/* fetch data from target, from given offset */
int cache_fetch_data(Cache *cache, unsigned int offset) {
int i, nb=-1;
unsigned int min;
mylog("cache_fetch_data(%p, %u)\n", cache, offset);
/* search for a free chunk */
for(i=0; i<cache_chunks; i++) {
if (cache->chunks[i] == NULL) {
nb = i;
break;
}
}
mylog("cache_fetch: found empty chunk slot %d\n", nb);
if (nb < 0) {
/* none free? use the smallest offset (assume seq. read - should use older) */
min = cache->chunks[0]->off_start;
nb = 0;
for(i=1; i<cache_chunks; i++) {
if (cache->chunks[i]->off_start < min) {
min = cache->chunks[i]->off_start;
nb = i;
}
}
} else {
/* allocate the chunk */
cache->chunks[nb] = malloc(sizeof(Chunk));
if (cache->chunks[nb] == NULL) {
return(0);
}
cache->chunks[nb]->off_start = 0;
cache->chunks[nb]->off_end = 0;
cache->chunks[nb]->data = malloc(cache_chunksize);
if (cache->chunks[nb]->data == NULL) {
free(cache->chunks[nb]);
cache->chunks[nb] = NULL;
return(0);
}
mylog("cache_fetch: chunk %d allocated (size=%d) [%p-%p[\n", nb, cache_chunksize,
cache->chunks[nb]->data, cache->chunks[nb]->data+cache_chunksize);
}
/* set new values */
cache->chunks[nb]->off_start = offset;
mylog("cache_fetch: put start=%u\n", offset);
if (offset+cache_chunksize > cache->size) {
/* after end of file. reduce */
cache->chunks[nb]->off_end = cache->size - 1;
} else {
cache->chunks[nb]->off_end = offset + cache_chunksize - 1;
}
mylog("cache_fetch: put end=%u\n", cache->chunks[nb]->off_end);
/* perform read */
mylog("cache_fetch: performing do_read (%p, %d)\n", cache, nb);
if (!cache_do_read(cache, nb)) {
/* argl. this chunk is no more valid. destroy it */
cache_chunk_free(cache->chunks[nb]);
cache->chunks[nb] = NULL;
return(0);
}
return(1);
}
errno_t cache_get( cache_t *c, long blk, void *data )
{
return cache_do_read( c, blk, data );
}