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  1. /*
  2.  * Input cache protocol.
  3.  * Copyright (c) 2011 Michael Niedermayer
  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.  * Based on file.c by Fabrice Bellard
  22.  */
  23.  
  24. /**
  25.  * @TODO
  26.  *      support non continuous caching
  27.  *      support keeping files
  28.  *      support filling with a background thread
  29.  */
  30.  
  31. #include "libavutil/avassert.h"
  32. #include "libavutil/avstring.h"
  33. #include "libavutil/file.h"
  34. #include "avformat.h"
  35. #include <fcntl.h>
  36. #if HAVE_IO_H
  37. #include <io.h>
  38. #endif
  39. #if HAVE_UNISTD_H
  40. #include <unistd.h>
  41. #endif
  42. #include <sys/stat.h>
  43. #include <stdlib.h>
  44. #include "os_support.h"
  45. #include "url.h"
  46.  
  47. typedef struct Context {
  48.     int fd;
  49.     int64_t end;
  50.     int64_t pos;
  51.     URLContext *inner;
  52. } Context;
  53.  
  54. static int cache_open(URLContext *h, const char *arg, int flags)
  55. {
  56.     char *buffername;
  57.     Context *c= h->priv_data;
  58.  
  59.     av_strstart(arg, "cache:", &arg);
  60.  
  61.     c->fd = av_tempfile("ffcache", &buffername, 0, h);
  62.     if (c->fd < 0){
  63.         av_log(h, AV_LOG_ERROR, "Failed to create tempfile\n");
  64.         return c->fd;
  65.     }
  66.  
  67.     unlink(buffername);
  68.     av_freep(&buffername);
  69.  
  70.     return ffurl_open(&c->inner, arg, flags, &h->interrupt_callback, NULL);
  71. }
  72.  
  73. static int cache_read(URLContext *h, unsigned char *buf, int size)
  74. {
  75.     Context *c= h->priv_data;
  76.     int r;
  77.  
  78.     if(c->pos<c->end){
  79.         r = read(c->fd, buf, FFMIN(size, c->end - c->pos));
  80.         if(r>0)
  81.             c->pos += r;
  82.         return (-1 == r)?AVERROR(errno):r;
  83.     }else{
  84.         r = ffurl_read(c->inner, buf, size);
  85.         if(r > 0){
  86.             int r2= write(c->fd, buf, r);
  87.             av_assert0(r2==r); // FIXME handle cache failure
  88.             c->pos += r;
  89.             c->end += r;
  90.         }
  91.         return r;
  92.     }
  93. }
  94.  
  95. static int64_t cache_seek(URLContext *h, int64_t pos, int whence)
  96. {
  97.     Context *c= h->priv_data;
  98.  
  99.     if (whence == AVSEEK_SIZE) {
  100.         pos= ffurl_seek(c->inner, pos, whence);
  101.         if(pos <= 0){
  102.             pos= ffurl_seek(c->inner, -1, SEEK_END);
  103.             ffurl_seek(c->inner, c->end, SEEK_SET);
  104.             if(pos <= 0)
  105.                 return c->end;
  106.         }
  107.         return pos;
  108.     }
  109.  
  110.     pos= lseek(c->fd, pos, whence);
  111.     if(pos<0){
  112.         return pos;
  113.     }else if(pos <= c->end){
  114.         c->pos= pos;
  115.         return pos;
  116.     }else{
  117.         if(lseek(c->fd, c->pos, SEEK_SET) < 0) {
  118.             av_log(h, AV_LOG_ERROR, "Failure to seek in cache\n");
  119.         }
  120.         return AVERROR(EPIPE);
  121.     }
  122. }
  123.  
  124. static int cache_close(URLContext *h)
  125. {
  126.     Context *c= h->priv_data;
  127.     close(c->fd);
  128.     ffurl_close(c->inner);
  129.  
  130.     return 0;
  131. }
  132.  
  133. URLProtocol ff_cache_protocol = {
  134.     .name                = "cache",
  135.     .url_open            = cache_open,
  136.     .url_read            = cache_read,
  137.     .url_seek            = cache_seek,
  138.     .url_close           = cache_close,
  139.     .priv_data_size      = sizeof(Context),
  140. };
  141.