1 /*
2  * This file is part of FFmpeg.
3  *
4  * FFmpeg is free software; you can redistribute it and/or
5  * modify it under the terms of the GNU Lesser General Public License
6  * as published by the Free Software Foundation; either
7  * version 2.1 of the License, or (at your option) any later version.
8  *
9  * FFmpeg is distributed in the hope that it will be useful,
10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
12  * GNU Lesser General Public License for more details.
13  *
14  * You should have received a copy of the GNU Lesser General Public License
15  * along with FFmpeg; if not, write to the Free Software Foundation, Inc.,
16  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
17  */
18 
19 #ifndef AVUTIL_THREADMESSAGE_H
20 #define AVUTIL_THREADMESSAGE_H
21 
22 typedef struct AVThreadMessageQueue AVThreadMessageQueue;
23 
24 typedef enum AVThreadMessageFlags {
25 
26     /**
27      * Perform non-blocking operation.
28      * If this flag is set, send and recv operations are non-blocking and
29      * return AVERROR(EAGAIN) immediately if they can not proceed.
30      */
31     AV_THREAD_MESSAGE_NONBLOCK = 1,
32 
33 } AVThreadMessageFlags;
34 
35 /**
36  * Allocate a new message queue.
37  *
38  * @param mq      pointer to the message queue
39  * @param nelem   maximum number of elements in the queue
40  * @param elsize  size of each element in the queue
41  * @return  >=0 for success; <0 for error, in particular AVERROR(ENOSYS) if
42  *          lavu was built without thread support
43  */
44 int av_thread_message_queue_alloc(AVThreadMessageQueue **mq,
45                                   unsigned nelem,
46                                   unsigned elsize);
47 
48 /**
49  * Free a message queue.
50  *
51  * The message queue must no longer be in use by another thread.
52  */
53 void av_thread_message_queue_free(AVThreadMessageQueue **mq);
54 
55 /**
56  * Send a message on the queue.
57  */
58 int av_thread_message_queue_send(AVThreadMessageQueue *mq,
59                                  void *msg,
60                                  unsigned flags);
61 
62 /**
63  * Receive a message from the queue.
64  */
65 int av_thread_message_queue_recv(AVThreadMessageQueue *mq,
66                                  void *msg,
67                                  unsigned flags);
68 
69 /**
70  * Set the sending error code.
71  *
72  * If the error code is set to non-zero, av_thread_message_queue_send() will
73  * return it immediately. Conventional values, such as AVERROR_EOF or
74  * AVERROR(EAGAIN), can be used to cause the sending thread to stop or
75  * suspend its operation.
76  */
77 void av_thread_message_queue_set_err_send(AVThreadMessageQueue *mq,
78                                           int err);
79 
80 /**
81  * Set the receiving error code.
82  *
83  * If the error code is set to non-zero, av_thread_message_queue_recv() will
84  * return it immediately when there are no longer available messages.
85  * Conventional values, such as AVERROR_EOF or AVERROR(EAGAIN), can be used
86  * to cause the receiving thread to stop or suspend its operation.
87  */
88 void av_thread_message_queue_set_err_recv(AVThreadMessageQueue *mq,
89                                           int err);
90 
91 /**
92  * Set the optional free message callback function which will be called if an
93  * operation is removing messages from the queue.
94  */
95 void av_thread_message_queue_set_free_func(AVThreadMessageQueue *mq,
96                                            void (*free_func)(void *msg));
97 
98 /**
99  * Flush the message queue
100  *
101  * This function is mostly equivalent to reading and free-ing every message
102  * except that it will be done in a single operation (no lock/unlock between
103  * reads).
104  */
105 void av_thread_message_flush(AVThreadMessageQueue *mq);
106 
107 #endif /* AVUTIL_THREADMESSAGE_H */
108