fifo.c (7669B)
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 <stdint.h> 24 #include <string.h> 25 26 #include "avassert.h" 27 #include "error.h" 28 #include "fifo.h" 29 #include "macros.h" 30 #include "mem.h" 31 32 // by default the FIFO can be auto-grown to 1MB 33 #define AUTO_GROW_DEFAULT_BYTES (1024 * 1024) 34 35 struct AVFifo { 36 uint8_t *buffer; 37 38 size_t elem_size, nb_elems; 39 size_t offset_r, offset_w; 40 // distinguishes the ambiguous situation offset_r == offset_w 41 int is_empty; 42 43 unsigned int flags; 44 size_t auto_grow_limit; 45 }; 46 47 AVFifo *av_fifo_alloc2(size_t nb_elems, size_t elem_size, 48 unsigned int flags) 49 { 50 AVFifo *f; 51 void *buffer = NULL; 52 53 if (!elem_size) 54 return NULL; 55 56 if (nb_elems) { 57 buffer = av_realloc_array(NULL, nb_elems, elem_size); 58 if (!buffer) 59 return NULL; 60 } 61 f = av_mallocz(sizeof(*f)); 62 if (!f) { 63 av_free(buffer); 64 return NULL; 65 } 66 f->buffer = buffer; 67 f->nb_elems = nb_elems; 68 f->elem_size = elem_size; 69 f->is_empty = 1; 70 71 f->flags = flags; 72 f->auto_grow_limit = FFMAX(AUTO_GROW_DEFAULT_BYTES / elem_size, 1); 73 74 return f; 75 } 76 77 void av_fifo_auto_grow_limit(AVFifo *f, size_t max_elems) 78 { 79 f->auto_grow_limit = max_elems; 80 } 81 82 size_t av_fifo_elem_size(const AVFifo *f) 83 { 84 return f->elem_size; 85 } 86 87 size_t av_fifo_can_read(const AVFifo *f) 88 { 89 if (f->offset_w <= f->offset_r && !f->is_empty) 90 return f->nb_elems - f->offset_r + f->offset_w; 91 return f->offset_w - f->offset_r; 92 } 93 94 size_t av_fifo_can_write(const AVFifo *f) 95 { 96 return f->nb_elems - av_fifo_can_read(f); 97 } 98 99 int av_fifo_grow2(AVFifo *f, size_t inc) 100 { 101 uint8_t *tmp; 102 103 if (inc > SIZE_MAX - f->nb_elems) 104 return AVERROR(EINVAL); 105 106 tmp = av_realloc_array(f->buffer, f->nb_elems + inc, f->elem_size); 107 if (!tmp) 108 return AVERROR(ENOMEM); 109 f->buffer = tmp; 110 111 // move the data from the beginning of the ring buffer 112 // to the newly allocated space 113 if (f->offset_w <= f->offset_r && !f->is_empty) { 114 const size_t copy = FFMIN(inc, f->offset_w); 115 memcpy(tmp + f->nb_elems * f->elem_size, tmp, copy * f->elem_size); 116 if (copy < f->offset_w) { 117 memmove(tmp, tmp + copy * f->elem_size, 118 (f->offset_w - copy) * f->elem_size); 119 f->offset_w -= copy; 120 } else 121 f->offset_w = copy == inc ? 0 : f->nb_elems + copy; 122 } 123 124 f->nb_elems += inc; 125 126 return 0; 127 } 128 129 static int fifo_check_space(AVFifo *f, size_t to_write) 130 { 131 const size_t can_write = av_fifo_can_write(f); 132 const size_t need_grow = to_write > can_write ? to_write - can_write : 0; 133 size_t can_grow; 134 135 if (!need_grow) 136 return 0; 137 138 can_grow = f->auto_grow_limit > f->nb_elems ? 139 f->auto_grow_limit - f->nb_elems : 0; 140 if ((f->flags & AV_FIFO_FLAG_AUTO_GROW) && need_grow <= can_grow) { 141 // allocate a bit more than necessary, if we can 142 const size_t inc = (need_grow < can_grow / 2 ) ? need_grow * 2 : can_grow; 143 return av_fifo_grow2(f, inc); 144 } 145 146 return AVERROR(ENOSPC); 147 } 148 149 static int fifo_write_common(AVFifo *f, const uint8_t *buf, size_t *nb_elems, 150 AVFifoCB read_cb, void *opaque) 151 { 152 size_t to_write = *nb_elems; 153 size_t offset_w; 154 int ret = 0; 155 156 ret = fifo_check_space(f, to_write); 157 if (ret < 0) 158 return ret; 159 160 offset_w = f->offset_w; 161 162 while (to_write > 0) { 163 size_t len = FFMIN(f->nb_elems - offset_w, to_write); 164 uint8_t *wptr = f->buffer + offset_w * f->elem_size; 165 166 if (read_cb) { 167 ret = read_cb(opaque, wptr, &len); 168 if (ret < 0 || len == 0) 169 break; 170 } else { 171 memcpy(wptr, buf, len * f->elem_size); 172 buf += len * f->elem_size; 173 } 174 offset_w += len; 175 if (offset_w >= f->nb_elems) 176 offset_w = 0; 177 to_write -= len; 178 } 179 f->offset_w = offset_w; 180 181 if (*nb_elems != to_write) 182 f->is_empty = 0; 183 *nb_elems -= to_write; 184 185 return ret; 186 } 187 188 int av_fifo_write(AVFifo *f, const void *buf, size_t nb_elems) 189 { 190 return fifo_write_common(f, buf, &nb_elems, NULL, NULL); 191 } 192 193 int av_fifo_write_from_cb(AVFifo *f, AVFifoCB read_cb, 194 void *opaque, size_t *nb_elems) 195 { 196 return fifo_write_common(f, NULL, nb_elems, read_cb, opaque); 197 } 198 199 static int fifo_peek_common(const AVFifo *f, uint8_t *buf, size_t *nb_elems, 200 size_t offset, AVFifoCB write_cb, void *opaque) 201 { 202 size_t to_read = *nb_elems; 203 size_t offset_r = f->offset_r; 204 size_t can_read = av_fifo_can_read(f); 205 int ret = 0; 206 207 if (offset > can_read || to_read > can_read - offset) { 208 *nb_elems = 0; 209 return AVERROR(EINVAL); 210 } 211 212 if (offset_r >= f->nb_elems - offset) 213 offset_r -= f->nb_elems - offset; 214 else 215 offset_r += offset; 216 217 while (to_read > 0) { 218 size_t len = FFMIN(f->nb_elems - offset_r, to_read); 219 uint8_t *rptr = f->buffer + offset_r * f->elem_size; 220 221 if (write_cb) { 222 ret = write_cb(opaque, rptr, &len); 223 if (ret < 0 || len == 0) 224 break; 225 } else { 226 memcpy(buf, rptr, len * f->elem_size); 227 buf += len * f->elem_size; 228 } 229 offset_r += len; 230 if (offset_r >= f->nb_elems) 231 offset_r = 0; 232 to_read -= len; 233 } 234 235 *nb_elems -= to_read; 236 237 return ret; 238 } 239 240 int av_fifo_read(AVFifo *f, void *buf, size_t nb_elems) 241 { 242 int ret = fifo_peek_common(f, buf, &nb_elems, 0, NULL, NULL); 243 av_fifo_drain2(f, nb_elems); 244 return ret; 245 } 246 247 int av_fifo_read_to_cb(AVFifo *f, AVFifoCB write_cb, 248 void *opaque, size_t *nb_elems) 249 { 250 int ret = fifo_peek_common(f, NULL, nb_elems, 0, write_cb, opaque); 251 av_fifo_drain2(f, *nb_elems); 252 return ret; 253 } 254 255 int av_fifo_peek(const AVFifo *f, void *buf, size_t nb_elems, size_t offset) 256 { 257 return fifo_peek_common(f, buf, &nb_elems, offset, NULL, NULL); 258 } 259 260 int av_fifo_peek_to_cb(const AVFifo *f, AVFifoCB write_cb, void *opaque, 261 size_t *nb_elems, size_t offset) 262 { 263 return fifo_peek_common(f, NULL, nb_elems, offset, write_cb, opaque); 264 } 265 266 void av_fifo_drain2(AVFifo *f, size_t size) 267 { 268 const size_t cur_size = av_fifo_can_read(f); 269 270 av_assert0(cur_size >= size); 271 if (cur_size == size) 272 f->is_empty = 1; 273 274 if (f->offset_r >= f->nb_elems - size) 275 f->offset_r -= f->nb_elems - size; 276 else 277 f->offset_r += size; 278 } 279 280 void av_fifo_reset2(AVFifo *f) 281 { 282 f->offset_r = f->offset_w = 0; 283 f->is_empty = 1; 284 } 285 286 void av_fifo_freep2(AVFifo **f) 287 { 288 if (*f) { 289 av_freep(&(*f)->buffer); 290 av_freep(f); 291 } 292 }