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;
}
}