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fifo.c
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1 /*
2  * a very simple circular buffer FIFO implementation
3  * Copyright (c) 2000, 2001, 2002 Fabrice Bellard
4  * Copyright (c) 2006 Roman Shaposhnik
5  *
6  * This file is part of FFmpeg.
7  *
8  * FFmpeg is free software; you can redistribute it and/or
9  * modify it under the terms of the GNU Lesser General Public
10  * License as published by the Free Software Foundation; either
11  * version 2.1 of the License, or (at your option) any later version.
12  *
13  * FFmpeg is distributed in the hope that it will be useful,
14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
16  * Lesser General Public License for more details.
17  *
18  * You should have received a copy of the GNU Lesser General Public
19  * License along with FFmpeg; if not, write to the Free Software
20  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
21  */
22 #include "common.h"
23 #include "fifo.h"
24 
26 {
27  AVFifoBuffer *f = av_mallocz(sizeof(AVFifoBuffer));
28  if (!f)
29  return NULL;
30  f->buffer = av_malloc(size);
31  f->end = f->buffer + size;
32  av_fifo_reset(f);
33  if (!f->buffer)
34  av_freep(&f);
35  return f;
36 }
37 
39 {
40  if (f) {
41  av_freep(&f->buffer);
42  av_free(f);
43  }
44 }
45 
47 {
48  f->wptr = f->rptr = f->buffer;
49  f->wndx = f->rndx = 0;
50 }
51 
53 {
54  return (uint32_t)(f->wndx - f->rndx);
55 }
56 
58 {
59  return f->end - f->buffer - av_fifo_size(f);
60 }
61 
62 int av_fifo_realloc2(AVFifoBuffer *f, unsigned int new_size)
63 {
64  unsigned int old_size = f->end - f->buffer;
65 
66  if (old_size < new_size) {
67  int len = av_fifo_size(f);
68  AVFifoBuffer *f2 = av_fifo_alloc(new_size);
69 
70  if (!f2)
71  return AVERROR(ENOMEM);
72  av_fifo_generic_read(f, f2->buffer, len, NULL);
73  f2->wptr += len;
74  f2->wndx += len;
75  av_free(f->buffer);
76  *f = *f2;
77  av_free(f2);
78  }
79  return 0;
80 }
81 
82 int av_fifo_grow(AVFifoBuffer *f, unsigned int size)
83 {
84  unsigned int old_size = f->end - f->buffer;
85  if(size + (unsigned)av_fifo_size(f) < size)
86  return AVERROR(EINVAL);
87 
88  size += av_fifo_size(f);
89 
90  if (old_size < size)
91  return av_fifo_realloc2(f, FFMAX(size, 2*size));
92  return 0;
93 }
94 
95 /* src must NOT be const as it can be a context for func that may need
96  * updating (like a pointer or byte counter) */
98  int (*func)(void *, void *, int))
99 {
100  int total = size;
101  uint32_t wndx= f->wndx;
102  uint8_t *wptr= f->wptr;
103 
104  do {
105  int len = FFMIN(f->end - wptr, size);
106  if (func) {
107  if (func(src, wptr, len) <= 0)
108  break;
109  } else {
110  memcpy(wptr, src, len);
111  src = (uint8_t *)src + len;
112  }
113 // Write memory barrier needed for SMP here in theory
114  wptr += len;
115  if (wptr >= f->end)
116  wptr = f->buffer;
117  wndx += len;
118  size -= len;
119  } while (size > 0);
120  f->wndx= wndx;
121  f->wptr= wptr;
122  return total - size;
123 }
124 
125 int av_fifo_generic_read(AVFifoBuffer *f, void *dest, int buf_size,
126  void (*func)(void *, void *, int))
127 {
128 // Read memory barrier needed for SMP here in theory
129  do {
130  int len = FFMIN(f->end - f->rptr, buf_size);
131  if (func)
132  func(dest, f->rptr, len);
133  else {
134  memcpy(dest, f->rptr, len);
135  dest = (uint8_t *)dest + len;
136  }
137 // memory barrier needed for SMP here in theory
138  av_fifo_drain(f, len);
139  buf_size -= len;
140  } while (buf_size > 0);
141  return 0;
142 }
143 
144 /** Discard data from the FIFO. */
145 void av_fifo_drain(AVFifoBuffer *f, int size)
146 {
147  f->rptr += size;
148  if (f->rptr >= f->end)
149  f->rptr -= f->end - f->buffer;
150  f->rndx += size;
151 }
152 
153 #ifdef TEST
154 
155 int main(void)
156 {
157  /* create a FIFO buffer */
158  AVFifoBuffer *fifo = av_fifo_alloc(13 * sizeof(int));
159  int i, j, n;
160 
161  /* fill data */
162  for (i = 0; av_fifo_space(fifo) >= sizeof(int); i++)
163  av_fifo_generic_write(fifo, &i, sizeof(int), NULL);
164 
165  /* peek at FIFO */
166  n = av_fifo_size(fifo) / sizeof(int);
167  for (i = -n + 1; i < n; i++) {
168  int *v = (int *)av_fifo_peek2(fifo, i * sizeof(int));
169  printf("%d: %d\n", i, *v);
170  }
171  printf("\n");
172 
173  /* read data */
174  for (i = 0; av_fifo_size(fifo) >= sizeof(int); i++) {
175  av_fifo_generic_read(fifo, &j, sizeof(int), NULL);
176  printf("%d ", j);
177  }
178  printf("\n");
179 
180  av_fifo_free(fifo);
181 
182  return 0;
183 }
184 
185 #endif