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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  * Initialize an AVFifoBuffer.
46  * @param nmemb number of elements
47  * @param size size of the single element
48  * @return AVFifoBuffer or NULL in case of memory allocation failure
49  */
50 AVFifoBuffer *av_fifo_alloc_array(size_t nmemb, size_t size);
51 
52 /**
53  * Free an AVFifoBuffer.
54  * @param f AVFifoBuffer to free
55  */
56 void av_fifo_free(AVFifoBuffer *f);
57 
58 /**
59  * Free an AVFifoBuffer and reset pointer to NULL.
60  * @param f AVFifoBuffer to free
61  */
62 void av_fifo_freep(AVFifoBuffer **f);
63 
64 /**
65  * Reset the AVFifoBuffer to the state right after av_fifo_alloc, in particular it is emptied.
66  * @param f AVFifoBuffer to reset
67  */
69 
70 /**
71  * Return the amount of data in bytes in the AVFifoBuffer, that is the
72  * amount of data you can read from it.
73  * @param f AVFifoBuffer to read from
74  * @return size
75  */
76 int av_fifo_size(const AVFifoBuffer *f);
77 
78 /**
79  * Return the amount of space in bytes in the AVFifoBuffer, that is the
80  * amount of data you can write into it.
81  * @param f AVFifoBuffer to write into
82  * @return size
83  */
84 int av_fifo_space(const AVFifoBuffer *f);
85 
86 /**
87  * Feed data from an AVFifoBuffer to a user-supplied callback.
88  * @param f AVFifoBuffer to read from
89  * @param buf_size number of bytes to read
90  * @param func generic read function
91  * @param dest data destination
92  */
93 int av_fifo_generic_read(AVFifoBuffer *f, void *dest, int buf_size, void (*func)(void*, void*, int));
94 
95 /**
96  * Feed data from a user-supplied callback to an AVFifoBuffer.
97  * @param f AVFifoBuffer to write to
98  * @param src data source; non-const since it may be used as a
99  * modifiable context by the function defined in func
100  * @param size number of bytes to write
101  * @param func generic write function; the first parameter is src,
102  * the second is dest_buf, the third is dest_buf_size.
103  * func must return the number of bytes written to dest_buf, or <= 0 to
104  * indicate no more data available to write.
105  * If func is NULL, src is interpreted as a simple byte array for source data.
106  * @return the number of bytes written to the FIFO
107  */
108 int av_fifo_generic_write(AVFifoBuffer *f, void *src, int size, int (*func)(void*, void*, int));
109 
110 /**
111  * Resize an AVFifoBuffer.
112  * In case of reallocation failure, the old FIFO is kept unchanged.
113  *
114  * @param f AVFifoBuffer to resize
115  * @param size new AVFifoBuffer size in bytes
116  * @return <0 for failure, >=0 otherwise
117  */
118 int av_fifo_realloc2(AVFifoBuffer *f, unsigned int size);
119 
120 /**
121  * Enlarge an AVFifoBuffer.
122  * In case of reallocation failure, the old FIFO is kept unchanged.
123  * The new fifo size may be larger than the requested size.
124  *
125  * @param f AVFifoBuffer to resize
126  * @param additional_space the amount of space in bytes to allocate in addition to av_fifo_size()
127  * @return <0 for failure, >=0 otherwise
128  */
129 int av_fifo_grow(AVFifoBuffer *f, unsigned int additional_space);
130 
131 /**
132  * Read and discard the specified amount of data from an AVFifoBuffer.
133  * @param f AVFifoBuffer to read from
134  * @param size amount of data to read in bytes
135  */
136 void av_fifo_drain(AVFifoBuffer *f, int size);
137 
138 /**
139  * Return a pointer to the data stored in a FIFO buffer at a certain offset.
140  * The FIFO buffer is not modified.
141  *
142  * @param f AVFifoBuffer to peek at, f must be non-NULL
143  * @param offs an offset in bytes, its absolute value must be less
144  * than the used buffer size or the returned pointer will
145  * point outside to the buffer data.
146  * The used buffer size can be checked with av_fifo_size().
147  */
148 static inline uint8_t *av_fifo_peek2(const AVFifoBuffer *f, int offs)
149 {
150  uint8_t *ptr = f->rptr + offs;
151  if (ptr >= f->end)
152  ptr = f->buffer + (ptr - f->end);
153  else if (ptr < f->buffer)
154  ptr = f->end - (f->buffer - ptr);
155  return ptr;
156 }
157 
158 #endif /* AVUTIL_FIFO_H */