internal bool TryRead(out ReadResult result)
{
lock (_sync)
{
if (_readerCompletion.IsCompleted)
{
ThrowHelper.ThrowInvalidOperationException_NoReadingAllowed();
}
result = new ReadResult();
if (_length > 0 || _readerAwaitable.IsCompleted)
{
GetResult(ref result);
return(true);
}
if (_readerAwaitable.HasContinuation)
{
ThrowHelper.ThrowInvalidOperationException_AlreadyReading();
}
return(false);
}
}
/// <summary>
/// Initializes the <see cref="Pipe"/> with the specified <see cref="PipeOptions"/>.
/// </summary>
public Pipe(PipeOptions options)
{
if (options == null)
{
ThrowHelper.ThrowArgumentNullException(ExceptionArgument.options);
}
_bufferSegmentPool = new BufferSegment[SegmentPoolSize];
_readingState = default;
_readerCompletion = default;
_writerCompletion = default;
_pool = options.Pool;
_minimumSegmentSize = options.MinimumSegmentSize;
_pauseWriterThreshold = options.PauseWriterThreshold;
_resumeWriterThreshold = options.ResumeWriterThreshold;
_readerScheduler = options.ReaderScheduler ?? PipeScheduler.Inline;
_writerScheduler = options.WriterScheduler ?? PipeScheduler.Inline;
_readerAwaitable = new PipeAwaitable(completed: false);
_writerAwaitable = new PipeAwaitable(completed: true);
_reader = new DefaultPipeReader(this);
_writer = new DefaultPipeWriter(this);
}
internal FlushResult GetFlushAsyncResult()
{
var result = new FlushResult();
lock (_sync)
{
if (!_writerAwaitable.IsCompleted)
{
ThrowHelper.ThrowInvalidOperationException_GetResultNotCompleted();
}
// Change the state from to be canceled -> observed
if (_writerAwaitable.ObserveCancelation())
{
result._resultFlags |= ResultFlags.Canceled;
}
if (_readerCompletion.IsCompletedOrThrow())
{
result._resultFlags |= ResultFlags.Completed;
}
}
return(result);
}
public override void Write(byte[] buffer, int offset, int count)
{
ThrowHelper.ThrowNotSupportedException();
}
public override void SetLength(long value)
{
ThrowHelper.ThrowNotSupportedException();
}
public override long Seek(long offset, SeekOrigin origin)
{
ThrowHelper.ThrowNotSupportedException();
return(0);
}
public override int Read(byte[] buffer, int offset, int count)
{
ThrowHelper.ThrowNotSupportedException();
return(0);
}
public override void Flush()
{
ThrowHelper.ThrowNotSupportedException();
}
private void AdvanceTo(BufferSegment?consumedSegment, int consumedIndex, BufferSegment?examinedSegment, int examinedIndex)
{
if (consumedSegment == null || examinedSegment == null)
{
return;
}
if (_readHead == null)
{
ThrowHelper.ThrowInvalidOperationException_AdvanceToInvalidCursor();
}
BufferSegment returnStart = _readHead;
BufferSegment?returnEnd = consumedSegment;
long consumedBytes = BufferSegment.GetLength(returnStart, _readIndex, consumedSegment, consumedIndex);
_bufferedBytes -= consumedBytes;
Debug.Assert(_bufferedBytes >= 0);
_examinedEverything = false;
if (examinedSegment == _readTail)
{
// If we examined everything, we force ReadAsync to actually read from the underlying stream
// instead of returning a ReadResult from TryRead.
_examinedEverything = examinedIndex == _readTail.End;
}
// Two cases here:
// 1. All data is consumed. If so, we empty clear everything so we don't hold onto any
// excess memory.
// 2. A segment is entirely consumed but there is still more data in nextSegments
// We are allowed to remove an extra segment. by setting returnEnd to be the next block.
// 3. We are in the middle of a segment.
// Move _readHead and _readIndex to consumedSegment and index
if (_bufferedBytes == 0)
{
returnEnd = null;
_readHead = null;
_readTail = null;
_readIndex = 0;
}
else if (consumedIndex == returnEnd.Length)
{
BufferSegment?nextBlock = returnEnd.NextSegment;
_readHead = nextBlock;
_readIndex = 0;
returnEnd = nextBlock;
}
else
{
_readHead = consumedSegment;
_readIndex = consumedIndex;
}
// Remove all blocks that are freed (except the last one)
while (returnStart != returnEnd)
{
BufferSegment next = returnStart.NextSegment !;
returnStart.ResetMemory();
ReturnSegmentUnsynchronized(returnStart);
returnStart = next;
}
}
internal void AdvanceReader(SequencePosition consumed, SequencePosition examined)
{
BufferSegment returnStart = null;
BufferSegment returnEnd = null;
Action continuation = null;
lock (_sync)
{
var examinedEverything = false;
if (examined.Segment == _commitHead)
{
examinedEverything = _commitHead != null ? examined.Index == _commitHeadIndex - _commitHead.Start : examined.Index == 0;
}
if (consumed.Segment != null)
{
if (_readHead == null)
{
ThrowHelper.ThrowInvalidOperationException_AdvanceToInvalidCursor();
return;
}
var consumedSegment = (BufferSegment)consumed.Segment;
returnStart = _readHead;
returnEnd = consumedSegment;
// Check if we crossed _maximumSizeLow and complete backpressure
long consumedBytes = new ReadOnlySequence <byte>(returnStart, _readHeadIndex, consumedSegment, consumed.Index).Length;
long oldLength = _length;
_length -= consumedBytes;
if (oldLength >= _resumeWriterThreshold &&
_length < _resumeWriterThreshold)
{
continuation = _writerAwaitable.Complete();
}
// Check if we consumed entire last segment
// if we are going to return commit head we need to check that there is no writing operation that
// might be using tailspace
if (consumed.Index == returnEnd.Length && _writingHead != returnEnd)
{
BufferSegment nextBlock = returnEnd.NextSegment;
if (_commitHead == returnEnd)
{
_commitHead = nextBlock;
_commitHeadIndex = 0;
}
_readHead = nextBlock;
_readHeadIndex = 0;
returnEnd = nextBlock;
}
else
{
_readHead = consumedSegment;
_readHeadIndex = consumed.Index;
}
}
// We reset the awaitable to not completed if we've examined everything the producer produced so far
// but only if writer is not completed yet
if (examinedEverything && !_writerCompletion.IsCompleted)
{
// Prevent deadlock where reader awaits new data and writer await backpressure
if (!_writerAwaitable.IsCompleted)
{
ThrowHelper.ThrowInvalidOperationException_BackpressureDeadlock();
}
_readerAwaitable.Reset();
}
while (returnStart != null && returnStart != returnEnd)
{
returnStart.ResetMemory();
ReturnSegmentUnsynchronized(returnStart);
returnStart = returnStart.NextSegment;
}
_readingState.End();
}
TrySchedule(_writerScheduler, continuation);
}
