FFmpeg: libavformat/subfile.c Source File

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libavformat

subfile.c

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1 /*

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 */

21 #include "libavutil/avassert.h"

22 #include "libavutil/avstring.h"

23 #include "libavutil/opt.h"

24 #include "avformat.h"

25 #include "url.h"

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;

35 #define OFFSET(field) offsetof(SubfileContext, field)

36 #define D AV_OPT_FLAG_DECODING_PARAM

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 };

44 #undef OFFSET

45 #undef D

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 };

54 static int slave_seek(URLContext *h)

55 {

56 SubfileContext *c = h->priv_data;

57 int64_t ret;

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 }

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;

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 }

91 static int subfile_close(URLContext *h)

92 {

93 SubfileContext *c = h->priv_data;

94 return ffurl_close(c->h);

95 }

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 };

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