| 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 | }; |