1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
|
/* ----------------------------------------------------------------------- *
*
* Copyright 2004 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);
}
|
