private bool TryDequeueSlow <T>(out T result) where T : unmanaged
{
while (true)
{
QueueSegment *head = _head;
if (head->TryDequeue(out result))
{
return(true);
}
if (head->_nextSegment == null)
{
result = default;
return(false);
}
UDebug.Assert(head->_frozen);
if (head->TryDequeue(out result))
{
return(true);
}
_crossSegmentLock.Lock();
if (head == _head)
{
var next = head->_nextSegment;
QueueSegment.Free(head);
_head = next;
}
_crossSegmentLock.Unlock();
}
}
public static void Clear(UnsafeMPMCQueue *queue)
{
UDebug.Assert(queue != null);
UDebug.Assert(queue->_head != null);
queue->_crossSegmentLock.Lock();
queue->_tail->EnsureFrozenForEnqueues();
var segmentsize = INITIAL_SEGMENT_LENGTH;
if (queue->_fixedSize)
{
segmentsize = queue->_tail->Capacity;
}
// Free all segments
var segment = queue->_head;
do
{
var next = segment->_nextSegment;
QueueSegment.Free(segment);
segment = next;
}while (segment != null);
queue->_tail = queue->_head = QueueSegment.Allocate(segmentsize, queue->_slotStride, queue->_slotOffset);
queue->_crossSegmentLock.Unlock();
}
private bool TryEnqueueSlow <T>(T item) where T : unmanaged
{
while (true)
{
QueueSegment *tail = _tail;
if (tail->TryEnqueue(item))
{
return(true);
}
// Do not create a new segment if the queue has a fixed size.
if (_fixedSize)
{
return(false);
}
_crossSegmentLock.Lock();
if (tail == _tail)
{
tail->EnsureFrozenForEnqueues();
int nextSize = tail->_preserved ? INITIAL_SEGMENT_LENGTH : Math.Min(tail->Capacity * 2, MAX_SEGMENT_LENGTH);
var newTail = QueueSegment.Allocate(nextSize, _slotStride, _slotOffset);
tail->_nextSegment = newTail;
_tail = newTail;
}
_crossSegmentLock.Unlock();
}
}
/// <summary>
/// Creates a Multi-Producer, Multi-Consumer concurrent queue.
/// </summary>
/// <param name="segmentSize">The size of a queue segment or the queue capacity when fixedSize = true.</param>
/// <param name="fixedSize">Creates a queue with a fixed size if true.</param>
public static UnsafeMPMCQueue *Allocate <T>(int segmentSize = INITIAL_SEGMENT_LENGTH, bool fixedSize = false) where T : unmanaged
{
if (segmentSize < 1)
{
throw new ArgumentOutOfRangeException(nameof(segmentSize), string.Format(ThrowHelper.ArgumentOutOfRange_MustBePositive, nameof(segmentSize)));
}
int slotStride = Marshal.SizeOf(new QueueSlot <T>());
int slotAlign = Memory.GetMaxAlignment(sizeof(T), sizeof(int));
int slotOffset = Memory.RoundToAlignment(sizeof(T), slotAlign);
var queue = Memory.MallocAndZero <UnsafeMPMCQueue>();
queue->_typeHandle = typeof(T).TypeHandle.Value;
queue->_slotStride = slotStride;
queue->_slotOffset = slotOffset;
queue->_fixedSize = fixedSize;
queue->_tail = queue->_head = QueueSegment.Allocate(segmentSize, slotStride, slotOffset);
return(queue);
}
public static void Free(UnsafeMPMCQueue *queue)
{
if (queue == null)
{
return;
}
// Free all segments
var segment = queue->_head;
do
{
var next = segment->_nextSegment;
QueueSegment.Free(segment);
segment = next;
}while (segment != null);
// Clear queue memory (just in case)
*queue = default;
// Free queue memory, if this is a fixed queue it frees the items memory at the same time
Memory.Free(queue);
}