1 /* $NetBSD: dosfs.c,v 1.20 2014/03/20 03:13:18 christos Exp $ */
2
3 /*
4 * Copyright (c) 1996, 1998 Robert Nordier
5 * All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 * 1. Redistributions of source code must retain the above copyright
11 * notice, this list of conditions and the following disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 * notice, this list of conditions and the following disclaimer in
14 * the documentation and/or other materials provided with the
15 * distribution.
16 *
17 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR(S) ``AS IS'' AND ANY EXPRESS
18 * OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
19 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR(S) BE LIABLE FOR ANY
21 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
23 * GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
24 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER
25 * IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
26 * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN
27 * IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
28 */
29
30 /*
31 * Readonly filesystem for Microsoft FAT12/FAT16/FAT32 filesystems,
32 * also supports VFAT.
33 */
34
35 /*
36 * XXX DOES NOT SUPPORT:
37 *
38 * LIBSA_FS_SINGLECOMPONENT
39 */
40
41 #include <sys/param.h>
42
43 #include <fs/msdosfs/bpb.h>
44 #include <fs/msdosfs/direntry.h>
45
46 #ifdef _STANDALONE
47 #include <lib/libkern/libkern.h>
48 #else
49 #include <string.h>
50 #include <stddef.h>
51 #endif
52
53 #include "stand.h"
54 #include "dosfs.h"
55
56 #define SECSIZ 512 /* sector size */
57 #define SSHIFT 9 /* SECSIZ shift */
58 #define DEPSEC 16 /* directory entries per sector */
59 #define DSHIFT 4 /* DEPSEC shift */
60 #define LOCLUS 2 /* lowest cluster number */
61
62 typedef union {
63 struct direntry de; /* standard directory entry */
64 struct winentry xde; /* extended directory entry */
65 } DOS_DIR;
66
67 typedef struct {
68 struct open_file *fd; /* file descriptor */
69 u_char *buf; /* buffer */
70 u_int bufsec; /* buffered sector */
71 u_int links; /* active links to structure */
72 u_int spc; /* sectors per cluster */
73 u_int bsize; /* cluster size in bytes */
74 u_int bshift; /* cluster conversion shift */
75 u_int dirents; /* root directory entries */
76 u_int spf; /* sectors per fat */
77 u_int rdcl; /* root directory start cluster */
78 u_int lsnfat; /* start of fat */
79 u_int lsndir; /* start of root dir */
80 u_int lsndta; /* start of data area */
81 u_int fatsz; /* FAT entry size */
82 u_int xclus; /* maximum cluster number */
83 } DOS_FS;
84
85 typedef struct {
86 DOS_FS *fs; /* associated filesystem */
87 struct direntry de; /* directory entry */
88 u_int offset; /* current offset */
89 u_int c; /* last cluster read */
90 } DOS_FILE;
91
92 /* Initial portion of DOS boot sector */
93 typedef struct {
94 u_char jmp[3]; /* usually 80x86 'jmp' opcode */
95 u_char oem[8]; /* OEM name and version */
96 struct byte_bpb710 bpb; /* BPB */
97 } DOS_BS;
98
99 /* Supply missing "." and ".." root directory entries */
100 static const char *const dotstr[2] = {".", ".."};
101 static const struct direntry dot[2] = {
102 {". ", " ", ATTR_DIRECTORY,
103 0, 0, {0, 0}, {0, 0}, {0, 0}, {0, 0},
104 {0, 0}, {0x21, 0}, {0, 0}, {0, 0, 0, 0}},
105
106 {".. ", " ", ATTR_DIRECTORY,
107 0, 0, {0, 0}, {0, 0}, {0, 0}, {0, 0},
108 {0, 0}, {0x21, 0}, {0, 0}, {0, 0, 0, 0}}
109 };
110
111 /* The usual conversion macros to avoid multiplication and division */
112 #define bytsec(n) ((n) >> SSHIFT)
113 #define secbyt(s) ((s) << SSHIFT)
114 #define entsec(e) ((e) >> DSHIFT)
115 #define bytblk(fs, n) ((n) >> (fs)->bshift)
116 #define blkbyt(fs, b) ((b) << (fs)->bshift)
117 #define secblk(fs, s) ((s) >> ((fs)->bshift - SSHIFT))
118 #define blksec(fs, b) ((b) << ((fs)->bshift - SSHIFT))
119
120 /* Convert cluster number to offset within filesystem */
121 #define blkoff(fs, b) (secbyt((fs)->lsndta) + blkbyt(fs, (b) - LOCLUS))
122
123 /* Convert cluster number to logical sector number */
124 #define blklsn(fs, b) ((fs)->lsndta + blksec(fs, (b) - LOCLUS))
125
126 /* Convert cluster number to offset within FAT */
127 #define fatoff(sz, c) ((sz) == 12 ? (c) + ((c) >> 1) : \
128 (sz) == 16 ? (c) << 1 : \
129 (c) << 2)
130
131 /* Does cluster number reference a valid data cluster? */
132 #define okclus(fs, c) ((c) >= LOCLUS && (c) <= (fs)->xclus)
133
134 /* Get start cluster from directory entry */
135 #define stclus(sz, de) ((sz) != 32 ? (u_int)getushort((de)->deStartCluster) : \
136 ((u_int)getushort((de)->deHighClust) << 16) | \
137 (u_int)getushort((de)->deStartCluster))
138
139 static int dosunmount(DOS_FS *);
140 static int parsebs(DOS_FS *, DOS_BS *);
141 static int namede(DOS_FS *, const char *, const struct direntry **);
142 static int lookup(DOS_FS *, u_int, const char *, const struct direntry **);
143 static void cp_xdnm(u_char *, struct winentry *);
144 static void cp_sfn(u_char *, struct direntry *);
145 static off_t fsize(DOS_FS *, struct direntry *);
146 static int fatcnt(DOS_FS *, u_int);
147 static int fatget(DOS_FS *, u_int *);
148 static int fatend(u_int, u_int);
149 static int ioread(DOS_FS *, u_int, void *, u_int);
150 static int iobuf(DOS_FS *, u_int);
151 static int ioget(struct open_file *, u_int, void *, u_int);
152
153 #define strcasecmp(s1, s2) dos_strcasecmp(s1, s2)
154 static int
strcasecmp(const char * s1,const char * s2)155 strcasecmp(const char *s1, const char *s2)
156 {
157 char c1, c2;
158 #define TO_UPPER(c) ((c) >= 'a' && (c) <= 'z' ? (c) - ('a' - 'A') : (c))
159 for (;;) {
160 c1 = *s1++;
161 c2 = *s2++;
162 if (TO_UPPER(c1) != TO_UPPER(c2))
163 return 1;
164 if (c1 == 0)
165 return 0;
166 }
167 #undef TO_UPPER
168 }
169
170 /*
171 * Mount DOS filesystem
172 */
173 static int
dos_mount(DOS_FS * fs,struct open_file * fd)174 dos_mount(DOS_FS *fs, struct open_file *fd)
175 {
176 int err;
177
178 (void)memset(fs, 0, sizeof(DOS_FS));
179 fs->fd = fd;
180 if ((err = !(fs->buf = alloc(SECSIZ)) ? errno : 0) ||
181 (err = ioget(fs->fd, 0, fs->buf, 1)) ||
182 (err = parsebs(fs, (DOS_BS *)fs->buf))) {
183 (void) dosunmount(fs);
184 return err;
185 }
186 return 0;
187 }
188
189 #ifndef LIBSA_NO_FS_CLOSE
190 /*
191 * Unmount mounted filesystem
192 */
193 static int
dos_unmount(DOS_FS * fs)194 dos_unmount(DOS_FS *fs)
195 {
196 int err;
197
198 if (fs->links)
199 return EBUSY;
200 if ((err = dosunmount(fs)))
201 return err;
202 return 0;
203 }
204 #endif
205
206 /*
207 * Common code shared by dos_mount() and dos_unmount()
208 */
209 static int
dosunmount(DOS_FS * fs)210 dosunmount(DOS_FS *fs)
211 {
212 if (fs->buf)
213 dealloc(fs->buf, SECSIZ);
214 dealloc(fs, sizeof(DOS_FS));
215 return 0;
216 }
217
218 /*
219 * Open DOS file
220 */
221 __compactcall int
dosfs_open(const char * path,struct open_file * fd)222 dosfs_open(const char *path, struct open_file *fd)
223 {
224 const struct direntry *de;
225 DOS_FILE *f;
226 DOS_FS *fs;
227 u_int size, clus;
228 int err = 0;
229
230 /* Allocate mount structure, associate with open */
231 fs = alloc(sizeof(DOS_FS));
232
233 if ((err = dos_mount(fs, fd)))
234 goto out;
235
236 if ((err = namede(fs, path, &de)))
237 goto out;
238
239 clus = stclus(fs->fatsz, de);
240 size = getulong(de->deFileSize);
241
242 if ((!(de->deAttributes & ATTR_DIRECTORY) && (!clus != !size)) ||
243 ((de->deAttributes & ATTR_DIRECTORY) && size) ||
244 (clus && !okclus(fs, clus))) {
245 err = EINVAL;
246 goto out;
247 }
248
249 f = alloc(sizeof(DOS_FILE));
250 #ifdef BOOTXX
251 /* due to __internal_memset_ causing all sorts of register spillage
252 (and being completely unoptimized for zeroing small amounts of
253 memory), if we hand-initialize the remaining members of f to zero,
254 the code size drops 68 bytes. This makes no sense, admittedly. */
255 f->offset = 0;
256 f->c = 0;
257 #else
258 (void)memset(f, 0, sizeof(DOS_FILE));
259 #endif
260 f->fs = fs;
261 fs->links++;
262 f->de = *de;
263 fd->f_fsdata = (void *)f;
264 fsmod = "msdos";
265
266 out:
267 return err;
268 }
269
270 /*
271 * Read from file
272 */
273 __compactcall int
dosfs_read(struct open_file * fd,void * vbuf,size_t nbyte,size_t * resid)274 dosfs_read(struct open_file *fd, void *vbuf, size_t nbyte, size_t *resid)
275 {
276 off_t size;
277 u_int8_t *buf = vbuf;
278 u_int nb, off, clus, c, cnt, n;
279 DOS_FILE *f = (DOS_FILE *)fd->f_fsdata;
280 int err = 0;
281
282 nb = (u_int) nbyte;
283 if ((size = fsize(f->fs, &f->de)) == -1)
284 return EINVAL;
285 if (nb > (n = size - f->offset))
286 nb = n;
287 off = f->offset;
288 if ((clus = stclus(f->fs->fatsz, &f->de)))
289 off &= f->fs->bsize - 1;
290 c = f->c;
291 cnt = nb;
292 while (cnt) {
293 n = 0;
294 if (!c) {
295 if ((c = clus))
296 n = bytblk(f->fs, f->offset);
297 } else if (!off) {
298 n++;
299 }
300 while (n--) {
301 if ((err = fatget(f->fs, &c)))
302 goto out;
303 if (!okclus(f->fs, c)) {
304 err = EINVAL;
305 goto out;
306 }
307 }
308 if (!clus || (n = f->fs->bsize - off) > cnt)
309 n = cnt;
310 if ((err = ioread(f->fs, (c ? blkoff(f->fs, c) :
311 secbyt(f->fs->lsndir)) + off,
312 buf, n)))
313 goto out;
314 f->offset += n;
315 f->c = c;
316 off = 0;
317 buf += n;
318 cnt -= n;
319 }
320 out:
321 if (resid)
322 *resid = nbyte - nb + cnt;
323 return err;
324 }
325
326 #ifndef LIBSA_NO_FS_WRITE
327 /*
328 * Not implemented.
329 */
330 __compactcall int
dosfs_write(struct open_file * fd,void * start,size_t size,size_t * resid)331 dosfs_write(struct open_file *fd, void *start, size_t size, size_t *resid)
332 {
333
334 return EROFS;
335 }
336 #endif /* !LIBSA_NO_FS_WRITE */
337
338 #ifndef LIBSA_NO_FS_SEEK
339 /*
340 * Reposition within file
341 */
342 __compactcall off_t
dosfs_seek(struct open_file * fd,off_t offset,int whence)343 dosfs_seek(struct open_file *fd, off_t offset, int whence)
344 {
345 off_t off;
346 u_int size;
347 DOS_FILE *f = (DOS_FILE *)fd->f_fsdata;
348
349 size = getulong(f->de.deFileSize);
350 switch (whence) {
351 case SEEK_SET:
352 off = 0;
353 break;
354 case SEEK_CUR:
355 off = f->offset;
356 break;
357 case SEEK_END:
358 off = size;
359 break;
360 default:
361 return -1;
362 }
363 off += offset;
364 if (off < 0 || off > size)
365 return -1;
366 f->offset = (u_int) off;
367 f->c = 0;
368 return off;
369 }
370 #endif /* !LIBSA_NO_FS_SEEK */
371
372 #ifndef LIBSA_NO_FS_CLOSE
373 /*
374 * Close open file
375 */
376 __compactcall int
dosfs_close(struct open_file * fd)377 dosfs_close(struct open_file *fd)
378 {
379 DOS_FILE *f = (DOS_FILE *)fd->f_fsdata;
380 DOS_FS *fs = f->fs;
381
382 f->fs->links--;
383 dealloc(f, sizeof(DOS_FILE));
384 dos_unmount(fs);
385 return 0;
386 }
387 #endif /* !LIBSA_NO_FS_CLOSE */
388
389 /*
390 * Return some stat information on a file.
391 */
392 __compactcall int
dosfs_stat(struct open_file * fd,struct stat * sb)393 dosfs_stat(struct open_file *fd, struct stat *sb)
394 {
395 DOS_FILE *f = (DOS_FILE *)fd->f_fsdata;
396
397 /* only important stuff */
398 sb->st_mode = (f->de.deAttributes & ATTR_DIRECTORY) ?
399 (S_IFDIR | 0555) : (S_IFREG | 0444);
400 sb->st_nlink = 1;
401 sb->st_uid = 0;
402 sb->st_gid = 0;
403 if ((sb->st_size = fsize(f->fs, &f->de)) == -1)
404 return EINVAL;
405 return 0;
406 }
407
408 #if defined(LIBSA_ENABLE_LS_OP)
409 #include "ls.h"
410 __compactcall void
dosfs_ls(struct open_file * f,const char * pattern)411 dosfs_ls(struct open_file *f, const char *pattern)
412 {
413 lsunsup("dosfs");
414 }
415
416 #if defined(__minix) && defined(LIBSA_ENABLE_LOAD_MODS_OP)
417 __compactcall void
dosfs_load_mods(struct open_file * f,const char * pattern,void (* funcp)(char *),char * path)418 dosfs_load_mods(struct open_file *f, const char *pattern,
419 void (*funcp)(char *), char *path)
420 {
421 load_modsunsup("dosfs");
422 }
423 #endif /* defined(__minix) && defined(LIBSA_ENABLE_LOAD_MODS_OP) */
424 #endif
425
426 /*
427 * Parse DOS boot sector
428 */
429 static int
parsebs(DOS_FS * fs,DOS_BS * bs)430 parsebs(DOS_FS *fs, DOS_BS *bs)
431 {
432 u_int sc;
433
434 if ((bs->jmp[0] != 0x69 &&
435 bs->jmp[0] != 0xe9 &&
436 (bs->jmp[0] != 0xeb || bs->jmp[2] != 0x90)) ||
437 bs->bpb.bpbMedia < 0xf0)
438 return EINVAL;
439 if (getushort(bs->bpb.bpbBytesPerSec) != SECSIZ)
440 return EINVAL;
441 if (!(fs->spc = bs->bpb.bpbSecPerClust) || fs->spc & (fs->spc - 1))
442 return EINVAL;
443 fs->bsize = secbyt(fs->spc);
444 fs->bshift = ffs(fs->bsize) - 1;
445 if ((fs->spf = getushort(bs->bpb.bpbFATsecs))) {
446 if (bs->bpb.bpbFATs != 2)
447 return EINVAL;
448 if (!(fs->dirents = getushort(bs->bpb.bpbRootDirEnts)))
449 return EINVAL;
450 } else {
451 if (!(fs->spf = getulong(bs->bpb.bpbBigFATsecs)))
452 return EINVAL;
453 if (!bs->bpb.bpbFATs || bs->bpb.bpbFATs > 16)
454 return EINVAL;
455 if ((fs->rdcl = getulong(bs->bpb.bpbRootClust)) < LOCLUS)
456 return EINVAL;
457 }
458 if (!(fs->lsnfat = getushort(bs->bpb.bpbResSectors)))
459 return EINVAL;
460 fs->lsndir = fs->lsnfat + fs->spf * bs->bpb.bpbFATs;
461 fs->lsndta = fs->lsndir + entsec(fs->dirents);
462 if (!(sc = getushort(bs->bpb.bpbSectors)) &&
463 !(sc = getulong(bs->bpb.bpbHugeSectors)))
464 return EINVAL;
465 if (fs->lsndta > sc)
466 return EINVAL;
467 if ((fs->xclus = secblk(fs, sc - fs->lsndta) + 1) < LOCLUS)
468 return EINVAL;
469 fs->fatsz = fs->dirents ? fs->xclus < 0xff6 ? 12 : 16 : 32;
470 sc = (secbyt(fs->spf) << 1) / (fs->fatsz >> 2) - 1;
471 if (fs->xclus > sc)
472 fs->xclus = sc;
473 return 0;
474 }
475
476 /*
477 * Return directory entry from path
478 */
479 static int
namede(DOS_FS * fs,const char * path,const struct direntry ** dep)480 namede(DOS_FS *fs, const char *path, const struct direntry **dep)
481 {
482 char name[256];
483 const struct direntry *de;
484 char *s;
485 size_t n;
486 int err;
487
488 err = 0;
489 de = dot;
490 if (*path == '/')
491 path++;
492 while (*path) {
493 if (!(s = strchr(path, '/')))
494 s = strchr(path, 0);
495 if ((n = s - path) > 255)
496 return ENAMETOOLONG;
497 memcpy(name, path, n);
498 name[n] = 0;
499 path = s;
500 if (!(de->deAttributes & ATTR_DIRECTORY))
501 return ENOTDIR;
502 if ((err = lookup(fs, stclus(fs->fatsz, de), name, &de)))
503 return err;
504 if (*path == '/')
505 path++;
506 }
507 *dep = de;
508 return 0;
509 }
510
511 /*
512 * Lookup path segment
513 */
514 static int
lookup(DOS_FS * fs,u_int clus,const char * name,const struct direntry ** dep)515 lookup(DOS_FS *fs, u_int clus, const char *name, const struct direntry **dep)
516 {
517 static DOS_DIR *dir = NULL;
518 u_char lfn[261];
519 u_char sfn[13];
520 u_int nsec, lsec, xdn, chk, sec, ent, x;
521 int err = 0, ok, i;
522
523 if (!clus)
524 for (ent = 0; ent < 2; ent++)
525 if (!strcasecmp(name, dotstr[ent])) {
526 *dep = dot + ent;
527 return 0;
528 }
529
530 if (dir == NULL) {
531 dir = alloc(sizeof(DOS_DIR) * DEPSEC);
532 if (dir == NULL)
533 return ENOMEM;
534 }
535
536 if (!clus && fs->fatsz == 32)
537 clus = fs->rdcl;
538 nsec = !clus ? entsec(fs->dirents) : fs->spc;
539 lsec = 0;
540 xdn = chk = 0;
541 for (;;) {
542 if (!clus && !lsec)
543 lsec = fs->lsndir;
544 else if (okclus(fs, clus))
545 lsec = blklsn(fs, clus);
546 else {
547 err = EINVAL;
548 goto out;
549 }
550 for (sec = 0; sec < nsec; sec++) {
551 if ((err = ioget(fs->fd, lsec + sec, dir, 1)))
552 goto out;
553 for (ent = 0; ent < DEPSEC; ent++) {
554 if (!*dir[ent].de.deName) {
555 err = ENOENT;
556 goto out;
557 }
558 if (*dir[ent].de.deName != 0xe5) {
559 if (dir[ent].de.deAttributes ==
560 ATTR_WIN95) {
561 x = dir[ent].xde.weCnt;
562 if (x & WIN_LAST ||
563 (x + 1 == xdn &&
564 dir[ent].xde.weChksum ==
565 chk)) {
566 if (x & WIN_LAST) {
567 chk = dir[ent].xde.weChksum;
568 x &= WIN_CNT;
569 }
570 if (x >= 1 && x <= 20) {
571 cp_xdnm(lfn, &dir[ent].xde);
572 xdn = x;
573 continue;
574 }
575 }
576 } else if (!(dir[ent].de.deAttributes &
577 ATTR_VOLUME)) {
578 if ((ok = xdn == 1)) {
579 for (x = 0, i = 0;
580 i < 11; i++)
581 x = ((((x & 1) << 7) | (x >> 1)) +
582 msdos_dirchar(&dir[ent].de,i)) & 0xff;
583 ok = chk == x &&
584 !strcasecmp(name, (const char *)lfn);
585 }
586 if (!ok) {
587 cp_sfn(sfn, &dir[ent].de);
588 ok = !strcasecmp(name, (const char *)sfn);
589 }
590 if (ok) {
591 *dep = &dir[ent].de;
592 goto out2;
593 }
594 }
595 }
596 xdn = 0;
597 }
598 }
599 if (!clus)
600 break;
601 if ((err = fatget(fs, &clus)))
602 goto out;
603 if (fatend(fs->fatsz, clus))
604 break;
605 }
606 err = ENOENT;
607 out:
608 dealloc(dir, sizeof(DOS_DIR) * DEPSEC);
609 dir = NULL;
610 out2:
611 return err;
612 }
613
614 /*
615 * Copy name from extended directory entry
616 */
617 static void
cp_xdnm(u_char * lfn,struct winentry * xde)618 cp_xdnm(u_char *lfn, struct winentry *xde)
619 {
620 static const struct {
621 u_int off;
622 u_int dim;
623 } ix[3] = {
624 { offsetof(struct winentry, wePart1),
625 sizeof(xde->wePart1) / 2 },
626 { offsetof(struct winentry, wePart2),
627 sizeof(xde->wePart2) / 2 },
628 { offsetof(struct winentry, wePart3),
629 sizeof(xde->wePart3) / 2 }
630 };
631 u_char *p;
632 u_int n, x, c;
633
634 lfn += 13 * ((xde->weCnt & WIN_CNT) - 1);
635 for (n = 0; n < 3; n++)
636 for (p = (u_char *)xde + ix[n].off, x = ix[n].dim; x;
637 p += 2, x--) {
638 if ((c = getushort(p)) && (c < 32 || c > 127))
639 c = '?';
640 if (!(*lfn++ = c))
641 return;
642 }
643 if (xde->weCnt & WIN_LAST)
644 *lfn = 0;
645 }
646
647 /*
648 * Copy short filename
649 */
650 static void
cp_sfn(u_char * sfn,struct direntry * de)651 cp_sfn(u_char *sfn, struct direntry *de)
652 {
653 u_char *p;
654 int j, i;
655
656 p = sfn;
657 if (*de->deName != ' ') {
658 for (j = 7; de->deName[j] == ' '; j--);
659 for (i = 0; i <= j; i++)
660 *p++ = de->deName[i];
661 if (*de->deExtension != ' ') {
662 *p++ = '.';
663 for (j = 2; de->deExtension[j] == ' '; j--);
664 for (i = 0; i <= j; i++)
665 *p++ = de->deExtension[i];
666 }
667 }
668 *p = 0;
669 if (*sfn == 5)
670 *sfn = 0xe5;
671 }
672
673 /*
674 * Return size of file in bytes
675 */
676 static off_t
fsize(DOS_FS * fs,struct direntry * de)677 fsize(DOS_FS *fs, struct direntry *de)
678 {
679 u_long size;
680 u_int c;
681 int n;
682
683 if (!(size = getulong(de->deFileSize)) &&
684 de->deAttributes & ATTR_DIRECTORY) {
685 if (!(c = getushort(de->deStartCluster))) {
686 size = fs->dirents * sizeof(struct direntry);
687 } else {
688 if ((n = fatcnt(fs, c)) == -1)
689 return n;
690 size = blkbyt(fs, n);
691 }
692 }
693 return size;
694 }
695
696 /*
697 * Count number of clusters in chain
698 */
699 static int
fatcnt(DOS_FS * fs,u_int c)700 fatcnt(DOS_FS *fs, u_int c)
701 {
702 int n;
703
704 for (n = 0; okclus(fs, c); n++)
705 if (fatget(fs, &c))
706 return -1;
707 return fatend(fs->fatsz, c) ? n : -1;
708 }
709
710 /*
711 * Get next cluster in cluster chain
712 */
713 static int
fatget(DOS_FS * fs,u_int * c)714 fatget(DOS_FS *fs, u_int *c)
715 {
716 u_char buf[4];
717 u_int x;
718 int err;
719
720 err = ioread(fs, secbyt(fs->lsnfat) + fatoff(fs->fatsz, *c), buf,
721 fs->fatsz != 32 ? 2 : 4);
722 if (err)
723 return err;
724 x = fs->fatsz != 32 ? getushort(buf) : getulong(buf);
725 *c = fs->fatsz == 12 ? *c & 1 ? x >> 4 : x & 0xfff : x;
726 return 0;
727 }
728
729 /*
730 * Is cluster an end-of-chain marker?
731 */
732 static int
fatend(u_int sz,u_int c)733 fatend(u_int sz, u_int c)
734 {
735 return c > (sz == 12 ? 0xff7U : sz == 16 ? 0xfff7U : 0xffffff7);
736 }
737
738 /*
739 * Offset-based I/O primitive
740 */
741 static int
ioread(DOS_FS * fs,u_int offset,void * buf,u_int nbyte)742 ioread(DOS_FS *fs, u_int offset, void *buf, u_int nbyte)
743 {
744 char *s;
745 u_int off, n;
746 int err;
747
748 s = buf;
749 if ((off = offset & (SECSIZ - 1))) {
750 offset -= off;
751 if ((err = iobuf(fs, bytsec(offset))))
752 return err;
753 offset += SECSIZ;
754 if ((n = SECSIZ - off) > nbyte)
755 n = nbyte;
756 memcpy(s, fs->buf + off, n);
757 s += n;
758 nbyte -= n;
759 }
760 n = nbyte & (SECSIZ - 1);
761 if (nbyte -= n) {
762 if ((err = ioget(fs->fd, bytsec(offset), s, bytsec(nbyte))))
763 return err;
764 offset += nbyte;
765 s += nbyte;
766 }
767 if (n) {
768 if ((err = iobuf(fs, bytsec(offset))))
769 return err;
770 memcpy(s, fs->buf, n);
771 }
772 return 0;
773 }
774
775 /*
776 * Buffered sector-based I/O primitive
777 */
778 static int
iobuf(DOS_FS * fs,u_int lsec)779 iobuf(DOS_FS *fs, u_int lsec)
780 {
781 int err;
782
783 if (fs->bufsec != lsec) {
784 if ((err = ioget(fs->fd, lsec, fs->buf, 1)))
785 return err;
786 fs->bufsec = lsec;
787 }
788 return 0;
789 }
790
791 /*
792 * Sector-based I/O primitive
793 */
794 static int
ioget(struct open_file * fd,u_int lsec,void * buf,u_int nsec)795 ioget(struct open_file *fd, u_int lsec, void *buf, u_int nsec)
796 {
797 size_t rsize;
798 int err;
799
800 #ifndef LIBSA_NO_TWIDDLE
801 twiddle();
802 #endif
803 err = DEV_STRATEGY(fd->f_dev)(fd->f_devdata, F_READ, lsec,
804 secbyt(nsec), buf, &rsize);
805 return err;
806 }
807