Finding Next Cluster

After reading the current cluster, how can we advance to the next cluster?

Answer: by checking the FAT table. With the current cluster number, we can get the next cluster in FAT, or a EOF.

How can we know the terminating condition? There are three conditions in total. If we encounter these during search, that means it reaches the end.

1. End of File

   EOF

   (0x0ffffff8)

2. Damaged (Bad Cluster Mark) (0x0ffffff7)

3. Unallocated (0x0)

uint32_t next_cluster(FILE *fp, off_t fat_offset, uint32_t current_cluster) {
    uint32_t next_cluster_number = 0;
    fseek(fp, fat_offset + current_cluster * sizeof next_cluster_number,
          SEEK_SET);
    size_t ret = fread(&next_cluster_number, 1, sizeof next_cluster_number, fp);
    return next_cluster_number;
}