/*
  * This file is part of FFmpeg.
  *
  * FFmpeg is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public License
  * as published by the Free Software Foundation; either
  * version 2.1 of the License, or (at your option) any later version.
  *
  * FFmpeg is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  * GNU Lesser General Public License for more details.
  *
  * You should have received a copy of the GNU Lesser General Public License
  * along with FFmpeg; if not, write to the Free Software Foundation, Inc.,
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */
 
 #ifndef AVUTIL_THREADMESSAGE_H
 #define AVUTIL_THREADMESSAGE_H
 
 typedef struct AVThreadMessageQueue AVThreadMessageQueue;
 
 typedef enum AVThreadMessageFlags {
 
     /**
      * Perform non-blocking operation.
      * If this flag is set, send and recv operations are non-blocking and
      * return AVERROR(EAGAIN) immediately if they can not proceed.
      */
     AV_THREAD_MESSAGE_NONBLOCK = 1,
 
 } AVThreadMessageFlags;
 
 /**
  * Allocate a new message queue.
  *
  * @param mq      pointer to the message queue
  * @param nelem   maximum number of elements in the queue
  * @param elsize  size of each element in the queue
  * @return  >=0 for success; <0 for error, in particular AVERROR(ENOSYS) if
  *          lavu was built without thread support
  */
 int av_thread_message_queue_alloc(AVThreadMessageQueue **mq,
                                   unsigned nelem,
                                   unsigned elsize);
 
 /**
  * Free a message queue.
  *
  * The message queue must no longer be in use by another thread.
  */
 void av_thread_message_queue_free(AVThreadMessageQueue **mq);
 
 /**
  * Send a message on the queue.
  */
 int av_thread_message_queue_send(AVThreadMessageQueue *mq,
                                  void *msg,
                                  unsigned flags);
 
 /**
  * Receive a message from the queue.
  */
 int av_thread_message_queue_recv(AVThreadMessageQueue *mq,
                                  void *msg,
                                  unsigned flags);
 
 /**
  * Set the sending error code.
  *

  * If the error code is set to non-zero, av_thread_message_queue_send() will
  * return it immediately. Conventional values, such as AVERROR_EOF or
  * AVERROR(EAGAIN), can be used to cause the sending thread to stop or
  * suspend its operation.

  */
 void av_thread_message_queue_set_err_send(AVThreadMessageQueue *mq,
                                           int err);
 
 /**
  * Set the receiving error code.
  *

  * If the error code is set to non-zero, av_thread_message_queue_recv() will
  * return it immediately when there are no longer available messages.
  * Conventional values, such as AVERROR_EOF or AVERROR(EAGAIN), can be used
  * to cause the receiving thread to stop or suspend its operation.

  */
 void av_thread_message_queue_set_err_recv(AVThreadMessageQueue *mq,
                                           int err);
 

 /**
  * Set the optional free message callback function which will be called if an
  * operation is removing messages from the queue.
  */
 void av_thread_message_queue_set_free_func(AVThreadMessageQueue *mq,
                                            void (*free_func)(void *msg));
 
 /**
  * Flush the message queue
  *
  * This function is mostly equivalent to reading and free-ing every message
  * except that it will be done in a single operation (no lock/unlock between
  * reads).
  */
 void av_thread_message_flush(AVThreadMessageQueue *mq);
 

 #endif /* AVUTIL_THREADMESSAGE_H */