dosfs.c revision 1.14
1 /* $NetBSD: dosfs.c,v 1.14 2008/03/25 21:23:50 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 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 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 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 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 int 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; 264 265 out: 266 return err; 267 } 268 269 /* 270 * Read from file 271 */ 272 int 273 dosfs_read(struct open_file *fd, void *vbuf, size_t nbyte, size_t *resid) 274 { 275 off_t size; 276 u_int8_t *buf = vbuf; 277 u_int nb, off, clus, c, cnt, n; 278 DOS_FILE *f = (DOS_FILE *)fd->f_fsdata; 279 int err = 0; 280 281 nb = (u_int) nbyte; 282 if ((size = fsize(f->fs, &f->de)) == -1) 283 return EINVAL; 284 if (nb > (n = size - f->offset)) 285 nb = n; 286 off = f->offset; 287 if ((clus = stclus(f->fs->fatsz, &f->de))) 288 off &= f->fs->bsize - 1; 289 c = f->c; 290 cnt = nb; 291 while (cnt) { 292 n = 0; 293 if (!c) { 294 if ((c = clus)) 295 n = bytblk(f->fs, f->offset); 296 } else if (!off) { 297 n++; 298 } 299 while (n--) { 300 if ((err = fatget(f->fs, &c))) 301 goto out; 302 if (!okclus(f->fs, c)) { 303 err = EINVAL; 304 goto out; 305 } 306 } 307 if (!clus || (n = f->fs->bsize - off) > cnt) 308 n = cnt; 309 if ((err = ioread(f->fs, (c ? blkoff(f->fs, c) : 310 secbyt(f->fs->lsndir)) + off, 311 buf, n))) 312 goto out; 313 f->offset += n; 314 f->c = c; 315 off = 0; 316 buf += n; 317 cnt -= n; 318 } 319 out: 320 if (resid) 321 *resid = nbyte - nb + cnt; 322 return err; 323 } 324 325 #ifndef LIBSA_NO_FS_WRITE 326 /* 327 * Not implemented. 328 */ 329 int 330 dosfs_write(struct open_file *fd, void *start, size_t size, size_t *resid) 331 { 332 333 return EROFS; 334 } 335 #endif /* !LIBSA_NO_FS_WRITE */ 336 337 #ifndef LIBSA_NO_FS_SEEK 338 /* 339 * Reposition within file 340 */ 341 off_t 342 dosfs_seek(struct open_file *fd, off_t offset, int whence) 343 { 344 off_t off; 345 u_int size; 346 DOS_FILE *f = (DOS_FILE *)fd->f_fsdata; 347 348 size = getulong(f->de.deFileSize); 349 switch (whence) { 350 case SEEK_SET: 351 off = 0; 352 break; 353 case SEEK_CUR: 354 off = f->offset; 355 break; 356 case SEEK_END: 357 off = size; 358 break; 359 default: 360 return -1; 361 } 362 off += offset; 363 if (off < 0 || off > size) 364 return -1; 365 f->offset = (u_int) off; 366 f->c = 0; 367 return off; 368 } 369 #endif /* !LIBSA_NO_FS_SEEK */ 370 371 #ifndef LIBSA_NO_FS_CLOSE 372 /* 373 * Close open file 374 */ 375 int 376 dosfs_close(struct open_file *fd) 377 { 378 DOS_FILE *f = (DOS_FILE *)fd->f_fsdata; 379 DOS_FS *fs = f->fs; 380 381 f->fs->links--; 382 dealloc(f, sizeof(DOS_FILE)); 383 dos_unmount(fs); 384 return 0; 385 } 386 #endif /* !LIBSA_NO_FS_CLOSE */ 387 388 /* 389 * Return some stat information on a file. 390 */ 391 int 392 dosfs_stat(struct open_file *fd, struct stat *sb) 393 { 394 DOS_FILE *f = (DOS_FILE *)fd->f_fsdata; 395 396 /* only important stuff */ 397 sb->st_mode = (f->de.deAttributes & ATTR_DIRECTORY) ? 398 (S_IFDIR | 0555) : (S_IFREG | 0444); 399 sb->st_nlink = 1; 400 sb->st_uid = 0; 401 sb->st_gid = 0; 402 if ((sb->st_size = fsize(f->fs, &f->de)) == -1) 403 return EINVAL; 404 return 0; 405 } 406 407 /* 408 * Parse DOS boot sector 409 */ 410 static int 411 parsebs(DOS_FS *fs, DOS_BS *bs) 412 { 413 u_int sc; 414 415 if ((bs->jmp[0] != 0x69 && 416 bs->jmp[0] != 0xe9 && 417 (bs->jmp[0] != 0xeb || bs->jmp[2] != 0x90)) || 418 bs->bpb.bpbMedia < 0xf0) 419 return EINVAL; 420 if (getushort(bs->bpb.bpbBytesPerSec) != SECSIZ) 421 return EINVAL; 422 if (!(fs->spc = bs->bpb.bpbSecPerClust) || fs->spc & (fs->spc - 1)) 423 return EINVAL; 424 fs->bsize = secbyt(fs->spc); 425 fs->bshift = ffs(fs->bsize) - 1; 426 if ((fs->spf = getushort(bs->bpb.bpbFATsecs))) { 427 if (bs->bpb.bpbFATs != 2) 428 return EINVAL; 429 if (!(fs->dirents = getushort(bs->bpb.bpbRootDirEnts))) 430 return EINVAL; 431 } else { 432 if (!(fs->spf = getulong(bs->bpb.bpbBigFATsecs))) 433 return EINVAL; 434 if (!bs->bpb.bpbFATs || bs->bpb.bpbFATs > 16) 435 return EINVAL; 436 if ((fs->rdcl = getulong(bs->bpb.bpbRootClust)) < LOCLUS) 437 return EINVAL; 438 } 439 if (!(fs->lsnfat = getushort(bs->bpb.bpbResSectors))) 440 return EINVAL; 441 fs->lsndir = fs->lsnfat + fs->spf * bs->bpb.bpbFATs; 442 fs->lsndta = fs->lsndir + entsec(fs->dirents); 443 if (!(sc = getushort(bs->bpb.bpbSectors)) && 444 !(sc = getulong(bs->bpb.bpbHugeSectors))) 445 return EINVAL; 446 if (fs->lsndta > sc) 447 return EINVAL; 448 if ((fs->xclus = secblk(fs, sc - fs->lsndta) + 1) < LOCLUS) 449 return EINVAL; 450 fs->fatsz = fs->dirents ? fs->xclus < 0xff6 ? 12 : 16 : 32; 451 sc = (secbyt(fs->spf) << 1) / (fs->fatsz >> 2) - 1; 452 if (fs->xclus > sc) 453 fs->xclus = sc; 454 return 0; 455 } 456 457 /* 458 * Return directory entry from path 459 */ 460 static int 461 namede(DOS_FS *fs, const char *path, const struct direntry **dep) 462 { 463 char name[256]; 464 const struct direntry *de; 465 char *s; 466 size_t n; 467 int err; 468 469 err = 0; 470 de = dot; 471 if (*path == '/') 472 path++; 473 while (*path) { 474 if (!(s = strchr(path, '/'))) 475 s = strchr(path, 0); 476 if ((n = s - path) > 255) 477 return ENAMETOOLONG; 478 memcpy(name, path, n); 479 name[n] = 0; 480 path = s; 481 if (!(de->deAttributes & ATTR_DIRECTORY)) 482 return ENOTDIR; 483 if ((err = lookup(fs, stclus(fs->fatsz, de), name, &de))) 484 return err; 485 if (*path == '/') 486 path++; 487 } 488 *dep = de; 489 return 0; 490 } 491 492 /* 493 * Lookup path segment 494 */ 495 static int 496 lookup(DOS_FS *fs, u_int clus, const char *name, const struct direntry **dep) 497 { 498 static DOS_DIR *dir = NULL; 499 u_char lfn[261]; 500 u_char sfn[13]; 501 u_int nsec, lsec, xdn, chk, sec, ent, x; 502 int err = 0, ok, i; 503 504 if (!clus) 505 for (ent = 0; ent < 2; ent++) 506 if (!strcasecmp(name, dotstr[ent])) { 507 *dep = dot + ent; 508 return 0; 509 } 510 511 if (dir == NULL) { 512 dir = alloc(sizeof(DOS_DIR) * DEPSEC); 513 if (dir == NULL) 514 return ENOMEM; 515 } 516 517 if (!clus && fs->fatsz == 32) 518 clus = fs->rdcl; 519 nsec = !clus ? entsec(fs->dirents) : fs->spc; 520 lsec = 0; 521 xdn = chk = 0; 522 for (;;) { 523 if (!clus && !lsec) 524 lsec = fs->lsndir; 525 else if (okclus(fs, clus)) 526 lsec = blklsn(fs, clus); 527 else { 528 err = EINVAL; 529 goto out; 530 } 531 for (sec = 0; sec < nsec; sec++) { 532 if ((err = ioget(fs->fd, lsec + sec, dir, 1))) 533 goto out; 534 for (ent = 0; ent < DEPSEC; ent++) { 535 if (!*dir[ent].de.deName) { 536 err = ENOENT; 537 goto out; 538 } 539 if (*dir[ent].de.deName != 0xe5) { 540 if (dir[ent].de.deAttributes == 541 ATTR_WIN95) { 542 x = dir[ent].xde.weCnt; 543 if (x & WIN_LAST || 544 (x + 1 == xdn && 545 dir[ent].xde.weChksum == 546 chk)) { 547 if (x & WIN_LAST) { 548 chk = dir[ent].xde.weChksum; 549 x &= WIN_CNT; 550 } 551 if (x >= 1 && x <= 20) { 552 cp_xdnm(lfn, &dir[ent].xde); 553 xdn = x; 554 continue; 555 } 556 } 557 } else if (!(dir[ent].de.deAttributes & 558 ATTR_VOLUME)) { 559 if ((ok = xdn == 1)) { 560 for (x = 0, i = 0; 561 i < 11; i++) 562 x = ((((x & 1) << 7) | (x >> 1)) + 563 dir[ent].de.deName[i]) & 0xff; 564 ok = chk == x && 565 !strcasecmp(name, (const char *)lfn); 566 } 567 if (!ok) { 568 cp_sfn(sfn, &dir[ent].de); 569 ok = !strcasecmp(name, (const char *)sfn); 570 } 571 if (ok) { 572 *dep = &dir[ent].de; 573 goto out2; 574 } 575 } 576 } 577 xdn = 0; 578 } 579 } 580 if (!clus) 581 break; 582 if ((err = fatget(fs, &clus))) 583 goto out; 584 if (fatend(fs->fatsz, clus)) 585 break; 586 } 587 err = ENOENT; 588 out: 589 dealloc(dir, sizeof(DOS_DIR) * DEPSEC); 590 dir = NULL; 591 out2: 592 return err; 593 } 594 595 /* 596 * Copy name from extended directory entry 597 */ 598 static void 599 cp_xdnm(u_char *lfn, struct winentry *xde) 600 { 601 static const struct { 602 u_int off; 603 u_int dim; 604 } ix[3] = { 605 { offsetof(struct winentry, wePart1), 606 sizeof(xde->wePart1) / 2 }, 607 { offsetof(struct winentry, wePart2), 608 sizeof(xde->wePart2) / 2 }, 609 { offsetof(struct winentry, wePart3), 610 sizeof(xde->wePart3) / 2 } 611 }; 612 u_char *p; 613 u_int n, x, c; 614 615 lfn += 13 * ((xde->weCnt & WIN_CNT) - 1); 616 for (n = 0; n < 3; n++) 617 for (p = (u_char *)xde + ix[n].off, x = ix[n].dim; x; 618 p += 2, x--) { 619 if ((c = getushort(p)) && (c < 32 || c > 127)) 620 c = '?'; 621 if (!(*lfn++ = c)) 622 return; 623 } 624 if (xde->weCnt & WIN_LAST) 625 *lfn = 0; 626 } 627 628 /* 629 * Copy short filename 630 */ 631 static void 632 cp_sfn(u_char *sfn, struct direntry *de) 633 { 634 u_char *p; 635 int j, i; 636 637 p = sfn; 638 if (*de->deName != ' ') { 639 for (j = 7; de->deName[j] == ' '; j--); 640 for (i = 0; i <= j; i++) 641 *p++ = de->deName[i]; 642 if (*de->deExtension != ' ') { 643 *p++ = '.'; 644 for (j = 2; de->deExtension[j] == ' '; j--); 645 for (i = 0; i <= j; i++) 646 *p++ = de->deExtension[i]; 647 } 648 } 649 *p = 0; 650 if (*sfn == 5) 651 *sfn = 0xe5; 652 } 653 654 /* 655 * Return size of file in bytes 656 */ 657 static off_t 658 fsize(DOS_FS *fs, struct direntry *de) 659 { 660 u_long size; 661 u_int c; 662 int n; 663 664 if (!(size = getulong(de->deFileSize)) && 665 de->deAttributes & ATTR_DIRECTORY) { 666 if (!(c = getushort(de->deStartCluster))) { 667 size = fs->dirents * sizeof(struct direntry); 668 } else { 669 if ((n = fatcnt(fs, c)) == -1) 670 return n; 671 size = blkbyt(fs, n); 672 } 673 } 674 return size; 675 } 676 677 /* 678 * Count number of clusters in chain 679 */ 680 static int 681 fatcnt(DOS_FS *fs, u_int c) 682 { 683 int n; 684 685 for (n = 0; okclus(fs, c); n++) 686 if (fatget(fs, &c)) 687 return -1; 688 return fatend(fs->fatsz, c) ? n : -1; 689 } 690 691 /* 692 * Get next cluster in cluster chain 693 */ 694 static int 695 fatget(DOS_FS *fs, u_int *c) 696 { 697 u_char buf[4]; 698 u_int x; 699 int err; 700 701 err = ioread(fs, secbyt(fs->lsnfat) + fatoff(fs->fatsz, *c), buf, 702 fs->fatsz != 32 ? 2 : 4); 703 if (err) 704 return err; 705 x = fs->fatsz != 32 ? getushort(buf) : getulong(buf); 706 *c = fs->fatsz == 12 ? *c & 1 ? x >> 4 : x & 0xfff : x; 707 return 0; 708 } 709 710 /* 711 * Is cluster an end-of-chain marker? 712 */ 713 static int 714 fatend(u_int sz, u_int c) 715 { 716 return c > (sz == 12 ? 0xff7U : sz == 16 ? 0xfff7U : 0xffffff7); 717 } 718 719 /* 720 * Offset-based I/O primitive 721 */ 722 static int 723 ioread(DOS_FS *fs, u_int offset, void *buf, u_int nbyte) 724 { 725 char *s; 726 u_int off, n; 727 int err; 728 729 s = buf; 730 if ((off = offset & (SECSIZ - 1))) { 731 offset -= off; 732 if ((err = iobuf(fs, bytsec(offset)))) 733 return err; 734 offset += SECSIZ; 735 if ((n = SECSIZ - off) > nbyte) 736 n = nbyte; 737 memcpy(s, fs->buf + off, n); 738 s += n; 739 nbyte -= n; 740 } 741 n = nbyte & (SECSIZ - 1); 742 if (nbyte -= n) { 743 if ((err = ioget(fs->fd, bytsec(offset), s, bytsec(nbyte)))) 744 return err; 745 offset += nbyte; 746 s += nbyte; 747 } 748 if (n) { 749 if ((err = iobuf(fs, bytsec(offset)))) 750 return err; 751 memcpy(s, fs->buf, n); 752 } 753 return 0; 754 } 755 756 /* 757 * Buffered sector-based I/O primitive 758 */ 759 static int 760 iobuf(DOS_FS *fs, u_int lsec) 761 { 762 int err; 763 764 if (fs->bufsec != lsec) { 765 if ((err = ioget(fs->fd, lsec, fs->buf, 1))) 766 return err; 767 fs->bufsec = lsec; 768 } 769 return 0; 770 } 771 772 /* 773 * Sector-based I/O primitive 774 */ 775 static int 776 ioget(struct open_file *fd, u_int lsec, void *buf, u_int nsec) 777 { 778 size_t rsize; 779 int err; 780 781 #ifndef LIBSA_NO_TWIDDLE 782 twiddle(); 783 #endif 784 err = DEV_STRATEGY(fd->f_dev)(fd->f_devdata, F_READ, lsec, 785 secbyt(nsec), buf, &rsize); 786 return err; 787 } 788
Indexes created Wed Oct 01 19:09:53 GMT 2025