/libavformat/cache.c

  1/*
  2 * Input cache protocol.
  3 * Copyright (c) 2011,2014 Michael Niedermayer
  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 */
 23
 24/**
 25 * @TODO
 26 *      support keeping files
 27 *      support filling with a background thread
 28 */
 29
 30#include "libavutil/avassert.h"
 31#include "libavutil/avstring.h"
 32#include "libavutil/internal.h"
 33#include "libavutil/opt.h"
 34#include "libavutil/tree.h"
 35#include "avformat.h"
 36#include <fcntl.h>
 37#if HAVE_IO_H
 38#include <io.h>
 39#endif
 40#if HAVE_UNISTD_H
 41#include <unistd.h>
 42#endif
 43#include <sys/stat.h>
 44#include <stdlib.h>
 45#include "os_support.h"
 46#include "url.h"
 47
 48typedef struct CacheEntry {
 49    int64_t logical_pos;
 50    int64_t physical_pos;
 51    int size;
 52} CacheEntry;
 53
 54typedef struct Context {
 55    AVClass *class;
 56    int fd;
 57    char *filename;
 58    struct AVTreeNode *root;
 59    int64_t logical_pos;
 60    int64_t cache_pos;
 61    int64_t inner_pos;
 62    int64_t end;
 63    int is_true_eof;
 64    URLContext *inner;
 65    int64_t cache_hit, cache_miss;
 66    int read_ahead_limit;
 67} Context;
 68
 69static int cmp(const void *key, const void *node)
 70{
 71    return FFDIFFSIGN(*(const int64_t *)key, ((const CacheEntry *) node)->logical_pos);
 72}
 73
 74static int cache_open(URLContext *h, const char *arg, int flags, AVDictionary **options)
 75{
 76    int ret;
 77    char *buffername;
 78    Context *c= h->priv_data;
 79
 80    av_strstart(arg, "cache:", &arg);
 81
 82    c->fd = avpriv_tempfile("ffcache", &buffername, 0, h);
 83    if (c->fd < 0){
 84        av_log(h, AV_LOG_ERROR, "Failed to create tempfile\n");
 85        return c->fd;
 86    }
 87
 88    ret = unlink(buffername);
 89
 90    if (ret >= 0)
 91        av_freep(&buffername);
 92    else
 93        c->filename = buffername;
 94
 95    return ffurl_open_whitelist(&c->inner, arg, flags, &h->interrupt_callback,
 96                                options, h->protocol_whitelist, h->protocol_blacklist, h);
 97}
 98
 99static int add_entry(URLContext *h, const unsigned char *buf, int size)
100{
101    Context *c= h->priv_data;
102    int64_t pos = -1;
103    int ret;
104    CacheEntry *entry = NULL, *next[2] = {NULL, NULL};
105    CacheEntry *entry_ret;
106    struct AVTreeNode *node = NULL;
107
108    //FIXME avoid lseek
109    pos = lseek(c->fd, 0, SEEK_END);
110    if (pos < 0) {
111        ret = AVERROR(errno);
112        av_log(h, AV_LOG_ERROR, "seek in cache failed\n");
113        goto fail;
114    }
115    c->cache_pos = pos;
116
117    ret = write(c->fd, buf, size);
118    if (ret < 0) {
119        ret = AVERROR(errno);
120        av_log(h, AV_LOG_ERROR, "write in cache failed\n");
121        goto fail;
122    }
123    c->cache_pos += ret;
124
125    entry = av_tree_find(c->root, &c->logical_pos, cmp, (void**)next);
126
127    if (!entry)
128        entry = next[0];
129
130    if (!entry ||
131        entry->logical_pos  + entry->size != c->logical_pos ||
132        entry->physical_pos + entry->size != pos
133    ) {
134        entry = av_malloc(sizeof(*entry));
135        node = av_tree_node_alloc();
136        if (!entry || !node) {
137            ret = AVERROR(ENOMEM);
138            goto fail;
139        }
140        entry->logical_pos = c->logical_pos;
141        entry->physical_pos = pos;
142        entry->size = ret;
143
144        entry_ret = av_tree_insert(&c->root, entry, cmp, &node);
145        if (entry_ret && entry_ret != entry) {
146            ret = -1;
147            av_log(h, AV_LOG_ERROR, "av_tree_insert failed\n");
148            goto fail;
149        }
150    } else
151        entry->size += ret;
152
153    return 0;
154fail:
155    //we could truncate the file to pos here if pos >=0 but ftruncate isn't available in VS so
156    //for simplicty we just leave the file a bit larger
157    av_free(entry);
158    av_free(node);
159    return ret;
160}
161
162static int cache_read(URLContext *h, unsigned char *buf, int size)
163{
164    Context *c= h->priv_data;
165    CacheEntry *entry, *next[2] = {NULL, NULL};
166    int64_t r;
167
168    entry = av_tree_find(c->root, &c->logical_pos, cmp, (void**)next);
169
170    if (!entry)
171        entry = next[0];
172
173    if (entry) {
174        int64_t in_block_pos = c->logical_pos - entry->logical_pos;
175        av_assert0(entry->logical_pos <= c->logical_pos);
176        if (in_block_pos < entry->size) {
177            int64_t physical_target = entry->physical_pos + in_block_pos;
178
179            if (c->cache_pos != physical_target) {
180                r = lseek(c->fd, physical_target, SEEK_SET);
181            } else
182                r = c->cache_pos;
183
184            if (r >= 0) {
185                c->cache_pos = r;
186                r = read(c->fd, buf, FFMIN(size, entry->size - in_block_pos));
187            }
188
189            if (r > 0) {
190                c->cache_pos += r;
191                c->logical_pos += r;
192                c->cache_hit ++;
193                return r;
194            }
195        }
196    }
197
198    // Cache miss or some kind of fault with the cache
199
200    if (c->logical_pos != c->inner_pos) {
201        r = ffurl_seek(c->inner, c->logical_pos, SEEK_SET);
202        if (r<0) {
203            av_log(h, AV_LOG_ERROR, "Failed to perform internal seek\n");
204            return r;
205        }
206        c->inner_pos = r;
207    }
208
209    r = ffurl_read(c->inner, buf, size);
210    if (r == AVERROR_EOF && size>0) {
211        c->is_true_eof = 1;
212        av_assert0(c->end >= c->logical_pos);
213    }
214    if (r<=0)
215        return r;
216    c->inner_pos += r;
217
218    c->cache_miss ++;
219
220    add_entry(h, buf, r);
221    c->logical_pos += r;
222    c->end = FFMAX(c->end, c->logical_pos);
223
224    return r;
225}
226
227static int64_t cache_seek(URLContext *h, int64_t pos, int whence)
228{
229    Context *c= h->priv_data;
230    int64_t ret;
231
232    if (whence == AVSEEK_SIZE) {
233        pos= ffurl_seek(c->inner, pos, whence);
234        if(pos <= 0){
235            pos= ffurl_seek(c->inner, -1, SEEK_END);
236            if (ffurl_seek(c->inner, c->inner_pos, SEEK_SET) < 0)
237                av_log(h, AV_LOG_ERROR, "Inner protocol failed to seekback end : %"PRId64"\n", pos);
238        }
239        if (pos > 0)
240            c->is_true_eof = 1;
241        c->end = FFMAX(c->end, pos);
242        return pos;
243    }
244
245    if (whence == SEEK_CUR) {
246        whence = SEEK_SET;
247        pos += c->logical_pos;
248    } else if (whence == SEEK_END && c->is_true_eof) {
249resolve_eof:
250        whence = SEEK_SET;
251        pos += c->end;
252    }
253
254    if (whence == SEEK_SET && pos >= 0 && pos < c->end) {
255        //Seems within filesize, assume it will not fail.
256        c->logical_pos = pos;
257        return pos;
258    }
259
260    //cache miss
261    ret= ffurl_seek(c->inner, pos, whence);
262    if ((whence == SEEK_SET && pos >= c->logical_pos ||
263         whence == SEEK_END && pos <= 0) && ret < 0) {
264        if (   (whence == SEEK_SET && c->read_ahead_limit >= pos - c->logical_pos)
265            || c->read_ahead_limit < 0) {
266            uint8_t tmp[32768];
267            while (c->logical_pos < pos || whence == SEEK_END) {
268                int size = sizeof(tmp);
269                if (whence == SEEK_SET)
270                    size = FFMIN(sizeof(tmp), pos - c->logical_pos);
271                ret = cache_read(h, tmp, size);
272                if (ret == AVERROR_EOF && whence == SEEK_END) {
273                    av_assert0(c->is_true_eof);
274                    goto resolve_eof;
275                }
276                if (ret < 0) {
277                    return ret;
278                }
279            }
280            return c->logical_pos;
281        }
282    }
283
284    if (ret >= 0) {
285        c->logical_pos = ret;
286        c->end = FFMAX(c->end, ret);
287    }
288
289    return ret;
290}
291
292static int enu_free(void *opaque, void *elem)
293{
294    av_free(elem);
295    return 0;
296}
297
298static int cache_close(URLContext *h)
299{
300    Context *c= h->priv_data;
301    int ret;
302
303    av_log(h, AV_LOG_INFO, "Statistics, cache hits:%"PRId64" cache misses:%"PRId64"\n",
304           c->cache_hit, c->cache_miss);
305
306    close(c->fd);
307    if (c->filename) {
308        ret = unlink(c->filename);
309        if (ret < 0)
310            av_log(h, AV_LOG_ERROR, "Could not delete %s.\n", c->filename);
311        av_freep(&c->filename);
312    }
313    ffurl_close(c->inner);
314    av_tree_enumerate(c->root, NULL, NULL, enu_free);
315    av_tree_destroy(c->root);
316
317    return 0;
318}
319
320#define OFFSET(x) offsetof(Context, x)
321#define D AV_OPT_FLAG_DECODING_PARAM
322
323static const AVOption options[] = {
324    { "read_ahead_limit", "Amount in bytes that may be read ahead when seeking isn't supported, -1 for unlimited", OFFSET(read_ahead_limit), AV_OPT_TYPE_INT, { .i64 = 65536 }, -1, INT_MAX, D },
325    {NULL},
326};
327
328static const AVClass cache_context_class = {
329    .class_name = "cache",
330    .item_name  = av_default_item_name,
331    .option     = options,
332    .version    = LIBAVUTIL_VERSION_INT,
333};
334
335const URLProtocol ff_cache_protocol = {
336    .name                = "cache",
337    .url_open2           = cache_open,
338    .url_read            = cache_read,
339    .url_seek            = cache_seek,
340    .url_close           = cache_close,
341    .priv_data_size      = sizeof(Context),
342    .priv_data_class     = &cache_context_class,
343};