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 "libavutil/intreadwrite.h"
  24 #include "avformat.h"
  25 #include "avio.h"
  26 #include <stdarg.h>
  27
  28 #define IO_BUFFER_SIZE 32768
  29
  30 static void fill_buffer(ByteIOContext *s);
  31 #if LIBAVFORMAT_VERSION_MAJOR >= 53
  32 static int url_resetbuf(ByteIOContext *s, int flags);
  33 #endif
  34
  35 int init_put_byte(ByteIOContext *s,
  36                   unsigned char *buffer,
  37                   int buffer_size,
  38                   int write_flag,
  39                   void *opaque,
  40                   int (*read_packet)(void *opaque, uint8_t *buf, int buf_size),
  41                   int (*write_packet)(void *opaque, uint8_t *buf, int buf_size),
  42                   int64_t (*seek)(void *opaque, int64_t offset, int whence))
  43 {
  44     s->buffer = buffer;
  45     s->buffer_size = buffer_size;
  46     s->buf_ptr = buffer;
  47     s->opaque = opaque;
  48     url_resetbuf(s, write_flag ? URL_WRONLY : URL_RDONLY);
  49     s->write_packet = write_packet;
  50     s->read_packet = read_packet;
  51     s->seek = seek;
  52     s->pos = 0;
  53     s->must_flush = 0;
  54     s->eof_reached = 0;
  55     s->error = 0;
  56     s->is_streamed = 0;
  57     s->max_packet_size = 0;
  58     s->update_checksum= NULL;
  59     if(!read_packet && !write_flag){
  60         s->pos = buffer_size;
  61         s->buf_end = s->buffer + buffer_size;
  62     }
  63     s->read_pause = NULL;
  64     s->read_seek  = NULL;
  65     return 0;
  66 }
  67
  68 ByteIOContext *av_alloc_put_byte(
  69                   unsigned char *buffer,
  70                   int buffer_size,
  71                   int write_flag,
  72                   void *opaque,
  73                   int (*read_packet)(void *opaque, uint8_t *buf, int buf_size),
  74                   int (*write_packet)(void *opaque, uint8_t *buf, int buf_size),
  75                   int64_t (*seek)(void *opaque, int64_t offset, int whence))
  76 {
  77     ByteIOContext *s = av_mallocz(sizeof(ByteIOContext));
  78     init_put_byte(s, buffer, buffer_size, write_flag, opaque,
  79                   read_packet, write_packet, seek);
  80     return s;
  81 }
  82
  83 static void flush_buffer(ByteIOContext *s)
  84 {
  85     if (s->buf_ptr > s->buffer) {
  86         if (s->write_packet && !s->error){
  87             int ret= s->write_packet(s->opaque, s->buffer, s->buf_ptr - s->buffer);
  88             if(ret < 0){
  89                 s->error = ret;
  90             }
  91         }
  92         if(s->update_checksum){
  93             s->checksum= s->update_checksum(s->checksum, s->checksum_ptr, s->buf_ptr - s->checksum_ptr);
  94             s->checksum_ptr= s->buffer;
  95         }
  96         s->pos += s->buf_ptr - s->buffer;
  97     }
  98     s->buf_ptr = s->buffer;
  99 }
 100
 101 void put_byte(ByteIOContext *s, int b)
 102 {
 103     *(s->buf_ptr)++ = b;
 104     if (s->buf_ptr >= s->buf_end)
 105         flush_buffer(s);
 106 }
 107
 108 void put_buffer(ByteIOContext *s, const unsigned char *buf, int size)
 109 {
 110     while (size > 0) {
 111         int len = FFMIN(s->buf_end - s->buf_ptr, size);
 112         memcpy(s->buf_ptr, buf, len);
 113         s->buf_ptr += len;
 114
 115         if (s->buf_ptr >= s->buf_end)
 116             flush_buffer(s);
 117
 118         buf += len;
 119         size -= len;
 120     }
 121 }
 122
 123 void put_flush_packet(ByteIOContext *s)
 124 {
 125     flush_buffer(s);
 126     s->must_flush = 0;
 127 }
 128
 129 int64_t url_fseek(ByteIOContext *s, int64_t offset, int whence)
 130 {
 131     int64_t offset1;
 132     int64_t pos;
 133     int force = whence & AVSEEK_FORCE;
 134     whence &= ~AVSEEK_FORCE;
 135
 136     if(!s)
 137         return AVERROR(EINVAL);
 138
 139     pos = s->pos - (s->write_flag ? 0 : (s->buf_end - s->buffer));
 140
 141     if (whence != SEEK_CUR && whence != SEEK_SET)
 142         return AVERROR(EINVAL);
 143
 144     if (whence == SEEK_CUR) {
 145         offset1 = pos + (s->buf_ptr - s->buffer);
 146         if (offset == 0)
 147             return offset1;
 148         offset += offset1;
 149     }
 150     offset1 = offset - pos;
 151     if (!s->must_flush &&
 152         offset1 >= 0 && offset1 <= (s->buf_end - s->buffer)) {
 153         /* can do the seek inside the buffer */
 154         s->buf_ptr = s->buffer + offset1;
 155     } else if(s->is_streamed && !s->write_flag && offset1 >= 0 &&
 156               (whence != SEEK_END || force)) {
 157         while(s->pos < offset && !s->eof_reached)
 158             fill_buffer(s);
 159         if (s->eof_reached)
 160             return AVERROR_EOF;
 161         s->buf_ptr = s->buf_end + offset - s->pos;
 162     } else {
 163         int64_t res = AVERROR(EPIPE);
 164
 165 #if CONFIG_MUXERS || CONFIG_NETWORK
 166         if (s->write_flag) {
 167             flush_buffer(s);
 168             s->must_flush = 1;
 169         }
 170 #endif /* CONFIG_MUXERS || CONFIG_NETWORK */
 171         if (!s->seek || (res = s->seek(s->opaque, offset, SEEK_SET)) < 0)
 172             return res;
 173         if (!s->write_flag)
 174             s->buf_end = s->buffer;
 175         s->buf_ptr = s->buffer;
 176         s->pos = offset;
 177     }
 178     s->eof_reached = 0;
 179     return offset;
 180 }
 181
 182 void url_fskip(ByteIOContext *s, int64_t offset)
 183 {
 184     url_fseek(s, offset, SEEK_CUR);
 185 }
 186
 187 int64_t url_ftell(ByteIOContext *s)
 188 {
 189     return url_fseek(s, 0, SEEK_CUR);
 190 }
 191
 192 int64_t url_fsize(ByteIOContext *s)
 193 {
 194     int64_t size;
 195
 196     if(!s)
 197         return AVERROR(EINVAL);
 198
 199     if (!s->seek)
 200         return AVERROR(EPIPE);
 201     size = s->seek(s->opaque, 0, AVSEEK_SIZE);
 202     if(size<0){
 203         if ((size = s->seek(s->opaque, -1, SEEK_END)) < 0)
 204             return size;
 205         size++;
 206         s->seek(s->opaque, s->pos, SEEK_SET);
 207     }
 208     return size;
 209 }
 210
 211 int url_feof(ByteIOContext *s)
 212 {
 213     if(!s)
 214         return 0;
 215     return s->eof_reached;
 216 }
 217
 218 int url_ferror(ByteIOContext *s)
 219 {
 220     if(!s)
 221         return 0;
 222     return s->error;
 223 }
 224
 225 void put_le32(ByteIOContext *s, unsigned int val)
 226 {
 227     put_byte(s, val);
 228     put_byte(s, val >> 8);
 229     put_byte(s, val >> 16);
 230     put_byte(s, val >> 24);
 231 }
 232
 233 void put_be32(ByteIOContext *s, unsigned int val)
 234 {
 235     put_byte(s, val >> 24);
 236     put_byte(s, val >> 16);
 237     put_byte(s, val >> 8);
 238     put_byte(s, val);
 239 }
 240
 241 void put_strz(ByteIOContext *s, const char *str)
 242 {
 243     if (str)
 244         put_buffer(s, (const unsigned char *) str, strlen(str) + 1);
 245     else
 246         put_byte(s, 0);
 247 }
 248
 249 void put_le64(ByteIOContext *s, uint64_t val)
 250 {
 251     put_le32(s, (uint32_t)(val & 0xffffffff));
 252     put_le32(s, (uint32_t)(val >> 32));
 253 }
 254
 255 void put_be64(ByteIOContext *s, uint64_t val)
 256 {
 257     put_be32(s, (uint32_t)(val >> 32));
 258     put_be32(s, (uint32_t)(val & 0xffffffff));
 259 }
 260
 261 void put_le16(ByteIOContext *s, unsigned int val)
 262 {
 263     put_byte(s, val);
 264     put_byte(s, val >> 8);
 265 }
 266
 267 void put_be16(ByteIOContext *s, unsigned int val)
 268 {
 269     put_byte(s, val >> 8);
 270     put_byte(s, val);
 271 }
 272
 273 void put_le24(ByteIOContext *s, unsigned int val)
 274 {
 275     put_le16(s, val & 0xffff);
 276     put_byte(s, val >> 16);
 277 }
 278
 279 void put_be24(ByteIOContext *s, unsigned int val)
 280 {
 281     put_be16(s, val >> 8);
 282     put_byte(s, val);
 283 }
 284
 285 void put_tag(ByteIOContext *s, const char *tag)
 286 {
 287     while (*tag) {
 288         put_byte(s, *tag++);
 289     }
 290 }
 291
 292 /* Input stream */
 293
 294 static void fill_buffer(ByteIOContext *s)
 295 {
 296     uint8_t *dst= !s->max_packet_size && s->buf_end - s->buffer < s->buffer_size ? s->buf_ptr : s->buffer;
 297     int len= s->buffer_size - (dst - s->buffer);
 298     int max_buffer_size = s->max_packet_size ? s->max_packet_size : IO_BUFFER_SIZE;
 299
 300     assert(s->buf_ptr == s->buf_end);
 301
 302     /* no need to do anything if EOF already reached */
 303     if (s->eof_reached)
 304         return;
 305
 306     if(s->update_checksum && dst == s->buffer){
 307         if(s->buf_end > s->checksum_ptr)
 308             s->checksum= s->update_checksum(s->checksum, s->checksum_ptr, s->buf_end - s->checksum_ptr);
 309         s->checksum_ptr= s->buffer;
 310     }
 311
 312     /* make buffer smaller in case it ended up large after probing */
 313     if (s->buffer_size > max_buffer_size) {
 314         url_setbufsize(s, max_buffer_size);
 315
 316         s->checksum_ptr = dst = s->buffer;
 317         len = s->buffer_size;
 318     }
 319
 320     if(s->read_packet)
 321         len = s->read_packet(s->opaque, dst, len);
 322     else
 323         len = 0;
 324     if (len <= 0) {
 325         /* do not modify buffer if EOF reached so that a seek back can
 326            be done without rereading data */
 327         s->eof_reached = 1;
 328         if(len<0)
 329             s->error= len;
 330     } else {
 331         s->pos += len;
 332         s->buf_ptr = dst;
 333         s->buf_end = dst + len;
 334     }
 335 }
 336
 337 unsigned long ff_crc04C11DB7_update(unsigned long checksum, const uint8_t *buf,
 338                                     unsigned int len)
 339 {
 340     return av_crc(av_crc_get_table(AV_CRC_32_IEEE), checksum, buf, len);
 341 }
 342
 343 unsigned long get_checksum(ByteIOContext *s)
 344 {
 345     s->checksum= s->update_checksum(s->checksum, s->checksum_ptr, s->buf_ptr - s->checksum_ptr);
 346     s->update_checksum= NULL;
 347     return s->checksum;
 348 }
 349
 350 void init_checksum(ByteIOContext *s,
 351                    unsigned long (*update_checksum)(unsigned long c, const uint8_t *p, unsigned int len),
 352                    unsigned long checksum)
 353 {
 354     s->update_checksum= update_checksum;
 355     if(s->update_checksum){
 356         s->checksum= checksum;
 357         s->checksum_ptr= s->buf_ptr;
 358     }
 359 }
 360
 361 /* XXX: put an inline version */
 362 int get_byte(ByteIOContext *s)
 363 {
 364     if (s->buf_ptr < s->buf_end) {
 365         return *s->buf_ptr++;
 366     } else {
 367         fill_buffer(s);
 368         if (s->buf_ptr < s->buf_end)
 369             return *s->buf_ptr++;
 370         else
 371             return 0;
 372     }
 373 }
 374
 375 int url_fgetc(ByteIOContext *s)
 376 {
 377     if (s->buf_ptr < s->buf_end) {
 378         return *s->buf_ptr++;
 379     } else {
 380         fill_buffer(s);
 381         if (s->buf_ptr < s->buf_end)
 382             return *s->buf_ptr++;
 383         else
 384             return URL_EOF;
 385     }
 386 }
 387
 388 int get_buffer(ByteIOContext *s, unsigned char *buf, int size)
 389 {
 390     int len, size1;
 391
 392     size1 = size;
 393     while (size > 0) {
 394         len = s->buf_end - s->buf_ptr;
 395         if (len > size)
 396             len = size;
 397         if (len == 0) {
 398             if(size > s->buffer_size && !s->update_checksum){
 399                 if(s->read_packet)
 400                     len = s->read_packet(s->opaque, buf, size);
 401                 if (len <= 0) {
 402                     /* do not modify buffer if EOF reached so that a seek back can
 403                     be done without rereading data */
 404                     s->eof_reached = 1;
 405                     if(len<0)
 406                         s->error= len;
 407                     break;
 408                 } else {
 409                     s->pos += len;
 410                     size -= len;
 411                     buf += len;
 412                     s->buf_ptr = s->buffer;
 413                     s->buf_end = s->buffer/* + len*/;
 414                 }
 415             }else{
 416                 fill_buffer(s);
 417                 len = s->buf_end - s->buf_ptr;
 418                 if (len == 0)
 419                     break;
 420             }
 421         } else {
 422             memcpy(buf, s->buf_ptr, len);
 423             buf += len;
 424             s->buf_ptr += len;
 425             size -= len;
 426         }
 427     }
 428     if (size1 == size) {
 429         if (url_ferror(s)) return url_ferror(s);
 430         if (url_feof(s))   return AVERROR_EOF;
 431     }
 432     return size1 - size;
 433 }
 434
 435 int get_partial_buffer(ByteIOContext *s, unsigned char *buf, int size)
 436 {
 437     int len;
 438
 439     if(size<0)
 440         return -1;
 441
 442     len = s->buf_end - s->buf_ptr;
 443     if (len == 0) {
 444         fill_buffer(s);
 445         len = s->buf_end - s->buf_ptr;
 446     }
 447     if (len > size)
 448         len = size;
 449     memcpy(buf, s->buf_ptr, len);
 450     s->buf_ptr += len;
 451     if (!len) {
 452         if (url_ferror(s)) return url_ferror(s);
 453         if (url_feof(s))   return AVERROR_EOF;
 454     }
 455     return len;
 456 }
 457
 458 unsigned int get_le16(ByteIOContext *s)
 459 {
 460     unsigned int val;
 461     val = get_byte(s);
 462     val |= get_byte(s) << 8;
 463     return val;
 464 }
 465
 466 unsigned int get_le24(ByteIOContext *s)
 467 {
 468     unsigned int val;
 469     val = get_le16(s);
 470     val |= get_byte(s) << 16;
 471     return val;
 472 }
 473
 474 unsigned int get_le32(ByteIOContext *s)
 475 {
 476     unsigned int val;
 477     val = get_le16(s);
 478     val |= get_le16(s) << 16;
 479     return val;
 480 }
 481
 482 uint64_t get_le64(ByteIOContext *s)
 483 {
 484     uint64_t val;
 485     val = (uint64_t)get_le32(s);
 486     val |= (uint64_t)get_le32(s) << 32;
 487     return val;
 488 }
 489
 490 unsigned int get_be16(ByteIOContext *s)
 491 {
 492     unsigned int val;
 493     val = get_byte(s) << 8;
 494     val |= get_byte(s);
 495     return val;
 496 }
 497
 498 unsigned int get_be24(ByteIOContext *s)
 499 {
 500     unsigned int val;
 501     val = get_be16(s) << 8;
 502     val |= get_byte(s);
 503     return val;
 504 }
 505 unsigned int get_be32(ByteIOContext *s)
 506 {
 507     unsigned int val;
 508     val = get_be16(s) << 16;
 509     val |= get_be16(s);
 510     return val;
 511 }
 512
 513 char *get_strz(ByteIOContext *s, char *buf, int maxlen)
 514 {
 515     int i = 0;
 516     char c;
 517
 518     while ((c = get_byte(s))) {
 519         if (i < maxlen-1)
 520             buf[i++] = c;
 521     }
 522
 523     buf[i] = 0; /* Ensure null terminated, but may be truncated */
 524
 525     return buf;
 526 }
 527
 528 uint64_t get_be64(ByteIOContext *s)
 529 {
 530     uint64_t val;
 531     val = (uint64_t)get_be32(s) << 32;
 532     val |= (uint64_t)get_be32(s);
 533     return val;
 534 }
 535
 536 uint64_t ff_get_v(ByteIOContext *bc){
 537     uint64_t val = 0;
 538     int tmp;
 539
 540     do{
 541         tmp = get_byte(bc);
 542         val= (val<<7) + (tmp&127);
 543     }while(tmp&128);
 544     return val;
 545 }
 546
 547 int url_fdopen(ByteIOContext **s, URLContext *h)
 548 {
 549     uint8_t *buffer;
 550     int buffer_size, max_packet_size;
 551
 552     max_packet_size = url_get_max_packet_size(h);
 553     if (max_packet_size) {
 554         buffer_size = max_packet_size; /* no need to bufferize more than one packet */
 555     } else {
 556         buffer_size = IO_BUFFER_SIZE;
 557     }
 558     buffer = av_malloc(buffer_size);
 559     if (!buffer)
 560         return AVERROR(ENOMEM);
 561
 562     *s = av_mallocz(sizeof(ByteIOContext));
 563     if(!*s) {
 564         av_free(buffer);
 565         return AVERROR(ENOMEM);
 566     }
 567
 568     if (init_put_byte(*s, buffer, buffer_size,
 569                       (h->flags & URL_WRONLY || h->flags & URL_RDWR), h,
 570                       url_read, url_write, url_seek) < 0) {
 571         av_free(buffer);
 572         av_freep(s);
 573         return AVERROR(EIO);
 574     }
 575     (*s)->is_streamed = h->is_streamed;
 576     (*s)->max_packet_size = max_packet_size;
 577     if(h->prot) {
 578         (*s)->read_pause = (int (*)(void *, int))h->prot->url_read_pause;
 579         (*s)->read_seek  = (int64_t (*)(void *, int, int64_t, int))h->prot->url_read_seek;
 580     }
 581     return 0;
 582 }
 583
 584 int url_setbufsize(ByteIOContext *s, int buf_size)
 585 {
 586     uint8_t *buffer;
 587     buffer = av_malloc(buf_size);
 588     if (!buffer)
 589         return AVERROR(ENOMEM);
 590
 591     av_free(s->buffer);
 592     s->buffer = buffer;
 593     s->buffer_size = buf_size;
 594     s->buf_ptr = buffer;
 595     url_resetbuf(s, s->write_flag ? URL_WRONLY : URL_RDONLY);
 596     return 0;
 597 }
 598
 599 #if LIBAVFORMAT_VERSION_MAJOR < 53
 600 int url_resetbuf(ByteIOContext *s, int flags)
 601 #else
 602 static int url_resetbuf(ByteIOContext *s, int flags)
 603 #endif
 604 {
 605 #if LIBAVFORMAT_VERSION_MAJOR < 53
 606     URLContext *h = s->opaque;
 607     if ((flags & URL_RDWR) || (h && h->flags != flags && !h->flags & URL_RDWR))
 608         return AVERROR(EINVAL);
 609 #else
 610     assert(flags == URL_WRONLY || flags == URL_RDONLY);
 611 #endif
 612
 613     if (flags & URL_WRONLY) {
 614         s->buf_end = s->buffer + s->buffer_size;
 615         s->write_flag = 1;
 616     } else {
 617         s->buf_end = s->buffer;
 618         s->write_flag = 0;
 619     }
 620     return 0;
 621 }
 622
 623 int ff_rewind_with_probe_data(ByteIOContext *s, unsigned char *buf, int buf_size)
 624 {
 625     int64_t buffer_start;
 626     int buffer_size;
 627     int overlap, new_size;
 628
 629     if (s->write_flag)
 630         return AVERROR(EINVAL);
 631
 632     buffer_size = s->buf_end - s->buffer;
 633
 634     /* the buffers must touch or overlap */
 635     if ((buffer_start = s->pos - buffer_size) > buf_size)
 636         return AVERROR(EINVAL);
 637
 638     overlap = buf_size - buffer_start;
 639     new_size = buf_size + buffer_size - overlap;
 640
 641     if (new_size > buf_size) {
 642         if (!(buf = av_realloc(buf, new_size)))
 643             return AVERROR(ENOMEM);
 644
 645         memcpy(buf + buf_size, s->buffer + overlap, buffer_size - overlap);
 646         buf_size = new_size;
 647     }
 648
 649     av_free(s->buffer);
 650     s->buf_ptr = s->buffer = buf;
 651     s->pos = s->buffer_size = buf_size;
 652     s->buf_end = s->buf_ptr + buf_size;
 653     s->eof_reached = 0;
 654     s->must_flush = 0;
 655
 656     return 0;
 657 }
 658
 659 int url_fopen(ByteIOContext **s, const char *filename, int flags)
 660 {
 661     URLContext *h;
 662     int err;
 663
 664     err = url_open(&h, filename, flags);
 665     if (err < 0)
 666         return err;
 667     err = url_fdopen(s, h);
 668     if (err < 0) {
 669         url_close(h);
 670         return err;
 671     }
 672     return 0;
 673 }
 674
 675 int url_fclose(ByteIOContext *s)
 676 {
 677     URLContext *h = s->opaque;
 678
 679     av_free(s->buffer);
 680     av_free(s);
 681     return url_close(h);
 682 }
 683
 684 URLContext *url_fileno(ByteIOContext *s)
 685 {
 686     return s->opaque;
 687 }
 688
 689 #if CONFIG_MUXERS
 690 int url_fprintf(ByteIOContext *s, const char *fmt, ...)
 691 {
 692     va_list ap;
 693     char buf[4096];
 694     int ret;
 695
 696     va_start(ap, fmt);
 697     ret = vsnprintf(buf, sizeof(buf), fmt, ap);
 698     va_end(ap);
 699     put_buffer(s, buf, strlen(buf));
 700     return ret;
 701 }
 702 #endif //CONFIG_MUXERS
 703
 704 char *url_fgets(ByteIOContext *s, char *buf, int buf_size)
 705 {
 706     int c;
 707     char *q;
 708
 709     c = url_fgetc(s);
 710     if (c == EOF)
 711         return NULL;
 712     q = buf;
 713     for(;;) {
 714         if (c == EOF || c == '\n')
 715             break;
 716         if ((q - buf) < buf_size - 1)
 717             *q++ = c;
 718         c = url_fgetc(s);
 719     }
 720     if (buf_size > 0)
 721         *q = '\0';
 722     return buf;
 723 }
 724
 725 int url_fget_max_packet_size(ByteIOContext *s)
 726 {
 727     return s->max_packet_size;
 728 }
 729
 730 int av_url_read_fpause(ByteIOContext *s, int pause)
 731 {
 732     if (!s->read_pause)
 733         return AVERROR(ENOSYS);
 734     return s->read_pause(s->opaque, pause);
 735 }
 736
 737 int64_t av_url_read_fseek(ByteIOContext *s, int stream_index,
 738                           int64_t timestamp, int flags)
 739 {
 740     URLContext *h = s->opaque;
 741     int64_t ret;
 742     if (!s->read_seek)
 743         return AVERROR(ENOSYS);
 744     ret = s->read_seek(h, stream_index, timestamp, flags);
 745     if(ret >= 0) {
 746         int64_t pos;
 747         s->buf_ptr = s->buf_end; // Flush buffer
 748         pos = s->seek(h, 0, SEEK_CUR);
 749         if (pos >= 0)
 750             s->pos = pos;
 751         else if (pos != AVERROR(ENOSYS))
 752             ret = pos;
 753     }
 754     return ret;
 755 }
 756
 757 /* url_open_dyn_buf and url_close_dyn_buf are used in rtp.c to send a response
 758  * back to the server even if CONFIG_MUXERS is false. */
 759 #if CONFIG_MUXERS || CONFIG_NETWORK
 760 /* buffer handling */
 761 int url_open_buf(ByteIOContext **s, uint8_t *buf, int buf_size, int flags)
 762 {
 763     int ret;
 764     *s = av_mallocz(sizeof(ByteIOContext));
 765     if(!*s)
 766         return AVERROR(ENOMEM);
 767     ret = init_put_byte(*s, buf, buf_size,
 768                         (flags & URL_WRONLY || flags & URL_RDWR),
 769                         NULL, NULL, NULL, NULL);
 770     if(ret != 0)
 771         av_freep(s);
 772     return ret;
 773 }
 774
 775 int url_close_buf(ByteIOContext *s)
 776 {
 777     put_flush_packet(s);
 778     return s->buf_ptr - s->buffer;
 779 }
 780
 781 /* output in a dynamic buffer */
 782
 783 typedef struct DynBuffer {
 784     int pos, size, allocated_size;
 785     uint8_t *buffer;
 786     int io_buffer_size;
 787     uint8_t io_buffer[1];
 788 } DynBuffer;
 789
 790 static int dyn_buf_write(void *opaque, uint8_t *buf, int buf_size)
 791 {
 792     DynBuffer *d = opaque;
 793     unsigned new_size, new_allocated_size;
 794
 795     /* reallocate buffer if needed */
 796     new_size = d->pos + buf_size;
 797     new_allocated_size = d->allocated_size;
 798     if(new_size < d->pos || new_size > INT_MAX/2)
 799         return -1;
 800     while (new_size > new_allocated_size) {
 801         if (!new_allocated_size)
 802             new_allocated_size = new_size;
 803         else
 804             new_allocated_size += new_allocated_size / 2 + 1;
 805     }
 806
 807     if (new_allocated_size > d->allocated_size) {
 808         d->buffer = av_realloc(d->buffer, new_allocated_size);
 809         if(d->buffer == NULL)
 810              return AVERROR(ENOMEM);
 811         d->allocated_size = new_allocated_size;
 812     }
 813     memcpy(d->buffer + d->pos, buf, buf_size);
 814     d->pos = new_size;
 815     if (d->pos > d->size)
 816         d->size = d->pos;
 817     return buf_size;
 818 }
 819
 820 static int dyn_packet_buf_write(void *opaque, uint8_t *buf, int buf_size)
 821 {
 822     unsigned char buf1[4];
 823     int ret;
 824
 825     /* packetized write: output the header */
 826     AV_WB32(buf1, buf_size);
 827     ret= dyn_buf_write(opaque, buf1, 4);
 828     if(ret < 0)
 829         return ret;
 830
 831     /* then the data */
 832     return dyn_buf_write(opaque, buf, buf_size);
 833 }
 834
 835 static int64_t dyn_buf_seek(void *opaque, int64_t offset, int whence)
 836 {
 837     DynBuffer *d = opaque;
 838
 839     if (whence == SEEK_CUR)
 840         offset += d->pos;
 841     else if (whence == SEEK_END)
 842         offset += d->size;
 843     if (offset < 0 || offset > 0x7fffffffLL)
 844         return -1;
 845     d->pos = offset;
 846     return 0;
 847 }
 848
 849 static int url_open_dyn_buf_internal(ByteIOContext **s, int max_packet_size)
 850 {
 851     DynBuffer *d;
 852     int ret;
 853     unsigned io_buffer_size = max_packet_size ? max_packet_size : 1024;
 854
 855     if(sizeof(DynBuffer) + io_buffer_size < io_buffer_size)
 856         return -1;
 857     d = av_mallocz(sizeof(DynBuffer) + io_buffer_size);
 858     if (!d)
 859         return AVERROR(ENOMEM);
 860     *s = av_mallocz(sizeof(ByteIOContext));
 861     if(!*s) {
 862         av_free(d);
 863         return AVERROR(ENOMEM);
 864     }
 865     d->io_buffer_size = io_buffer_size;
 866     ret = init_put_byte(*s, d->io_buffer, io_buffer_size,
 867                         1, d, NULL,
 868                         max_packet_size ? dyn_packet_buf_write : dyn_buf_write,
 869                         max_packet_size ? NULL : dyn_buf_seek);
 870     if (ret == 0) {
 871         (*s)->max_packet_size = max_packet_size;
 872     } else {
 873         av_free(d);
 874         av_freep(s);
 875     }
 876     return ret;
 877 }
 878
 879 int url_open_dyn_buf(ByteIOContext **s)
 880 {
 881     return url_open_dyn_buf_internal(s, 0);
 882 }
 883
 884 int url_open_dyn_packet_buf(ByteIOContext **s, int max_packet_size)
 885 {
 886     if (max_packet_size <= 0)
 887         return -1;
 888     return url_open_dyn_buf_internal(s, max_packet_size);
 889 }
 890
 891 int url_close_dyn_buf(ByteIOContext *s, uint8_t **pbuffer)
 892 {
 893     DynBuffer *d = s->opaque;
 894     int size;
 895
 896     put_flush_packet(s);
 897
 898     *pbuffer = d->buffer;
 899     size = d->size;
 900     av_free(d);
 901     av_free(s);
 902     return size;
 903 }
 904 #endif /* CONFIG_MUXERS || CONFIG_NETWORK */