ext2/3 Block Semantics

[dsoprea]

I'm having a hard-time finding clarification on ind/dind/tind blocks. Could you provide an explanation or a URL?

https://github.com/gerard/ext4fuse/blob/master/inode.c#L25:

/* These #defines are only relevant for ext2/3 style block indexing */
#define ADDRESSES_IN_IND_BLOCK      (BLOCK_SIZE / sizeof(uint32_t))
#define ADDRESSES_IN_DIND_BLOCK     (ADDRESSES_IN_IND_BLOCK * ADDRESSES_IN_IND_BLOCK)
#define ADDRESSES_IN_TIND_BLOCK     (ADDRESSES_IN_DIND_BLOCK * ADDRESSES_IN_IND_BLOCK)
#define MAX_IND_BLOCK               (EXT4_NDIR_BLOCKS + ADDRESSES_IN_IND_BLOCK)
#define MAX_DIND_BLOCK              (MAX_IND_BLOCK + ADDRESSES_IN_DIND_BLOCK)
#define MAX_TIND_BLOCK              (MAX_DIND_BLOCK + ADDRESSES_IN_TIND_BLOCK)