+
+int exfat_get_next_clus(struct exfat *exfat, clus_t clus, clus_t *next)
+{
+ off_t offset;
+
+ *next = EXFAT_EOF_CLUSTER;
+
+ if (!exfat_heap_clus(exfat, clus))
+ return -EINVAL;
+
+ offset = (off_t)le32_to_cpu(exfat->bs->bsx.fat_offset) <<
+ exfat->bs->bsx.sect_size_bits;
+ offset += sizeof(clus_t) * clus;
+
+ if (exfat_read(exfat->blk_dev->dev_fd, next, sizeof(*next), offset)
+ != sizeof(*next))
+ return -EIO;
+ *next = le32_to_cpu(*next);
+ return 0;
+}
+
+int exfat_get_inode_next_clus(struct exfat *exfat, struct exfat_inode *node,
+ clus_t clus, clus_t *next)
+{
+ *next = EXFAT_EOF_CLUSTER;
+
+ if (node->is_contiguous) {
+ if (!exfat_heap_clus(exfat, clus))
+ return -EINVAL;
+ *next = clus + 1;
+ return 0;
+ }
+
+ return exfat_get_next_clus(exfat, clus, next);
+}
+
+int exfat_set_fat(struct exfat *exfat, clus_t clus, clus_t next_clus)
+{
+ off_t offset;
+
+ offset = le32_to_cpu(exfat->bs->bsx.fat_offset) <<
+ exfat->bs->bsx.sect_size_bits;
+ offset += sizeof(clus_t) * clus;
+
+ if (exfat_write(exfat->blk_dev->dev_fd, &next_clus, sizeof(next_clus),
+ offset) != sizeof(next_clus))
+ return -EIO;
+ return 0;
+}
+
+off_t exfat_s2o(struct exfat *exfat, off_t sect)
+{
+ return sect << exfat->bs->bsx.sect_size_bits;
+}
+
+off_t exfat_c2o(struct exfat *exfat, unsigned int clus)
+{
+ if (clus < EXFAT_FIRST_CLUSTER)
+ return ~0L;
+
+ return exfat_s2o(exfat, le32_to_cpu(exfat->bs->bsx.clu_offset) +
+ ((off_t)(clus - EXFAT_FIRST_CLUSTER) <<
+ exfat->bs->bsx.sect_per_clus_bits));
+}
+
+int exfat_o2c(struct exfat *exfat, off_t device_offset,
+ unsigned int *clu, unsigned int *offset)
+{
+ off_t heap_offset;
+
+ heap_offset = exfat_s2o(exfat, le32_to_cpu(exfat->bs->bsx.clu_offset));
+ if (device_offset < heap_offset)
+ return -ERANGE;
+
+ *clu = (unsigned int)((device_offset - heap_offset) /
+ exfat->clus_size) + EXFAT_FIRST_CLUSTER;
+ if (!exfat_heap_clus(exfat, *clu))
+ return -ERANGE;
+ *offset = (device_offset - heap_offset) % exfat->clus_size;
+ return 0;
+}
+
+bool exfat_heap_clus(struct exfat *exfat, clus_t clus)
+{
+ return clus >= EXFAT_FIRST_CLUSTER &&
+ (clus - EXFAT_FIRST_CLUSTER) < exfat->clus_count;
+}
+
+int exfat_root_clus_count(struct exfat *exfat)
+{
+ struct exfat_inode *node = exfat->root;
+ clus_t clus, next;
+ int clus_count = 0;
+
+ if (!exfat_heap_clus(exfat, node->first_clus))
+ return -EIO;
+
+ clus = node->first_clus;
+ do {
+ if (exfat_bitmap_get(exfat->alloc_bitmap, clus))
+ return -EINVAL;
+
+ exfat_bitmap_set(exfat->alloc_bitmap, clus);
+
+ if (exfat_get_inode_next_clus(exfat, node, clus, &next)) {
+ exfat_err("ERROR: failed to read the fat entry of root");
+ return -EIO;
+ }
+
+ if (next != EXFAT_EOF_CLUSTER && !exfat_heap_clus(exfat, next))
+ return -EINVAL;
+
+ clus = next;
+ clus_count++;
+ } while (clus != EXFAT_EOF_CLUSTER);
+
+ node->size = clus_count * exfat->clus_size;
+ return 0;
+}
+
+int read_boot_sect(struct exfat_blk_dev *bdev, struct pbr **bs)
+{
+ struct pbr *pbr;
+ int err = 0;
+ unsigned int sect_size, clu_size;
+
+ pbr = malloc(sizeof(struct pbr));
+
+ if (exfat_read(bdev->dev_fd, pbr, sizeof(*pbr), 0) !=
+ (ssize_t)sizeof(*pbr)) {
+ exfat_err("failed to read a boot sector\n");
+ err = -EIO;
+ goto err;
+ }
+
+ err = -EINVAL;
+ if (memcmp(pbr->bpb.oem_name, "EXFAT ", 8) != 0) {
+ exfat_err("failed to find exfat file system\n");
+ goto err;
+ }
+
+ sect_size = 1 << pbr->bsx.sect_size_bits;
+ clu_size = 1 << (pbr->bsx.sect_size_bits +
+ pbr->bsx.sect_per_clus_bits);
+
+ if (sect_size < 512 || sect_size > 4 * KB) {
+ exfat_err("too small or big sector size: %d\n",
+ sect_size);
+ goto err;
+ }
+
+ if (clu_size < sect_size || clu_size > 32 * MB) {
+ exfat_err("too small or big cluster size: %d\n",
+ clu_size);
+ goto err;
+ }
+
+ *bs = pbr;
+ return 0;
+err:
+ free(pbr);
+ return err;
+}