public MemoryPoolIterator BeginWrite(int minimumSize = 0)
{
MemoryPoolBlock block = null;
if (_tail != null)
{
int remaining = _tail.Data.Offset + _tail.Data.Count - _tail.End;
if (minimumSize <= remaining && remaining > 0)
{
block = _tail;
}
}
if (block == null)
{
block = _memory.Lease();
}
lock (_sync)
{
if (_head == null)
{
_head = block;
}
else if (block != _tail)
{
Volatile.Write(ref _tail.Next, block);
_tail = block;
}
return(new MemoryPoolIterator(block, block.End));
}
}
public void Ensure(int count)
{
if (_tail == null)
{
_tail = new MemoryBlockSegment(_pool.Lease());
_tailIndex = _tail.End;
_head = _tail;
_headIndex = _tail.Start;
}
Debug.Assert(_tail.Block != null);
Debug.Assert(_tail.Next == null);
Debug.Assert(_tail.End == _tailIndex);
var segment = _tail;
var block = _tail.Block;
var blockIndex = _tailIndex;
var remaining = count;
var bytesLeftInBlock = block.Data.Offset + block.Data.Count - blockIndex;
// If inadequate bytes left or if the segment is readonly
if (bytesLeftInBlock < count || segment.ReadOnly)
{
var nextBlock = _pool.Lease();
var nextSegment = new MemoryBlockSegment(nextBlock);
segment.End = blockIndex;
Volatile.Write(ref segment.Next, nextSegment);
segment = nextSegment;
block = nextBlock;
blockIndex = block.Data.Offset;
segment.End = blockIndex;
segment.Block = block;
_tail = segment;
_tailIndex = blockIndex;
}
}
public WritableBuffer Alloc(int minimumSize = 0)
{
if (Interlocked.CompareExchange(ref _producingState, 1, 0) != 0)
{
throw new InvalidOperationException("Already producing.");
}
MemoryBlockSegment segment = null;
if (_tail != null && !_tail.ReadOnly)
{
// Try to return the tail so the calling code can append to it
int remaining = _tail.Block.Data.Offset + _tail.Block.Data.Count - _tail.End;
if (minimumSize <= remaining)
{
segment = _tail;
}
}
if (segment == null && minimumSize > 0)
{
// We're out of tail space so lease a new segment only if the requested size > 0
segment = new MemoryBlockSegment(_pool.Lease());
}
lock (_sync)
{
if (_head == null)
{
_head = segment;
}
else if (segment != null && segment != _tail)
{
// Append the segment to the tail if it's non-null
Volatile.Write(ref _tail.Next, segment);
_tail = segment;
}
return(new WritableBuffer(this, _pool, segment));
}
}