diff options
| -rw-r--r-- | ufs/bmap.c | 79 |
1 files changed, 79 insertions, 0 deletions
@@ -22,3 +22,82 @@ #include "ufs.h" #include "dinode.h" #include "fs.h" + +/* Number of block pointers that fit in a single disk block */ +#define NIPTR (sblock->fs_bsize / sizeof (daddr_t)) + +/* For logical block number LBN of file NP, look it the block address, + giving the "path" of indirect blocks to the file, starting + with the least indirect. Fill *INDIRS with information for + the block. */ +error_t +fetch_indir_spec (struct node *np, daddr_t lbn, struct iblock_spec *indirs) +{ + struct dinode *di = dino (np->dn->number); + int boff; + error_t err; + daddr_t *siblock; + + if (err = diskfs_catch_exception ()) + return err; + + if (lbn < NDADDR) + { + indirs[0].bno = di->di_db[lbn]; + indirs[0].offset = -1; + + diskfs_end_catch_exception (); + return 0; + } + + lbn -= NDADDR; + + indirs[0].offset = lbn % NIPTR; + + if (lbn / NIPTR) + { + /* We will use the double indirect block */ + int ibn; + daddr_t *diblock; + + ibn = lbn / NIPTR - 1; + + indirs[1].offset = ibn % NIPTR; + + /* We don't support triple indirect blocks, but this + is where we'd do it. */ + assert (!(ibn / NIPTR)); + + indirs[2].offset = -1; + indirs[2].bno = di->di_ib[INDIR_DOUBLE]; + + if (indirs[2].bno) + { + diblock = indir_block (indirs[2].bno); + indirs[1].bno = diblock[indirs[1].offset]; + } + else + indirs[1].bno = 0; + } + else + { + indirs[1].offset = -1; + indirs[1].bno = di->di_ib[INDIR_DOUBLE]; + } + + if (indirs[1].bno) + { + siblock = indir_block (indirs[1].bno); + indirs[0].bno = siblock[indirs[0].offset]; + } + else + indirs[0].bno = 0; + + diskfs_end_catch_exception (); + return 0; +} + + + + + |