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Merged
merged 14 commits into from
May 10, 2021
Merged

Add ReadAtLeastAsync implementation for StreamPipeReader #52246

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7cfcd69
Add ReadAtLeastAsync implementation for StreamPipeReader
manandre May 2, 2021
e3a5cea
Increase segment size based on minimumSize
manandre May 2, 2021
b0fd4e0
Fix according to remarks
manandre May 4, 2021
2126bd8
Use MaxBufferSize from custom memory pool
manandre May 5, 2021
50ac96e
Align segment allocation logic on Pipe one
manandre May 5, 2021
cc9a5df
Move read optimization out of the loop
manandre May 5, 2021
494f610
Group ReadAtLeastAsync tests
manandre May 7, 2021
9007614
Test logic around MaxBufferSize
manandre May 7, 2021
42d5198
Move first missing test
manandre May 7, 2021
9c6bb87
Move to static local functions
manandre May 8, 2021
1eb3b89
Fix net48 build
manandre May 8, 2021
fa26f09
Revert "Fix net48 build"
manandre May 8, 2021
c12c44e
Move second missing test
manandre May 9, 2021
82cdb8f
Use implementation assembly in test project for all TFM
manandre May 10, 2021
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178 changes: 97 additions & 81 deletions src/libraries/System.IO.Pipelines/src/System/IO/Pipelines/StreamPipeReader.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -189,152 +189,168 @@ public override void Complete(Exception? exception = null)
}

/// <inheritdoc />
public override async ValueTask<ReadResult> ReadAsync(CancellationToken cancellationToken = default)
public override ValueTask<ReadResult> ReadAsync(CancellationToken cancellationToken = default)
{
// TODO ReadyAsync needs to throw if there are overlapping reads.
ThrowIfCompleted();

cancellationToken.ThrowIfCancellationRequested();

// PERF: store InternalTokenSource locally to avoid querying it twice (which acquires a lock)
CancellationTokenSource tokenSource = InternalTokenSource;
if (TryReadInternal(tokenSource, out ReadResult readResult))
{
return readResult;
return new ValueTask<ReadResult>(readResult);
}

if (_isStreamCompleted)
{
return new ReadResult(buffer: default, isCanceled: false, isCompleted: true);
ReadResult completedResult = new ReadResult(buffer: default, isCanceled: false, isCompleted: true);
return new ValueTask<ReadResult>(completedResult);
}

CancellationTokenRegistration reg = default;
if (cancellationToken.CanBeCanceled)
{
reg = cancellationToken.UnsafeRegister(state => ((StreamPipeReader)state!).Cancel(), this);
}
return Core(tokenSource, cancellationToken);

using (reg)
async ValueTask<ReadResult> Core(CancellationTokenSource tokenSource, CancellationToken cancellationToken)
{
var isCanceled = false;
try
CancellationTokenRegistration reg = default;
if (cancellationToken.CanBeCanceled)
{
// This optimization only makes sense if we don't have anything buffered
if (UseZeroByteReads && _bufferedBytes == 0)
{
// Wait for data by doing 0 byte read before
await InnerStream.ReadAsync(Memory<byte>.Empty, tokenSource.Token).ConfigureAwait(false);
}
reg = cancellationToken.UnsafeRegister(state => ((StreamPipeReader)state!).Cancel(), this);
}

AllocateReadTail();
using (reg)
{
var isCanceled = false;
try
{
// This optimization only makes sense if we don't have anything buffered
if (UseZeroByteReads && _bufferedBytes == 0)
{
// Wait for data by doing 0 byte read before
await InnerStream.ReadAsync(Memory<byte>.Empty, tokenSource.Token).ConfigureAwait(false);
}

Memory<byte> buffer = _readTail!.AvailableMemory.Slice(_readTail.End);
AllocateReadTail();

int length = await InnerStream.ReadAsync(buffer, tokenSource.Token).ConfigureAwait(false);
Memory<byte> buffer = _readTail!.AvailableMemory.Slice(_readTail.End);

Debug.Assert(length + _readTail.End <= _readTail.AvailableMemory.Length);
int length = await InnerStream.ReadAsync(buffer, tokenSource.Token).ConfigureAwait(false);

_readTail.End += length;
_bufferedBytes += length;
Debug.Assert(length + _readTail.End <= _readTail.AvailableMemory.Length);

if (length == 0)
{
_isStreamCompleted = true;
}
}
catch (OperationCanceledException)
{
ClearCancellationToken();
_readTail.End += length;
_bufferedBytes += length;

if (tokenSource.IsCancellationRequested && !cancellationToken.IsCancellationRequested)
{
// Catch cancellation and translate it into setting isCanceled = true
isCanceled = true;
if (length == 0)
{
_isStreamCompleted = true;
}
}
else
catch (OperationCanceledException)
{
throw;
ClearCancellationToken();

if (tokenSource.IsCancellationRequested && !cancellationToken.IsCancellationRequested)
{
// Catch cancellation and translate it into setting isCanceled = true
isCanceled = true;
}
else
{
throw;
}

}

return new ReadResult(GetCurrentReadOnlySequence(), isCanceled, _isStreamCompleted);
}

return new ReadResult(GetCurrentReadOnlySequence(), isCanceled, _isStreamCompleted);
}
}

protected override async ValueTask<ReadResult> ReadAtLeastAsyncCore(int minimumSize, CancellationToken cancellationToken)
protected override ValueTask<ReadResult> ReadAtLeastAsyncCore(int minimumSize, CancellationToken cancellationToken)
{
// TODO ReadyAsync needs to throw if there are overlapping reads.
ThrowIfCompleted();

cancellationToken.ThrowIfCancellationRequested();
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@stephentoub stephentoub May 26, 2021

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This should really be:

if (cancellationToken.IsCancellationRequested)
{
    return ValueTask.FromCanceled<ReadResult>(cancellationToken);
}

or to be able to target downlevel as well:

if (cancellationToken.IsCancellationRequested)
{
    return new ValueTask<ReadResult>(Task.FromCanceled<ReadResult>(cancellationToken));
}

Otherwise, this is going to propagate the OperationCanceledException synchronously out of the ReadAtLeastAsync call, when we generally prefer to propagate it as part of the returned task.

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@davidfowl davidfowl May 26, 2021

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@manandre would you like to take this one?

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@manandre manandre May 26, 2021

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Sure!
Fix proposal available in PR #53306


// PERF: store InternalTokenSource locally to avoid querying it twice (which acquires a lock)
CancellationTokenSource tokenSource = InternalTokenSource;
if (TryReadInternal(tokenSource, out ReadResult readResult))
{
if (readResult.Buffer.Length >= minimumSize || readResult.IsCompleted || readResult.IsCanceled)
{
return readResult;
return new ValueTask<ReadResult>(readResult);
}
}

if (_isStreamCompleted)
{
return new ReadResult(buffer: default, isCanceled: false, isCompleted: true);
ReadResult completedResult = new ReadResult(buffer: default, isCanceled: false, isCompleted: true);
return new ValueTask<ReadResult>(completedResult);
}

CancellationTokenRegistration reg = default;
if (cancellationToken.CanBeCanceled)
{
reg = cancellationToken.UnsafeRegister(state => ((StreamPipeReader)state!).Cancel(), this);
}
return Core(minimumSize, tokenSource, cancellationToken);

using (reg)
async ValueTask<ReadResult> Core(int minimumSize, CancellationTokenSource tokenSource, CancellationToken cancellationToken)
{
var isCanceled = false;
try
CancellationTokenRegistration reg = default;
if (cancellationToken.CanBeCanceled)
{
// This optimization only makes sense if we don't have anything buffered
if (UseZeroByteReads && _bufferedBytes == 0)
{
// Wait for data by doing 0 byte read before
await InnerStream.ReadAsync(Memory<byte>.Empty, tokenSource.Token).ConfigureAwait(false);
}
reg = cancellationToken.UnsafeRegister(state => ((StreamPipeReader)state!).Cancel(), this);
}

while (_bufferedBytes < minimumSize)
using (reg)
{
var isCanceled = false;
try
{
AllocateReadTail(minimumSize);
// This optimization only makes sense if we don't have anything buffered
if (UseZeroByteReads && _bufferedBytes == 0)
{
// Wait for data by doing 0 byte read before
await InnerStream.ReadAsync(Memory<byte>.Empty, tokenSource.Token).ConfigureAwait(false);
}

Memory<byte> buffer = _readTail!.AvailableMemory.Slice(_readTail.End);
do
{
AllocateReadTail(minimumSize);

int length = await InnerStream.ReadAsync(buffer, tokenSource.Token).ConfigureAwait(false);
Memory<byte> buffer = _readTail!.AvailableMemory.Slice(_readTail.End);

Debug.Assert(length + _readTail.End <= _readTail.AvailableMemory.Length);
int length = await InnerStream.ReadAsync(buffer, tokenSource.Token).ConfigureAwait(false);

_readTail.End += length;
_bufferedBytes += length;
Debug.Assert(length + _readTail.End <= _readTail.AvailableMemory.Length);

if (length == 0)
{
_isStreamCompleted = true;
break;
}
}
}
catch (OperationCanceledException)
{
ClearCancellationToken();
_readTail.End += length;
_bufferedBytes += length;

if (tokenSource.IsCancellationRequested && !cancellationToken.IsCancellationRequested)
{
// Catch cancellation and translate it into setting isCanceled = true
isCanceled = true;
if (length == 0)
{
_isStreamCompleted = true;
break;
}
} while (_bufferedBytes < minimumSize);
}
else
catch (OperationCanceledException)
{
throw;
ClearCancellationToken();

if (tokenSource.IsCancellationRequested && !cancellationToken.IsCancellationRequested)
{
// Catch cancellation and translate it into setting isCanceled = true
isCanceled = true;
}
else
{
throw;
}

}

return new ReadResult(GetCurrentReadOnlySequence(), isCanceled, _isStreamCompleted);
}

return new ReadResult(GetCurrentReadOnlySequence(), isCanceled, _isStreamCompleted);
}
}

Expand Down
11 changes: 11 additions & 0 deletions src/libraries/System.IO.Pipelines/tests/BasePipeReaderReadAtLeastAsyncTests.cs
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Original file line number Diff line number Diff line change
@@ -0,0 +1,11 @@
// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.

namespace System.IO.Pipelines.Tests
{
public class BasePipeReaderReadAtLeastAsyncTests : ReadAtLeastAsyncTests
{
private PipeReader? _pipeReader;
protected override PipeReader PipeReader => _pipeReader ?? (_pipeReader = new BasePipeReader(Pipe.Reader));
}
}
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