uint32_t reallocate_cluster_chain(uint32_t first_cluster, uint32_t new_size) {
uint32_t next_cluster = first_cluster;
uint32_t current_size = BYTES_PER_CLUSTER;
uint8_t extending = 0;
while (current_size < new_size) {
if (FAT_ENTRIES[next_cluster] == FAT_EOFC_ENTRY) {
// new size is larger than previous so extend the cluster
extending = 1;
}
if (extending == 1) {
FAT_ENTRIES[next_cluster] = find_free_cluster();
DIR_ENTRIES[next_cluster] = DIR_ENTRIES[first_cluster];
}
next_cluster = FAT_ENTRIES[next_cluster];
current_size += BYTES_PER_CLUSTER;
}
if (extending == 0 && FAT_ENTRIES[next_cluster] != FAT_EOFC_ENTRY) {
// free clusters since we have shrunk current chain
free_cluster_chain(FAT_ENTRIES[next_cluster]);
}
FAT_ENTRIES[next_cluster] = FAT_EOFC_ENTRY;
DIR_ENTRIES[next_cluster] = DIR_ENTRIES[first_cluster];
return first_cluster;
}
int syscall_unlink(const char *pathname)
{
int drive;
int curdir_handle;
char name_comp[13], conv_name[11], dir_path[501];
struct dir_entry dent;
int err;
if (strlen(pathname) > 500) return ELONGPATH;
parse_path(pathname, &drive, dir_path, name_comp);
if (dir_path[0] != 0)
{
curdir_handle = open_path(drive, dir_path);
if (curdir_handle < 0)
return curdir_handle; // Error
}
else
{
curdir_handle = get_curdir_handle(drive);
increment_ref_count(curdir_handle);
}
// Last file name component.
if (convert_name(name_comp, conv_name) < 0)
{
err = EINVALIDNAME; // Error
}
else if (find_entry(curdir_handle, conv_name, &dent) == 1)
{ // Check whether it is a deletable file
if ((dent.attrib & (FTYPE_READONLY | FTYPE_DIR | FTYPE_VOLUME)) == 0)
{
delete_dir_entry(curdir_handle, conv_name);
free_cluster_chain(dent.start_cluster);
err = 0;
}
else
{
err = EACCESS; // Error
}
}
else
{
err = EFILE_NOT_FOUND;
}
close_dir(curdir_handle);
return err;
}
void filesystem::free_cluster_chain(uint32_t cluster)
{
if(cluster == 2)
throw std::runtime_error("Cluster 2 can't be freed");
if(cluster / CLUSTERS_PER_SUPER >= supercluster_count)
throw std::runtime_error("Bad cluster to free");
uint32_t oldnext = superclusters[cluster / CLUSTERS_PER_SUPER].clusters[cluster % CLUSTERS_PER_SUPER];
if(oldnext == 0)
throw std::runtime_error("Attempted to free free cluster");
if(oldnext == 0xFFFFFFFFU)
throw std::runtime_error("Attempted to free system cluster");
superclusters[cluster / CLUSTERS_PER_SUPER].clusters[cluster % CLUSTERS_PER_SUPER] = 0;
//If there is no next block, or the next block is in different supercluster, save the cluster table.
if(oldnext == 1 || oldnext / CLUSTERS_PER_SUPER != cluster / CLUSTERS_PER_SUPER)
superclusters[cluster / CLUSTERS_PER_SUPER].save(backing, cluster / CLUSTERS_PER_SUPER);
if(oldnext != 1)
free_cluster_chain(oldnext);
}