/*
  * Copyright (c) 2014 Nicolas George
  *
  * This file is part of FFmpeg.
  *
  * FFmpeg is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public License
  * as published by the Free Software Foundation; either
  * version 2.1 of the License, or (at your option) any later version.
  *
  * FFmpeg is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  * GNU Lesser General Public License for more details.
  *
  * You should have received a copy of the GNU Lesser General Public License
  * along with FFmpeg; if not, write to the Free Software Foundation, Inc.,
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */
 
 #include "libavutil/avassert.h"
 #include "libavutil/avstring.h"
 #include "libavutil/opt.h"
 #include "avformat.h"
 #include "url.h"
 
 typedef struct SubfileContext {
     const AVClass *class;
     URLContext *h;
     int64_t start;
     int64_t end;
     int64_t pos;
 } SubfileContext;
 
 #define OFFSET(field) offsetof(SubfileContext, field)
 #define D AV_OPT_FLAG_DECODING_PARAM
 
 static const AVOption subfile_options[] = {
     { "start", "start offset", OFFSET(start), AV_OPT_TYPE_INT64, {.i64 = 0}, 0, INT64_MAX, D },
     { "end",   "end offset",   OFFSET(end),   AV_OPT_TYPE_INT64, {.i64 = 0}, 0, INT64_MAX, D },
     { NULL }
 };
 
 #undef OFFSET
 #undef D
 
 static const AVClass subfile_class = {
     .class_name = "subfile",
     .item_name  = av_default_item_name,
     .option     = subfile_options,
     .version    = LIBAVUTIL_VERSION_INT,
 };
 
 static int slave_seek(URLContext *h)
 {
     SubfileContext *c = h->priv_data;
     int64_t ret;
 
     if ((ret = ffurl_seek(c->h, c->pos, SEEK_SET)) != c->pos) {
         if (ret >= 0)
             ret = AVERROR_BUG;
         av_log(h, AV_LOG_ERROR, "Impossible to seek in file: %s\n",
                av_err2str(ret));
         return ret;
     }
     return 0;
 }
 
 static int subfile_open(URLContext *h, const char *filename, int flags,
                         AVDictionary **options)
 {
     SubfileContext *c = h->priv_data;
     int ret;
 

     if (!c->end)
         c->end = INT64_MAX;
 

     if (c->end <= c->start) {
         av_log(h, AV_LOG_ERROR, "end before start\n");
         return AVERROR(EINVAL);
     }
     av_strstart(filename, "subfile:", &filename);

     ret = ffurl_open_whitelist(&c->h, filename, flags, &h->interrupt_callback,

                                options, h->protocol_whitelist, h->protocol_blacklist, h);

     if (ret < 0)
         return ret;
     c->pos = c->start;
     if ((ret = slave_seek(h)) < 0) {
         ffurl_close(c->h);
         return ret;
     }
     return 0;
 }
 
 static int subfile_close(URLContext *h)
 {
     SubfileContext *c = h->priv_data;
     return ffurl_close(c->h);
 }
 
 static int subfile_read(URLContext *h, unsigned char *buf, int size)
 {
     SubfileContext *c = h->priv_data;
     int64_t rest = c->end - c->pos;
     int ret;
 
     if (rest <= 0)

         return AVERROR_EOF;

     size = FFMIN(size, rest);
     ret = ffurl_read(c->h, buf, size);
     if (ret >= 0)
         c->pos += ret;
     return ret;
 }
 
 static int64_t subfile_seek(URLContext *h, int64_t pos, int whence)
 {
     SubfileContext *c = h->priv_data;
     int64_t new_pos = -1;
     int ret;
 
     if (whence == AVSEEK_SIZE)
         return c->end - c->start;
     switch (whence) {
     case SEEK_SET:
         new_pos = c->start + pos;
         break;
     case SEEK_CUR:
         new_pos += pos;
         break;
     case SEEK_END:
         new_pos = c->end + c->pos;
         break;
     }
     if (new_pos < c->start)
         return AVERROR(EINVAL);
     c->pos = new_pos;
     if ((ret = slave_seek(h)) < 0)
         return ret;
     return c->pos - c->start;
 }
 

 const URLProtocol ff_subfile_protocol = {

     .name                = "subfile",
     .url_open2           = subfile_open,
     .url_read            = subfile_read,
     .url_seek            = subfile_seek,
     .url_close           = subfile_close,
     .priv_data_size      = sizeof(SubfileContext),
     .priv_data_class     = &subfile_class,

     .default_whitelist   = "file",

 };