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avformat/cache: Support user specified read-ahead for non seekable media

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Fixes Ticket2406

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
This commit is contained in:
Michael Niedermayer 2014-12-25 21:39:51 +01:00
parent 7018d3d351
commit 8706910c4c
1 changed files with 41 additions and 1 deletions
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42
libavformat/cache.c
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@ -30,6 +30,7 @@
#include "libavutil/avassert.h"
#include "libavutil/avstring.h"
#include "libavutil/file.h"
#include "libavutil/opt.h"
#include "libavutil/tree.h"
#include "avformat.h"
#include <fcntl.h>
@ -51,6 +52,7 @@ typedef struct CacheEntry {
} CacheEntry;
typedef struct Context {
AVClass *class;
int fd;
struct AVTreeNode *root;
int64_t logical_pos;
@ -60,6 +62,7 @@ typedef struct Context {
int is_true_eof;
URLContext *inner;
int64_t cache_hit, cache_miss;
int read_ahead_limit;
} Context;
static int cmp(void *key, const void *node)
@ -214,6 +217,7 @@ static int64_t cache_seek(URLContext *h, int64_t pos, int whence)
whence = SEEK_SET;
pos += c->logical_pos;
} else if (whence == SEEK_END && c->is_true_eof) {
resolve_eof:
whence = SEEK_SET;
pos += c->end;
}
@ -226,6 +230,27 @@ static int64_t cache_seek(URLContext *h, int64_t pos, int whence)
//cache miss
ret= ffurl_seek(c->inner, pos, whence);
if ((whence == SEEK_SET && pos >= c->logical_pos ||
whence == SEEK_END && pos <= 0) && ret < 0) {
if ( (whence == SEEK_SET && c->read_ahead_limit >= pos - c->logical_pos)
|| c->read_ahead_limit < 0) {
uint8_t tmp[32768];
while (c->logical_pos < pos || whence == SEEK_END) {
int size = sizeof(tmp);
if (whence == SEEK_SET)
size = FFMIN(sizeof(tmp), pos - c->logical_pos);
ret = cache_read(h, tmp, size);
if (ret == 0 && whence == SEEK_END) {
av_assert0(c->is_true_eof);
goto resolve_eof;
}
if (ret < 0) {
return ret;
}
}
return c->logical_pos;
}
}
if (ret >= 0) {
c->logical_pos = ret;
@ -246,10 +271,24 @@ static int cache_close(URLContext *h)
ffurl_close(c->inner);
av_tree_destroy(c->root);
return 0;
}
#define OFFSET(x) offsetof(Context, x)
#define D AV_OPT_FLAG_DECODING_PARAM
static const AVOption options[] = {
{ "read_ahead_limit", "Amount in bytes that may be read ahead when seeking isnt supported, -1 for unlimited", OFFSET(read_ahead_limit), AV_OPT_TYPE_INT, { .i64 = 65536 }, -1, INT_MAX, D },
{NULL},
};
static const AVClass cache_context_class = {
.class_name = "Cache",
.item_name = av_default_item_name,
.option = options,
.version = LIBAVUTIL_VERSION_INT,
};
URLProtocol ff_cache_protocol = {
.name = "cache",
.url_open = cache_open,
@ -257,4 +296,5 @@ URLProtocol ff_cache_protocol = {
.url_seek = cache_seek,
.url_close = cache_close,
.priv_data_size = sizeof(Context),
.priv_data_class = &cache_context_class,
};