dosfs.c revision 1.11.20.1
1 /* $NetBSD: dosfs.c,v 1.11.20.1 2008/01/09 01:56:38 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 <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 /* 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 #ifndef LIBSA_NO_FS_CLOSE 173 /* 174 * Unmount mounted filesystem 175 */ 176 static int 177 dos_unmount(DOS_FS *fs) 178 { 179 int err; 180 181 if (fs->links) 182 return EBUSY; 183 if ((err = dosunmount(fs))) 184 return err; 185 return 0; 186 } 187 #endif 188 189 /* 190 * Common code shared by dos_mount() and dos_unmount() 191 */ 192 static int 193 dosunmount(DOS_FS *fs) 194 { 195 if (fs->buf) 196 dealloc(fs->buf, SECSIZ); 197 dealloc(fs, sizeof(DOS_FS)); 198 return 0; 199 } 200 201 /* 202 * Open DOS file 203 */ 204 int 205 dosfs_open(const char *path, struct open_file *fd) 206 { 207 const struct direntry *de; 208 DOS_FILE *f; 209 DOS_FS *fs; 210 u_int size, clus; 211 int err = 0; 212 213 /* Allocate mount structure, associate with open */ 214 fs = alloc(sizeof(DOS_FS)); 215 216 if ((err = dos_mount(fs, fd))) 217 goto out; 218 219 if ((err = namede(fs, path, &de))) 220 goto out; 221 222 clus = stclus(fs->fatsz, de); 223 size = getulong(de->deFileSize); 224 225 if ((!(de->deAttributes & ATTR_DIRECTORY) && (!clus != !size)) || 226 ((de->deAttributes & ATTR_DIRECTORY) && size) || 227 (clus && !okclus(fs, clus))) { 228 err = EINVAL; 229 goto out; 230 } 231 232 f = alloc(sizeof(DOS_FILE)); 233 #ifdef BOOTXX 234 /* due to __internal_memset_ causing all sorts of register spillage 235 (and being completely unoptimized for zeroing small amounts of 236 memory), if we hand-initialize the remaining members of f to zero, 237 the code size drops 68 bytes. This makes no sense, admittedly. */ 238 f->offset = 0; 239 f->c = 0; 240 #else 241 bzero(f, sizeof(DOS_FILE)); 242 #endif 243 f->fs = fs; 244 fs->links++; 245 f->de = *de; 246 fd->f_fsdata = (void *)f; 247 248 out: 249 return err; 250 } 251 252 /* 253 * Read from file 254 */ 255 int 256 dosfs_read(struct open_file *fd, void *vbuf, size_t nbyte, size_t *resid) 257 { 258 off_t size; 259 u_int8_t *buf = vbuf; 260 u_int nb, off, clus, c, cnt, n; 261 DOS_FILE *f = (DOS_FILE *)fd->f_fsdata; 262 int err = 0; 263 264 nb = (u_int) nbyte; 265 if ((size = fsize(f->fs, &f->de)) == -1) 266 return EINVAL; 267 if (nb > (n = size - f->offset)) 268 nb = n; 269 off = f->offset; 270 if ((clus = stclus(f->fs->fatsz, &f->de))) 271 off &= f->fs->bsize - 1; 272 c = f->c; 273 cnt = nb; 274 while (cnt) { 275 n = 0; 276 if (!c) { 277 if ((c = clus)) 278 n = bytblk(f->fs, f->offset); 279 } else if (!off) { 280 n++; 281 } 282 while (n--) { 283 if ((err = fatget(f->fs, &c))) 284 goto out; 285 if (!okclus(f->fs, c)) { 286 err = EINVAL; 287 goto out; 288 } 289 } 290 if (!clus || (n = f->fs->bsize - off) > cnt) 291 n = cnt; 292 if ((err = ioread(f->fs, (c ? blkoff(f->fs, c) : 293 secbyt(f->fs->lsndir)) + off, 294 buf, n))) 295 goto out; 296 f->offset += n; 297 f->c = c; 298 off = 0; 299 buf += n; 300 cnt -= n; 301 } 302 out: 303 if (resid) 304 *resid = nbyte - nb + cnt; 305 return err; 306 } 307 308 #ifndef LIBSA_NO_FS_WRITE 309 /* 310 * Not implemented. 311 */ 312 int 313 dosfs_write(struct open_file *fd, void *start, size_t size, size_t *resid) 314 { 315 316 return EROFS; 317 } 318 #endif /* !LIBSA_NO_FS_WRITE */ 319 320 #ifndef LIBSA_NO_FS_SEEK 321 /* 322 * Reposition within file 323 */ 324 off_t 325 dosfs_seek(struct open_file *fd, off_t offset, int whence) 326 { 327 off_t off; 328 u_int size; 329 DOS_FILE *f = (DOS_FILE *)fd->f_fsdata; 330 331 size = getulong(f->de.deFileSize); 332 switch (whence) { 333 case SEEK_SET: 334 off = 0; 335 break; 336 case SEEK_CUR: 337 off = f->offset; 338 break; 339 case SEEK_END: 340 off = size; 341 break; 342 default: 343 return -1; 344 } 345 off += offset; 346 if (off < 0 || off > size) 347 return -1; 348 f->offset = (u_int) off; 349 f->c = 0; 350 return off; 351 } 352 #endif /* !LIBSA_NO_FS_SEEK */ 353 354 #ifndef LIBSA_NO_FS_CLOSE 355 /* 356 * Close open file 357 */ 358 int 359 dosfs_close(struct open_file *fd) 360 { 361 DOS_FILE *f = (DOS_FILE *)fd->f_fsdata; 362 DOS_FS *fs = f->fs; 363 364 f->fs->links--; 365 dealloc(f, sizeof(DOS_FILE)); 366 dos_unmount(fs); 367 return 0; 368 } 369 #endif /* !LIBSA_NO_FS_CLOSE */ 370 371 /* 372 * Return some stat information on a file. 373 */ 374 int 375 dosfs_stat(struct open_file *fd, struct stat *sb) 376 { 377 DOS_FILE *f = (DOS_FILE *)fd->f_fsdata; 378 379 /* only important stuff */ 380 sb->st_mode = (f->de.deAttributes & ATTR_DIRECTORY) ? 381 (S_IFDIR | 0555) : (S_IFREG | 0444); 382 sb->st_nlink = 1; 383 sb->st_uid = 0; 384 sb->st_gid = 0; 385 if ((sb->st_size = fsize(f->fs, &f->de)) == -1) 386 return EINVAL; 387 return 0; 388 } 389 390 /* 391 * Parse DOS boot sector 392 */ 393 static int 394 parsebs(DOS_FS *fs, DOS_BS *bs) 395 { 396 u_int sc; 397 398 if ((bs->jmp[0] != 0x69 && 399 bs->jmp[0] != 0xe9 && 400 (bs->jmp[0] != 0xeb || bs->jmp[2] != 0x90)) || 401 bs->bpb.bpbMedia < 0xf0) 402 return EINVAL; 403 if (getushort(bs->bpb.bpbBytesPerSec) != SECSIZ) 404 return EINVAL; 405 if (!(fs->spc = bs->bpb.bpbSecPerClust) || fs->spc & (fs->spc - 1)) 406 return EINVAL; 407 fs->bsize = secbyt(fs->spc); 408 fs->bshift = ffs(fs->bsize) - 1; 409 if ((fs->spf = getushort(bs->bpb.bpbFATsecs))) { 410 if (bs->bpb.bpbFATs != 2) 411 return EINVAL; 412 if (!(fs->dirents = getushort(bs->bpb.bpbRootDirEnts))) 413 return EINVAL; 414 } else { 415 if (!(fs->spf = getulong(bs->bpb.bpbBigFATsecs))) 416 return EINVAL; 417 if (!bs->bpb.bpbFATs || bs->bpb.bpbFATs > 16) 418 return EINVAL; 419 if ((fs->rdcl = getulong(bs->bpb.bpbRootClust)) < LOCLUS) 420 return EINVAL; 421 } 422 if (!(fs->lsnfat = getushort(bs->bpb.bpbResSectors))) 423 return EINVAL; 424 fs->lsndir = fs->lsnfat + fs->spf * bs->bpb.bpbFATs; 425 fs->lsndta = fs->lsndir + entsec(fs->dirents); 426 if (!(sc = getushort(bs->bpb.bpbSectors)) && 427 !(sc = getulong(bs->bpb.bpbHugeSectors))) 428 return EINVAL; 429 if (fs->lsndta > sc) 430 return EINVAL; 431 if ((fs->xclus = secblk(fs, sc - fs->lsndta) + 1) < LOCLUS) 432 return EINVAL; 433 fs->fatsz = fs->dirents ? fs->xclus < 0xff6 ? 12 : 16 : 32; 434 sc = (secbyt(fs->spf) << 1) / (fs->fatsz >> 2) - 1; 435 if (fs->xclus > sc) 436 fs->xclus = sc; 437 return 0; 438 } 439 440 /* 441 * Return directory entry from path 442 */ 443 static int 444 namede(DOS_FS *fs, const char *path, const struct direntry **dep) 445 { 446 char name[256]; 447 const struct direntry *de; 448 char *s; 449 size_t n; 450 int err; 451 452 err = 0; 453 de = dot; 454 if (*path == '/') 455 path++; 456 while (*path) { 457 if (!(s = strchr(path, '/'))) 458 s = strchr(path, 0); 459 if ((n = s - path) > 255) 460 return ENAMETOOLONG; 461 memcpy(name, path, n); 462 name[n] = 0; 463 path = s; 464 if (!(de->deAttributes & ATTR_DIRECTORY)) 465 return ENOTDIR; 466 if ((err = lookup(fs, stclus(fs->fatsz, de), name, &de))) 467 return err; 468 if (*path == '/') 469 path++; 470 } 471 *dep = de; 472 return 0; 473 } 474 475 /* 476 * Lookup path segment 477 */ 478 static int 479 lookup(DOS_FS *fs, u_int clus, const char *name, const struct direntry **dep) 480 { 481 static DOS_DIR *dir = NULL; 482 u_char lfn[261]; 483 u_char sfn[13]; 484 u_int nsec, lsec, xdn, chk, sec, ent, x; 485 int err = 0, ok, i; 486 487 if (!clus) 488 for (ent = 0; ent < 2; ent++) 489 if (!strcasecmp(name, dotstr[ent])) { 490 *dep = dot + ent; 491 return 0; 492 } 493 494 if (dir == NULL) { 495 dir = alloc(sizeof(DOS_DIR) * DEPSEC); 496 if (dir == NULL) 497 return ENOMEM; 498 } 499 500 if (!clus && fs->fatsz == 32) 501 clus = fs->rdcl; 502 nsec = !clus ? entsec(fs->dirents) : fs->spc; 503 lsec = 0; 504 xdn = chk = 0; 505 for (;;) { 506 if (!clus && !lsec) 507 lsec = fs->lsndir; 508 else if (okclus(fs, clus)) 509 lsec = blklsn(fs, clus); 510 else { 511 err = EINVAL; 512 goto out; 513 } 514 for (sec = 0; sec < nsec; sec++) { 515 if ((err = ioget(fs->fd, lsec + sec, dir, 1))) 516 goto out; 517 for (ent = 0; ent < DEPSEC; ent++) { 518 if (!*dir[ent].de.deName) { 519 err = ENOENT; 520 goto out; 521 } 522 if (*dir[ent].de.deName != 0xe5) { 523 if (dir[ent].de.deAttributes == 524 ATTR_WIN95) { 525 x = dir[ent].xde.weCnt; 526 if (x & WIN_LAST || 527 (x + 1 == xdn && 528 dir[ent].xde.weChksum == 529 chk)) { 530 if (x & WIN_LAST) { 531 chk = dir[ent].xde.weChksum; 532 x &= WIN_CNT; 533 } 534 if (x >= 1 && x <= 20) { 535 cp_xdnm(lfn, &dir[ent].xde); 536 xdn = x; 537 continue; 538 } 539 } 540 } else if (!(dir[ent].de.deAttributes & 541 ATTR_VOLUME)) { 542 if ((ok = xdn == 1)) { 543 for (x = 0, i = 0; 544 i < 11; i++) 545 x = ((((x & 1) << 7) | (x >> 1)) + 546 dir[ent].de.deName[i]) & 0xff; 547 ok = chk == x && 548 !strcasecmp(name, (const char *)lfn); 549 } 550 if (!ok) { 551 cp_sfn(sfn, &dir[ent].de); 552 ok = !strcasecmp(name, (const char *)sfn); 553 } 554 if (ok) { 555 *dep = &dir[ent].de; 556 goto out2; 557 } 558 } 559 } 560 xdn = 0; 561 } 562 } 563 if (!clus) 564 break; 565 if ((err = fatget(fs, &clus))) 566 goto out; 567 if (fatend(fs->fatsz, clus)) 568 break; 569 } 570 err = ENOENT; 571 out: 572 dealloc(dir, sizeof(DOS_DIR) * DEPSEC); 573 dir = NULL; 574 out2: 575 return err; 576 } 577 578 /* 579 * Copy name from extended directory entry 580 */ 581 static void 582 cp_xdnm(u_char *lfn, struct winentry *xde) 583 { 584 static const struct { 585 u_int off; 586 u_int dim; 587 } ix[3] = { 588 { offsetof(struct winentry, wePart1), 589 sizeof(xde->wePart1) / 2 }, 590 { offsetof(struct winentry, wePart2), 591 sizeof(xde->wePart2) / 2 }, 592 { offsetof(struct winentry, wePart3), 593 sizeof(xde->wePart3) / 2 } 594 }; 595 u_char *p; 596 u_int n, x, c; 597 598 lfn += 13 * ((xde->weCnt & WIN_CNT) - 1); 599 for (n = 0; n < 3; n++) 600 for (p = (u_char *)xde + ix[n].off, x = ix[n].dim; x; 601 p += 2, x--) { 602 if ((c = getushort(p)) && (c < 32 || c > 127)) 603 c = '?'; 604 if (!(*lfn++ = c)) 605 return; 606 } 607 if (xde->weCnt & WIN_LAST) 608 *lfn = 0; 609 } 610 611 /* 612 * Copy short filename 613 */ 614 static void 615 cp_sfn(u_char *sfn, struct direntry *de) 616 { 617 u_char *p; 618 int j, i; 619 620 p = sfn; 621 if (*de->deName != ' ') { 622 for (j = 7; de->deName[j] == ' '; j--); 623 for (i = 0; i <= j; i++) 624 *p++ = de->deName[i]; 625 if (*de->deExtension != ' ') { 626 *p++ = '.'; 627 for (j = 2; de->deExtension[j] == ' '; j--); 628 for (i = 0; i <= j; i++) 629 *p++ = de->deExtension[i]; 630 } 631 } 632 *p = 0; 633 if (*sfn == 5) 634 *sfn = 0xe5; 635 } 636 637 /* 638 * Return size of file in bytes 639 */ 640 static off_t 641 fsize(DOS_FS *fs, struct direntry *de) 642 { 643 u_long size; 644 u_int c; 645 int n; 646 647 if (!(size = getulong(de->deFileSize)) && 648 de->deAttributes & ATTR_DIRECTORY) { 649 if (!(c = getushort(de->deStartCluster))) { 650 size = fs->dirents * sizeof(struct direntry); 651 } else { 652 if ((n = fatcnt(fs, c)) == -1) 653 return n; 654 size = blkbyt(fs, n); 655 } 656 } 657 return size; 658 } 659 660 /* 661 * Count number of clusters in chain 662 */ 663 static int 664 fatcnt(DOS_FS *fs, u_int c) 665 { 666 int n; 667 668 for (n = 0; okclus(fs, c); n++) 669 if (fatget(fs, &c)) 670 return -1; 671 return fatend(fs->fatsz, c) ? n : -1; 672 } 673 674 /* 675 * Get next cluster in cluster chain 676 */ 677 static int 678 fatget(DOS_FS *fs, u_int *c) 679 { 680 u_char buf[4]; 681 u_int x; 682 int err; 683 684 err = ioread(fs, secbyt(fs->lsnfat) + fatoff(fs->fatsz, *c), buf, 685 fs->fatsz != 32 ? 2 : 4); 686 if (err) 687 return err; 688 x = fs->fatsz != 32 ? getushort(buf) : getulong(buf); 689 *c = fs->fatsz == 12 ? *c & 1 ? x >> 4 : x & 0xfff : x; 690 return 0; 691 } 692 693 /* 694 * Is cluster an end-of-chain marker? 695 */ 696 static int 697 fatend(u_int sz, u_int c) 698 { 699 return c > (sz == 12 ? 0xff7U : sz == 16 ? 0xfff7U : 0xffffff7); 700 } 701 702 /* 703 * Offset-based I/O primitive 704 */ 705 static int 706 ioread(DOS_FS *fs, u_int offset, void *buf, u_int nbyte) 707 { 708 char *s; 709 u_int off, n; 710 int err; 711 712 s = buf; 713 if ((off = offset & (SECSIZ - 1))) { 714 offset -= off; 715 if ((err = iobuf(fs, bytsec(offset)))) 716 return err; 717 offset += SECSIZ; 718 if ((n = SECSIZ - off) > nbyte) 719 n = nbyte; 720 memcpy(s, fs->buf + off, n); 721 s += n; 722 nbyte -= n; 723 } 724 n = nbyte & (SECSIZ - 1); 725 if (nbyte -= n) { 726 if ((err = ioget(fs->fd, bytsec(offset), s, bytsec(nbyte)))) 727 return err; 728 offset += nbyte; 729 s += nbyte; 730 } 731 if (n) { 732 if ((err = iobuf(fs, bytsec(offset)))) 733 return err; 734 memcpy(s, fs->buf, n); 735 } 736 return 0; 737 } 738 739 /* 740 * Buffered sector-based I/O primitive 741 */ 742 static int 743 iobuf(DOS_FS *fs, u_int lsec) 744 { 745 int err; 746 747 if (fs->bufsec != lsec) { 748 if ((err = ioget(fs->fd, lsec, fs->buf, 1))) 749 return err; 750 fs->bufsec = lsec; 751 } 752 return 0; 753 } 754 755 /* 756 * Sector-based I/O primitive 757 */ 758 static int 759 ioget(struct open_file *fd, u_int lsec, void *buf, u_int nsec) 760 { 761 size_t rsize; 762 int err; 763 764 #ifndef LIBSA_NO_TWIDDLE 765 twiddle(); 766 #endif 767 err = DEV_STRATEGY(fd->f_dev)(fd->f_devdata, F_READ, lsec, 768 secbyt(nsec), buf, &rsize); 769 return err; 770 } 771
Indexes created Wed Oct 01 19:09:53 GMT 2025