lib/string.c

   1 /*
   2  *  linux/lib/string.c
   3  *
   4  *  Copyright (C) 1991, 1992  Linus Torvalds
   5  */
   6
   7 /*
   8  * stupid library routines.. The optimized versions should generally be found
   9  * as inline code in <asm-xx/string.h>
  10  *
  11  * These are buggy as well..
  12  *
  13  * * Fri Jun 25 1999, Ingo Oeser <ioe@informatik.tu-chemnitz.de>
  14  * -  Added strsep() which will replace strtok() soon (because strsep() is
  15  *    reentrant and should be faster). Use only strsep() in new code, please.
  16  *
  17  * * Sat Feb 09 2002, Jason Thomas <jason@topic.com.au>,
  18  *                    Matthew Hawkins <matt@mh.dropbear.id.au>
  19  * -  Kissed strtok() goodbye
  20  */
  21
  22 #include <linux/types.h>
  23 #include <linux/string.h>
  24 #include <linux/ctype.h>
  25 #include <linux/kernel.h>
  26 #include <linux/export.h>
  27 #include <linux/bug.h>
  28 #include <linux/errno.h>
  29
  30 #ifndef __HAVE_ARCH_STRNICMP
  31 /**
  32  * strnicmp - Case insensitive, length-limited string comparison
  33  * @s1: One string
  34  * @s2: The other string
  35  * @len: the maximum number of characters to compare
  36  */
  37 int strnicmp(const char *s1, const char *s2, size_t len)
  38 {
  39         /* Yes, Virginia, it had better be unsigned */
  40         unsigned char c1, c2;
  41
  42         if (!len)
  43                 return 0;
  44
  45         do {
  46                 c1 = *s1++;
  47                 c2 = *s2++;
  48                 if (!c1 || !c2)
  49                         break;
  50                 if (c1 == c2)
  51                         continue;
  52                 c1 = tolower(c1);
  53                 c2 = tolower(c2);
  54                 if (c1 != c2)
  55                         break;
  56         } while (--len);
  57         return (int)c1 - (int)c2;
  58 }
  59 EXPORT_SYMBOL(strnicmp);
  60 #endif
  61
  62 #ifndef __HAVE_ARCH_STRCASECMP
  63 int strcasecmp(const char *s1, const char *s2)
  64 {
  65         int c1, c2;
  66
  67         do {
  68                 c1 = tolower(*s1++);
  69                 c2 = tolower(*s2++);
  70         } while (c1 == c2 && c1 != 0);
  71         return c1 - c2;
  72 }
  73 EXPORT_SYMBOL(strcasecmp);
  74 #endif
  75
  76 #ifndef __HAVE_ARCH_STRNCASECMP
  77 int strncasecmp(const char *s1, const char *s2, size_t n)
  78 {
  79         int c1, c2;
  80
  81         do {
  82                 c1 = tolower(*s1++);
  83                 c2 = tolower(*s2++);
  84         } while ((--n > 0) && c1 == c2 && c1 != 0);
  85         return c1 - c2;
  86 }
  87 EXPORT_SYMBOL(strncasecmp);
  88 #endif
  89
  90 #ifndef __HAVE_ARCH_STRCPY
  91 /**
  92  * strcpy - Copy a %NUL terminated string
  93  * @dest: Where to copy the string to
  94  * @src: Where to copy the string from
  95  */
  96 #undef strcpy
  97 char *strcpy(char *dest, const char *src)
  98 {
  99         char *tmp = dest;
 100
 101         while ((*dest++ = *src++) != '\0')
 102                 /* nothing */;
 103         return tmp;
 104 }
 105 EXPORT_SYMBOL(strcpy);
 106 #endif
 107
 108 #ifndef __HAVE_ARCH_STRNCPY
 109 /**
 110  * strncpy - Copy a length-limited, C-string
 111  * @dest: Where to copy the string to
 112  * @src: Where to copy the string from
 113  * @count: The maximum number of bytes to copy
 114  *
 115  * The result is not %NUL-terminated if the source exceeds
 116  * @count bytes.
 117  *
 118  * In the case where the length of @src is less than  that  of
 119  * count, the remainder of @dest will be padded with %NUL.
 120  *
 121  */
 122 char *strncpy(char *dest, const char *src, size_t count)
 123 {
 124         char *tmp = dest;
 125
 126         while (count) {
 127                 if ((*tmp = *src) != 0)
 128                         src++;
 129                 tmp++;
 130                 count--;
 131         }
 132         return dest;
 133 }
 134 EXPORT_SYMBOL(strncpy);
 135 #endif
 136
 137 #ifndef __HAVE_ARCH_STRLCPY
 138 /**
 139  * strlcpy - Copy a C-string into a sized buffer
 140  * @dest: Where to copy the string to
 141  * @src: Where to copy the string from
 142  * @size: size of destination buffer
 143  *
 144  * Compatible with *BSD: the result is always a valid
 145  * NUL-terminated string that fits in the buffer (unless,
 146  * of course, the buffer size is zero). It does not pad
 147  * out the result like strncpy() does.
 148  */
 149 size_t strlcpy(char *dest, const char *src, size_t size)
 150 {
 151         size_t ret = strlen(src);
 152
 153         if (size) {
 154                 size_t len = (ret >= size) ? size - 1 : ret;
 155                 memcpy(dest, src, len);
 156                 dest[len] = '\0';
 157         }
 158         return ret;
 159 }
 160 EXPORT_SYMBOL(strlcpy);
 161 #endif
 162
 163 #ifndef __HAVE_ARCH_STRCAT
 164 /**
 165  * strcat - Append one %NUL-terminated string to another
 166  * @dest: The string to be appended to
 167  * @src: The string to append to it
 168  */
 169 #undef strcat
 170 char *strcat(char *dest, const char *src)
 171 {
 172         char *tmp = dest;
 173
 174         while (*dest)
 175                 dest++;
 176         while ((*dest++ = *src++) != '\0')
 177                 ;
 178         return tmp;
 179 }
 180 EXPORT_SYMBOL(strcat);
 181 #endif
 182
 183 #ifndef __HAVE_ARCH_STRNCAT
 184 /**
 185  * strncat - Append a length-limited, C-string to another
 186  * @dest: The string to be appended to
 187  * @src: The string to append to it
 188  * @count: The maximum numbers of bytes to copy
 189  *
 190  * Note that in contrast to strncpy(), strncat() ensures the result is
 191  * terminated.
 192  */
 193 char *strncat(char *dest, const char *src, size_t count)
 194 {
 195         char *tmp = dest;
 196
 197         if (count) {
 198                 while (*dest)
 199                         dest++;
 200                 while ((*dest++ = *src++) != 0) {
 201                         if (--count == 0) {
 202                                 *dest = '\0';
 203                                 break;
 204                         }
 205                 }
 206         }
 207         return tmp;
 208 }
 209 EXPORT_SYMBOL(strncat);
 210 #endif
 211
 212 #ifndef __HAVE_ARCH_STRLCAT
 213 /**
 214  * strlcat - Append a length-limited, C-string to another
 215  * @dest: The string to be appended to
 216  * @src: The string to append to it
 217  * @count: The size of the destination buffer.
 218  */
 219 size_t strlcat(char *dest, const char *src, size_t count)
 220 {
 221         size_t dsize = strlen(dest);
 222         size_t len = strlen(src);
 223         size_t res = dsize + len;
 224
 225         /* This would be a bug */
 226         BUG_ON(dsize >= count);
 227
 228         dest += dsize;
 229         count -= dsize;
 230         if (len >= count)
 231                 len = count-1;
 232         memcpy(dest, src, len);
 233         dest[len] = 0;
 234         return res;
 235 }
 236 EXPORT_SYMBOL(strlcat);
 237 #endif
 238
 239 #ifndef __HAVE_ARCH_STRCMP
 240 /**
 241  * strcmp - Compare two strings
 242  * @cs: One string
 243  * @ct: Another string
 244  */
 245 #undef strcmp
 246 int strcmp(const char *cs, const char *ct)
 247 {
 248         unsigned char c1, c2;
 249
 250         while (1) {
 251                 c1 = *cs++;
 252                 c2 = *ct++;
 253                 if (c1 != c2)
 254                         return c1 < c2 ? -1 : 1;
 255                 if (!c1)
 256                         break;
 257         }
 258         return 0;
 259 }
 260 EXPORT_SYMBOL(strcmp);
 261 #endif
 262
 263 #ifndef __HAVE_ARCH_STRNCMP
 264 /**
 265  * strncmp - Compare two length-limited strings
 266  * @cs: One string
 267  * @ct: Another string
 268  * @count: The maximum number of bytes to compare
 269  */
 270 int strncmp(const char *cs, const char *ct, size_t count)
 271 {
 272         unsigned char c1, c2;
 273
 274         while (count) {
 275                 c1 = *cs++;
 276                 c2 = *ct++;
 277                 if (c1 != c2)
 278                         return c1 < c2 ? -1 : 1;
 279                 if (!c1)
 280                         break;
 281                 count--;
 282         }
 283         return 0;
 284 }
 285 EXPORT_SYMBOL(strncmp);
 286 #endif
 287
 288 #ifndef __HAVE_ARCH_STRCHR
 289 /**
 290  * strchr - Find the first occurrence of a character in a string
 291  * @s: The string to be searched
 292  * @c: The character to search for
 293  */
 294 char *strchr(const char *s, int c)
 295 {
 296         for (; *s != (char)c; ++s)
 297                 if (*s == '\0')
 298                         return NULL;
 299         return (char *)s;
 300 }
 301 EXPORT_SYMBOL(strchr);
 302 #endif
 303
 304 #ifndef __HAVE_ARCH_STRCHRNUL
 305 /**
 306  * strchrnul - Find and return a character in a string, or end of string
 307  * @s: The string to be searched
 308  * @c: The character to search for
 309  *
 310  * Returns pointer to first occurrence of 'c' in s. If c is not found, then
 311  * return a pointer to the null byte at the end of s.
 312  */
 313 char *strchrnul(const char *s, int c)
 314 {
 315         while (*s && *s != (char)c)
 316                 s++;
 317         return (char *)s;
 318 }
 319 EXPORT_SYMBOL(strchrnul);
 320 #endif
 321
 322 #ifndef __HAVE_ARCH_STRRCHR
 323 /**
 324  * strrchr - Find the last occurrence of a character in a string
 325  * @s: The string to be searched
 326  * @c: The character to search for
 327  */
 328 char *strrchr(const char *s, int c)
 329 {
 330        const char *p = s + strlen(s);
 331        do {
 332            if (*p == (char)c)
 333                return (char *)p;
 334        } while (--p >= s);
 335        return NULL;
 336 }
 337 EXPORT_SYMBOL(strrchr);
 338 #endif
 339
 340 #ifndef __HAVE_ARCH_STRNCHR
 341 /**
 342  * strnchr - Find a character in a length limited string
 343  * @s: The string to be searched
 344  * @count: The number of characters to be searched
 345  * @c: The character to search for
 346  */
 347 char *strnchr(const char *s, size_t count, int c)
 348 {
 349         for (; count-- && *s != '\0'; ++s)
 350                 if (*s == (char)c)
 351                         return (char *)s;
 352         return NULL;
 353 }
 354 EXPORT_SYMBOL(strnchr);
 355 #endif
 356
 357 /**
 358  * skip_spaces - Removes leading whitespace from @str.
 359  * @str: The string to be stripped.
 360  *
 361  * Returns a pointer to the first non-whitespace character in @str.
 362  */
 363 char *skip_spaces(const char *str)
 364 {
 365         while (isspace(*str))
 366                 ++str;
 367         return (char *)str;
 368 }
 369 EXPORT_SYMBOL(skip_spaces);
 370
 371 /**
 372  * strim - Removes leading and trailing whitespace from @s.
 373  * @s: The string to be stripped.
 374  *
 375  * Note that the first trailing whitespace is replaced with a %NUL-terminator
 376  * in the given string @s. Returns a pointer to the first non-whitespace
 377  * character in @s.
 378  */
 379 char *strim(char *s)
 380 {
 381         size_t size;
 382         char *end;
 383
 384         size = strlen(s);
 385         if (!size)
 386                 return s;
 387
 388         end = s + size - 1;
 389         while (end >= s && isspace(*end))
 390                 end--;
 391         *(end + 1) = '\0';
 392
 393         return skip_spaces(s);
 394 }
 395 EXPORT_SYMBOL(strim);
 396
 397 #ifndef __HAVE_ARCH_STRLEN
 398 /**
 399  * strlen - Find the length of a string
 400  * @s: The string to be sized
 401  */
 402 size_t strlen(const char *s)
 403 {
 404         const char *sc;
 405
 406         for (sc = s; *sc != '\0'; ++sc)
 407                 /* nothing */;
 408         return sc - s;
 409 }
 410 EXPORT_SYMBOL(strlen);
 411 #endif
 412
 413 #ifndef __HAVE_ARCH_STRNLEN
 414 /**
 415  * strnlen - Find the length of a length-limited string
 416  * @s: The string to be sized
 417  * @count: The maximum number of bytes to search
 418  */
 419 size_t strnlen(const char *s, size_t count)
 420 {
 421         const char *sc;
 422
 423         for (sc = s; count-- && *sc != '\0'; ++sc)
 424                 /* nothing */;
 425         return sc - s;
 426 }
 427 EXPORT_SYMBOL(strnlen);
 428 #endif
 429
 430 #ifndef __HAVE_ARCH_STRSPN
 431 /**
 432  * strspn - Calculate the length of the initial substring of @s which only contain letters in @accept
 433  * @s: The string to be searched
 434  * @accept: The string to search for
 435  */
 436 size_t strspn(const char *s, const char *accept)
 437 {
 438         const char *p;
 439         const char *a;
 440         size_t count = 0;
 441
 442         for (p = s; *p != '\0'; ++p) {
 443                 for (a = accept; *a != '\0'; ++a) {
 444                         if (*p == *a)
 445                                 break;
 446                 }
 447                 if (*a == '\0')
 448                         return count;
 449                 ++count;
 450         }
 451         return count;
 452 }
 453
 454 EXPORT_SYMBOL(strspn);
 455 #endif
 456
 457 #ifndef __HAVE_ARCH_STRCSPN
 458 /**
 459  * strcspn - Calculate the length of the initial substring of @s which does not contain letters in @reject
 460  * @s: The string to be searched
 461  * @reject: The string to avoid
 462  */
 463 size_t strcspn(const char *s, const char *reject)
 464 {
 465         const char *p;
 466         const char *r;
 467         size_t count = 0;
 468
 469         for (p = s; *p != '\0'; ++p) {
 470                 for (r = reject; *r != '\0'; ++r) {
 471                         if (*p == *r)
 472                                 return count;
 473                 }
 474                 ++count;
 475         }
 476         return count;
 477 }
 478 EXPORT_SYMBOL(strcspn);
 479 #endif
 480
 481 #ifndef __HAVE_ARCH_STRPBRK
 482 /**
 483  * strpbrk - Find the first occurrence of a set of characters
 484  * @cs: The string to be searched
 485  * @ct: The characters to search for
 486  */
 487 char *strpbrk(const char *cs, const char *ct)
 488 {
 489         const char *sc1, *sc2;
 490
 491         for (sc1 = cs; *sc1 != '\0'; ++sc1) {
 492                 for (sc2 = ct; *sc2 != '\0'; ++sc2) {
 493                         if (*sc1 == *sc2)
 494                                 return (char *)sc1;
 495                 }
 496         }
 497         return NULL;
 498 }
 499 EXPORT_SYMBOL(strpbrk);
 500 #endif
 501
 502 #ifndef __HAVE_ARCH_STRSEP
 503 /**
 504  * strsep - Split a string into tokens
 505  * @s: The string to be searched
 506  * @ct: The characters to search for
 507  *
 508  * strsep() updates @s to point after the token, ready for the next call.
 509  *
 510  * It returns empty tokens, too, behaving exactly like the libc function
 511  * of that name. In fact, it was stolen from glibc2 and de-fancy-fied.
 512  * Same semantics, slimmer shape. ;)
 513  */
 514 char *strsep(char **s, const char *ct)
 515 {
 516         char *sbegin = *s;
 517         char *end;
 518
 519         if (sbegin == NULL)
 520                 return NULL;
 521
 522         end = strpbrk(sbegin, ct);
 523         if (end)
 524                 *end++ = '\0';
 525         *s = end;
 526         return sbegin;
 527 }
 528 EXPORT_SYMBOL(strsep);
 529 #endif
 530
 531 /**
 532  * sysfs_streq - return true if strings are equal, modulo trailing newline
 533  * @s1: one string
 534  * @s2: another string
 535  *
 536  * This routine returns true iff two strings are equal, treating both
 537  * NUL and newline-then-NUL as equivalent string terminations.  It's
 538  * geared for use with sysfs input strings, which generally terminate
 539  * with newlines but are compared against values without newlines.
 540  */
 541 bool sysfs_streq(const char *s1, const char *s2)
 542 {
 543         while (*s1 && *s1 == *s2) {
 544                 s1++;
 545                 s2++;
 546         }
 547
 548         if (*s1 == *s2)
 549                 return true;
 550         if (!*s1 && *s2 == '\n' && !s2[1])
 551                 return true;
 552         if (*s1 == '\n' && !s1[1] && !*s2)
 553                 return true;
 554         return false;
 555 }
 556 EXPORT_SYMBOL(sysfs_streq);
 557
 558 /**
 559  * strtobool - convert common user inputs into boolean values
 560  * @s: input string
 561  * @res: result
 562  *
 563  * This routine returns 0 iff the first character is one of 'Yy1Nn0'.
 564  * Otherwise it will return -EINVAL.  Value pointed to by res is
 565  * updated upon finding a match.
 566  */
 567 int strtobool(const char *s, bool *res)
 568 {
 569         switch (s[0]) {
 570         case 'y':
 571         case 'Y':
 572         case '1':
 573                 *res = true;
 574                 break;
 575         case 'n':
 576         case 'N':
 577         case '0':
 578                 *res = false;
 579                 break;
 580         default:
 581                 return -EINVAL;
 582         }
 583         return 0;
 584 }
 585 EXPORT_SYMBOL(strtobool);
 586
 587 #ifndef __HAVE_ARCH_MEMSET
 588 /**
 589  * memset - Fill a region of memory with the given value
 590  * @s: Pointer to the start of the area.
 591  * @c: The byte to fill the area with
 592  * @count: The size of the area.
 593  *
 594  * Do not use memset() to access IO space, use memset_io() instead.
 595  */
 596 void *memset(void *s, int c, size_t count)
 597 {
 598         char *xs = s;
 599
 600         while (count--)
 601                 *xs++ = c;
 602         return s;
 603 }
 604 EXPORT_SYMBOL(memset);
 605 #endif
 606
 607 /**
 608  * memzero_explicit - Fill a region of memory (e.g. sensitive
 609  *                    keying data) with 0s.
 610  * @s: Pointer to the start of the area.
 611  * @count: The size of the area.
 612  *
 613  * memzero_explicit() doesn't need an arch-specific version as
 614  * it just invokes the one of memset() implicitly.
 615  */
 616 void memzero_explicit(void *s, size_t count)
 617 {
 618         memset(s, 0, count);
 619         OPTIMIZER_HIDE_VAR(s);
 620 }
 621 EXPORT_SYMBOL(memzero_explicit);
 622
 623 #ifndef __HAVE_ARCH_MEMCPY
 624 /**
 625  * memcpy - Copy one area of memory to another
 626  * @dest: Where to copy to
 627  * @src: Where to copy from
 628  * @count: The size of the area.
 629  *
 630  * You should not use this function to access IO space, use memcpy_toio()
 631  * or memcpy_fromio() instead.
 632  */
 633 void *memcpy(void *dest, const void *src, size_t count)
 634 {
 635         char *tmp = dest;
 636         const char *s = src;
 637
 638         while (count--)
 639                 *tmp++ = *s++;
 640         return dest;
 641 }
 642 EXPORT_SYMBOL(memcpy);
 643 #endif
 644
 645 #ifndef __HAVE_ARCH_MEMMOVE
 646 /**
 647  * memmove - Copy one area of memory to another
 648  * @dest: Where to copy to
 649  * @src: Where to copy from
 650  * @count: The size of the area.
 651  *
 652  * Unlike memcpy(), memmove() copes with overlapping areas.
 653  */
 654 void *memmove(void *dest, const void *src, size_t count)
 655 {
 656         char *tmp;
 657         const char *s;
 658
 659         if (dest <= src) {
 660                 tmp = dest;
 661                 s = src;
 662                 while (count--)
 663                         *tmp++ = *s++;
 664         } else {
 665                 tmp = dest;
 666                 tmp += count;
 667                 s = src;
 668                 s += count;
 669                 while (count--)
 670                         *--tmp = *--s;
 671         }
 672         return dest;
 673 }
 674 EXPORT_SYMBOL(memmove);
 675 #endif
 676
 677 #ifndef __HAVE_ARCH_MEMCMP
 678 /**
 679  * memcmp - Compare two areas of memory
 680  * @cs: One area of memory
 681  * @ct: Another area of memory
 682  * @count: The size of the area.
 683  */
 684 #undef memcmp
 685 __visible int memcmp(const void *cs, const void *ct, size_t count)
 686 {
 687         const unsigned char *su1, *su2;
 688         int res = 0;
 689
 690         for (su1 = cs, su2 = ct; 0 < count; ++su1, ++su2, count--)
 691                 if ((res = *su1 - *su2) != 0)
 692                         break;
 693         return res;
 694 }
 695 EXPORT_SYMBOL(memcmp);
 696 #endif
 697
 698 #ifndef __HAVE_ARCH_MEMSCAN
 699 /**
 700  * memscan - Find a character in an area of memory.
 701  * @addr: The memory area
 702  * @c: The byte to search for
 703  * @size: The size of the area.
 704  *
 705  * returns the address of the first occurrence of @c, or 1 byte past
 706  * the area if @c is not found
 707  */
 708 void *memscan(void *addr, int c, size_t size)
 709 {
 710         unsigned char *p = addr;
 711
 712         while (size) {
 713                 if (*p == c)
 714                         return (void *)p;
 715                 p++;
 716                 size--;
 717         }
 718         return (void *)p;
 719 }
 720 EXPORT_SYMBOL(memscan);
 721 #endif
 722
 723 #ifndef __HAVE_ARCH_STRSTR
 724 /**
 725  * strstr - Find the first substring in a %NUL terminated string
 726  * @s1: The string to be searched
 727  * @s2: The string to search for
 728  */
 729 char *strstr(const char *s1, const char *s2)
 730 {
 731         size_t l1, l2;
 732
 733         l2 = strlen(s2);
 734         if (!l2)
 735                 return (char *)s1;
 736         l1 = strlen(s1);
 737         while (l1 >= l2) {
 738                 l1--;
 739                 if (!memcmp(s1, s2, l2))
 740                         return (char *)s1;
 741                 s1++;
 742         }
 743         return NULL;
 744 }
 745 EXPORT_SYMBOL(strstr);
 746 #endif
 747
 748 #ifndef __HAVE_ARCH_STRNSTR
 749 /**
 750  * strnstr - Find the first substring in a length-limited string
 751  * @s1: The string to be searched
 752  * @s2: The string to search for
 753  * @len: the maximum number of characters to search
 754  */
 755 char *strnstr(const char *s1, const char *s2, size_t len)
 756 {
 757         size_t l2;
 758
 759         l2 = strlen(s2);
 760         if (!l2)
 761                 return (char *)s1;
 762         while (len >= l2) {
 763                 len--;
 764                 if (!memcmp(s1, s2, l2))
 765                         return (char *)s1;
 766                 s1++;
 767         }
 768         return NULL;
 769 }
 770 EXPORT_SYMBOL(strnstr);
 771 #endif
 772
 773 #ifndef __HAVE_ARCH_MEMCHR
 774 /**
 775  * memchr - Find a character in an area of memory.
 776  * @s: The memory area
 777  * @c: The byte to search for
 778  * @n: The size of the area.
 779  *
 780  * returns the address of the first occurrence of @c, or %NULL
 781  * if @c is not found
 782  */
 783 void *memchr(const void *s, int c, size_t n)
 784 {
 785         const unsigned char *p = s;
 786         while (n-- != 0) {
 787                 if ((unsigned char)c == *p++) {
 788                         return (void *)(p - 1);
 789                 }
 790         }
 791         return NULL;
 792 }
 793 EXPORT_SYMBOL(memchr);
 794 #endif
 795
 796 static void *check_bytes8(const u8 *start, u8 value, unsigned int bytes)
 797 {
 798         while (bytes) {
 799                 if (*start != value)
 800                         return (void *)start;
 801                 start++;
 802                 bytes--;
 803         }
 804         return NULL;
 805 }
 806
 807 /**
 808  * memchr_inv - Find an unmatching character in an area of memory.
 809  * @start: The memory area
 810  * @c: Find a character other than c
 811  * @bytes: The size of the area.
 812  *
 813  * returns the address of the first character other than @c, or %NULL
 814  * if the whole buffer contains just @c.
 815  */
 816 void *memchr_inv(const void *start, int c, size_t bytes)
 817 {
 818         u8 value = c;
 819         u64 value64;
 820         unsigned int words, prefix;
 821
 822         if (bytes <= 16)
 823                 return check_bytes8(start, value, bytes);
 824
 825         value64 = value;
 826 #if defined(CONFIG_ARCH_HAS_FAST_MULTIPLIER) && BITS_PER_LONG == 64
 827         value64 *= 0x0101010101010101;
 828 #elif defined(CONFIG_ARCH_HAS_FAST_MULTIPLIER)
 829         value64 *= 0x01010101;
 830         value64 |= value64 << 32;
 831 #else
 832         value64 |= value64 << 8;
 833         value64 |= value64 << 16;
 834         value64 |= value64 << 32;
 835 #endif
 836
 837         prefix = (unsigned long)start % 8;
 838         if (prefix) {
 839                 u8 *r;
 840
 841                 prefix = 8 - prefix;
 842                 r = check_bytes8(start, value, prefix);
 843                 if (r)
 844                         return r;
 845                 start += prefix;
 846                 bytes -= prefix;
 847         }
 848
 849         words = bytes / 8;
 850
 851         while (words) {
 852                 if (*(u64 *)start != value64)
 853                         return check_bytes8(start, value, 8);
 854                 start += 8;
 855                 words--;
 856         }
 857
 858         return check_bytes8(start, value, bytes % 8);
 859 }
 860 EXPORT_SYMBOL(memchr_inv);