path: root/libavformat/subfile.c (plain)
blob: fa971e190210a2a55de82b7ff5390a7c00d5da0d

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
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
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 <= c->start) {
76	av_log(h, AV_LOG_ERROR, "end before start\n");
77	return AVERROR(EINVAL);
78	}
79	av_strstart(filename, "subfile:", &filename);
80	ret = ffurl_open_whitelist(&c->h, filename, flags, &h->interrupt_callback,
81	options, h->protocol_whitelist, h->protocol_blacklist, h);
82	if (ret < 0)
83	return ret;
84	c->pos = c->start;
85	if ((ret = slave_seek(h)) < 0) {
86	ffurl_close(c->h);
87	return ret;
88	}
89	return 0;
90	}
91
92	static int subfile_close(URLContext *h)
93	{
94	SubfileContext *c = h->priv_data;
95	return ffurl_close(c->h);
96	}
97
98	static int subfile_read(URLContext *h, unsigned char *buf, int size)
99	{
100	SubfileContext *c = h->priv_data;
101	int64_t rest = c->end - c->pos;
102	int ret;
103
104	if (rest <= 0)
105	return 0;
106	size = FFMIN(size, rest);
107	ret = ffurl_read(c->h, buf, size);
108	if (ret >= 0)
109	c->pos += ret;
110	return ret;
111	}
112
113	static int64_t subfile_seek(URLContext *h, int64_t pos, int whence)
114	{
115	SubfileContext *c = h->priv_data;
116	int64_t new_pos = -1;
117	int ret;
118
119	if (whence == AVSEEK_SIZE)
120	return c->end - c->start;
121	switch (whence) {
122	case SEEK_SET:
123	new_pos = c->start + pos;
124	break;
125	case SEEK_CUR:
126	new_pos += pos;
127	break;
128	case SEEK_END:
129	new_pos = c->end + c->pos;
130	break;
131	}
132	if (new_pos < c->start)
133	return AVERROR(EINVAL);
134	c->pos = new_pos;
135	if ((ret = slave_seek(h)) < 0)
136	return ret;
137	return c->pos - c->start;
138	}
139
140	const URLProtocol ff_subfile_protocol = {
141	.name = "subfile",
142	.url_open2 = subfile_open,
143	.url_read = subfile_read,
144	.url_seek = subfile_seek,
145	.url_close = subfile_close,
146	.priv_data_size = sizeof(SubfileContext),
147	.priv_data_class = &subfile_class,
148	.default_whitelist = "file",
149	};
150