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/* Interpretation of indirect block structure
Copyright (C) 1994 Free Software Foundation, Inc.
Written by Michael I. Bushnell.
This file is part of the GNU Hurd.
The GNU Hurd is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License as
published by the Free Software Foundation; either version 2, or (at
your option) any later version.
The GNU Hurd is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. */
#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;
}
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