1 /*
2 * Copyright (c) 2014 Nicolas George
3 *
4 * This file is part of FFmpeg.
5 *
6 * FFmpeg is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU Lesser General Public License
8 * as published by the Free Software Foundation; either
9 * version 2.1 of the License, or (at your option) any later version.
10 *
11 * FFmpeg is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 * GNU Lesser General Public License for more details.
15 *
16 * You should have received a copy of the GNU Lesser General Public License
17 * along with FFmpeg; if not, write to the Free Software Foundation, Inc.,
18 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
19 */
20
21 #include "libavutil/avstring.h"
22 #include "libavutil/opt.h"
23 #include "avformat.h"
24 #include "url.h"
25
26 typedef struct SubfileContext {
27 const AVClass *class;
28 URLContext *h;
29 int64_t start;
30 int64_t end;
31 int64_t pos;
32 } SubfileContext;
33
34 #define OFFSET(field) offsetof(SubfileContext, field)
35 #define D AV_OPT_FLAG_DECODING_PARAM
36
37 static const AVOption subfile_options[] = {
38 { "start", "start offset", OFFSET(start), AV_OPT_TYPE_INT64, {.i64 = 0}, 0, INT64_MAX, D },
39 { "end", "end offset", OFFSET(end), AV_OPT_TYPE_INT64, {.i64 = 0}, 0, INT64_MAX, D },
40 { NULL }
41 };
42
43 #undef OFFSET
44 #undef D
45
46 static const AVClass subfile_class = {
47 .class_name = "subfile",
48 .item_name = av_default_item_name,
49 .option = subfile_options,
50 .version = LIBAVUTIL_VERSION_INT,
51 };
52
slave_seek(URLContext * h)53 static int slave_seek(URLContext *h)
54 {
55 SubfileContext *c = h->priv_data;
56 int64_t ret;
57
58 if ((ret = ffurl_seek(c->h, c->pos, SEEK_SET)) != c->pos) {
59 if (ret >= 0)
60 ret = AVERROR_BUG;
61 av_log(h, AV_LOG_ERROR, "Impossible to seek in file: %s\n",
62 av_err2str(ret));
63 return ret;
64 }
65 return 0;
66 }
67
subfile_open(URLContext * h,const char * filename,int flags,AVDictionary ** options)68 static int subfile_open(URLContext *h, const char *filename, int flags,
69 AVDictionary **options)
70 {
71 SubfileContext *c = h->priv_data;
72 int ret;
73
74 if (!c->end)
75 c->end = INT64_MAX;
76
77 if (c->end <= c->start) {
78 av_log(h, AV_LOG_ERROR, "end before start\n");
79 return AVERROR(EINVAL);
80 }
81 av_strstart(filename, "subfile:", &filename);
82 ret = ffurl_open_whitelist(&c->h, filename, flags, &h->interrupt_callback,
83 options, h->protocol_whitelist, h->protocol_blacklist, h);
84 if (ret < 0)
85 return ret;
86 c->pos = c->start;
87 if ((ret = slave_seek(h)) < 0) {
88 ffurl_closep(&c->h);
89 return ret;
90 }
91 return 0;
92 }
93
subfile_close(URLContext * h)94 static int subfile_close(URLContext *h)
95 {
96 SubfileContext *c = h->priv_data;
97 return ffurl_closep(&c->h);
98 }
99
subfile_read(URLContext * h,unsigned char * buf,int size)100 static int subfile_read(URLContext *h, unsigned char *buf, int size)
101 {
102 SubfileContext *c = h->priv_data;
103 int64_t rest = c->end - c->pos;
104 int ret;
105
106 if (rest <= 0)
107 return AVERROR_EOF;
108 size = FFMIN(size, rest);
109 ret = ffurl_read(c->h, buf, size);
110 if (ret >= 0)
111 c->pos += ret;
112 return ret;
113 }
114
subfile_seek(URLContext * h,int64_t pos,int whence)115 static int64_t subfile_seek(URLContext *h, int64_t pos, int whence)
116 {
117 SubfileContext *c = h->priv_data;
118 int64_t new_pos, end;
119 int ret;
120
121 if (whence == AVSEEK_SIZE || whence == SEEK_END) {
122 end = c->end;
123 if (end == INT64_MAX && (end = ffurl_seek(c->h, 0, AVSEEK_SIZE)) < 0)
124 return end;
125 }
126
127 if (whence == AVSEEK_SIZE)
128 return end - c->start;
129 switch (whence) {
130 case SEEK_SET:
131 new_pos = c->start + pos;
132 break;
133 case SEEK_CUR:
134 new_pos = c->pos + pos;
135 break;
136 case SEEK_END:
137 new_pos = end + pos;
138 break;
139 }
140 if (new_pos < c->start)
141 return AVERROR(EINVAL);
142 c->pos = new_pos;
143 if ((ret = slave_seek(h)) < 0)
144 return ret;
145 return c->pos - c->start;
146 }
147
148 const URLProtocol ff_subfile_protocol = {
149 .name = "subfile",
150 .url_open2 = subfile_open,
151 .url_read = subfile_read,
152 .url_seek = subfile_seek,
153 .url_close = subfile_close,
154 .priv_data_size = sizeof(SubfileContext),
155 .priv_data_class = &subfile_class,
156 .default_whitelist = "file",
157 };
158