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/* ----------------------------------------------------------------------- *
*
* Copyright 2004-2008 H. Peter Anvin - All Rights Reserved
*
* This program 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, Inc., 53 Temple Place Ste 330,
* Boston MA 02111-1307, USA; either version 2 of the License, or
* (at your option) any later version; incorporated herein by reference.
*
* ----------------------------------------------------------------------- */
/*
* open.c
*
* Open a FAT filesystem and compute some initial values; return NULL
* on failure.
*/
#include <stdlib.h>
#include "libfatint.h"
#include "ulint.h"
struct libfat_filesystem *
libfat_open(int (*readfunc) (intptr_t, void *, size_t, libfat_sector_t),
intptr_t readptr)
{
struct libfat_filesystem *fs = NULL;
struct fat_bootsect *bs;
int i;
uint32_t sectors, fatsize, minfatsize, rootdirsize;
uint32_t nclusters;
fs = malloc(sizeof(struct libfat_filesystem));
if (!fs)
goto barf;
fs->sectors = NULL;
fs->read = readfunc;
fs->readptr = readptr;
bs = libfat_get_sector(fs, 0);
if (!bs)
goto barf;
if (read16(&bs->bsBytesPerSec) != LIBFAT_SECTOR_SIZE)
goto barf;
for (i = 0; i <= 8; i++) {
if ((uint8_t) (1 << i) == read8(&bs->bsSecPerClust))
break;
}
if (i > 8)
goto barf;
fs->clustsize = 1 << i; /* Treat 0 as 2^8 = 64K */
fs->clustshift = i;
sectors = read16(&bs->bsSectors);
if (!sectors)
sectors = read32(&bs->bsHugeSectors);
fs->end = sectors;
fs->fat = read16(&bs->bsResSectors);
fatsize = read16(&bs->bsFATsecs);
if (!fatsize)
fatsize = read32(&bs->u.fat32.bpb_fatsz32);
fs->rootdir = fs->fat + fatsize * read8(&bs->bsFATs);
rootdirsize = ((read16(&bs->bsRootDirEnts) << 5) + LIBFAT_SECTOR_MASK)
>> LIBFAT_SECTOR_SHIFT;
fs->data = fs->rootdir + rootdirsize;
/* Sanity checking */
if (fs->data >= fs->end)
goto barf;
/* Figure out how many clusters */
nclusters = (fs->end - fs->data) >> fs->clustshift;
fs->endcluster = nclusters + 2;
if (nclusters <= 0xff4) {
fs->fat_type = FAT12;
minfatsize = fs->endcluster + (fs->endcluster >> 1);
} else if (nclusters <= 0xfff4) {
fs->fat_type = FAT16;
minfatsize = fs->endcluster << 1;
} else if (nclusters <= 0xffffff4) {
fs->fat_type = FAT28;
minfatsize = fs->endcluster << 2;
} else
goto barf; /* Impossibly many clusters */
minfatsize = (minfatsize + LIBFAT_SECTOR_SIZE - 1) >> LIBFAT_SECTOR_SHIFT;
if (minfatsize > fatsize)
goto barf; /* The FATs don't fit */
if (fs->fat_type == FAT28)
fs->rootcluster = read32(&bs->u.fat32.bpb_rootclus);
else
fs->rootcluster = 0;
return fs; /* All good */
barf:
if (fs)
free(fs);
return NULL;
}
void libfat_close(struct libfat_filesystem *fs)
{
libfat_flush(fs);
free(fs);
}
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