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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 
23 #include "avassert.h"
24 #include "common.h"
25 #include "fifo.h"
26 
27 static AVFifoBuffer *fifo_alloc_common(void *buffer, size_t size)
28 {
29  AVFifoBuffer *f;
30  if (!buffer)
31  return NULL;
32  f = av_mallocz(sizeof(AVFifoBuffer));
33  if (!f) {
34  av_free(buffer);
35  return NULL;
36  }
37  f->buffer = buffer;
38  f->end = f->buffer + size;
39  av_fifo_reset(f);
40  return f;
41 }
42 
44 {
45  void *buffer = av_malloc(size);
46  return fifo_alloc_common(buffer, size);
47 }
48 
49 AVFifoBuffer *av_fifo_alloc_array(size_t nmemb, size_t size)
50 {
51  void *buffer = av_malloc_array(nmemb, size);
52  return fifo_alloc_common(buffer, nmemb * size);
53 }
54 
56 {
57  if (f) {
58  av_freep(&f->buffer);
59  av_free(f);
60  }
61 }
62 
64 {
65  if (f) {
66  av_fifo_free(*f);
67  *f = NULL;
68  }
69 }
70 
72 {
73  f->wptr = f->rptr = f->buffer;
74  f->wndx = f->rndx = 0;
75 }
76 
78 {
79  return (uint32_t)(f->wndx - f->rndx);
80 }
81 
83 {
84  return f->end - f->buffer - av_fifo_size(f);
85 }
86 
87 int av_fifo_realloc2(AVFifoBuffer *f, unsigned int new_size)
88 {
89  unsigned int old_size = f->end - f->buffer;
90 
91  if (old_size < new_size) {
92  int len = av_fifo_size(f);
93  AVFifoBuffer *f2 = av_fifo_alloc(new_size);
94 
95  if (!f2)
96  return AVERROR(ENOMEM);
97  av_fifo_generic_read(f, f2->buffer, len, NULL);
98  f2->wptr += len;
99  f2->wndx += len;
100  av_free(f->buffer);
101  *f = *f2;
102  av_free(f2);
103  }
104  return 0;
105 }
106 
107 int av_fifo_grow(AVFifoBuffer *f, unsigned int size)
108 {
109  unsigned int old_size = f->end - f->buffer;
110  if(size + (unsigned)av_fifo_size(f) < size)
111  return AVERROR(EINVAL);
112 
113  size += av_fifo_size(f);
114 
115  if (old_size < size)
116  return av_fifo_realloc2(f, FFMAX(size, 2*size));
117  return 0;
118 }
119 
120 /* src must NOT be const as it can be a context for func that may need
121  * updating (like a pointer or byte counter) */
123  int (*func)(void *, void *, int))
124 {
125  int total = size;
126  uint32_t wndx= f->wndx;
127  uint8_t *wptr= f->wptr;
128 
129  do {
130  int len = FFMIN(f->end - wptr, size);
131  if (func) {
132  if (func(src, wptr, len) <= 0)
133  break;
134  } else {
135  memcpy(wptr, src, len);
136  src = (uint8_t *)src + len;
137  }
138 // Write memory barrier needed for SMP here in theory
139  wptr += len;
140  if (wptr >= f->end)
141  wptr = f->buffer;
142  wndx += len;
143  size -= len;
144  } while (size > 0);
145  f->wndx= wndx;
146  f->wptr= wptr;
147  return total - size;
148 }
149 
150 int av_fifo_generic_read(AVFifoBuffer *f, void *dest, int buf_size,
151  void (*func)(void *, void *, int))
152 {
153 // Read memory barrier needed for SMP here in theory
154  do {
155  int len = FFMIN(f->end - f->rptr, buf_size);
156  if (func)
157  func(dest, f->rptr, len);
158  else {
159  memcpy(dest, f->rptr, len);
160  dest = (uint8_t *)dest + len;
161  }
162 // memory barrier needed for SMP here in theory
163  av_fifo_drain(f, len);
164  buf_size -= len;
165  } while (buf_size > 0);
166  return 0;
167 }
168 
169 /** Discard data from the FIFO. */
170 void av_fifo_drain(AVFifoBuffer *f, int size)
171 {
172  av_assert2(av_fifo_size(f) >= size);
173  f->rptr += size;
174  if (f->rptr >= f->end)
175  f->rptr -= f->end - f->buffer;
176  f->rndx += size;
177 }
178 
179 #ifdef TEST
180 
181 int main(void)
182 {
183  /* create a FIFO buffer */
184  AVFifoBuffer *fifo = av_fifo_alloc(13 * sizeof(int));
185  int i, j, n;
186 
187  /* fill data */
188  for (i = 0; av_fifo_space(fifo) >= sizeof(int); i++)
189  av_fifo_generic_write(fifo, &i, sizeof(int), NULL);
190 
191  /* peek at FIFO */
192  n = av_fifo_size(fifo) / sizeof(int);
193  for (i = -n + 1; i < n; i++) {
194  int *v = (int *)av_fifo_peek2(fifo, i * sizeof(int));
195  printf("%d: %d\n", i, *v);
196  }
197  printf("\n");
198 
199  /* read data */
200  for (i = 0; av_fifo_size(fifo) >= sizeof(int); i++) {
201  av_fifo_generic_read(fifo, &j, sizeof(int), NULL);
202  printf("%d ", j);
203  }
204  printf("\n");
205 
206  av_fifo_free(fifo);
207 
208  return 0;
209 }
210 
211 #endif