text: /*
  Copyright (c) 2012, Broadcom Europe Ltd
  All rights reserved.
  
  Redistribution and use in source and binary forms, with or without
  modification, are permitted provided that the following conditions are met:
      * Redistributions of source code must retain the above copyright
        notice, this list of conditions and the following disclaimer.
      * Redistributions in binary form must reproduce the above copyright
        notice, this list of conditions and the following disclaimer in the
        documentation and/or other materials provided with the distribution.
      * Neither the name of the copyright holder nor the
        names of its contributors may be used to endorse or promote products
        derived from this software without specific prior written permission.
  
  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
  ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
  WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
  DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY
  DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
  (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
  ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
  SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
  
  #include "mmal.h"
  #include "mmal_queue.h"
  
  /** Definition of the QUEUE */
  struct MMAL_QUEUE_T
  {
     VCOS_MUTEX_T lock;
     unsigned int length;
     MMAL_BUFFER_HEADER_T *first;
     MMAL_BUFFER_HEADER_T **last;
     VCOS_SEMAPHORE_T semaphore;
  };
  
  /** Create a QUEUE of MMAL_BUFFER_HEADER_T */
  MMAL_QUEUE_T *mmal_queue_create(void)
  {
     MMAL_QUEUE_T *queue;
  
     queue = vcos_malloc(sizeof(*queue), "MMAL queue");
     if(!queue) return 0;
  
     if(vcos_mutex_create(&queue->lock, "MMAL queue lock") != VCOS_SUCCESS )
     {
        vcos_free(queue);
        return 0;
     }
  
     if(vcos_semaphore_create(&queue->semaphore, "MMAL queue sema", 0) != VCOS_SUCCESS )
     {
        vcos_mutex_delete(&queue->lock);
        vcos_free(queue);
        return 0;
     }
  
     queue->length = 0;
     queue->first = 0;
     queue->last = &queue->first;
     return queue;
  }
  
  /** Put a MMAL_BUFFER_HEADER_T into a QUEUE */
  void mmal_queue_put(MMAL_QUEUE_T *queue, MMAL_BUFFER_HEADER_T *buffer)
  {
     if(!queue || !buffer) return;
  
  	vcos_mutex_lock(&queue->lock);
     queue->length++;
     *queue->last = buffer;
     buffer->next = 0;
     queue->last = &buffer->next;
     vcos_semaphore_post(&queue->semaphore);
     vcos_mutex_unlock(&queue->lock);
  }
  
  /** Put a MMAL_BUFFER_HEADER_T back at the start of a QUEUE. */
  void mmal_queue_put_back(MMAL_QUEUE_T *queue, MMAL_BUFFER_HEADER_T *buffer)
  {
     if(!queue || !buffer) return;
  
  	vcos_mutex_lock(&queue->lock);
     queue->length++;
     buffer->next = queue->first;
     queue->first = buffer;
     if(queue->last == &queue->first) queue->last = &buffer->next;
     vcos_semaphore_post(&queue->semaphore);
     vcos_mutex_unlock(&queue->lock);
  }
  
  /** Get a MMAL_BUFFER_HEADER_T from a QUEUE. */
  MMAL_BUFFER_HEADER_T *mmal_queue_get(MMAL_QUEUE_T *queue)
  {
     MMAL_BUFFER_HEADER_T *buffer;
  
  	if(!queue) return 0;
  
     vcos_mutex_lock(&queue->lock);
     buffer = queue->first;
     if(!buffer)
     {
        vcos_mutex_unlock(&queue->lock);
        return 0;
     }
  
     /* coverity[lock] This semaphore isn't being used as a mutex */
     vcos_semaphore_wait(&queue->semaphore); /* Will always succeed */
  
     queue->first = buffer->next;
     if(!queue->first) queue->last = &queue->first;
  
     queue->length--;
     vcos_mutex_unlock(&queue->lock);
  
     return buffer;
  }
  
  /** Wait for a MMAL_BUFFER_HEADER_T from a QUEUE. */
  MMAL_BUFFER_HEADER_T *mmal_queue_wait(MMAL_QUEUE_T *queue)
  {
  	if(!queue) return 0;
  
  	vcos_semaphore_wait(&queue->semaphore);
     vcos_semaphore_post(&queue->semaphore);
     return mmal_queue_get(queue);
  }
  
  MMAL_BUFFER_HEADER_T *mmal_queue_timedwait(MMAL_QUEUE_T *queue, VCOS_UNSIGNED timeout)
  {
      int ret = 0;
      if (!queue)
          return NULL;
  
      ret = vcos_semaphore_wait_timeout(&queue->semaphore, timeout);
  
      if (ret != VCOS_SUCCESS)
          return NULL;
  
      vcos_semaphore_post(&queue->semaphore);
      return mmal_queue_get(queue);
  }
  
  /** Get the number of MMAL_BUFFER_HEADER_T currently in a QUEUE */
  unsigned int mmal_queue_length(MMAL_QUEUE_T *queue)
  {
  	if(!queue) return 0;
  
  	return queue->length;
  }
  
  /** Destroy a queue of MMAL_BUFFER_HEADER_T */
  void mmal_queue_destroy(MMAL_QUEUE_T *queue)
  {
     if(!queue) return;
     vcos_mutex_delete(&queue->lock);
     vcos_semaphore_delete(&queue->semaphore);
     vcos_free(queue);
  }
  