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/avassert.h"
22 #include "libavutil/avstring.h"
23 #include "libavutil/opt.h"
24 #include "avformat.h"
25 #include "url.h"
26
27 typedef struct SubfileContext {
28 const AVClass *class;
29 URLContext *h;
30 int64_t start;
31 int64_t end;
32 int64_t pos;
33 } SubfileContext;
34
35 #define OFFSET(field) offsetof(SubfileContext, field)
36 #define D AV_OPT_FLAG_DECODING_PARAM
37
38 static const AVOption subfile_options[] = {
39 { "start", "start offset", OFFSET(start), AV_OPT_TYPE_INT64, {.i64 = 0}, 0, INT64_MAX, D },
40 { "end", "end offset", OFFSET(end), AV_OPT_TYPE_INT64, {.i64 = 0}, 0, INT64_MAX, D },
41 { NULL }
42 };
43
44 #undef OFFSET
45 #undef D
46
47 static const AVClass subfile_class = {
48 .class_name = "subfile",
49 .item_name = av_default_item_name,
50 .option = subfile_options,
51 .version = LIBAVUTIL_VERSION_INT,
52 };
53
slave_seek(URLContext * h)54 static int slave_seek(URLContext *h)
55 {
56 SubfileContext *c = h->priv_data;
57 int64_t ret;
58
59 if ((ret = ffurl_seek(c->h, c->pos, SEEK_SET)) != c->pos) {
60 if (ret >= 0)
61 ret = AVERROR_BUG;
62 av_log(h, AV_LOG_ERROR, "Impossible to seek in file: %s\n",
63 av_err2str(ret));
64 return ret;
65 }
66 return 0;
67 }
68
subfile_open(URLContext * h,const char * filename,int flags,AVDictionary ** options)69 static int subfile_open(URLContext *h, const char *filename, int flags,
70 AVDictionary **options)
71 {
72 SubfileContext *c = h->priv_data;
73 int ret;
74
75 if (!c->end)
76 c->end = INT64_MAX;
77
78 if (c->end <= c->start) {
79 av_log(h, AV_LOG_ERROR, "end before start\n");
80 return AVERROR(EINVAL);
81 }
82 av_strstart(filename, "subfile:", &filename);
83 ret = ffurl_open_whitelist(&c->h, filename, flags, &h->interrupt_callback,
84 options, h->protocol_whitelist, h->protocol_blacklist, h);
85 if (ret < 0)
86 return ret;
87 c->pos = c->start;
88 if ((ret = slave_seek(h)) < 0) {
89 ffurl_closep(&c->h);
90 return ret;
91 }
92 return 0;
93 }
94
subfile_close(URLContext * h)95 static int subfile_close(URLContext *h)
96 {
97 SubfileContext *c = h->priv_data;
98 return ffurl_closep(&c->h);
99 }
100
subfile_read(URLContext * h,unsigned char * buf,int size)101 static int subfile_read(URLContext *h, unsigned char *buf, int size)
102 {
103 SubfileContext *c = h->priv_data;
104 int64_t rest = c->end - c->pos;
105 int ret;
106
107 if (rest <= 0)
108 return AVERROR_EOF;
109 size = FFMIN(size, rest);
110 ret = ffurl_read(c->h, buf, size);
111 if (ret >= 0)
112 c->pos += ret;
113 return ret;
114 }
115
subfile_seek(URLContext * h,int64_t pos,int whence)116 static int64_t subfile_seek(URLContext *h, int64_t pos, int whence)
117 {
118 SubfileContext *c = h->priv_data;
119 int64_t new_pos, end;
120 int ret;
121
122 if (whence == AVSEEK_SIZE || whence == SEEK_END) {
123 end = c->end;
124 if (end == INT64_MAX && (end = ffurl_seek(c->h, 0, AVSEEK_SIZE)) < 0)
125 return end;
126 }
127
128 if (whence == AVSEEK_SIZE)
129 return end - c->start;
130 switch (whence) {
131 case SEEK_SET:
132 new_pos = c->start + pos;
133 break;
134 case SEEK_CUR:
135 new_pos = c->pos + pos;
136 break;
137 case SEEK_END:
138 new_pos = end + pos;
139 break;
140 }
141 if (new_pos < c->start)
142 return AVERROR(EINVAL);
143 c->pos = new_pos;
144 if ((ret = slave_seek(h)) < 0)
145 return ret;
146 return c->pos - c->start;
147 }
148
149 const URLProtocol ff_subfile_protocol = {
150 .name = "subfile",
151 .url_open2 = subfile_open,
152 .url_read = subfile_read,
153 .url_seek = subfile_seek,
154 .url_close = subfile_close,
155 .priv_data_size = sizeof(SubfileContext),
156 .priv_data_class = &subfile_class,
157 .default_whitelist = "file",
158 };
159