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         } else
 167 #endif /* defined(CONFIG_MUXERS) || defined(CONFIG_NETWORK) */
 168         {
 169             s->buf_end = s->buffer;
 170         }
 171         s->buf_ptr = s->buffer;
 172         if (!s->seek || (res = s->seek(s->opaque, offset, SEEK_SET)) < 0)
 173             return res;
 174         s->pos = offset;
 175     }
 176     s->eof_reached = 0;
 177     return offset;
 178 }
 179
 180 void url_fskip(ByteIOContext *s, offset_t offset)
 181 {
 182     url_fseek(s, offset, SEEK_CUR);
 183 }
 184
 185 offset_t url_ftell(ByteIOContext *s)
 186 {
 187     return url_fseek(s, 0, SEEK_CUR);
 188 }
 189
 190 offset_t url_fsize(ByteIOContext *s)
 191 {
 192     offset_t size;
 193
 194     if(!s)
 195         return AVERROR(EINVAL);
 196
 197     if (!s->seek)
 198         return AVERROR(EPIPE);
 199     size = s->seek(s->opaque, 0, AVSEEK_SIZE);
 200     if(size<0){
 201         if ((size = s->seek(s->opaque, -1, SEEK_END)) < 0)
 202             return size;
 203         size++;
 204         s->seek(s->opaque, s->pos, SEEK_SET);
 205     }
 206     return size;
 207 }
 208
 209 int url_feof(ByteIOContext *s)
 210 {
 211     if(!s)
 212         return 0;
 213     return s->eof_reached;
 214 }
 215
 216 int url_ferror(ByteIOContext *s)
 217 {
 218     if(!s)
 219         return 0;
 220     return s->error;
 221 }
 222
 223 void put_le32(ByteIOContext *s, unsigned int val)
 224 {
 225     put_byte(s, val);
 226     put_byte(s, val >> 8);
 227     put_byte(s, val >> 16);
 228     put_byte(s, val >> 24);
 229 }
 230
 231 void put_be32(ByteIOContext *s, unsigned int val)
 232 {
 233     put_byte(s, val >> 24);
 234     put_byte(s, val >> 16);
 235     put_byte(s, val >> 8);
 236     put_byte(s, val);
 237 }
 238
 239 void put_strz(ByteIOContext *s, const char *str)
 240 {
 241     if (str)
 242         put_buffer(s, (const unsigned char *) str, strlen(str) + 1);
 243     else
 244         put_byte(s, 0);
 245 }
 246
 247 void put_le64(ByteIOContext *s, uint64_t val)
 248 {
 249     put_le32(s, (uint32_t)(val & 0xffffffff));
 250     put_le32(s, (uint32_t)(val >> 32));
 251 }
 252
 253 void put_be64(ByteIOContext *s, uint64_t val)
 254 {
 255     put_be32(s, (uint32_t)(val >> 32));
 256     put_be32(s, (uint32_t)(val & 0xffffffff));
 257 }
 258
 259 void put_le16(ByteIOContext *s, unsigned int val)
 260 {
 261     put_byte(s, val);
 262     put_byte(s, val >> 8);
 263 }
 264
 265 void put_be16(ByteIOContext *s, unsigned int val)
 266 {
 267     put_byte(s, val >> 8);
 268     put_byte(s, val);
 269 }
 270
 271 void put_le24(ByteIOContext *s, unsigned int val)
 272 {
 273     put_le16(s, val & 0xffff);
 274     put_byte(s, val >> 16);
 275 }
 276
 277 void put_be24(ByteIOContext *s, unsigned int val)
 278 {
 279     put_be16(s, val >> 8);
 280     put_byte(s, val);
 281 }
 282
 283 void put_tag(ByteIOContext *s, const char *tag)
 284 {
 285     while (*tag) {
 286         put_byte(s, *tag++);
 287     }
 288 }
 289
 290 /* Input stream */
 291
 292 static void fill_buffer(ByteIOContext *s)
 293 {
 294     int len=0;
 295
 296     /* no need to do anything if EOF already reached */
 297     if (s->eof_reached)
 298         return;
 299
 300     if(s->update_checksum){
 301         if(s->buf_end > s->checksum_ptr)
 302             s->checksum= s->update_checksum(s->checksum, s->checksum_ptr, s->buf_end - s->checksum_ptr);
 303         s->checksum_ptr= s->buffer;
 304     }
 305
 306     if(s->read_packet)
 307         len = s->read_packet(s->opaque, s->buffer, s->buffer_size);
 308     if (len <= 0) {
 309         /* do not modify buffer if EOF reached so that a seek back can
 310            be done without rereading data */
 311         s->eof_reached = 1;
 312         if(len<0)
 313             s->error= len;
 314     } else {
 315         s->pos += len;
 316         s->buf_ptr = s->buffer;
 317         s->buf_end = s->buffer + len;
 318     }
 319 }
 320
 321 unsigned long ff_crc04C11DB7_update(unsigned long checksum, const uint8_t *buf, unsigned int len){
 322     return av_crc(av_crc_get_table(AV_CRC_32_IEEE), checksum, buf, len);
 323 }
 324
 325 unsigned long get_checksum(ByteIOContext *s){
 326     s->checksum= s->update_checksum(s->checksum, s->checksum_ptr, s->buf_ptr - s->checksum_ptr);
 327     s->update_checksum= NULL;
 328     return s->checksum;
 329 }
 330
 331 void init_checksum(ByteIOContext *s, unsigned long (*update_checksum)(unsigned long c, const uint8_t *p, unsigned int len), unsigned long checksum){
 332     s->update_checksum= update_checksum;
 333     if(s->update_checksum){
 334         s->checksum= checksum;
 335         s->checksum_ptr= s->buf_ptr;
 336     }
 337 }
 338
 339 /* XXX: put an inline version */
 340 int get_byte(ByteIOContext *s)
 341 {
 342     if (s->buf_ptr < s->buf_end) {
 343         return *s->buf_ptr++;
 344     } else {
 345         fill_buffer(s);
 346         if (s->buf_ptr < s->buf_end)
 347             return *s->buf_ptr++;
 348         else
 349             return 0;
 350     }
 351 }
 352
 353 int url_fgetc(ByteIOContext *s)
 354 {
 355     if (s->buf_ptr < s->buf_end) {
 356         return *s->buf_ptr++;
 357     } else {
 358         fill_buffer(s);
 359         if (s->buf_ptr < s->buf_end)
 360             return *s->buf_ptr++;
 361         else
 362             return URL_EOF;
 363     }
 364 }
 365
 366 int get_buffer(ByteIOContext *s, unsigned char *buf, int size)
 367 {
 368     int len, size1;
 369
 370     size1 = size;
 371     while (size > 0) {
 372         len = s->buf_end - s->buf_ptr;
 373         if (len > size)
 374             len = size;
 375         if (len == 0) {
 376             if(size > s->buffer_size && !s->update_checksum){
 377                 if(s->read_packet)
 378                     len = s->read_packet(s->opaque, buf, size);
 379                 if (len <= 0) {
 380                     /* do not modify buffer if EOF reached so that a seek back can
 381                     be done without rereading data */
 382                     s->eof_reached = 1;
 383                     if(len<0)
 384                         s->error= len;
 385                     break;
 386                 } else {
 387                     s->pos += len;
 388                     size -= len;
 389                     buf += len;
 390                     s->buf_ptr = s->buffer;
 391                     s->buf_end = s->buffer/* + len*/;
 392                 }
 393             }else{
 394                 fill_buffer(s);
 395                 len = s->buf_end - s->buf_ptr;
 396                 if (len == 0)
 397                     break;
 398             }
 399         } else {
 400             memcpy(buf, s->buf_ptr, len);
 401             buf += len;
 402             s->buf_ptr += len;
 403             size -= len;
 404         }
 405     }
 406     return size1 - size;
 407 }
 408
 409 int get_partial_buffer(ByteIOContext *s, unsigned char *buf, int size)
 410 {
 411     int len;
 412
 413     if(size<0)
 414         return -1;
 415
 416     len = s->buf_end - s->buf_ptr;
 417     if (len == 0) {
 418         fill_buffer(s);
 419         len = s->buf_end - s->buf_ptr;
 420     }
 421     if (len > size)
 422         len = size;
 423     memcpy(buf, s->buf_ptr, len);
 424     s->buf_ptr += len;
 425     return len;
 426 }
 427
 428 unsigned int get_le16(ByteIOContext *s)
 429 {
 430     unsigned int val;
 431     val = get_byte(s);
 432     val |= get_byte(s) << 8;
 433     return val;
 434 }
 435
 436 unsigned int get_le24(ByteIOContext *s)
 437 {
 438     unsigned int val;
 439     val = get_le16(s);
 440     val |= get_byte(s) << 16;
 441     return val;
 442 }
 443
 444 unsigned int get_le32(ByteIOContext *s)
 445 {
 446     unsigned int val;
 447     val = get_le16(s);
 448     val |= get_le16(s) << 16;
 449     return val;
 450 }
 451
 452 uint64_t get_le64(ByteIOContext *s)
 453 {
 454     uint64_t val;
 455     val = (uint64_t)get_le32(s);
 456     val |= (uint64_t)get_le32(s) << 32;
 457     return val;
 458 }
 459
 460 unsigned int get_be16(ByteIOContext *s)
 461 {
 462     unsigned int val;
 463     val = get_byte(s) << 8;
 464     val |= get_byte(s);
 465     return val;
 466 }
 467
 468 unsigned int get_be24(ByteIOContext *s)
 469 {
 470     unsigned int val;
 471     val = get_be16(s) << 8;
 472     val |= get_byte(s);
 473     return val;
 474 }
 475 unsigned int get_be32(ByteIOContext *s)
 476 {
 477     unsigned int val;
 478     val = get_be16(s) << 16;
 479     val |= get_be16(s);
 480     return val;
 481 }
 482
 483 char *get_strz(ByteIOContext *s, char *buf, int maxlen)
 484 {
 485     int i = 0;
 486     char c;
 487
 488     while ((c = get_byte(s))) {
 489         if (i < maxlen-1)
 490             buf[i++] = c;
 491     }
 492
 493     buf[i] = 0; /* Ensure null terminated, but may be truncated */
 494
 495     return buf;
 496 }
 497
 498 uint64_t get_be64(ByteIOContext *s)
 499 {
 500     uint64_t val;
 501     val = (uint64_t)get_be32(s) << 32;
 502     val |= (uint64_t)get_be32(s);
 503     return val;
 504 }
 505
 506 uint64_t ff_get_v(ByteIOContext *bc){
 507     uint64_t val = 0;
 508     int tmp;
 509
 510     do{
 511         tmp = get_byte(bc);
 512         val= (val<<7) + (tmp&127);
 513     }while(tmp&128);
 514     return val;
 515 }
 516
 517 int url_fdopen(ByteIOContext **s, URLContext *h)
 518 {
 519     uint8_t *buffer;
 520     int buffer_size, max_packet_size;
 521
 522
 523     max_packet_size = url_get_max_packet_size(h);
 524     if (max_packet_size) {
 525         buffer_size = max_packet_size; /* no need to bufferize more than one packet */
 526     } else {
 527         buffer_size = IO_BUFFER_SIZE;
 528     }
 529     buffer = av_malloc(buffer_size);
 530     if (!buffer)
 531         return AVERROR(ENOMEM);
 532
 533     *s = av_mallocz(sizeof(ByteIOContext));
 534     if(!*s) {
 535         av_free(buffer);
 536         return AVERROR(ENOMEM);
 537     }
 538
 539     if (init_put_byte(*s, buffer, buffer_size,
 540                       (h->flags & URL_WRONLY || h->flags & URL_RDWR), h,
 541                       url_read, url_write, url_seek) < 0) {
 542         av_free(buffer);
 543         av_freep(s);
 544         return AVERROR(EIO);
 545     }
 546     (*s)->is_streamed = h->is_streamed;
 547     (*s)->max_packet_size = max_packet_size;
 548     if(h->prot) {
 549         (*s)->read_pause = (int (*)(void *, int))h->prot->url_read_pause;
 550         (*s)->read_seek  = (offset_t (*)(void *, int, int64_t, int))h->prot->url_read_seek;
 551     }
 552     return 0;
 553 }
 554
 555 int url_setbufsize(ByteIOContext *s, int buf_size)
 556 {
 557     uint8_t *buffer;
 558     buffer = av_malloc(buf_size);
 559     if (!buffer)
 560         return AVERROR(ENOMEM);
 561
 562     av_free(s->buffer);
 563     s->buffer = buffer;
 564     s->buffer_size = buf_size;
 565     s->buf_ptr = buffer;
 566     url_resetbuf(s, s->write_flag ? URL_WRONLY : URL_RDONLY);
 567     return 0;
 568 }
 569
 570 int url_resetbuf(ByteIOContext *s, int flags)
 571 {
 572     URLContext *h = s->opaque;
 573     if ((flags & URL_RDWR) || (h && h->flags != flags && !h->flags & URL_RDWR))
 574         return AVERROR(EINVAL);
 575
 576     if (flags & URL_WRONLY) {
 577         s->buf_end = s->buffer + s->buffer_size;
 578         s->write_flag = 1;
 579     } else {
 580         s->buf_end = s->buffer;
 581         s->write_flag = 0;
 582     }
 583     return 0;
 584 }
 585
 586 int url_fopen(ByteIOContext **s, const char *filename, int flags)
 587 {
 588     URLContext *h;
 589     int err;
 590
 591     err = url_open(&h, filename, flags);
 592     if (err < 0)
 593         return err;
 594     err = url_fdopen(s, h);
 595     if (err < 0) {
 596         url_close(h);
 597         return err;
 598     }
 599     return 0;
 600 }
 601
 602 int url_fclose(ByteIOContext *s)
 603 {
 604     URLContext *h = s->opaque;
 605
 606     av_free(s->buffer);
 607     av_free(s);
 608     return url_close(h);
 609 }
 610
 611 URLContext *url_fileno(ByteIOContext *s)
 612 {
 613     return s->opaque;
 614 }
 615
 616 #ifdef CONFIG_MUXERS
 617 int url_fprintf(ByteIOContext *s, const char *fmt, ...)
 618 {
 619     va_list ap;
 620     char buf[4096];
 621     int ret;
 622
 623     va_start(ap, fmt);
 624     ret = vsnprintf(buf, sizeof(buf), fmt, ap);
 625     va_end(ap);
 626     put_buffer(s, buf, strlen(buf));
 627     return ret;
 628 }
 629 #endif //CONFIG_MUXERS
 630
 631 char *url_fgets(ByteIOContext *s, char *buf, int buf_size)
 632 {
 633     int c;
 634     char *q;
 635
 636     c = url_fgetc(s);
 637     if (c == EOF)
 638         return NULL;
 639     q = buf;
 640     for(;;) {
 641         if (c == EOF || c == '\n')
 642             break;
 643         if ((q - buf) < buf_size - 1)
 644             *q++ = c;
 645         c = url_fgetc(s);
 646     }
 647     if (buf_size > 0)
 648         *q = '\0';
 649     return buf;
 650 }
 651
 652 int url_fget_max_packet_size(ByteIOContext *s)
 653 {
 654     return s->max_packet_size;
 655 }
 656
 657 int av_url_read_fpause(ByteIOContext *s, int pause)
 658 {
 659     if (!s->read_pause)
 660         return AVERROR(ENOSYS);
 661     return s->read_pause(s->opaque, pause);
 662 }
 663
 664 offset_t av_url_read_fseek(ByteIOContext *s,
 665         int stream_index, int64_t timestamp, int flags)
 666 {
 667     URLContext *h = s->opaque;
 668     offset_t ret;
 669     if (!s->read_seek)
 670         return AVERROR(ENOSYS);
 671     ret = s->read_seek(h, stream_index, timestamp, flags);
 672     if(ret >= 0) {
 673         s->buf_ptr = s->buf_end; // Flush buffer
 674         s->pos = s->seek(h, 0, SEEK_CUR);
 675     }
 676     return ret;
 677 }
 678
 679 /* url_open_dyn_buf and url_close_dyn_buf are used in rtp.c to send a response
 680  * back to the server even if CONFIG_MUXERS is not set. */
 681 #if defined(CONFIG_MUXERS) || defined(CONFIG_NETWORK)
 682 /* buffer handling */
 683 int url_open_buf(ByteIOContext **s, uint8_t *buf, int buf_size, int flags)
 684 {
 685     int ret;
 686     *s = av_mallocz(sizeof(ByteIOContext));
 687     if(!*s)
 688         return AVERROR(ENOMEM);
 689     ret = init_put_byte(*s, buf, buf_size,
 690                         (flags & URL_WRONLY || flags & URL_RDWR),
 691                         NULL, NULL, NULL, NULL);
 692     if(ret != 0)
 693         av_freep(s);
 694     return ret;
 695 }
 696
 697 int url_close_buf(ByteIOContext *s)
 698 {
 699     put_flush_packet(s);
 700     return s->buf_ptr - s->buffer;
 701 }
 702
 703 /* output in a dynamic buffer */
 704
 705 typedef struct DynBuffer {
 706     int pos, size, allocated_size;
 707     uint8_t *buffer;
 708     int io_buffer_size;
 709     uint8_t io_buffer[1];
 710 } DynBuffer;
 711
 712 static int dyn_buf_write(void *opaque, uint8_t *buf, int buf_size)
 713 {
 714     DynBuffer *d = opaque;
 715     int new_size, new_allocated_size;
 716
 717     /* reallocate buffer if needed */
 718     new_size = d->pos + buf_size;
 719     new_allocated_size = d->allocated_size;
 720     if(new_size < d->pos || new_size > INT_MAX/2)
 721         return -1;
 722     while (new_size > new_allocated_size) {
 723         if (!new_allocated_size)
 724             new_allocated_size = new_size;
 725         else
 726             new_allocated_size += new_allocated_size / 2 + 1;
 727     }
 728
 729     if (new_allocated_size > d->allocated_size) {
 730         d->buffer = av_realloc(d->buffer, new_allocated_size);
 731         if(d->buffer == NULL)
 732              return -1234;
 733         d->allocated_size = new_allocated_size;
 734     }
 735     memcpy(d->buffer + d->pos, buf, buf_size);
 736     d->pos = new_size;
 737     if (d->pos > d->size)
 738         d->size = d->pos;
 739     return buf_size;
 740 }
 741
 742 static int dyn_packet_buf_write(void *opaque, uint8_t *buf, int buf_size)
 743 {
 744     unsigned char buf1[4];
 745     int ret;
 746
 747     /* packetized write: output the header */
 748     buf1[0] = (buf_size >> 24);
 749     buf1[1] = (buf_size >> 16);
 750     buf1[2] = (buf_size >> 8);
 751     buf1[3] = (buf_size);
 752     ret= dyn_buf_write(opaque, buf1, 4);
 753     if(ret < 0)
 754         return ret;
 755
 756     /* then the data */
 757     return dyn_buf_write(opaque, buf, buf_size);
 758 }
 759
 760 static offset_t dyn_buf_seek(void *opaque, offset_t offset, int whence)
 761 {
 762     DynBuffer *d = opaque;
 763
 764     if (whence == SEEK_CUR)
 765         offset += d->pos;
 766     else if (whence == SEEK_END)
 767         offset += d->size;
 768     if (offset < 0 || offset > 0x7fffffffLL)
 769         return -1;
 770     d->pos = offset;
 771     return 0;
 772 }
 773
 774 static int url_open_dyn_buf_internal(ByteIOContext **s, int max_packet_size)
 775 {
 776     DynBuffer *d;
 777     int io_buffer_size, ret;
 778
 779     if (max_packet_size)
 780         io_buffer_size = max_packet_size;
 781     else
 782         io_buffer_size = 1024;
 783
 784     if(sizeof(DynBuffer) + io_buffer_size < io_buffer_size)
 785         return -1;
 786     d = av_malloc(sizeof(DynBuffer) + io_buffer_size);
 787     if (!d)
 788         return -1;
 789     *s = av_mallocz(sizeof(ByteIOContext));
 790     if(!*s) {
 791         av_free(d);
 792         return AVERROR(ENOMEM);
 793     }
 794     d->io_buffer_size = io_buffer_size;
 795     d->buffer = NULL;
 796     d->pos = 0;
 797     d->size = 0;
 798     d->allocated_size = 0;
 799     ret = init_put_byte(*s, d->io_buffer, io_buffer_size,
 800                         1, d, NULL,
 801                         max_packet_size ? dyn_packet_buf_write : dyn_buf_write,
 802                         max_packet_size ? NULL : dyn_buf_seek);
 803     if (ret == 0) {
 804         (*s)->max_packet_size = max_packet_size;
 805     } else {
 806         av_free(d);
 807         av_freep(s);
 808     }
 809     return ret;
 810 }
 811
 812 int url_open_dyn_buf(ByteIOContext **s)
 813 {
 814     return url_open_dyn_buf_internal(s, 0);
 815 }
 816
 817 int url_open_dyn_packet_buf(ByteIOContext **s, int max_packet_size)
 818 {
 819     if (max_packet_size <= 0)
 820         return -1;
 821     return url_open_dyn_buf_internal(s, max_packet_size);
 822 }
 823
 824 int url_close_dyn_buf(ByteIOContext *s, uint8_t **pbuffer)
 825 {
 826     DynBuffer *d = s->opaque;
 827     int size;
 828
 829     put_flush_packet(s);
 830
 831     *pbuffer = d->buffer;
 832     size = d->size;
 833     av_free(d);
 834     av_free(s);
 835     return size;
 836 }
 837 #endif /* CONFIG_MUXERS || CONFIG_NETWORK */