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/*
* Copyright (c) 1996, 1998 Robert Nordier
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR(S) ``AS IS'' AND ANY EXPRESS
* OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR(S) BE LIABLE FOR ANY
* DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
* GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER
* IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
* OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN
* IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
/*
* Readonly filesystem for Microsoft FAT12/FAT16/FAT32 filesystems,
* also supports VFAT.
*/
#include <sys/types.h>
#include <string.h>
#include <stddef.h>
#include "stand.h"
#include "disk.h"
#include "dosfs.h"
typedef struct dos_mnt {
char *dos_dev;
DOS_FS *dos_fs;
int dos_fd;
STAILQ_ENTRY(dos_mnt) dos_link;
} dos_mnt_t;
typedef STAILQ_HEAD(dos_mnt_list, dos_mnt) dos_mnt_list_t;
static dos_mnt_list_t mnt_list = STAILQ_HEAD_INITIALIZER(mnt_list);
static int dos_open(const char *path, struct open_file *fd);
static int dos_close(struct open_file *fd);
static int dos_read(struct open_file *fd, void *buf, size_t size, size_t *resid);
static off_t dos_seek(struct open_file *fd, off_t offset, int whence);
static int dos_stat(struct open_file *fd, struct stat *sb);
static int dos_readdir(struct open_file *fd, struct dirent *d);
static int dos_mount(const char *dev, const char *path, void **data);
static int dos_unmount(const char *dev, void *data);
struct fs_ops dosfs_fsops = {
.fs_name = "dosfs",
.fo_open = dos_open,
.fo_close = dos_close,
.fo_read = dos_read,
.fo_write = null_write,
.fo_seek = dos_seek,
.fo_stat = dos_stat,
.fo_readdir = dos_readdir,
.fo_mount = dos_mount,
.fo_unmount = dos_unmount
};
#define SECSIZ 512 /* sector size */
#define SSHIFT 9 /* SECSIZ shift */
#define DEPSEC 16 /* directory entries per sector */
#define DSHIFT 4 /* DEPSEC shift */
#define LOCLUS 2 /* lowest cluster number */
#define FATBLKSZ 0x20000 /* size of block in the FAT cache buffer */
/* DOS "BIOS Parameter Block" */
typedef struct {
u_char secsiz[2]; /* sector size */
u_char spc; /* sectors per cluster */
u_char ressec[2]; /* reserved sectors */
u_char fats; /* FATs */
u_char dirents[2]; /* root directory entries */
u_char secs[2]; /* total sectors */
u_char media; /* media descriptor */
u_char spf[2]; /* sectors per FAT */
u_char spt[2]; /* sectors per track */
u_char heads[2]; /* drive heads */
u_char hidsec[4]; /* hidden sectors */
u_char lsecs[4]; /* huge sectors */
u_char lspf[4]; /* huge sectors per FAT */
u_char xflg[2]; /* flags */
u_char vers[2]; /* filesystem version */
u_char rdcl[4]; /* root directory start cluster */
u_char infs[2]; /* filesystem info sector */
u_char bkbs[2]; /* backup boot sector */
} DOS_BPB;
/* Initial portion of DOS boot sector */
typedef struct {
u_char jmp[3]; /* usually 80x86 'jmp' opcode */
u_char oem[8]; /* OEM name and version */
DOS_BPB bpb; /* BPB */
} DOS_BS;
/* Supply missing "." and ".." root directory entries */
static const char *const dotstr[2] = {".", ".."};
static DOS_DE dot[2] = {
{". ", " ", FA_DIR, {0, 0, {0, 0}, {0, 0}, {0, 0}, {0, 0}},
{0, 0}, {0x21, 0}, {0, 0}, {0, 0, 0, 0}},
{".. ", " ", FA_DIR, {0, 0, {0, 0}, {0, 0}, {0, 0}, {0, 0}},
{0, 0}, {0x21, 0}, {0, 0}, {0, 0, 0, 0}}
};
/* The usual conversion macros to avoid multiplication and division */
#define bytsec(n) ((n) >> SSHIFT)
#define secbyt(s) ((s) << SSHIFT)
#define entsec(e) ((e) >> DSHIFT)
#define bytblk(fs, n) ((n) >> (fs)->bshift)
#define blkbyt(fs, b) ((b) << (fs)->bshift)
#define secblk(fs, s) ((s) >> ((fs)->bshift - SSHIFT))
#define blksec(fs, b) ((b) << ((fs)->bshift - SSHIFT))
/* Convert cluster number to offset within filesystem */
#define blkoff(fs, b) (secbyt((fs)->lsndta) + blkbyt(fs, (b) - LOCLUS))
/* Convert cluster number to logical sector number */
#define blklsn(fs, b) ((fs)->lsndta + blksec(fs, (b) - LOCLUS))
/* Convert cluster number to offset within FAT */
#define fatoff(sz, c) ((sz) == 12 ? (c) + ((c) >> 1) : \
(sz) == 16 ? (c) << 1 : \
(c) << 2)
/* Does cluster number reference a valid data cluster? */
#define okclus(fs, c) ((c) >= LOCLUS && (c) <= (fs)->xclus)
/* Get start cluster from directory entry */
#define stclus(sz, de) ((sz) != 32 ? cv2((de)->clus) : \
((u_int)cv2((de)->dex.h_clus) << 16) | \
cv2((de)->clus))
static int parsebs(DOS_FS *, DOS_BS *);
static int namede(DOS_FS *, const char *, DOS_DE **);
static int lookup(DOS_FS *, u_int, const char *, DOS_DE **);
static void cp_xdnm(u_char *, DOS_XDE *);
static void cp_sfn(u_char *, DOS_DE *);
static off_t fsize(DOS_FS *, DOS_DE *);
static int fatcnt(DOS_FS *, u_int);
static int fatget(DOS_FS *, u_int *);
static int fatend(u_int, u_int);
static int ioread(DOS_FS *, u_int, void *, size_t);
static int ioget(struct open_file *, daddr_t, void *, size_t);
static int
dos_read_fatblk(DOS_FS *fs, struct open_file *fd, u_int blknum)
{
int err;
size_t io_size;
daddr_t offset_in_fat, max_offset_in_fat;
offset_in_fat = ((daddr_t)blknum) * FATBLKSZ;
max_offset_in_fat = secbyt(fs->spf);
io_size = FATBLKSZ;
if (offset_in_fat > max_offset_in_fat)
offset_in_fat = max_offset_in_fat;
if (offset_in_fat + io_size > max_offset_in_fat)
io_size = ((size_t)(max_offset_in_fat - offset_in_fat));
if (io_size != 0) {
err = ioget(fd, fs->lsnfat + bytsec(offset_in_fat),
fs->fatbuf, io_size);
if (err != 0) {
fs->fatbuf_blknum = ((u_int)(-1));
return (err);
}
}
if (io_size < FATBLKSZ)
memset(fs->fatbuf + io_size, 0, FATBLKSZ - io_size);
fs->fatbuf_blknum = blknum;
return (0);
}
/*
* Mount DOS filesystem
*/
static int
dos_mount_impl(DOS_FS *fs, struct open_file *fd)
{
int err;
u_char *buf;
fs->fd = fd;
if ((buf = malloc(secbyt(1))) == NULL)
return (errno);
if ((err = ioget(fs->fd, 0, buf, secbyt(1))) ||
(err = parsebs(fs, (DOS_BS *)buf))) {
free(buf);
return (err);
}
free(buf);
if ((fs->fatbuf = malloc(FATBLKSZ)) == NULL)
return (errno);
err = dos_read_fatblk(fs, fd, 0);
if (err != 0) {
free(fs->fatbuf);
return (err);
}
fs->root = dot[0];
fs->root.name[0] = ' ';
if (fs->fatsz == 32) {
fs->root.clus[0] = fs->rdcl & 0xff;
fs->root.clus[1] = (fs->rdcl >> 8) & 0xff;
fs->root.dex.h_clus[0] = (fs->rdcl >> 16) & 0xff;
fs->root.dex.h_clus[1] = (fs->rdcl >> 24) & 0xff;
}
return (0);
}
static int
dos_mount(const char *dev, const char *path, void **data)
{
char *fs;
dos_mnt_t *mnt;
struct open_file *f;
DOS_FILE *df;
errno = 0;
mnt = calloc(1, sizeof(*mnt));
if (mnt == NULL)
return (errno);
mnt->dos_fd = -1;
mnt->dos_dev = strdup(dev);
if (mnt->dos_dev == NULL)
goto done;
if (asprintf(&fs, "%s%s", dev, path) < 0)
goto done;
mnt->dos_fd = open(fs, O_RDONLY);
free(fs);
if (mnt->dos_fd == -1)
goto done;
f = fd2open_file(mnt->dos_fd);
if (strcmp(f->f_ops->fs_name, "dosfs") == 0) {
df = f->f_fsdata;
mnt->dos_fs = df->fs;
STAILQ_INSERT_TAIL(&mnt_list, mnt, dos_link);
} else {
errno = ENXIO;
}
done:
if (errno != 0) {
free(mnt->dos_dev);
if (mnt->dos_fd >= 0)
close(mnt->dos_fd);
free(mnt);
} else {
*data = mnt;
}
return (errno);
}
static int
dos_unmount(const char *dev __unused, void *data)
{
dos_mnt_t *mnt = data;
STAILQ_REMOVE(&mnt_list, mnt, dos_mnt, dos_link);
free(mnt->dos_dev);
close(mnt->dos_fd);
free(mnt);
return (0);
}
/*
* Unmount mounted filesystem
*/
static int
dos_unmount_impl(DOS_FS *fs)
{
if (fs->links)
return (EBUSY);
free(fs->fatbuf);
free(fs);
return (0);
}
/*
* Open DOS file
*/
static int
dos_open(const char *path, struct open_file *fd)
{
DOS_DE *de;
DOS_FILE *f;
DOS_FS *fs;
dos_mnt_t *mnt;
const char *dev;
u_int size, clus;
int err;
dev = disk_fmtdev(fd->f_devdata);
STAILQ_FOREACH(mnt, &mnt_list, dos_link) {
if (strcmp(dev, mnt->dos_dev) == 0)
break;
}
if (mnt == NULL) {
/* Allocate mount structure, associate with open */
if ((fs = malloc(sizeof(DOS_FS))) == NULL)
return (errno);
if ((err = dos_mount_impl(fs, fd))) {
free(fs);
return (err);
}
} else {
fs = mnt->dos_fs;
}
if ((err = namede(fs, path, &de))) {
if (mnt == NULL)
dos_unmount_impl(fs);
return (err);
}
clus = stclus(fs->fatsz, de);
size = cv4(de->size);
if ((!(de->attr & FA_DIR) && (!clus != !size)) ||
((de->attr & FA_DIR) && size) ||
(clus && !okclus(fs, clus))) {
if (mnt == NULL)
dos_unmount_impl(fs);
return (EINVAL);
}
if ((f = calloc(1, sizeof(DOS_FILE))) == NULL) {
err = errno;
if (mnt == NULL)
dos_unmount_impl(fs);
return (err);
}
f->fs = fs;
fs->links++;
f->de = *de;
fd->f_fsdata = f;
return (0);
}
/*
* Read from file
*/
static int
dos_read(struct open_file *fd, void *buf, size_t nbyte, size_t *resid)
{
off_t size;
u_int nb, off, clus, c, cnt, n;
DOS_FILE *f = (DOS_FILE *)fd->f_fsdata;
int err = 0;
/*
* as ioget() can be called *a lot*, use twiddle here.
* also 4 seems to be good value not to slow loading down too much:
* with 270MB file (~540k ioget() calls, twiddle can easily waste
* 4-5 sec.
*/
twiddle(4);
nb = (u_int)nbyte;
if ((size = fsize(f->fs, &f->de)) == -1)
return (EINVAL);
if (nb > (n = size - f->offset))
nb = n;
off = f->offset;
if ((clus = stclus(f->fs->fatsz, &f->de)))
off &= f->fs->bsize - 1;
c = f->c;
cnt = nb;
while (cnt) {
n = 0;
if (!c) {
if ((c = clus))
n = bytblk(f->fs, f->offset);
} else if (!off)
n++;
while (n--) {
if ((err = fatget(f->fs, &c)))
goto out;
if (!okclus(f->fs, c)) {
err = EINVAL;
goto out;
}
}
if (!clus || (n = f->fs->bsize - off) > cnt)
n = cnt;
if ((err = ioread(f->fs, (c ? blkoff(f->fs, c) :
secbyt(f->fs->lsndir)) + off, buf, n)))
goto out;
f->offset += n;
f->c = c;
off = 0;
buf = (char *)buf + n;
cnt -= n;
}
out:
if (resid)
*resid = nbyte - nb + cnt;
return (err);
}
/*
* Reposition within file
*/
static off_t
dos_seek(struct open_file *fd, off_t offset, int whence)
{
off_t off;
u_int size;
DOS_FILE *f = (DOS_FILE *)fd->f_fsdata;
size = cv4(f->de.size);
switch (whence) {
case SEEK_SET:
off = 0;
break;
case SEEK_CUR:
off = f->offset;
break;
case SEEK_END:
off = size;
break;
default:
errno = EINVAL;
return (-1);
}
off += offset;
if (off < 0 || off > size) {
errno = EINVAL;
return (-1);
}
f->offset = (u_int)off;
f->c = 0;
return (off);
}
/*
* Close open file
*/
static int
dos_close(struct open_file *fd)
{
DOS_FILE *f = (DOS_FILE *)fd->f_fsdata;
DOS_FS *fs = f->fs;
f->fs->links--;
free(f);
dos_unmount_impl(fs);
return (0);
}
/*
* Return some stat information on a file.
*/
static int
dos_stat(struct open_file *fd, struct stat *sb)
{
DOS_FILE *f = (DOS_FILE *)fd->f_fsdata;
/* only important stuff */
sb->st_mode = f->de.attr & FA_DIR ? S_IFDIR | 0555 : S_IFREG | 0444;
sb->st_nlink = 1;
sb->st_uid = 0;
sb->st_gid = 0;
if ((sb->st_size = fsize(f->fs, &f->de)) == -1)
return (EINVAL);
return (0);
}
static int
dos_checksum(unsigned char *name, unsigned char *ext)
{
int x, i;
char buf[11];
bcopy(name, buf, 8);
bcopy(ext, buf+8, 3);
x = 0;
for (i = 0; i < 11; i++) {
x = ((x & 1) << 7) | (x >> 1);
x += buf[i];
x &= 0xff;
}
return (x);
}
static int
dos_readdir(struct open_file *fd, struct dirent *d)
{
/* DOS_FILE *f = (DOS_FILE *)fd->f_fsdata; */
u_char fn[261];
DOS_DIR dd;
size_t res;
u_int chk, x, xdn;
int err;
x = chk = 0;
for (;;) {
xdn = x;
x = 0;
err = dos_read(fd, &dd, sizeof(dd), &res);
if (err)
return (err);
if (res == sizeof(dd))
return (ENOENT);
if (dd.de.name[0] == 0)
return (ENOENT);
/* Skip deleted entries */
if (dd.de.name[0] == 0xe5)
continue;
/* Check if directory entry is volume label */
if (dd.de.attr & FA_LABEL) {
/*
* If volume label set, check if the current entry is
* extended entry (FA_XDE) for long file names.
*/
if ((dd.de.attr & FA_MASK) == FA_XDE) {
/*
* Read through all following extended entries
* to get the long file name. 0x40 marks the
* last entry containing part of long file name.
*/
if (dd.xde.seq & 0x40)
chk = dd.xde.chk;
else if (dd.xde.seq != xdn - 1 ||
dd.xde.chk != chk)
continue;
x = dd.xde.seq & ~0x40;
if (x < 1 || x > 20) {
x = 0;
continue;
}
cp_xdnm(fn, &dd.xde);
} else {
/* skip only volume label entries */
continue;
}
} else {
if (xdn == 1) {
x = dos_checksum(dd.de.name, dd.de.ext);
if (x == chk)
break;
} else {
cp_sfn(fn, &dd.de);
break;
}
x = 0;
}
}
d->d_fileno = (dd.de.clus[1] << 8) + dd.de.clus[0];
d->d_reclen = sizeof(*d);
d->d_type = (dd.de.attr & FA_DIR) ? DT_DIR : DT_REG;
memcpy(d->d_name, fn, sizeof(d->d_name));
return (0);
}
/*
* Parse DOS boot sector
*/
static int
parsebs(DOS_FS *fs, DOS_BS *bs)
{
u_int sc;
if ((bs->jmp[0] != 0x69 &&
bs->jmp[0] != 0xe9 &&
(bs->jmp[0] != 0xeb || bs->jmp[2] != 0x90)) ||
bs->bpb.media < 0xf0)
return (EINVAL);
if (cv2(bs->bpb.secsiz) != SECSIZ)
return (EINVAL);
if (!(fs->spc = bs->bpb.spc) || fs->spc & (fs->spc - 1))
return (EINVAL);
fs->bsize = secbyt(fs->spc);
fs->bshift = ffs(fs->bsize) - 1;
if ((fs->spf = cv2(bs->bpb.spf))) {
if (bs->bpb.fats != 2)
return (EINVAL);
if (!(fs->dirents = cv2(bs->bpb.dirents)))
return (EINVAL);
} else {
if (!(fs->spf = cv4(bs->bpb.lspf)))
return (EINVAL);
if (!bs->bpb.fats || bs->bpb.fats > 16)
return (EINVAL);
if ((fs->rdcl = cv4(bs->bpb.rdcl)) < LOCLUS)
return (EINVAL);
}
if (!(fs->lsnfat = cv2(bs->bpb.ressec)))
return (EINVAL);
fs->lsndir = fs->lsnfat + fs->spf * bs->bpb.fats;
fs->lsndta = fs->lsndir + entsec(fs->dirents);
if (!(sc = cv2(bs->bpb.secs)) && !(sc = cv4(bs->bpb.lsecs)))
return (EINVAL);
if (fs->lsndta > sc)
return (EINVAL);
if ((fs->xclus = secblk(fs, sc - fs->lsndta) + 1) < LOCLUS)
return (EINVAL);
fs->fatsz = fs->dirents ? fs->xclus < 0xff6 ? 12 : 16 : 32;
sc = (secbyt(fs->spf) << 1) / (fs->fatsz >> 2) - 1;
if (fs->xclus > sc)
fs->xclus = sc;
return (0);
}
/*
* Return directory entry from path
*/
static int
namede(DOS_FS *fs, const char *path, DOS_DE **dep)
{
char name[256];
DOS_DE *de;
char *s;
size_t n;
int err;
err = 0;
de = &fs->root;
while (*path) {
while (*path == '/')
path++;
if (*path == '\0')
break;
if (!(s = strchr(path, '/')))
s = strchr(path, 0);
if ((n = s - path) > 255)
return (ENAMETOOLONG);
memcpy(name, path, n);
name[n] = 0;
path = s;
if (!(de->attr & FA_DIR))
return (ENOTDIR);
if ((err = lookup(fs, stclus(fs->fatsz, de), name, &de)))
return (err);
}
*dep = de;
return (0);
}
/*
* Lookup path segment
*/
static int
lookup(DOS_FS *fs, u_int clus, const char *name, DOS_DE **dep)
{
static DOS_DIR dir[DEPSEC];
u_char lfn[261];
u_char sfn[13];
u_int nsec, lsec, xdn, chk, sec, ent, x;
int err, ok;
if (!clus)
for (ent = 0; ent < 2; ent++)
if (!strcasecmp(name, dotstr[ent])) {
*dep = dot + ent;
return (0);
}
if (!clus && fs->fatsz == 32)
clus = fs->rdcl;
nsec = !clus ? entsec(fs->dirents) : fs->spc;
lsec = 0;
xdn = chk = 0;
for (;;) {
if (!clus && !lsec)
lsec = fs->lsndir;
else if (okclus(fs, clus))
lsec = blklsn(fs, clus);
else
return (EINVAL);
for (sec = 0; sec < nsec; sec++) {
if ((err = ioget(fs->fd, lsec + sec, dir, secbyt(1))))
return (err);
for (ent = 0; ent < DEPSEC; ent++) {
if (!*dir[ent].de.name)
return (ENOENT);
if (*dir[ent].de.name != 0xe5) {
if ((dir[ent].de.attr & FA_MASK) ==
FA_XDE) {
x = dir[ent].xde.seq;
if (x & 0x40 || (x + 1 == xdn &&
dir[ent].xde.chk == chk)) {
if (x & 0x40) {
chk = dir[ent].xde.chk;
x &= ~0x40;
}
if (x >= 1 && x <= 20) {
cp_xdnm(lfn, &dir[ent].xde);
xdn = x;
continue;
}
}
} else if (!(dir[ent].de.attr &
FA_LABEL)) {
if ((ok = xdn == 1)) {
x = dos_checksum(
dir[ent].de.name,
dir[ent].de.ext);
ok = chk == x &&
!strcasecmp(name,
(const char *)lfn);
}
if (!ok) {
cp_sfn(sfn,
&dir[ent].de);
ok = !strcasecmp(name,
(const char *)sfn);
}
if (ok) {
*dep = &dir[ent].de;
return (0);
}
}
}
xdn = 0;
}
}
if (!clus)
break;
if ((err = fatget(fs, &clus)))
return (err);
if (fatend(fs->fatsz, clus))
break;
}
return (ENOENT);
}
/*
* Copy name from extended directory entry
*/
static void
cp_xdnm(u_char *lfn, DOS_XDE *xde)
{
static struct {
u_int off;
u_int dim;
} ix[3] = {
{offsetof(DOS_XDE, name1), sizeof(xde->name1) / 2},
{offsetof(DOS_XDE, name2), sizeof(xde->name2) / 2},
{offsetof(DOS_XDE, name3), sizeof(xde->name3) / 2}
};
u_char *p;
u_int n, x, c;
lfn += 13 * ((xde->seq & ~0x40) - 1);
for (n = 0; n < 3; n++)
for (p = (u_char *)xde + ix[n].off, x = ix[n].dim; x;
p += 2, x--) {
if ((c = cv2(p)) && (c < 32 || c > 127))
c = '?';
if (!(*lfn++ = c))
return;
}
if (xde->seq & 0x40)
*lfn = 0;
}
/*
* Copy short filename
*/
static void
cp_sfn(u_char *sfn, DOS_DE *de)
{
u_char *p;
int j, i;
p = sfn;
if (*de->name != ' ') {
for (j = 7; de->name[j] == ' '; j--)
;
for (i = 0; i <= j; i++)
*p++ = de->name[i];
if (*de->ext != ' ') {
*p++ = '.';
for (j = 2; de->ext[j] == ' '; j--)
;
for (i = 0; i <= j; i++)
*p++ = de->ext[i];
}
}
*p = 0;
if (*sfn == 5)
*sfn = 0xe5;
}
/*
* Return size of file in bytes
*/
static off_t
fsize(DOS_FS *fs, DOS_DE *de)
{
u_long size;
u_int c;
int n;
if (!(size = cv4(de->size)) && de->attr & FA_DIR) {
if (!(c = cv2(de->clus))) {
size = fs->dirents * sizeof(DOS_DE);
} else {
if ((n = fatcnt(fs, c)) == -1)
return (n);
size = blkbyt(fs, n);
}
}
return (size);
}
/*
* Count number of clusters in chain
*/
static int
fatcnt(DOS_FS *fs, u_int c)
{
int n;
for (n = 0; okclus(fs, c); n++)
if (fatget(fs, &c))
return (-1);
return (fatend(fs->fatsz, c) ? n : -1);
}
/*
* Get next cluster in cluster chain. Use in core fat cache unless
* the number of current 128K block in FAT has changed.
*/
static int
fatget(DOS_FS *fs, u_int *c)
{
u_int val_in, val_out, offset, blknum, nbyte;
const u_char *p_entry;
int err;
/* check input value to prevent overflow in fatoff() */
val_in = *c;
if (val_in & 0xf0000000)
return (EINVAL);
/* ensure that current 128K FAT block is cached */
offset = fatoff(fs->fatsz, val_in);
nbyte = fs->fatsz != 32 ? 2 : 4;
if (offset + nbyte > secbyt(fs->spf))
return (EINVAL);
blknum = offset / FATBLKSZ;
offset %= FATBLKSZ;
if (offset + nbyte > FATBLKSZ)
return (EINVAL);
if (blknum != fs->fatbuf_blknum) {
err = dos_read_fatblk(fs, fs->fd, blknum);
if (err != 0)
return (err);
}
p_entry = fs->fatbuf + offset;
/* extract cluster number from FAT entry */
switch (fs->fatsz) {
case 32:
val_out = cv4(p_entry);
val_out &= 0x0fffffff;
break;
case 16:
val_out = cv2(p_entry);
break;
case 12:
val_out = cv2(p_entry);
if (val_in & 1)
val_out >>= 4;
else
val_out &= 0xfff;
break;
default:
return (EINVAL);
}
*c = val_out;
return (0);
}
/*
* Is cluster an end-of-chain marker?
*/
static int
fatend(u_int sz, u_int c)
{
return (c > (sz == 12 ? 0xff7U : sz == 16 ? 0xfff7U : 0xffffff7));
}
/*
* Offset-based I/O primitive
*/
static int
ioread(DOS_FS *fs, u_int offset, void *buf, size_t nbyte)
{
char *s;
u_int off, n;
int err;
u_char local_buf[SECSIZ];
s = buf;
if ((off = offset & (SECSIZ - 1))) {
offset -= off;
if ((n = SECSIZ - off) > nbyte)
n = nbyte;
err = ioget(fs->fd, bytsec(offset), local_buf,
sizeof(local_buf));
if (err != 0)
return (err);
memcpy(s, local_buf + off, n);
offset += SECSIZ;
s += n;
nbyte -= n;
}
n = nbyte & (SECSIZ - 1);
if (nbyte -= n) {
if ((err = ioget(fs->fd, bytsec(offset), s, nbyte)))
return (err);
offset += nbyte;
s += nbyte;
}
if (n != 0) {
err = ioget(fs->fd, bytsec(offset), local_buf,
sizeof(local_buf));
if (err != 0)
return (err);
memcpy(s, local_buf, n);
}
return (0);
}
/*
* Sector-based I/O primitive
*/
static int
ioget(struct open_file *fd, daddr_t lsec, void *buf, size_t size)
{
size_t rsize;
int rv;
/* Make sure we get full read or error. */
rsize = 0;
rv = (fd->f_dev->dv_strategy)(fd->f_devdata, F_READ, lsec,
size, buf, &rsize);
if ((rv == 0) && (size != rsize))
rv = EIO;
return (rv);
}