/** Allocate clusters in FAT.
*
* This function will attempt to allocate the requested number of clusters in
* the FAT. The FAT will be altered so that the allocated
* clusters form an independent chain (i.e. a chain which does not belong to any
* file yet).
*
* @param bs Buffer holding the boot sector of the file system.
* @param service_id Service ID of the file system.
* @param nclsts Number of clusters to allocate.
* @param mcl Output parameter where the first cluster in the chain
* will be returned.
* @param lcl Output parameter where the last cluster in the chain
* will be returned.
*
* @return EOK on success, a negative error code otherwise.
*/
int
exfat_alloc_clusters(exfat_bs_t *bs, service_id_t service_id, unsigned nclsts,
exfat_cluster_t *mcl, exfat_cluster_t *lcl)
{
exfat_cluster_t *lifo; /* stack for storing free cluster numbers */
unsigned found = 0; /* top of the free cluster number stack */
exfat_cluster_t clst;
int rc = EOK;
lifo = (exfat_cluster_t *) malloc(nclsts * sizeof(exfat_cluster_t));
if (!lifo)
return ENOMEM;
fibril_mutex_lock(&exfat_alloc_lock);
for (clst = EXFAT_CLST_FIRST; clst < DATA_CNT(bs) + 2 && found < nclsts;
clst++) {
/* Need to rewrite because of multiple exfat_bitmap_get calls */
if (exfat_bitmap_is_free(bs, service_id, clst) == EOK) {
/*
* The cluster is free. Put it into our stack
* of found clusters and mark it as non-free.
*/
lifo[found] = clst;
rc = exfat_set_cluster(bs, service_id, clst,
(found == 0) ? EXFAT_CLST_EOF : lifo[found - 1]);
if (rc != EOK)
goto exit_error;
found++;
rc = exfat_bitmap_set_cluster(bs, service_id, clst);
if (rc != EOK)
goto exit_error;
}
}
if (rc == EOK && found == nclsts) {
*mcl = lifo[found - 1];
*lcl = lifo[0];
free(lifo);
fibril_mutex_unlock(&exfat_alloc_lock);
return EOK;
}
rc = ENOSPC;
exit_error:
/* If something wrong - free the clusters */
while (found--) {
(void) exfat_bitmap_clear_cluster(bs, service_id, lifo[found]);
(void) exfat_set_cluster(bs, service_id, lifo[found], 0);
}
free(lifo);
fibril_mutex_unlock(&exfat_alloc_lock);
return rc;
}
int exfat_bitmap_alloc_clusters(exfat_bs_t *bs, service_id_t service_id,
exfat_cluster_t *firstc, exfat_cluster_t count)
{
exfat_cluster_t startc, endc;
startc = EXFAT_CLST_FIRST;
while (startc < DATA_CNT(bs) + 2) {
endc = startc;
while (exfat_bitmap_is_free(bs, service_id, endc) == EOK) {
if ((endc - startc) + 1 == count) {
*firstc = startc;
return exfat_bitmap_set_clusters(bs, service_id, startc, count);
} else
endc++;
}
startc = endc+1;
}
return ENOSPC;
}
int exfat_bitmap_append_clusters(exfat_bs_t *bs, exfat_node_t *nodep,
exfat_cluster_t count)
{
if (nodep->firstc == 0) {
return exfat_bitmap_alloc_clusters(bs, nodep->idx->service_id,
&nodep->firstc, count);
} else {
exfat_cluster_t lastc, clst;
lastc = nodep->firstc + ROUND_UP(nodep->size, BPC(bs)) / BPC(bs) - 1;
clst = lastc + 1;
while (exfat_bitmap_is_free(bs, nodep->idx->service_id, clst) == EOK) {
if (clst - lastc == count){
return exfat_bitmap_set_clusters(bs, nodep->idx->service_id,
lastc + 1, count);
} else
clst++;
}
return ENOSPC;
}
}