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fifo.h
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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
6  * License 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 GNU
12  * Lesser General Public License for more details.
13  *
14  * You should have received a copy of the GNU Lesser General Public
15  * License along with FFmpeg; if not, write to the Free Software
16  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
17  */
18 
19 /**
20  * @file
21  * a very simple circular buffer FIFO implementation
22  */
23 
24 #ifndef AVUTIL_FIFO_H
25 #define AVUTIL_FIFO_H
26 
27 #include <stdint.h>
28 #include "avutil.h"
29 #include "attributes.h"
30 
31 typedef struct AVFifoBuffer {
34  uint32_t rndx, wndx;
35 } AVFifoBuffer;
36 
37 /**
38  * Initialize an AVFifoBuffer.
39  * @param size of FIFO
40  * @return AVFifoBuffer or NULL in case of memory allocation failure
41  */
42 AVFifoBuffer *av_fifo_alloc(unsigned int size);
43 
44 /**
45  * Free an AVFifoBuffer.
46  * @param f AVFifoBuffer to free
47  */
48 void av_fifo_free(AVFifoBuffer *f);
49 
50 /**
51  * Reset the AVFifoBuffer to the state right after av_fifo_alloc, in particular it is emptied.
52  * @param f AVFifoBuffer to reset
53  */
55 
56 /**
57  * Return the amount of data in bytes in the AVFifoBuffer, that is the
58  * amount of data you can read from it.
59  * @param f AVFifoBuffer to read from
60  * @return size
61  */
63 
64 /**
65  * Return the amount of space in bytes in the AVFifoBuffer, that is the
66  * amount of data you can write into it.
67  * @param f AVFifoBuffer to write into
68  * @return size
69  */
71 
72 /**
73  * Feed data from an AVFifoBuffer to a user-supplied callback.
74  * @param f AVFifoBuffer to read from
75  * @param buf_size number of bytes to read
76  * @param func generic read function
77  * @param dest data destination
78  */
79 int av_fifo_generic_read(AVFifoBuffer *f, void *dest, int buf_size, void (*func)(void*, void*, int));
80 
81 /**
82  * Feed data from a user-supplied callback to an AVFifoBuffer.
83  * @param f AVFifoBuffer to write to
84  * @param src data source; non-const since it may be used as a
85  * modifiable context by the function defined in func
86  * @param size number of bytes to write
87  * @param func generic write function; the first parameter is src,
88  * the second is dest_buf, the third is dest_buf_size.
89  * func must return the number of bytes written to dest_buf, or <= 0 to
90  * indicate no more data available to write.
91  * If func is NULL, src is interpreted as a simple byte array for source data.
92  * @return the number of bytes written to the FIFO
93  */
94 int av_fifo_generic_write(AVFifoBuffer *f, void *src, int size, int (*func)(void*, void*, int));
95 
96 /**
97  * Resize an AVFifoBuffer.
98  * In case of reallocation failure, the old FIFO is kept unchanged.
99  *
100  * @param f AVFifoBuffer to resize
101  * @param size new AVFifoBuffer size in bytes
102  * @return <0 for failure, >=0 otherwise
103  */
104 int av_fifo_realloc2(AVFifoBuffer *f, unsigned int size);
105 
106 /**
107  * Enlarge an AVFifoBuffer.
108  * In case of reallocation failure, the old FIFO is kept unchanged.
109  * The new fifo size may be larger than the requested size.
110  *
111  * @param f AVFifoBuffer to resize
112  * @param additional_space the amount of space in bytes to allocate in addition to av_fifo_size()
113  * @return <0 for failure, >=0 otherwise
114  */
115 int av_fifo_grow(AVFifoBuffer *f, unsigned int additional_space);
116 
117 /**
118  * Read and discard the specified amount of data from an AVFifoBuffer.
119  * @param f AVFifoBuffer to read from
120  * @param size amount of data to read in bytes
121  */
122 void av_fifo_drain(AVFifoBuffer *f, int size);
123 
124 /**
125  * Return a pointer to the data stored in a FIFO buffer at a certain offset.
126  * The FIFO buffer is not modified.
127  *
128  * @param f AVFifoBuffer to peek at, f must be non-NULL
129  * @param offs an offset in bytes, its absolute value must be less
130  * than the used buffer size or the returned pointer will
131  * point outside to the buffer data.
132  * The used buffer size can be checked with av_fifo_size().
133  */
134 static inline uint8_t *av_fifo_peek2(const AVFifoBuffer *f, int offs)
135 {
136  uint8_t *ptr = f->rptr + offs;
137  if (ptr >= f->end)
138  ptr = f->buffer + (ptr - f->end);
139  else if (ptr < f->buffer)
140  ptr = f->end - (f->buffer - ptr);
141  return ptr;
142 }
143 
144 #endif /* AVUTIL_FIFO_H */