FFmpeg: libavformat/cache.c Source File

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libavformat

cache.c

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1 /*

2 * Input cache protocol.

4 *

5 * This file is part of FFmpeg.

6 *

7 * FFmpeg is free software; you can redistribute it and/or

8 * modify it under the terms of the GNU Lesser General Public

9 * License as published by the Free Software Foundation; either

10 * version 2.1 of the License, or (at your option) any later version.

11 *

12 * FFmpeg is distributed in the hope that it will be useful,

13 * but WITHOUT ANY WARRANTY; without even the implied warranty of

14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU

15 * Lesser General Public License for more details.

16 *

17 * You should have received a copy of the GNU Lesser General Public

18 * License along with FFmpeg; if not, write to the Free Software

19 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA

20 *

21 * Based on file.c by Fabrice Bellard

22 */

24 /**

25 * @TODO

26 * support non continuous caching

27 * support keeping files

28 * support filling with a background thread

29 */

31 #include "libavutil/avassert.h"

32 #include "libavutil/avstring.h"

33 #include "libavutil/file.h"

34 #include "avformat.h"

35 #include <fcntl.h>

36 #if HAVE_IO_H

37 #include <io.h>

38 #endif

39 #if HAVE_UNISTD_H

40 #include <unistd.h>

41 #endif

42 #include <sys/stat.h>

43 #include <stdlib.h>

44 #include "os_support.h"

45 #include "url.h"

47 typedef struct Context {

48 int fd;

49 int64_t end;

50 int64_t pos;

51 URLContext *inner;

52 } Context;

54 static int cache_open(URLContext *h, const char *arg, int flags)

55 {

56 char *buffername;

57 Context *c= h->priv_data;

59 av_strstart(arg, "cache:", &arg);

61 c->fd = av_tempfile("ffcache", &buffername, 0, h);

62 if (c->fd < 0){

63 av_log(h, AV_LOG_ERROR, "Failed to create tempfile\n");

64 return c->fd;

65 }

67 unlink(buffername);

68 av_freep(&buffername);

70 return ffurl_open(&c->inner, arg, flags, &h->interrupt_callback, NULL);

71 }

73 static int cache_read(URLContext *h, unsigned char *buf, int size)

74 {

75 Context *c= h->priv_data;

76 int r;

78 if(c->pos<c->end){

79 r = read(c->fd, buf, FFMIN(size, c->end - c->pos));

80 if(r>0)

81 c->pos += r;

82 return (-1 == r)?AVERROR(errno):r;

83 }else{

84 r = ffurl_read(c->inner, buf, size);

85 if(r > 0){

86 int r2= write(c->fd, buf, r);

87 av_assert0(r2==r); // FIXME handle cache failure

88 c->pos += r;

89 c->end += r;

90 }

91 return r;

92 }

93 }

95 static int64_t cache_seek(URLContext *h, int64_t pos, int whence)

96 {

97 Context *c= h->priv_data;

99 if (whence == AVSEEK_SIZE) {

100 pos= ffurl_seek(c->inner, pos, whence);

101 if(pos <= 0){

102 pos= ffurl_seek(c->inner, -1, SEEK_END);

103 ffurl_seek(c->inner, c->end, SEEK_SET);

104 if(pos <= 0)

105 return c->end;

106 }

107 return pos;

108 }

109

110 pos= lseek(c->fd, pos, whence);

111 if(pos<0){

112 return pos;

113 }else if(pos <= c->end){

114 c->pos= pos;

115 return pos;

116 }else{

117 if(lseek(c->fd, c->pos, SEEK_SET) < 0) {

118 av_log(h, AV_LOG_ERROR, "Failure to seek in cache\n");

119 }

120 return AVERROR(EPIPE);

121 }

122 }

123

124 static int cache_close(URLContext *h)

125 {

126 Context *c= h->priv_data;

127 close(c->fd);

128 ffurl_close(c->inner);

129

130 return 0;

131 }

132

133 URLProtocol ff_cache_protocol = {

134 .name = "cache",

135 .url_open = cache_open,

136 .url_read = cache_read,

137 .url_seek = cache_seek,

138 .url_close = cache_close,

139 .priv_data_size = sizeof(Context),

140 };

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