescriptor pSD, IntPtr buffer, uint cb, out uint cbRead);

internal unsafe delegate int Seek(ref StreamDescriptor pSD, long offset, uint origin, long* plibNewPostion);
internal delegate int Stat(ref StreamDescriptor pSD, out System.Runtime.InteropServices.ComTypes.STATSTG statstg, uint grfStatFlag);
Expand Down Expand Up @@ -237,7 +238,7 @@ public int CopyTo(IntPtr /* IStream */ pstm, long cb, out long cbRead, out long

uint read = 0;

hr = Read(buffer, toRead, out read);
hr = Read(buffer.AsSpan(0, (int) toRead), out read);

if (read == 0)
{
Expand Down Expand Up @@ -290,7 +291,7 @@ public int LockRegion(long libOffset, long cb, uint dwLockType)
return NativeMethods.E_NOTIMPL;
}

public int Read(byte[] buffer, uint cb, out uint cbRead)
public int Read(Span<byte> buffer, out uint cbRead)
{
cbRead = 0;

Expand All @@ -301,7 +302,7 @@ public int Read(byte[] buffer, uint cb, out uint cbRead)
Verify();
ActualizeVirtualPosition();

cbRead = (uint) dataStream.Read(buffer, 0, (int) cb);
cbRead = (uint) dataStream.Read(buffer);
}
catch (Exception e)
{
Expand Down Expand Up @@ -597,9 +598,10 @@ internal static int LockRegion(ref StreamDescriptor pSD, long libOffset, long cb
return (StreamAsIStream.FromSD(ref pSD)).LockRegion(libOffset, cb, dwLockType);
}

internal static int Read(ref StreamDescriptor pSD, byte[] buffer, uint cb, out uint cbRead)
internal static unsafe int Read(ref StreamDescriptor pSD, IntPtr buffer, uint cb, out uint cbRead)
{
return (StreamAsIStream.FromSD(ref pSD)).Read(buffer, cb, out cbRead);
var span = new Span<byte>(buffer.ToPointer(), (int) cb);
return (StreamAsIStream.FromSD(ref pSD)).Read(span, out cbRead);
}

internal static int Revert(ref StreamDescriptor pSD)
Expand Down