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Fix Length for ReadOnlySequence created out of sliced Memory owned by MemoryManager #57479

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merged 4 commits into from
Aug 16, 2021
Merged

Fix Length for ReadOnlySequence created out of sliced Memory owned by MemoryManager #57479

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203b4ff
write a failing test
adamsitnik Aug 16, 2021
aff7e30
change MemoryTestSequenceFactory to test this scenario as well
adamsitnik Aug 16, 2021
c57990d
fix
adamsitnik Aug 16, 2021
07048a3
there is no need to use unmanaged memory
adamsitnik Aug 16, 2021
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2 changes: 1 addition & 1 deletion src/libraries/System.Memory/src/System/Buffers/ReadOnlySequence.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -150,7 +150,7 @@ public ReadOnlySequence(ReadOnlyMemory<T> memory)
_startObject = manager;
_endObject = manager;
_startInteger = ReadOnlySequence.MemoryManagerToSequenceStart(index);
_endInteger = length;
_endInteger = index + length;
}
else if (MemoryMarshal.TryGetArray(memory, out ArraySegment<T> segment))
{
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53 changes: 52 additions & 1 deletion src/libraries/System.Memory/tests/ReadOnlyBuffer/ReadOnlySequenceFactory.byte.cs
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Expand Up @@ -4,13 +4,17 @@
using System.Buffers;
using System.Collections.Generic;
using System.Linq;
using System.Runtime.CompilerServices;
using System.Runtime.InteropServices;
using System.Threading;

namespace System.Memory.Tests
{
public abstract class ReadOnlySequenceFactory<T>
{
public static ReadOnlySequenceFactory<T> ArrayFactory { get; } = new ArrayTestSequenceFactory();
public static ReadOnlySequenceFactory<T> MemoryFactory { get; } = new MemoryTestSequenceFactory();
public static ReadOnlySequenceFactory<T> MemoryManagerFactory { get; } = new MemoryManagerTestSequenceFactory();
public static ReadOnlySequenceFactory<T> SingleSegmentFactory { get; } = new SingleSegmentTestSequenceFactory();
public static ReadOnlySequenceFactory<T> SegmentPerItemFactory { get; } = new BytePerSegmentTestSequenceFactory();
public static ReadOnlySequenceFactory<T> SplitInThree { get; } = new SegmentsTestSequenceFactory(3);
Expand All @@ -37,7 +41,11 @@ internal class MemoryTestSequenceFactory : ReadOnlySequenceFactory<T>
{
public override ReadOnlySequence<T> CreateOfSize(int size)
{
return CreateWithContent(new T[size]);
#if DEBUG
return new ReadOnlySequence<T>(new ReadOnlyMemory<T>(new T[size + 1]).Slice(1));
#else
return new ReadOnlySequence<T>(new ReadOnlyMemory<T>(new T[size]));
#endif
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I generally prefer for the ifdef to be around the minimal thing that's different, so that it's clear what exactly the difference is. e.g.

ReadOnlyMemory<T> m = new T[size + 1];
#if DEBUG
m = m.Slice(1);
#endif
return new ReadOnlySequence<T>(m);

}

public override ReadOnlySequence<T> CreateWithContent(T[] data)
Expand Down Expand Up @@ -112,6 +120,49 @@ public override ReadOnlySequence<T> CreateWithContent(T[] data)
}
}

internal class MemoryManagerTestSequenceFactory : ReadOnlySequenceFactory<T>
{
public override ReadOnlySequence<T> CreateOfSize(int size)
{
#if DEBUG
return new ReadOnlySequence<T>(new CustomMemoryManager(size + 1).Memory.Slice(1));
#else
return new ReadOnlySequence<T>(new CustomMemoryManager(size).Memory);
#endif
}

public override ReadOnlySequence<T> CreateWithContent(T[] data)
{
return new ReadOnlySequence<T>(new CustomMemoryManager(data).Memory);
}

private unsafe class CustomMemoryManager : MemoryManager<T>
{
private readonly T[] _buffer;

public CustomMemoryManager(int size) => _buffer = new T[size];

public CustomMemoryManager(T[] content) => _buffer = content;

public unsafe override Span<T> GetSpan() => _buffer;

public override unsafe MemoryHandle Pin(int elementIndex = 0)
{
if ((uint)elementIndex > (uint)_buffer.Length)
{
throw new ArgumentOutOfRangeException(nameof(elementIndex));
}

var handle = GCHandle.Alloc(_buffer, GCHandleType.Pinned);
return new MemoryHandle(Unsafe.Add<T>((void*)handle.AddrOfPinnedObject(), elementIndex), handle, this);
}

public override void Unpin() { }

protected override void Dispose(bool disposing) { }
}
}

public static ReadOnlySequence<T> CreateSegments(params T[][] inputs) => CreateSegments(inputs.Select(input => (ReadOnlyMemory<T>)input.AsMemory()));

public static ReadOnlySequence<T> CreateSegments(IEnumerable<ReadOnlyMemory<T>> inputs)
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5 changes: 5 additions & 0 deletions src/libraries/System.Memory/tests/ReadOnlyBuffer/ReadOnlySequenceTests.byte.cs
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Expand Up @@ -20,6 +20,11 @@ public class Memory : ReadOnlySequenceTestsByte
public Memory() : base(ReadOnlySequenceFactory<byte>.MemoryFactory) { }
}

public class MemoryManager : ReadOnlySequenceTestsByte
{
public MemoryManager() : base(ReadOnlySequenceFactory<byte>.MemoryManagerFactory) { }
}

public class SingleSegment : ReadOnlySequenceTestsByte
{
public SingleSegment() : base(ReadOnlySequenceFactory<byte>.SingleSegmentFactory) { }
Expand Down