/// <summary>
/// Called to return a block to the pool. Once Return has been called the memory no longer belongs to the caller, and
/// Very Bad Things will happen if the memory is read of modified subsequently. If a caller fails to call Return and the
/// block tracking object is garbage collected, the block tracking object's finalizer will automatically re-create and return
/// a new tracking object into the pool. This will only happen if there is a bug in the server, however it is necessary to avoid
/// leaving "dead zones" in the slab due to lost block tracking objects.
/// </summary>
/// <param name="block">The block to return. It must have been acquired by calling Lease on the same memory pool instance.</param>
public void Return(MemoryPoolBlock block)
{
#if DEBUG
Debug.Assert(block.Pool == this, "Returned block was not leased from this pool");
Debug.Assert(block.IsLeased, $"Block being returned to pool twice: {block.Leaser}{Environment.NewLine}");
block.IsLeased = false;
#endif
if (block.Slab != null && block.Slab.IsActive)
{
_blocks.Enqueue(block);
}
else
{
GC.SuppressFinalize(block);
}
}
/// <summary>
/// Internal method called when a block is requested and the pool is empty. It allocates one additional slab, creates all of the
/// block tracking objects, and adds them all to the pool.
/// </summary>
private MemoryPoolBlock AllocateSlab()
{
var slab = MemoryPoolSlab.Create(_slabLength);
_slabs.Push(slab);
_slabAllocationCallback?.Invoke(slab);
slab._deallocationCallback = _slabDeallocationCallback;
var basePtr = slab.NativePointer;
var firstOffset = (int)((_blockStride - 1) - ((ulong)(basePtr + _blockStride - 1) % _blockStride));
var poolAllocationLength = _slabLength - _blockStride;
var offset = firstOffset;
for (;
offset + _blockLength < poolAllocationLength;
offset += _blockStride)
{
var block = MemoryPoolBlock.Create(
offset,
_blockLength,
this,
slab);
#if DEBUG
block.IsLeased = true;
#endif
Return(block);
}
// return last block rather than adding to pool
var newBlock = MemoryPoolBlock.Create(
offset,
_blockLength,
this,
slab);
return(newBlock);
}