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