illumos gate

http://src.illumos.org/source/xref/illumos-gate/usr/src/cmd/zdb/zdb.c#zdb_read_block

This function provides for "zdb -R poolname vdev:offset:psize:b" flag option to interpret the on-disk data as a block pointer and output its contents in human-readable form. This works for the first blkptr_t in the block (at offset 0x0 from the on-disk block's start).

This function does not seem to actually accept specification of optional non-zero offsets in neither decimal nor hex forms, even though the code provides for that:

root@openindiana:~# zdb -R pool 0:822002f000:4000:bb19456
Invalid flag: 1
*Invalid flag: 9
Invalid flag: 4
Invalid flag: 5
**Invalid flag: 6
Found vdev type: raidz
<hole>

root@openindiana:~# zdb -R pool 0:acbe2201000:4000:b0x7000
Invalid flag: 0
*Invalid flag: x
Invalid flag: 7
Invalid flag: 0
Invalid flag: 0
*Invalid flag: 0
Found vdev type: raidz
<hole>