dosfs.c revision 1.3
1 /* $NetBSD: dosfs.c,v 1.3 2000/11/08 19:38:12 matt 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 <msdosfs/bpb.h> 44 #include <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 ? getushort((de)->deStartCluster) : \ 136 ((u_int)getushort((de)->deHighClust) << 16) | \ 137 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 /* 154 * Mount DOS filesystem 155 */ 156 static int 157 dos_mount(DOS_FS * fs, struct open_file * fd) 158 { 159 int err; 160 161 bzero(fs, sizeof(DOS_FS)); 162 fs->fd = fd; 163 if ((err = !(fs->buf = alloc(SECSIZ)) ? errno : 0) || 164 (err = ioget(fs->fd, 0, fs->buf, 1)) || 165 (err = parsebs(fs, (DOS_BS *) fs->buf))) { 166 (void) dosunmount(fs); 167 return (err); 168 } 169 return 0; 170 } 171 172 /* 173 * Unmount mounted filesystem 174 */ 175 static int 176 dos_unmount(DOS_FS * fs) 177 { 178 int err; 179 180 if (fs->links) 181 return (EBUSY); 182 if ((err = dosunmount(fs))) 183 return (err); 184 return 0; 185 } 186 187 /* 188 * Common code shared by dos_mount() and dos_unmount() 189 */ 190 static int 191 dosunmount(DOS_FS * fs) 192 { 193 if (fs->buf) 194 free(fs->buf, SECSIZ); 195 free(fs, sizeof(DOS_FS)); 196 return (0); 197 } 198 199 /* 200 * Open DOS file 201 */ 202 int 203 dosfs_open(char *path, struct open_file *fd) 204 { 205 const struct direntry *de; 206 DOS_FILE *f; 207 DOS_FS *fs; 208 u_int size, clus; 209 int err = 0; 210 211 /* Allocate mount structure, associate with open */ 212 fs = alloc(sizeof(DOS_FS)); 213 214 if ((err = dos_mount(fs, fd))) 215 goto out; 216 217 if ((err = namede(fs, path, &de))) 218 goto out; 219 220 clus = stclus(fs->fatsz, de); 221 size = getulong(de->deFileSize); 222 223 if ((!(de->deAttributes & ATTR_DIRECTORY) && (!clus != !size)) || 224 ((de->deAttributes & ATTR_DIRECTORY) && size) || 225 (clus && !okclus(fs, clus))) { 226 err = EINVAL; 227 goto out; 228 } 229 f = alloc(sizeof(DOS_FILE)); 230 bzero(f, sizeof(DOS_FILE)); 231 f->fs = fs; 232 fs->links++; 233 f->de = *de; 234 fd->f_fsdata = (void *) f; 235 236 out: 237 return (err); 238 } 239 240 /* 241 * Read from file 242 */ 243 int 244 dosfs_read(struct open_file * fd, void *vbuf, size_t nbyte, size_t * resid) 245 { 246 off_t size; 247 u_int8_t *buf = vbuf; 248 u_int nb, off, clus, c, cnt, n; 249 DOS_FILE *f = (DOS_FILE *) fd->f_fsdata; 250 int err = 0; 251 252 nb = (u_int) nbyte; 253 if ((size = fsize(f->fs, &f->de)) == -1) 254 return EINVAL; 255 if (nb > (n = size - f->offset)) 256 nb = n; 257 off = f->offset; 258 if ((clus = stclus(f->fs->fatsz, &f->de))) 259 off &= f->fs->bsize - 1; 260 c = f->c; 261 cnt = nb; 262 while (cnt) { 263 n = 0; 264 if (!c) { 265 if ((c = clus)) 266 n = bytblk(f->fs, f->offset); 267 } else if (!off) 268 n++; 269 while (n--) { 270 if ((err = fatget(f->fs, &c))) 271 goto out; 272 if (!okclus(f->fs, c)) { 273 err = EINVAL; 274 goto out; 275 } 276 } 277 if (!clus || (n = f->fs->bsize - off) > cnt) 278 n = cnt; 279 if ((err = ioread(f->fs, (c ? blkoff(f->fs, c) : 280 secbyt(f->fs->lsndir)) + off, 281 buf, n))) 282 goto out; 283 f->offset += n; 284 f->c = c; 285 off = 0; 286 buf += n; 287 cnt -= n; 288 } 289 out: 290 if (resid) 291 *resid = nbyte - nb + cnt; 292 return (err); 293 } 294 295 #ifndef LIBSA_NO_FS_WRITE 296 /* 297 * Not implemented. 298 */ 299 int 300 dosfs_write(struct open_file *fd, void *start, size_t size, size_t *resid) 301 { 302 303 return (EROFS); 304 } 305 #endif /* !LIBSA_NO_FS_WRITE */ 306 307 #ifndef LIBSA_NO_FS_SEEK 308 /* 309 * Reposition within file 310 */ 311 off_t 312 dosfs_seek(struct open_file * fd, off_t offset, int whence) 313 { 314 off_t off; 315 u_int size; 316 DOS_FILE *f = (DOS_FILE *) fd->f_fsdata; 317 318 size = getulong(f->de.deFileSize); 319 switch (whence) { 320 case SEEK_SET: 321 off = 0; 322 break; 323 case SEEK_CUR: 324 off = f->offset; 325 break; 326 case SEEK_END: 327 off = size; 328 break; 329 default: 330 return (-1); 331 } 332 off += offset; 333 if (off < 0 || off > size) 334 return (-1); 335 f->offset = (u_int) off; 336 f->c = 0; 337 return (off); 338 } 339 #endif /* !LIBSA_NO_FS_SEEK */ 340 341 #ifndef LIBSA_NO_FS_CLOSE 342 /* 343 * Close open file 344 */ 345 int 346 dosfs_close(struct open_file * fd) 347 { 348 DOS_FILE *f = (DOS_FILE *) fd->f_fsdata; 349 DOS_FS *fs = f->fs; 350 351 f->fs->links--; 352 free(f, sizeof(DOS_FILE)); 353 dos_unmount(fs); 354 return 0; 355 } 356 #endif /* !LIBSA_NO_FS_CLOSE */ 357 358 /* 359 * Return some stat information on a file. 360 */ 361 int 362 dosfs_stat(struct open_file * fd, struct stat * sb) 363 { 364 DOS_FILE *f = (DOS_FILE *) fd->f_fsdata; 365 366 /* only important stuff */ 367 sb->st_mode = (f->de.deAttributes & ATTR_DIRECTORY) ? 368 (S_IFDIR | 0555) : (S_IFREG | 0444); 369 sb->st_nlink = 1; 370 sb->st_uid = 0; 371 sb->st_gid = 0; 372 if ((sb->st_size = fsize(f->fs, &f->de)) == -1) 373 return EINVAL; 374 return (0); 375 } 376 377 /* 378 * Parse DOS boot sector 379 */ 380 static int 381 parsebs(DOS_FS * fs, DOS_BS * bs) 382 { 383 u_int sc; 384 385 if ((bs->jmp[0] != 0x69 && 386 bs->jmp[0] != 0xe9 && 387 (bs->jmp[0] != 0xeb || bs->jmp[2] != 0x90)) || 388 bs->bpb.bpbMedia < 0xf0) 389 return EINVAL; 390 if (getushort(bs->bpb.bpbBytesPerSec) != SECSIZ) 391 return EINVAL; 392 if (!(fs->spc = bs->bpb.bpbSecPerClust) || fs->spc & (fs->spc - 1)) 393 return EINVAL; 394 fs->bsize = secbyt(fs->spc); 395 fs->bshift = ffs(fs->bsize) - 1; 396 if ((fs->spf = getushort(bs->bpb.bpbFATsecs))) { 397 if (bs->bpb.bpbFATs != 2) 398 return EINVAL; 399 if (!(fs->dirents = getushort(bs->bpb.bpbRootDirEnts))) 400 return EINVAL; 401 } else { 402 if (!(fs->spf = getulong(bs->bpb.bpbBigFATsecs))) 403 return EINVAL; 404 if (!bs->bpb.bpbFATs || bs->bpb.bpbFATs > 16) 405 return EINVAL; 406 if ((fs->rdcl = getulong(bs->bpb.bpbRootClust)) < LOCLUS) 407 return EINVAL; 408 } 409 if (!(fs->lsnfat = getushort(bs->bpb.bpbResSectors))) 410 return EINVAL; 411 fs->lsndir = fs->lsnfat + fs->spf * bs->bpb.bpbFATs; 412 fs->lsndta = fs->lsndir + entsec(fs->dirents); 413 if (!(sc = getushort(bs->bpb.bpbSectors)) && 414 !(sc = getulong(bs->bpb.bpbHugeSectors))) 415 return EINVAL; 416 if (fs->lsndta > sc) 417 return EINVAL; 418 if ((fs->xclus = secblk(fs, sc - fs->lsndta) + 1) < LOCLUS) 419 return EINVAL; 420 fs->fatsz = fs->dirents ? fs->xclus < 0xff6 ? 12 : 16 : 32; 421 sc = (secbyt(fs->spf) << 1) / (fs->fatsz >> 2) - 1; 422 if (fs->xclus > sc) 423 fs->xclus = sc; 424 return 0; 425 } 426 427 /* 428 * Return directory entry from path 429 */ 430 static int 431 namede(DOS_FS * fs, const char *path, const struct direntry ** dep) 432 { 433 char name[256]; 434 const struct direntry *de; 435 char *s; 436 size_t n; 437 int err; 438 439 err = 0; 440 de = dot; 441 if (*path == '/') 442 path++; 443 while (*path) { 444 if (!(s = strchr(path, '/'))) 445 s = strchr(path, 0); 446 if ((n = s - path) > 255) 447 return ENAMETOOLONG; 448 memcpy(name, path, n); 449 name[n] = 0; 450 path = s; 451 if (!(de->deAttributes & ATTR_DIRECTORY)) 452 return ENOTDIR; 453 if ((err = lookup(fs, stclus(fs->fatsz, de), name, &de))) 454 return err; 455 if (*path == '/') 456 path++; 457 } 458 *dep = de; 459 return 0; 460 } 461 462 /* 463 * Lookup path segment 464 */ 465 static int 466 lookup(DOS_FS * fs, u_int clus, const char *name, const struct direntry ** dep) 467 { 468 DOS_DIR *dir; 469 u_char lfn[261]; 470 u_char sfn[13]; 471 u_int nsec, lsec, xdn, chk, sec, ent, x; 472 int err = 0, ok, i; 473 474 if (!clus) 475 for (ent = 0; ent < 2; ent++) 476 if (!strcasecmp(name, dotstr[ent])) { 477 *dep = dot + ent; 478 return 0; 479 } 480 481 dir = alloc(sizeof(DOS_DIR) * DEPSEC); 482 483 if (!clus && fs->fatsz == 32) 484 clus = fs->rdcl; 485 nsec = !clus ? entsec(fs->dirents) : fs->spc; 486 lsec = 0; 487 xdn = chk = 0; 488 for (;;) { 489 if (!clus && !lsec) 490 lsec = fs->lsndir; 491 else if (okclus(fs, clus)) 492 lsec = blklsn(fs, clus); 493 else { 494 err = EINVAL; 495 goto out; 496 } 497 for (sec = 0; sec < nsec; sec++) { 498 if ((err = ioget(fs->fd, lsec + sec, dir, 1))) 499 goto out; 500 for (ent = 0; ent < DEPSEC; ent++) { 501 if (!*dir[ent].de.deName) { 502 err = ENOENT; 503 goto out; 504 } 505 if (*dir[ent].de.deName != 0xe5) { 506 if (dir[ent].de.deAttributes == 507 ATTR_WIN95) { 508 x = dir[ent].xde.weCnt; 509 if (x & WIN_LAST || 510 (x + 1 == xdn && 511 dir[ent].xde.weChksum == 512 chk)) { 513 if (x & WIN_LAST) { 514 chk = dir[ent].xde.weChksum; 515 x &= WIN_CNT; 516 } 517 if (x >= 1 && x <= 20) { 518 cp_xdnm(lfn, &dir[ent].xde); 519 xdn = x; 520 continue; 521 } 522 } 523 } else if (!(dir[ent].de.deAttributes & 524 ATTR_VOLUME)) { 525 if ((ok = xdn == 1)) { 526 for (x = 0, i = 0; 527 i < 11; i++) 528 x = ((((x & 1) << 7) | (x >> 1)) + 529 dir[ent].de.deName[i]) & 0xff; 530 ok = chk == x && 531 !strcasecmp(name, (const char *) lfn); 532 } 533 if (!ok) { 534 cp_sfn(sfn, &dir[ent].de); 535 ok = !strcasecmp(name, (const char *) sfn); 536 } 537 if (ok) { 538 *dep = &dir[ent].de; 539 goto out; 540 } 541 } 542 } 543 xdn = 0; 544 } 545 } 546 if (!clus) 547 break; 548 if ((err = fatget(fs, &clus))) 549 goto out; 550 if (fatend(fs->fatsz, clus)) 551 break; 552 } 553 err = ENOENT; 554 out: 555 free(dir, sizeof(DOS_DIR) * DEPSEC); 556 return (err); 557 } 558 559 /* 560 * Copy name from extended directory entry 561 */ 562 static void 563 cp_xdnm(u_char * lfn, struct winentry * xde) 564 { 565 static const struct { 566 u_int off; 567 u_int dim; 568 } ix[3] = { 569 { offsetof(struct winentry, wePart1), 570 sizeof(xde->wePart1) / 2 }, 571 { offsetof(struct winentry, wePart2), 572 sizeof(xde->wePart2) / 2 }, 573 { offsetof(struct winentry, wePart3), 574 sizeof(xde->wePart3) / 2 } 575 }; 576 u_char *p; 577 u_int n, x, c; 578 579 lfn += 13 * ((xde->weCnt & WIN_CNT) - 1); 580 for (n = 0; n < 3; n++) 581 for (p = (u_char *) xde + ix[n].off, x = ix[n].dim; x; 582 p += 2, x--) { 583 if ((c = getushort(p)) && (c < 32 || c > 127)) 584 c = '?'; 585 if (!(*lfn++ = c)) 586 return; 587 } 588 if (xde->weCnt & WIN_LAST) 589 *lfn = 0; 590 } 591 592 /* 593 * Copy short filename 594 */ 595 static void 596 cp_sfn(u_char * sfn, struct direntry * de) 597 { 598 u_char *p; 599 int j, i; 600 601 p = sfn; 602 if (*de->deName != ' ') { 603 for (j = 7; de->deName[j] == ' '; j--); 604 for (i = 0; i <= j; i++) 605 *p++ = de->deName[i]; 606 if (*de->deExtension != ' ') { 607 *p++ = '.'; 608 for (j = 2; de->deExtension[j] == ' '; j--); 609 for (i = 0; i <= j; i++) 610 *p++ = de->deExtension[i]; 611 } 612 } 613 *p = 0; 614 if (*sfn == 5) 615 *sfn = 0xe5; 616 } 617 618 /* 619 * Return size of file in bytes 620 */ 621 static off_t 622 fsize(DOS_FS * fs, struct direntry * de) 623 { 624 u_long size; 625 u_int c; 626 int n; 627 628 if (!(size = getulong(de->deFileSize)) && 629 de->deAttributes & ATTR_DIRECTORY) { 630 if (!(c = getushort(de->deStartCluster))) 631 size = fs->dirents * sizeof(struct direntry); 632 else { 633 if ((n = fatcnt(fs, c)) == -1) 634 return n; 635 size = blkbyt(fs, n); 636 } 637 } 638 return size; 639 } 640 641 /* 642 * Count number of clusters in chain 643 */ 644 static int 645 fatcnt(DOS_FS * fs, u_int c) 646 { 647 int n; 648 649 for (n = 0; okclus(fs, c); n++) 650 if (fatget(fs, &c)) 651 return -1; 652 return fatend(fs->fatsz, c) ? n : -1; 653 } 654 655 /* 656 * Get next cluster in cluster chain 657 */ 658 static int 659 fatget(DOS_FS * fs, u_int * c) 660 { 661 u_char buf[4]; 662 u_int x; 663 int err; 664 665 err = ioread(fs, secbyt(fs->lsnfat) + fatoff(fs->fatsz, *c), buf, 666 fs->fatsz != 32 ? 2 : 4); 667 if (err) 668 return err; 669 x = fs->fatsz != 32 ? getushort(buf) : getulong(buf); 670 *c = fs->fatsz == 12 ? *c & 1 ? x >> 4 : x & 0xfff : x; 671 return 0; 672 } 673 674 /* 675 * Is cluster an end-of-chain marker? 676 */ 677 static int 678 fatend(u_int sz, u_int c) 679 { 680 return c > (sz == 12 ? 0xff7U : sz == 16 ? 0xfff7U : 0xffffff7); 681 } 682 683 /* 684 * Offset-based I/O primitive 685 */ 686 static int 687 ioread(DOS_FS * fs, u_int offset, void *buf, u_int nbyte) 688 { 689 char *s; 690 u_int off, n; 691 int err; 692 693 s = buf; 694 if ((off = offset & (SECSIZ - 1))) { 695 offset -= off; 696 if ((err = iobuf(fs, bytsec(offset)))) 697 return err; 698 offset += SECSIZ; 699 if ((n = SECSIZ - off) > nbyte) 700 n = nbyte; 701 memcpy(s, fs->buf + off, n); 702 s += n; 703 nbyte -= n; 704 } 705 n = nbyte & (SECSIZ - 1); 706 if (nbyte -= n) { 707 if ((err = ioget(fs->fd, bytsec(offset), s, bytsec(nbyte)))) 708 return err; 709 offset += nbyte; 710 s += nbyte; 711 } 712 if (n) { 713 if ((err = iobuf(fs, bytsec(offset)))) 714 return err; 715 memcpy(s, fs->buf, n); 716 } 717 return 0; 718 } 719 720 /* 721 * Buffered sector-based I/O primitive 722 */ 723 static int 724 iobuf(DOS_FS * fs, u_int lsec) 725 { 726 int err; 727 728 if (fs->bufsec != lsec) { 729 if ((err = ioget(fs->fd, lsec, fs->buf, 1))) 730 return err; 731 fs->bufsec = lsec; 732 } 733 return 0; 734 } 735 736 /* 737 * Sector-based I/O primitive 738 */ 739 static int 740 ioget(struct open_file * fd, u_int lsec, void *buf, u_int nsec) 741 { 742 size_t rsize; 743 int err; 744 745 #ifndef LIBSA_NO_TWIDDLE 746 twiddle(); 747 #endif 748 err = DEV_STRATEGY(fd->f_dev)(fd->f_devdata, F_READ, lsec, 749 secbyt(nsec), buf, &rsize); 750 return (err); 751 } 752
Indexes created Tue Sep 23 02:09:52 GMT 2025