libavformat/aviobuf.c

   1 /*
   2  * Buffered I/O for ffmpeg system
   3  * Copyright (c) 2000,2001 Fabrice Bellard
   4  *
   5  * This file is part of FFmpeg.
   6  *
   7  * FFmpeg is free software; you can redistribute it and/or
   8  * modify it under the terms of the GNU Lesser General Public
   9  * License as published by the Free Software Foundation; either
  10  * version 2.1 of the License, or (at your option) any later version.
  11  *
  12  * FFmpeg is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15  * Lesser General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU Lesser General Public
  18  * License along with FFmpeg; if not, write to the Free Software
  19  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  20  */
  21
  22 #include "libavutil/crc.h"
  23 #include "avformat.h"
  24 #include "avio.h"
  25 #include <stdarg.h>
  26
  27 #define IO_BUFFER_SIZE 32768
  28
  29 static void fill_buffer(ByteIOContext *s);
  30
  31 int init_put_byte(ByteIOContext *s,
  32                   unsigned char *buffer,
  33                   int buffer_size,
  34                   int write_flag,
  35                   void *opaque,
  36                   int (*read_packet)(void *opaque, uint8_t *buf, int buf_size),
  37                   int (*write_packet)(void *opaque, uint8_t *buf, int buf_size),
  38                   offset_t (*seek)(void *opaque, offset_t offset, int whence))
  39 {
  40     s->buffer = buffer;
  41     s->buffer_size = buffer_size;
  42     s->buf_ptr = buffer;
  43     url_resetbuf(s, write_flag ? URL_WRONLY : URL_RDONLY);
  44     s->opaque = opaque;
  45     s->write_packet = write_packet;
  46     s->read_packet = read_packet;
  47     s->seek = seek;
  48     s->pos = 0;
  49     s->must_flush = 0;
  50     s->eof_reached = 0;
  51     s->error = 0;
  52     s->is_streamed = 0;
  53     s->max_packet_size = 0;
  54     s->update_checksum= NULL;
  55     if(!read_packet && !write_flag){
  56         s->pos = buffer_size;
  57         s->buf_end = s->buffer + buffer_size;
  58     }
  59     s->read_pause = NULL;
  60     s->read_seek  = NULL;
  61     return 0;
  62 }
  63
  64 ByteIOContext *av_alloc_put_byte(
  65                   unsigned char *buffer,
  66                   int buffer_size,
  67                   int write_flag,
  68                   void *opaque,
  69                   int (*read_packet)(void *opaque, uint8_t *buf, int buf_size),
  70                   int (*write_packet)(void *opaque, uint8_t *buf, int buf_size),
  71                   offset_t (*seek)(void *opaque, offset_t offset, int whence)) {
  72     ByteIOContext *s = av_mallocz(sizeof(ByteIOContext));
  73     init_put_byte(s, buffer, buffer_size, write_flag, opaque,
  74                   read_packet, write_packet, seek);
  75     return s;
  76 }
  77
  78 static void flush_buffer(ByteIOContext *s)
  79 {
  80     if (s->buf_ptr > s->buffer) {
  81         if (s->write_packet && !s->error){
  82             int ret= s->write_packet(s->opaque, s->buffer, s->buf_ptr - s->buffer);
  83             if(ret < 0){
  84                 s->error = ret;
  85             }
  86         }
  87         if(s->update_checksum){
  88             s->checksum= s->update_checksum(s->checksum, s->checksum_ptr, s->buf_ptr - s->checksum_ptr);
  89             s->checksum_ptr= s->buffer;
  90         }
  91         s->pos += s->buf_ptr - s->buffer;
  92     }
  93     s->buf_ptr = s->buffer;
  94 }
  95
  96 void put_byte(ByteIOContext *s, int b)
  97 {
  98     *(s->buf_ptr)++ = b;
  99     if (s->buf_ptr >= s->buf_end)
 100         flush_buffer(s);
 101 }
 102
 103 void put_buffer(ByteIOContext *s, const unsigned char *buf, int size)
 104 {
 105     int len;
 106
 107     while (size > 0) {
 108         len = (s->buf_end - s->buf_ptr);
 109         if (len > size)
 110             len = size;
 111         memcpy(s->buf_ptr, buf, len);
 112         s->buf_ptr += len;
 113
 114         if (s->buf_ptr >= s->buf_end)
 115             flush_buffer(s);
 116
 117         buf += len;
 118         size -= len;
 119     }
 120 }
 121
 122 void put_flush_packet(ByteIOContext *s)
 123 {
 124     flush_buffer(s);
 125     s->must_flush = 0;
 126 }
 127
 128 offset_t url_fseek(ByteIOContext *s, offset_t offset, int whence)
 129 {
 130     offset_t offset1;
 131     offset_t pos;
 132
 133     if(!s)
 134         return AVERROR(EINVAL);
 135
 136     pos = s->pos - (s->write_flag ? 0 : (s->buf_end - s->buffer));
 137
 138     if (whence != SEEK_CUR && whence != SEEK_SET)
 139         return AVERROR(EINVAL);
 140
 141     if (whence == SEEK_CUR) {
 142         offset1 = pos + (s->buf_ptr - s->buffer);
 143         if (offset == 0)
 144             return offset1;
 145         offset += offset1;
 146     }
 147     offset1 = offset - pos;
 148     if (!s->must_flush &&
 149         offset1 >= 0 && offset1 < (s->buf_end - s->buffer)) {
 150         /* can do the seek inside the buffer */
 151         s->buf_ptr = s->buffer + offset1;
 152     } else if(s->is_streamed && !s->write_flag &&
 153               offset1 >= 0 && offset1 < (s->buf_end - s->buffer) + (1<<16)){
 154         while(s->pos < offset && !s->eof_reached)
 155             fill_buffer(s);
 156         if (s->eof_reached)
 157             return AVERROR(EPIPE);
 158         s->buf_ptr = s->buf_end + offset - s->pos;
 159     } else {
 160         offset_t res = AVERROR(EPIPE);
 161
 162 #if defined(CONFIG_MUXERS) || defined(CONFIG_NETWORK)
 163         if (s->write_flag) {
 164             flush_buffer(s);
 165             s->must_flush = 1;
 166         }
 167 #endif /* defined(CONFIG_MUXERS) || defined(CONFIG_NETWORK) */
 168         if (!s->seek || (res = s->seek(s->opaque, offset, SEEK_SET)) < 0)
 169             return res;
 170         if (!s->write_flag)
 171             s->buf_end = s->buffer;
 172         s->buf_ptr = s->buffer;
 173         s->pos = offset;
 174     }
 175     s->eof_reached = 0;
 176     return offset;
 177 }
 178
 179 void url_fskip(ByteIOContext *s, offset_t offset)
 180 {
 181     url_fseek(s, offset, SEEK_CUR);
 182 }
 183
 184 offset_t url_ftell(ByteIOContext *s)
 185 {
 186     return url_fseek(s, 0, SEEK_CUR);
 187 }
 188
 189 offset_t url_fsize(ByteIOContext *s)
 190 {
 191     offset_t size;
 192
 193     if(!s)
 194         return AVERROR(EINVAL);
 195
 196     if (!s->seek)
 197         return AVERROR(EPIPE);
 198     size = s->seek(s->opaque, 0, AVSEEK_SIZE);
 199     if(size<0){
 200         if ((size = s->seek(s->opaque, -1, SEEK_END)) < 0)
 201             return size;
 202         size++;
 203         s->seek(s->opaque, s->pos, SEEK_SET);
 204     }
 205     return size;
 206 }
 207
 208 int url_feof(ByteIOContext *s)
 209 {
 210     if(!s)
 211         return 0;
 212     return s->eof_reached;
 213 }
 214
 215 int url_ferror(ByteIOContext *s)
 216 {
 217     if(!s)
 218         return 0;
 219     return s->error;
 220 }
 221
 222 void put_le32(ByteIOContext *s, unsigned int val)
 223 {
 224     put_byte(s, val);
 225     put_byte(s, val >> 8);
 226     put_byte(s, val >> 16);
 227     put_byte(s, val >> 24);
 228 }
 229
 230 void put_be32(ByteIOContext *s, unsigned int val)
 231 {
 232     put_byte(s, val >> 24);
 233     put_byte(s, val >> 16);
 234     put_byte(s, val >> 8);
 235     put_byte(s, val);
 236 }
 237
 238 void put_strz(ByteIOContext *s, const char *str)
 239 {
 240     if (str)
 241         put_buffer(s, (const unsigned char *) str, strlen(str) + 1);
 242     else
 243         put_byte(s, 0);
 244 }
 245
 246 void put_le64(ByteIOContext *s, uint64_t val)
 247 {
 248     put_le32(s, (uint32_t)(val & 0xffffffff));
 249     put_le32(s, (uint32_t)(val >> 32));
 250 }
 251
 252 void put_be64(ByteIOContext *s, uint64_t val)
 253 {
 254     put_be32(s, (uint32_t)(val >> 32));
 255     put_be32(s, (uint32_t)(val & 0xffffffff));
 256 }
 257
 258 void put_le16(ByteIOContext *s, unsigned int val)
 259 {
 260     put_byte(s, val);
 261     put_byte(s, val >> 8);
 262 }
 263
 264 void put_be16(ByteIOContext *s, unsigned int val)
 265 {
 266     put_byte(s, val >> 8);
 267     put_byte(s, val);
 268 }
 269
 270 void put_le24(ByteIOContext *s, unsigned int val)
 271 {
 272     put_le16(s, val & 0xffff);
 273     put_byte(s, val >> 16);
 274 }
 275
 276 void put_be24(ByteIOContext *s, unsigned int val)
 277 {
 278     put_be16(s, val >> 8);
 279     put_byte(s, val);
 280 }
 281
 282 void put_tag(ByteIOContext *s, const char *tag)
 283 {
 284     while (*tag) {
 285         put_byte(s, *tag++);
 286     }
 287 }
 288
 289 /* Input stream */
 290
 291 static void fill_buffer(ByteIOContext *s)
 292 {
 293     int len=0;
 294
 295     /* no need to do anything if EOF already reached */
 296     if (s->eof_reached)
 297         return;
 298
 299     if(s->update_checksum){
 300         if(s->buf_end > s->checksum_ptr)
 301             s->checksum= s->update_checksum(s->checksum, s->checksum_ptr, s->buf_end - s->checksum_ptr);
 302         s->checksum_ptr= s->buffer;
 303     }
 304
 305     if(s->read_packet)
 306         len = s->read_packet(s->opaque, s->buffer, s->buffer_size);
 307     if (len <= 0) {
 308         /* do not modify buffer if EOF reached so that a seek back can
 309            be done without rereading data */
 310         s->eof_reached = 1;
 311         if(len<0)
 312             s->error= len;
 313     } else {
 314         s->pos += len;
 315         s->buf_ptr = s->buffer;
 316         s->buf_end = s->buffer + len;
 317     }
 318 }
 319
 320 unsigned long ff_crc04C11DB7_update(unsigned long checksum, const uint8_t *buf, unsigned int len){
 321     return av_crc(av_crc_get_table(AV_CRC_32_IEEE), checksum, buf, len);
 322 }
 323
 324 unsigned long get_checksum(ByteIOContext *s){
 325     s->checksum= s->update_checksum(s->checksum, s->checksum_ptr, s->buf_ptr - s->checksum_ptr);
 326     s->update_checksum= NULL;
 327     return s->checksum;
 328 }
 329
 330 void init_checksum(ByteIOContext *s, unsigned long (*update_checksum)(unsigned long c, const uint8_t *p, unsigned int len), unsigned long checksum){
 331     s->update_checksum= update_checksum;
 332     if(s->update_checksum){
 333         s->checksum= checksum;
 334         s->checksum_ptr= s->buf_ptr;
 335     }
 336 }
 337
 338 /* XXX: put an inline version */
 339 int get_byte(ByteIOContext *s)
 340 {
 341     if (s->buf_ptr < s->buf_end) {
 342         return *s->buf_ptr++;
 343     } else {
 344         fill_buffer(s);
 345         if (s->buf_ptr < s->buf_end)
 346             return *s->buf_ptr++;
 347         else
 348             return 0;
 349     }
 350 }
 351
 352 int url_fgetc(ByteIOContext *s)
 353 {
 354     if (s->buf_ptr < s->buf_end) {
 355         return *s->buf_ptr++;
 356     } else {
 357         fill_buffer(s);
 358         if (s->buf_ptr < s->buf_end)
 359             return *s->buf_ptr++;
 360         else
 361             return URL_EOF;
 362     }
 363 }
 364
 365 int get_buffer(ByteIOContext *s, unsigned char *buf, int size)
 366 {
 367     int len, size1;
 368
 369     size1 = size;
 370     while (size > 0) {
 371         len = s->buf_end - s->buf_ptr;
 372         if (len > size)
 373             len = size;
 374         if (len == 0) {
 375             if(size > s->buffer_size && !s->update_checksum){
 376                 if(s->read_packet)
 377                     len = s->read_packet(s->opaque, buf, size);
 378                 if (len <= 0) {
 379                     /* do not modify buffer if EOF reached so that a seek back can
 380                     be done without rereading data */
 381                     s->eof_reached = 1;
 382                     if(len<0)
 383                         s->error= len;
 384                     break;
 385                 } else {
 386                     s->pos += len;
 387                     size -= len;
 388                     buf += len;
 389                     s->buf_ptr = s->buffer;
 390                     s->buf_end = s->buffer/* + len*/;
 391                 }
 392             }else{
 393                 fill_buffer(s);
 394                 len = s->buf_end - s->buf_ptr;
 395                 if (len == 0)
 396                     break;
 397             }
 398         } else {
 399             memcpy(buf, s->buf_ptr, len);
 400             buf += len;
 401             s->buf_ptr += len;
 402             size -= len;
 403         }
 404     }
 405     return size1 - size;
 406 }
 407
 408 int get_partial_buffer(ByteIOContext *s, unsigned char *buf, int size)
 409 {
 410     int len;
 411
 412     if(size<0)
 413         return -1;
 414
 415     len = s->buf_end - s->buf_ptr;
 416     if (len == 0) {
 417         fill_buffer(s);
 418         len = s->buf_end - s->buf_ptr;
 419     }
 420     if (len > size)
 421         len = size;
 422     memcpy(buf, s->buf_ptr, len);
 423     s->buf_ptr += len;
 424     return len;
 425 }
 426
 427 unsigned int get_le16(ByteIOContext *s)
 428 {
 429     unsigned int val;
 430     val = get_byte(s);
 431     val |= get_byte(s) << 8;
 432     return val;
 433 }
 434
 435 unsigned int get_le24(ByteIOContext *s)
 436 {
 437     unsigned int val;
 438     val = get_le16(s);
 439     val |= get_byte(s) << 16;
 440     return val;
 441 }
 442
 443 unsigned int get_le32(ByteIOContext *s)
 444 {
 445     unsigned int val;
 446     val = get_le16(s);
 447     val |= get_le16(s) << 16;
 448     return val;
 449 }
 450
 451 uint64_t get_le64(ByteIOContext *s)
 452 {
 453     uint64_t val;
 454     val = (uint64_t)get_le32(s);
 455     val |= (uint64_t)get_le32(s) << 32;
 456     return val;
 457 }
 458
 459 unsigned int get_be16(ByteIOContext *s)
 460 {
 461     unsigned int val;
 462     val = get_byte(s) << 8;
 463     val |= get_byte(s);
 464     return val;
 465 }
 466
 467 unsigned int get_be24(ByteIOContext *s)
 468 {
 469     unsigned int val;
 470     val = get_be16(s) << 8;
 471     val |= get_byte(s);
 472     return val;
 473 }
 474 unsigned int get_be32(ByteIOContext *s)
 475 {
 476     unsigned int val;
 477     val = get_be16(s) << 16;
 478     val |= get_be16(s);
 479     return val;
 480 }
 481
 482 char *get_strz(ByteIOContext *s, char *buf, int maxlen)
 483 {
 484     int i = 0;
 485     char c;
 486
 487     while ((c = get_byte(s))) {
 488         if (i < maxlen-1)
 489             buf[i++] = c;
 490     }
 491
 492     buf[i] = 0; /* Ensure null terminated, but may be truncated */
 493
 494     return buf;
 495 }
 496
 497 uint64_t get_be64(ByteIOContext *s)
 498 {
 499     uint64_t val;
 500     val = (uint64_t)get_be32(s) << 32;
 501     val |= (uint64_t)get_be32(s);
 502     return val;
 503 }
 504
 505 uint64_t ff_get_v(ByteIOContext *bc){
 506     uint64_t val = 0;
 507     int tmp;
 508
 509     do{
 510         tmp = get_byte(bc);
 511         val= (val<<7) + (tmp&127);
 512     }while(tmp&128);
 513     return val;
 514 }
 515
 516 int url_fdopen(ByteIOContext **s, URLContext *h)
 517 {
 518     uint8_t *buffer;
 519     int buffer_size, max_packet_size;
 520
 521
 522     max_packet_size = url_get_max_packet_size(h);
 523     if (max_packet_size) {
 524         buffer_size = max_packet_size; /* no need to bufferize more than one packet */
 525     } else {
 526         buffer_size = IO_BUFFER_SIZE;
 527     }
 528     buffer = av_malloc(buffer_size);
 529     if (!buffer)
 530         return AVERROR(ENOMEM);
 531
 532     *s = av_mallocz(sizeof(ByteIOContext));
 533     if(!*s) {
 534         av_free(buffer);
 535         return AVERROR(ENOMEM);
 536     }
 537
 538     if (init_put_byte(*s, buffer, buffer_size,
 539                       (h->flags & URL_WRONLY || h->flags & URL_RDWR), h,
 540                       url_read, url_write, url_seek) < 0) {
 541         av_free(buffer);
 542         av_freep(s);
 543         return AVERROR(EIO);
 544     }
 545     (*s)->is_streamed = h->is_streamed;
 546     (*s)->max_packet_size = max_packet_size;
 547     if(h->prot) {
 548         (*s)->read_pause = (int (*)(void *, int))h->prot->url_read_pause;
 549         (*s)->read_seek  = (offset_t (*)(void *, int, int64_t, int))h->prot->url_read_seek;
 550     }
 551     return 0;
 552 }
 553
 554 int url_setbufsize(ByteIOContext *s, int buf_size)
 555 {
 556     uint8_t *buffer;
 557     buffer = av_malloc(buf_size);
 558     if (!buffer)
 559         return AVERROR(ENOMEM);
 560
 561     av_free(s->buffer);
 562     s->buffer = buffer;
 563     s->buffer_size = buf_size;
 564     s->buf_ptr = buffer;
 565     url_resetbuf(s, s->write_flag ? URL_WRONLY : URL_RDONLY);
 566     return 0;
 567 }
 568
 569 int url_resetbuf(ByteIOContext *s, int flags)
 570 {
 571     URLContext *h = s->opaque;
 572     if ((flags & URL_RDWR) || (h && h->flags != flags && !h->flags & URL_RDWR))
 573         return AVERROR(EINVAL);
 574
 575     if (flags & URL_WRONLY) {
 576         s->buf_end = s->buffer + s->buffer_size;
 577         s->write_flag = 1;
 578     } else {
 579         s->buf_end = s->buffer;
 580         s->write_flag = 0;
 581     }
 582     return 0;
 583 }
 584
 585 int url_fopen(ByteIOContext **s, const char *filename, int flags)
 586 {
 587     URLContext *h;
 588     int err;
 589
 590     err = url_open(&h, filename, flags);
 591     if (err < 0)
 592         return err;
 593     err = url_fdopen(s, h);
 594     if (err < 0) {
 595         url_close(h);
 596         return err;
 597     }
 598     return 0;
 599 }
 600
 601 int url_fclose(ByteIOContext *s)
 602 {
 603     URLContext *h = s->opaque;
 604
 605     av_free(s->buffer);
 606     av_free(s);
 607     return url_close(h);
 608 }
 609
 610 URLContext *url_fileno(ByteIOContext *s)
 611 {
 612     return s->opaque;
 613 }
 614
 615 #ifdef CONFIG_MUXERS
 616 int url_fprintf(ByteIOContext *s, const char *fmt, ...)
 617 {
 618     va_list ap;
 619     char buf[4096];
 620     int ret;
 621
 622     va_start(ap, fmt);
 623     ret = vsnprintf(buf, sizeof(buf), fmt, ap);
 624     va_end(ap);
 625     put_buffer(s, buf, strlen(buf));
 626     return ret;
 627 }
 628 #endif //CONFIG_MUXERS
 629
 630 char *url_fgets(ByteIOContext *s, char *buf, int buf_size)
 631 {
 632     int c;
 633     char *q;
 634
 635     c = url_fgetc(s);
 636     if (c == EOF)
 637         return NULL;
 638     q = buf;
 639     for(;;) {
 640         if (c == EOF || c == '\n')
 641             break;
 642         if ((q - buf) < buf_size - 1)
 643             *q++ = c;
 644         c = url_fgetc(s);
 645     }
 646     if (buf_size > 0)
 647         *q = '\0';
 648     return buf;
 649 }
 650
 651 int url_fget_max_packet_size(ByteIOContext *s)
 652 {
 653     return s->max_packet_size;
 654 }
 655
 656 int av_url_read_fpause(ByteIOContext *s, int pause)
 657 {
 658     if (!s->read_pause)
 659         return AVERROR(ENOSYS);
 660     return s->read_pause(s->opaque, pause);
 661 }
 662
 663 offset_t av_url_read_fseek(ByteIOContext *s,
 664         int stream_index, int64_t timestamp, int flags)
 665 {
 666     URLContext *h = s->opaque;
 667     offset_t ret;
 668     if (!s->read_seek)
 669         return AVERROR(ENOSYS);
 670     ret = s->read_seek(h, stream_index, timestamp, flags);
 671     if(ret >= 0) {
 672         s->buf_ptr = s->buf_end; // Flush buffer
 673         s->pos = s->seek(h, 0, SEEK_CUR);
 674     }
 675     return ret;
 676 }
 677
 678 /* url_open_dyn_buf and url_close_dyn_buf are used in rtp.c to send a response
 679  * back to the server even if CONFIG_MUXERS is not set. */
 680 #if defined(CONFIG_MUXERS) || defined(CONFIG_NETWORK)
 681 /* buffer handling */
 682 int url_open_buf(ByteIOContext **s, uint8_t *buf, int buf_size, int flags)
 683 {
 684     int ret;
 685     *s = av_mallocz(sizeof(ByteIOContext));
 686     if(!*s)
 687         return AVERROR(ENOMEM);
 688     ret = init_put_byte(*s, buf, buf_size,
 689                         (flags & URL_WRONLY || flags & URL_RDWR),
 690                         NULL, NULL, NULL, NULL);
 691     if(ret != 0)
 692         av_freep(s);
 693     return ret;
 694 }
 695
 696 int url_close_buf(ByteIOContext *s)
 697 {
 698     put_flush_packet(s);
 699     return s->buf_ptr - s->buffer;
 700 }
 701
 702 /* output in a dynamic buffer */
 703
 704 typedef struct DynBuffer {
 705     int pos, size, allocated_size;
 706     uint8_t *buffer;
 707     int io_buffer_size;
 708     uint8_t io_buffer[1];
 709 } DynBuffer;
 710
 711 static int dyn_buf_write(void *opaque, uint8_t *buf, int buf_size)
 712 {
 713     DynBuffer *d = opaque;
 714     int new_size, new_allocated_size;
 715
 716     /* reallocate buffer if needed */
 717     new_size = d->pos + buf_size;
 718     new_allocated_size = d->allocated_size;
 719     if(new_size < d->pos || new_size > INT_MAX/2)
 720         return -1;
 721     while (new_size > new_allocated_size) {
 722         if (!new_allocated_size)
 723             new_allocated_size = new_size;
 724         else
 725             new_allocated_size += new_allocated_size / 2 + 1;
 726     }
 727
 728     if (new_allocated_size > d->allocated_size) {
 729         d->buffer = av_realloc(d->buffer, new_allocated_size);
 730         if(d->buffer == NULL)
 731              return -1234;
 732         d->allocated_size = new_allocated_size;
 733     }
 734     memcpy(d->buffer + d->pos, buf, buf_size);
 735     d->pos = new_size;
 736     if (d->pos > d->size)
 737         d->size = d->pos;
 738     return buf_size;
 739 }
 740
 741 static int dyn_packet_buf_write(void *opaque, uint8_t *buf, int buf_size)
 742 {
 743     unsigned char buf1[4];
 744     int ret;
 745
 746     /* packetized write: output the header */
 747     buf1[0] = (buf_size >> 24);
 748     buf1[1] = (buf_size >> 16);
 749     buf1[2] = (buf_size >> 8);
 750     buf1[3] = (buf_size);
 751     ret= dyn_buf_write(opaque, buf1, 4);
 752     if(ret < 0)
 753         return ret;
 754
 755     /* then the data */
 756     return dyn_buf_write(opaque, buf, buf_size);
 757 }
 758
 759 static offset_t dyn_buf_seek(void *opaque, offset_t offset, int whence)
 760 {
 761     DynBuffer *d = opaque;
 762
 763     if (whence == SEEK_CUR)
 764         offset += d->pos;
 765     else if (whence == SEEK_END)
 766         offset += d->size;
 767     if (offset < 0 || offset > 0x7fffffffLL)
 768         return -1;
 769     d->pos = offset;
 770     return 0;
 771 }
 772
 773 static int url_open_dyn_buf_internal(ByteIOContext **s, int max_packet_size)
 774 {
 775     DynBuffer *d;
 776     int io_buffer_size, ret;
 777
 778     if (max_packet_size)
 779         io_buffer_size = max_packet_size;
 780     else
 781         io_buffer_size = 1024;
 782
 783     if(sizeof(DynBuffer) + io_buffer_size < io_buffer_size)
 784         return -1;
 785     d = av_malloc(sizeof(DynBuffer) + io_buffer_size);
 786     if (!d)
 787         return -1;
 788     *s = av_mallocz(sizeof(ByteIOContext));
 789     if(!*s) {
 790         av_free(d);
 791         return AVERROR(ENOMEM);
 792     }
 793     d->io_buffer_size = io_buffer_size;
 794     d->buffer = NULL;
 795     d->pos = 0;
 796     d->size = 0;
 797     d->allocated_size = 0;
 798     ret = init_put_byte(*s, d->io_buffer, io_buffer_size,
 799                         1, d, NULL,
 800                         max_packet_size ? dyn_packet_buf_write : dyn_buf_write,
 801                         max_packet_size ? NULL : dyn_buf_seek);
 802     if (ret == 0) {
 803         (*s)->max_packet_size = max_packet_size;
 804     } else {
 805         av_free(d);
 806         av_freep(s);
 807     }
 808     return ret;
 809 }
 810
 811 int url_open_dyn_buf(ByteIOContext **s)
 812 {
 813     return url_open_dyn_buf_internal(s, 0);
 814 }
 815
 816 int url_open_dyn_packet_buf(ByteIOContext **s, int max_packet_size)
 817 {
 818     if (max_packet_size <= 0)
 819         return -1;
 820     return url_open_dyn_buf_internal(s, max_packet_size);
 821 }
 822
 823 int url_close_dyn_buf(ByteIOContext *s, uint8_t **pbuffer)
 824 {
 825     DynBuffer *d = s->opaque;
 826     int size;
 827
 828     put_flush_packet(s);
 829
 830     *pbuffer = d->buffer;
 831     size = d->size;
 832     av_free(d);
 833     av_free(s);
 834     return size;
 835 }
 836 #endif /* CONFIG_MUXERS || CONFIG_NETWORK */