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bufferqueue.h
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1 /*
2  * Generic buffer queue
3  * Copyright (c) 2012 Nicolas George
4  *
5  * This file is part of FFmpeg.
6  *
7  * FFmpeg is free software; you can redistribute it and/or
8  * modify it under the terms of the GNU Lesser General Public
9  * License as published by the Free Software Foundation; either
10  * version 2.1 of the License, or (at your option) any later version.
11  *
12  * FFmpeg is distributed in the hope that it will be useful,
13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15  * Lesser General Public License for more details.
16  *
17  * You should have received a copy of the GNU Lesser General Public
18  * License along with FFmpeg; if not, write to the Free Software
19  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
20  */
21 
22 #ifndef AVFILTER_BUFFERQUEUE_H
23 #define AVFILTER_BUFFERQUEUE_H
24 
25 /**
26  * FFBufQueue: simple AVFrame queue API
27  *
28  * Note: this API is not thread-safe. Concurrent access to the same queue
29  * must be protected by a mutex or any synchronization mechanism.
30  */
31 
32 /**
33  * Maximum size of the queue.
34  *
35  * This value can be overridden by definying it before including this
36  * header.
37  * Powers of 2 are recommended.
38  */
39 #ifndef FF_BUFQUEUE_SIZE
40 #define FF_BUFQUEUE_SIZE 64
41 #endif
42 
43 #include "avfilter.h"
44 #include "libavutil/avassert.h"
45 
46 /**
47  * Structure holding the queue
48  */
49 struct FFBufQueue {
51  unsigned short head;
52  unsigned short available; /**< number of available buffers */
53 };
54 
55 #define BUCKET(i) queue->queue[(queue->head + (i)) % FF_BUFQUEUE_SIZE]
56 
57 /**
58  * Test if a buffer queue is full.
59  */
60 static inline int ff_bufqueue_is_full(struct FFBufQueue *queue)
61 {
62  return queue->available == FF_BUFQUEUE_SIZE;
63 }
64 
65 /**
66  * Add a buffer to the queue.
67  *
68  * If the queue is already full, then the current last buffer is dropped
69  * (and unrefed) with a warning before adding the new buffer.
70  */
71 static inline void ff_bufqueue_add(void *log, struct FFBufQueue *queue,
72  AVFrame *buf)
73 {
74  if (ff_bufqueue_is_full(queue)) {
75  av_log(log, AV_LOG_WARNING, "Buffer queue overflow, dropping.\n");
76  av_frame_free(&BUCKET(--queue->available));
77  }
78  BUCKET(queue->available++) = buf;
79 }
80 
81 /**
82  * Get a buffer from the queue without altering it.
83  *
84  * Buffer with index 0 is the first buffer in the queue.
85  * Return NULL if the queue has not enough buffers.
86  */
87 static inline AVFrame *ff_bufqueue_peek(struct FFBufQueue *queue,
88  unsigned index)
89 {
90  return index < queue->available ? BUCKET(index) : NULL;
91 }
92 
93 /**
94  * Get the first buffer from the queue and remove it.
95  *
96  * Do not use on an empty queue.
97  */
98 static inline AVFrame *ff_bufqueue_get(struct FFBufQueue *queue)
99 {
100  AVFrame *ret = queue->queue[queue->head];
101  av_assert0(queue->available);
102  queue->available--;
103  queue->queue[queue->head] = NULL;
104  queue->head = (queue->head + 1) % FF_BUFQUEUE_SIZE;
105  return ret;
106 }
107 
108 /**
109  * Unref and remove all buffers from the queue.
110  */
111 static inline void ff_bufqueue_discard_all(struct FFBufQueue *queue)
112 {
113  while (queue->available) {
114  AVFrame *buf = ff_bufqueue_get(queue);
115  av_frame_free(&buf);
116  }
117 }
118 
119 #undef BUCKET
120 
121 #endif /* AVFILTER_BUFFERQUEUE_H */
static AVFrame * ff_bufqueue_get(struct FFBufQueue *queue)
Get the first buffer from the queue and remove it.
Definition: bufferqueue.h:98
#define NULL
Definition: coverity.c:32
#define BUCKET(i)
Definition: bufferqueue.h:55
This structure describes decoded (raw) audio or video data.
Definition: frame.h:184
#define AV_LOG_WARNING
Something somehow does not look correct.
Definition: log.h:182
Main libavfilter public API header.
Structure holding the queue.
Definition: bufferqueue.h:49
#define av_assert0(cond)
assert() equivalent, that is always enabled.
Definition: avassert.h:37
#define av_log(a,...)
void av_frame_free(AVFrame **frame)
Free the frame and any dynamically allocated objects in it, e.g.
Definition: frame.c:153
simple assert() macros that are a bit more flexible than ISO C assert().
unsigned short head
Definition: bufferqueue.h:51
AVFrame * queue[FF_BUFQUEUE_SIZE]
Definition: bufferqueue.h:50
static int ff_bufqueue_is_full(struct FFBufQueue *queue)
Test if a buffer queue is full.
Definition: bufferqueue.h:60
static void ff_bufqueue_discard_all(struct FFBufQueue *queue)
Unref and remove all buffers from the queue.
Definition: bufferqueue.h:111
unsigned short available
number of available buffers
Definition: bufferqueue.h:52
void * buf
Definition: avisynth_c.h:690
int index
Definition: gxfenc.c:89
#define FF_BUFQUEUE_SIZE
FFBufQueue: simple AVFrame queue API.
Definition: bufferqueue.h:40
static void ff_bufqueue_add(void *log, struct FFBufQueue *queue, AVFrame *buf)
Add a buffer to the queue.
Definition: bufferqueue.h:71
static AVFrame * ff_bufqueue_peek(struct FFBufQueue *queue, unsigned index)
Get a buffer from the queue without altering it.
Definition: bufferqueue.h:87