iokit/Kernel/IODataQueue.cpp

48     IODataQueue *dataQueue = new IODataQueue;
50     if (dataQueue) {
51         if  (!dataQueue->initWithCapacity(size)) {
52             dataQueue->release();
53             dataQueue = 0;
57     return dataQueue;
62     IODataQueue *dataQueue = new IODataQueue;
64     if (dataQueue) {
65         if (!dataQueue->initWithEntries(numEntries, entrySize)) {
66             dataQueue->release();
67             dataQueue = 0;
71     return dataQueue;
88     dataQueue = (IODataQueueMemory *)IOMallocAligned(allocSize, PAGE_SIZE);
89     if (dataQueue == 0) {
93     dataQueue->queueSize    = size;
94     dataQueue->head         = 0;
95     dataQueue->tail         = 0;
107     if (dataQueue) {
108         IOFreeAligned(dataQueue, round_page(dataQueue->queueSize + DATA_QUEUE_MEMORY_HEADER_SIZE));
118     const UInt32       head      = dataQueue->head;  // volatile
119     const UInt32       tail      = dataQueue->tail;
126         if ( (tail + entrySize) <= dataQueue->queueSize )
128             entry = (IODataQueueEntry *)((UInt8 *)dataQueue->queue + tail);
135             // The tail can range from 0 to dataQueue->queueSize inclusive.
137             dataQueue->tail += entrySize;
144             dataQueue->queue->size = dataSize;
150             if ( ( dataQueue->queueSize - tail ) >= DATA_QUEUE_ENTRY_HEADER_SIZE )
152                 ((IODataQueueEntry *)((UInt8 *)dataQueue->queue + tail))->size = dataSize;
155             memcpy(&dataQueue->queue->data, data, dataSize);
156             dataQueue->tail = entrySize;
170             entry = (IODataQueueEntry *)((UInt8 *)dataQueue->queue + tail);
174             dataQueue->tail += entrySize;
185     ||   ( dataQueue->head == tail ) )   /* queue was emptied during enqueue() */
236     if (dataQueue != 0) {
237         descriptor = IOMemoryDescriptor::withAddress(dataQueue, dataQueue->queueSize + DATA_QUEUE_MEMORY_HEADER_SIZE, kIODirectionOutIn);