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 #include <asm/byteorder.h>
  31 #include <asm/word-at-a-time.h>
  32 #include <asm/page.h>
  33
  34 #ifndef __HAVE_ARCH_STRNCASECMP
  35 /**
  36  * strncasecmp - Case insensitive, length-limited string comparison
  37  * @s1: One string
  38  * @s2: The other string
  39  * @len: the maximum number of characters to compare
  40  */
  41 int strncasecmp(const char *s1, const char *s2, size_t len)
  42 {
  43         /* Yes, Virginia, it had better be unsigned */
  44         unsigned char c1, c2;
  45
  46         if (!len)
  47                 return 0;
  48
  49         do {
  50                 c1 = *s1++;
  51                 c2 = *s2++;
  52                 if (!c1 || !c2)
  53                         break;
  54                 if (c1 == c2)
  55                         continue;
  56                 c1 = tolower(c1);
  57                 c2 = tolower(c2);
  58                 if (c1 != c2)
  59                         break;
  60         } while (--len);
  61         return (int)c1 - (int)c2;
  62 }
  63 EXPORT_SYMBOL(strncasecmp);
  64 #endif
  65 #ifndef __HAVE_ARCH_STRNICMP
  66 #undef strnicmp
  67 int strnicmp(const char *s1, const char *s2, size_t len)
  68 {
  69         return strncasecmp(s1, s2, len);
  70 }
  71 EXPORT_SYMBOL(strnicmp);
  72 #endif
  73
  74 #ifndef __HAVE_ARCH_STRCASECMP
  75 int strcasecmp(const char *s1, const char *s2)
  76 {
  77         int c1, c2;
  78
  79         do {
  80                 c1 = tolower(*s1++);
  81                 c2 = tolower(*s2++);
  82         } while (c1 == c2 && c1 != 0);
  83         return c1 - c2;
  84 }
  85 EXPORT_SYMBOL(strcasecmp);
  86 #endif
  87
  88 #ifndef __HAVE_ARCH_STRCPY
  89 /**
  90  * strcpy - Copy a %NUL terminated string
  91  * @dest: Where to copy the string to
  92  * @src: Where to copy the string from
  93  */
  94 #undef strcpy
  95 char *strcpy(char *dest, const char *src)
  96 {
  97         char *tmp = dest;
  98
  99         while ((*dest++ = *src++) != '\0')
 100                 /* nothing */;
 101         return tmp;
 102 }
 103 EXPORT_SYMBOL(strcpy);
 104 #endif
 105
 106 #ifndef __HAVE_ARCH_STRNCPY
 107 /**
 108  * strncpy - Copy a length-limited, C-string
 109  * @dest: Where to copy the string to
 110  * @src: Where to copy the string from
 111  * @count: The maximum number of bytes to copy
 112  *
 113  * The result is not %NUL-terminated if the source exceeds
 114  * @count bytes.
 115  *
 116  * In the case where the length of @src is less than  that  of
 117  * count, the remainder of @dest will be padded with %NUL.
 118  *
 119  */
 120 char *strncpy(char *dest, const char *src, size_t count)
 121 {
 122         char *tmp = dest;
 123
 124         while (count) {
 125                 if ((*tmp = *src) != 0)
 126                         src++;
 127                 tmp++;
 128                 count--;
 129         }
 130         return dest;
 131 }
 132 EXPORT_SYMBOL(strncpy);
 133 #endif
 134
 135 #ifndef __HAVE_ARCH_STRLCPY
 136 /**
 137  * strlcpy - Copy a C-string into a sized buffer
 138  * @dest: Where to copy the string to
 139  * @src: Where to copy the string from
 140  * @size: size of destination buffer
 141  *
 142  * Compatible with *BSD: the result is always a valid
 143  * NUL-terminated string that fits in the buffer (unless,
 144  * of course, the buffer size is zero). It does not pad
 145  * out the result like strncpy() does.
 146  */
 147 size_t strlcpy(char *dest, const char *src, size_t size)
 148 {
 149         size_t ret = strlen(src);
 150
 151         if (size) {
 152                 size_t len = (ret >= size) ? size - 1 : ret;
 153                 memcpy(dest, src, len);
 154                 dest[len] = '\0';
 155         }
 156         return ret;
 157 }
 158 EXPORT_SYMBOL(strlcpy);
 159 #endif
 160
 161 #ifndef __HAVE_ARCH_STRSCPY
 162 /**
 163  * strscpy - Copy a C-string into a sized buffer
 164  * @dest: Where to copy the string to
 165  * @src: Where to copy the string from
 166  * @count: Size of destination buffer
 167  *
 168  * Copy the string, or as much of it as fits, into the dest buffer.
 169  * The routine returns the number of characters copied (not including
 170  * the trailing NUL) or -E2BIG if the destination buffer wasn't big enough.
 171  * The behavior is undefined if the string buffers overlap.
 172  * The destination buffer is always NUL terminated, unless it's zero-sized.
 173  *
 174  * Preferred to strlcpy() since the API doesn't require reading memory
 175  * from the src string beyond the specified "count" bytes, and since
 176  * the return value is easier to error-check than strlcpy()'s.
 177  * In addition, the implementation is robust to the string changing out
 178  * from underneath it, unlike the current strlcpy() implementation.
 179  *
 180  * Preferred to strncpy() since it always returns a valid string, and
 181  * doesn't unnecessarily force the tail of the destination buffer to be
 182  * zeroed.  If the zeroing is desired, it's likely cleaner to use strscpy()
 183  * with an overflow test, then just memset() the tail of the dest buffer.
 184  */
 185 ssize_t strscpy(char *dest, const char *src, size_t count)
 186 {
 187         const struct word_at_a_time constants = WORD_AT_A_TIME_CONSTANTS;
 188         size_t max = count;
 189         long res = 0;
 190
 191         if (count == 0)
 192                 return -E2BIG;
 193
 194 #ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
 195         /*
 196          * If src is unaligned, don't cross a page boundary,
 197          * since we don't know if the next page is mapped.
 198          */
 199         if ((long)src & (sizeof(long) - 1)) {
 200                 size_t limit = PAGE_SIZE - ((long)src & (PAGE_SIZE - 1));
 201                 if (limit < max)
 202                         max = limit;
 203         }
 204 #else
 205         /* If src or dest is unaligned, don't do word-at-a-time. */
 206         if (((long) dest | (long) src) & (sizeof(long) - 1))
 207                 max = 0;
 208 #endif
 209
 210         while (max >= sizeof(unsigned long)) {
 211                 unsigned long c, data;
 212
 213                 c = *(unsigned long *)(src+res);
 214                 if (has_zero(c, &data, &constants)) {
 215                         data = prep_zero_mask(c, data, &constants);
 216                         data = create_zero_mask(data);
 217                         *(unsigned long *)(dest+res) = c & zero_bytemask(data);
 218                         return res + find_zero(data);
 219                 }
 220                 *(unsigned long *)(dest+res) = c;
 221                 res += sizeof(unsigned long);
 222                 count -= sizeof(unsigned long);
 223                 max -= sizeof(unsigned long);
 224         }
 225
 226         while (count) {
 227                 char c;
 228
 229                 c = src[res];
 230                 dest[res] = c;
 231                 if (!c)
 232                         return res;
 233                 res++;
 234                 count--;
 235         }
 236
 237         /* Hit buffer length without finding a NUL; force NUL-termination. */
 238         if (res)
 239                 dest[res-1] = '\0';
 240
 241         return -E2BIG;
 242 }
 243 EXPORT_SYMBOL(strscpy);
 244 #endif
 245
 246 #ifndef __HAVE_ARCH_STRCAT
 247 /**
 248  * strcat - Append one %NUL-terminated string to another
 249  * @dest: The string to be appended to
 250  * @src: The string to append to it
 251  */
 252 #undef strcat
 253 char *strcat(char *dest, const char *src)
 254 {
 255         char *tmp = dest;
 256
 257         while (*dest)
 258                 dest++;
 259         while ((*dest++ = *src++) != '\0')
 260                 ;
 261         return tmp;
 262 }
 263 EXPORT_SYMBOL(strcat);
 264 #endif
 265
 266 #ifndef __HAVE_ARCH_STRNCAT
 267 /**
 268  * strncat - Append a length-limited, C-string to another
 269  * @dest: The string to be appended to
 270  * @src: The string to append to it
 271  * @count: The maximum numbers of bytes to copy
 272  *
 273  * Note that in contrast to strncpy(), strncat() ensures the result is
 274  * terminated.
 275  */
 276 char *strncat(char *dest, const char *src, size_t count)
 277 {
 278         char *tmp = dest;
 279
 280         if (count) {
 281                 while (*dest)
 282                         dest++;
 283                 while ((*dest++ = *src++) != 0) {
 284                         if (--count == 0) {
 285                                 *dest = '\0';
 286                                 break;
 287                         }
 288                 }
 289         }
 290         return tmp;
 291 }
 292 EXPORT_SYMBOL(strncat);
 293 #endif
 294
 295 #ifndef __HAVE_ARCH_STRLCAT
 296 /**
 297  * strlcat - Append a length-limited, C-string to another
 298  * @dest: The string to be appended to
 299  * @src: The string to append to it
 300  * @count: The size of the destination buffer.
 301  */
 302 size_t strlcat(char *dest, const char *src, size_t count)
 303 {
 304         size_t dsize = strlen(dest);
 305         size_t len = strlen(src);
 306         size_t res = dsize + len;
 307
 308         /* This would be a bug */
 309         BUG_ON(dsize >= count);
 310
 311         dest += dsize;
 312         count -= dsize;
 313         if (len >= count)
 314                 len = count-1;
 315         memcpy(dest, src, len);
 316         dest[len] = 0;
 317         return res;
 318 }
 319 EXPORT_SYMBOL(strlcat);
 320 #endif
 321
 322 #ifndef __HAVE_ARCH_STRCMP
 323 /**
 324  * strcmp - Compare two strings
 325  * @cs: One string
 326  * @ct: Another string
 327  */
 328 #undef strcmp
 329 int strcmp(const char *cs, const char *ct)
 330 {
 331         unsigned char c1, c2;
 332
 333         while (1) {
 334                 c1 = *cs++;
 335                 c2 = *ct++;
 336                 if (c1 != c2)
 337                         return c1 < c2 ? -1 : 1;
 338                 if (!c1)
 339                         break;
 340         }
 341         return 0;
 342 }
 343 EXPORT_SYMBOL(strcmp);
 344 #endif
 345
 346 #ifndef __HAVE_ARCH_STRNCMP
 347 /**
 348  * strncmp - Compare two length-limited strings
 349  * @cs: One string
 350  * @ct: Another string
 351  * @count: The maximum number of bytes to compare
 352  */
 353 int strncmp(const char *cs, const char *ct, size_t count)
 354 {
 355         unsigned char c1, c2;
 356
 357         while (count) {
 358                 c1 = *cs++;
 359                 c2 = *ct++;
 360                 if (c1 != c2)
 361                         return c1 < c2 ? -1 : 1;
 362                 if (!c1)
 363                         break;
 364                 count--;
 365         }
 366         return 0;
 367 }
 368 EXPORT_SYMBOL(strncmp);
 369 #endif
 370
 371 #ifndef __HAVE_ARCH_STRCHR
 372 /**
 373  * strchr - Find the first occurrence of a character in a string
 374  * @s: The string to be searched
 375  * @c: The character to search for
 376  */
 377 char *strchr(const char *s, int c)
 378 {
 379         for (; *s != (char)c; ++s)
 380                 if (*s == '\0')
 381                         return NULL;
 382         return (char *)s;
 383 }
 384 EXPORT_SYMBOL(strchr);
 385 #endif
 386
 387 #ifndef __HAVE_ARCH_STRCHRNUL
 388 /**
 389  * strchrnul - Find and return a character in a string, or end of string
 390  * @s: The string to be searched
 391  * @c: The character to search for
 392  *
 393  * Returns pointer to first occurrence of 'c' in s. If c is not found, then
 394  * return a pointer to the null byte at the end of s.
 395  */
 396 char *strchrnul(const char *s, int c)
 397 {
 398         while (*s && *s != (char)c)
 399                 s++;
 400         return (char *)s;
 401 }
 402 EXPORT_SYMBOL(strchrnul);
 403 #endif
 404
 405 #ifndef __HAVE_ARCH_STRRCHR
 406 /**
 407  * strrchr - Find the last occurrence of a character in a string
 408  * @s: The string to be searched
 409  * @c: The character to search for
 410  */
 411 char *strrchr(const char *s, int c)
 412 {
 413        const char *p = s + strlen(s);
 414        do {
 415            if (*p == (char)c)
 416                return (char *)p;
 417        } while (--p >= s);
 418        return NULL;
 419 }
 420 EXPORT_SYMBOL(strrchr);
 421 #endif
 422
 423 #ifndef __HAVE_ARCH_STRNCHR
 424 /**
 425  * strnchr - Find a character in a length limited string
 426  * @s: The string to be searched
 427  * @count: The number of characters to be searched
 428  * @c: The character to search for
 429  */
 430 char *strnchr(const char *s, size_t count, int c)
 431 {
 432         for (; count-- && *s != '\0'; ++s)
 433                 if (*s == (char)c)
 434                         return (char *)s;
 435         return NULL;
 436 }
 437 EXPORT_SYMBOL(strnchr);
 438 #endif
 439
 440 /**
 441  * skip_spaces - Removes leading whitespace from @str.
 442  * @str: The string to be stripped.
 443  *
 444  * Returns a pointer to the first non-whitespace character in @str.
 445  */
 446 char *skip_spaces(const char *str)
 447 {
 448         while (isspace(*str))
 449                 ++str;
 450         return (char *)str;
 451 }
 452 EXPORT_SYMBOL(skip_spaces);
 453
 454 /**
 455  * strim - Removes leading and trailing whitespace from @s.
 456  * @s: The string to be stripped.
 457  *
 458  * Note that the first trailing whitespace is replaced with a %NUL-terminator
 459  * in the given string @s. Returns a pointer to the first non-whitespace
 460  * character in @s.
 461  */
 462 char *strim(char *s)
 463 {
 464         size_t size;
 465         char *end;
 466
 467         size = strlen(s);
 468         if (!size)
 469                 return s;
 470
 471         end = s + size - 1;
 472         while (end >= s && isspace(*end))
 473                 end--;
 474         *(end + 1) = '\0';
 475
 476         return skip_spaces(s);
 477 }
 478 EXPORT_SYMBOL(strim);
 479
 480 #ifndef __HAVE_ARCH_STRLEN
 481 /**
 482  * strlen - Find the length of a string
 483  * @s: The string to be sized
 484  */
 485 size_t strlen(const char *s)
 486 {
 487         const char *sc;
 488
 489         for (sc = s; *sc != '\0'; ++sc)
 490                 /* nothing */;
 491         return sc - s;
 492 }
 493 EXPORT_SYMBOL(strlen);
 494 #endif
 495
 496 #ifndef __HAVE_ARCH_STRNLEN
 497 /**
 498  * strnlen - Find the length of a length-limited string
 499  * @s: The string to be sized
 500  * @count: The maximum number of bytes to search
 501  */
 502 size_t strnlen(const char *s, size_t count)
 503 {
 504         const char *sc;
 505
 506         for (sc = s; count-- && *sc != '\0'; ++sc)
 507                 /* nothing */;
 508         return sc - s;
 509 }
 510 EXPORT_SYMBOL(strnlen);
 511 #endif
 512
 513 #ifndef __HAVE_ARCH_STRSPN
 514 /**
 515  * strspn - Calculate the length of the initial substring of @s which only contain letters in @accept
 516  * @s: The string to be searched
 517  * @accept: The string to search for
 518  */
 519 size_t strspn(const char *s, const char *accept)
 520 {
 521         const char *p;
 522         const char *a;
 523         size_t count = 0;
 524
 525         for (p = s; *p != '\0'; ++p) {
 526                 for (a = accept; *a != '\0'; ++a) {
 527                         if (*p == *a)
 528                                 break;
 529                 }
 530                 if (*a == '\0')
 531                         return count;
 532                 ++count;
 533         }
 534         return count;
 535 }
 536
 537 EXPORT_SYMBOL(strspn);
 538 #endif
 539
 540 #ifndef __HAVE_ARCH_STRCSPN
 541 /**
 542  * strcspn - Calculate the length of the initial substring of @s which does not contain letters in @reject
 543  * @s: The string to be searched
 544  * @reject: The string to avoid
 545  */
 546 size_t strcspn(const char *s, const char *reject)
 547 {
 548         const char *p;
 549         const char *r;
 550         size_t count = 0;
 551
 552         for (p = s; *p != '\0'; ++p) {
 553                 for (r = reject; *r != '\0'; ++r) {
 554                         if (*p == *r)
 555                                 return count;
 556                 }
 557                 ++count;
 558         }
 559         return count;
 560 }
 561 EXPORT_SYMBOL(strcspn);
 562 #endif
 563
 564 #ifndef __HAVE_ARCH_STRPBRK
 565 /**
 566  * strpbrk - Find the first occurrence of a set of characters
 567  * @cs: The string to be searched
 568  * @ct: The characters to search for
 569  */
 570 char *strpbrk(const char *cs, const char *ct)
 571 {
 572         const char *sc1, *sc2;
 573
 574         for (sc1 = cs; *sc1 != '\0'; ++sc1) {
 575                 for (sc2 = ct; *sc2 != '\0'; ++sc2) {
 576                         if (*sc1 == *sc2)
 577                                 return (char *)sc1;
 578                 }
 579         }
 580         return NULL;
 581 }
 582 EXPORT_SYMBOL(strpbrk);
 583 #endif
 584
 585 #ifndef __HAVE_ARCH_STRSEP
 586 /**
 587  * strsep - Split a string into tokens
 588  * @s: The string to be searched
 589  * @ct: The characters to search for
 590  *
 591  * strsep() updates @s to point after the token, ready for the next call.
 592  *
 593  * It returns empty tokens, too, behaving exactly like the libc function
 594  * of that name. In fact, it was stolen from glibc2 and de-fancy-fied.
 595  * Same semantics, slimmer shape. ;)
 596  */
 597 char *strsep(char **s, const char *ct)
 598 {
 599         char *sbegin = *s;
 600         char *end;
 601
 602         if (sbegin == NULL)
 603                 return NULL;
 604
 605         end = strpbrk(sbegin, ct);
 606         if (end)
 607                 *end++ = '\0';
 608         *s = end;
 609         return sbegin;
 610 }
 611 EXPORT_SYMBOL(strsep);
 612 #endif
 613
 614 /**
 615  * sysfs_streq - return true if strings are equal, modulo trailing newline
 616  * @s1: one string
 617  * @s2: another string
 618  *
 619  * This routine returns true iff two strings are equal, treating both
 620  * NUL and newline-then-NUL as equivalent string terminations.  It's
 621  * geared for use with sysfs input strings, which generally terminate
 622  * with newlines but are compared against values without newlines.
 623  */
 624 bool sysfs_streq(const char *s1, const char *s2)
 625 {
 626         while (*s1 && *s1 == *s2) {
 627                 s1++;
 628                 s2++;
 629         }
 630
 631         if (*s1 == *s2)
 632                 return true;
 633         if (!*s1 && *s2 == '\n' && !s2[1])
 634                 return true;
 635         if (*s1 == '\n' && !s1[1] && !*s2)
 636                 return true;
 637         return false;
 638 }
 639 EXPORT_SYMBOL(sysfs_streq);
 640
 641 /**
 642  * strtobool - convert common user inputs into boolean values
 643  * @s: input string
 644  * @res: result
 645  *
 646  * This routine returns 0 iff the first character is one of 'Yy1Nn0'.
 647  * Otherwise it will return -EINVAL.  Value pointed to by res is
 648  * updated upon finding a match.
 649  */
 650 int strtobool(const char *s, bool *res)
 651 {
 652         switch (s[0]) {
 653         case 'y':
 654         case 'Y':
 655         case '1':
 656                 *res = true;
 657                 break;
 658         case 'n':
 659         case 'N':
 660         case '0':
 661                 *res = false;
 662                 break;
 663         default:
 664                 return -EINVAL;
 665         }
 666         return 0;
 667 }
 668 EXPORT_SYMBOL(strtobool);
 669
 670 #ifndef __HAVE_ARCH_MEMSET
 671 /**
 672  * memset - Fill a region of memory with the given value
 673  * @s: Pointer to the start of the area.
 674  * @c: The byte to fill the area with
 675  * @count: The size of the area.
 676  *
 677  * Do not use memset() to access IO space, use memset_io() instead.
 678  */
 679 void *memset(void *s, int c, size_t count)
 680 {
 681         char *xs = s;
 682
 683         while (count--)
 684                 *xs++ = c;
 685         return s;
 686 }
 687 EXPORT_SYMBOL(memset);
 688 #endif
 689
 690 /**
 691  * memzero_explicit - Fill a region of memory (e.g. sensitive
 692  *                    keying data) with 0s.
 693  * @s: Pointer to the start of the area.
 694  * @count: The size of the area.
 695  *
 696  * memzero_explicit() doesn't need an arch-specific version as
 697  * it just invokes the one of memset() implicitly.
 698  */
 699 void memzero_explicit(void *s, size_t count)
 700 {
 701         memset(s, 0, count);
 702         barrier();
 703 }
 704 EXPORT_SYMBOL(memzero_explicit);
 705
 706 #ifndef __HAVE_ARCH_MEMCPY
 707 /**
 708  * memcpy - Copy one area of memory to another
 709  * @dest: Where to copy to
 710  * @src: Where to copy from
 711  * @count: The size of the area.
 712  *
 713  * You should not use this function to access IO space, use memcpy_toio()
 714  * or memcpy_fromio() instead.
 715  */
 716 void *memcpy(void *dest, const void *src, size_t count)
 717 {
 718         char *tmp = dest;
 719         const char *s = src;
 720
 721         while (count--)
 722                 *tmp++ = *s++;
 723         return dest;
 724 }
 725 EXPORT_SYMBOL(memcpy);
 726 #endif
 727
 728 #ifndef __HAVE_ARCH_MEMMOVE
 729 /**
 730  * memmove - Copy one area of memory to another
 731  * @dest: Where to copy to
 732  * @src: Where to copy from
 733  * @count: The size of the area.
 734  *
 735  * Unlike memcpy(), memmove() copes with overlapping areas.
 736  */
 737 void *memmove(void *dest, const void *src, size_t count)
 738 {
 739         char *tmp;
 740         const char *s;
 741
 742         if (dest <= src) {
 743                 tmp = dest;
 744                 s = src;
 745                 while (count--)
 746                         *tmp++ = *s++;
 747         } else {
 748                 tmp = dest;
 749                 tmp += count;
 750                 s = src;
 751                 s += count;
 752                 while (count--)
 753                         *--tmp = *--s;
 754         }
 755         return dest;
 756 }
 757 EXPORT_SYMBOL(memmove);
 758 #endif
 759
 760 #ifndef __HAVE_ARCH_MEMCMP
 761 /**
 762  * memcmp - Compare two areas of memory
 763  * @cs: One area of memory
 764  * @ct: Another area of memory
 765  * @count: The size of the area.
 766  */
 767 #undef memcmp
 768 __visible int memcmp(const void *cs, const void *ct, size_t count)
 769 {
 770         const unsigned char *su1, *su2;
 771         int res = 0;
 772
 773         for (su1 = cs, su2 = ct; 0 < count; ++su1, ++su2, count--)
 774                 if ((res = *su1 - *su2) != 0)
 775                         break;
 776         return res;
 777 }
 778 EXPORT_SYMBOL(memcmp);
 779 #endif
 780
 781 #ifndef __HAVE_ARCH_MEMSCAN
 782 /**
 783  * memscan - Find a character in an area of memory.
 784  * @addr: The memory area
 785  * @c: The byte to search for
 786  * @size: The size of the area.
 787  *
 788  * returns the address of the first occurrence of @c, or 1 byte past
 789  * the area if @c is not found
 790  */
 791 void *memscan(void *addr, int c, size_t size)
 792 {
 793         unsigned char *p = addr;
 794
 795         while (size) {
 796                 if (*p == c)
 797                         return (void *)p;
 798                 p++;
 799                 size--;
 800         }
 801         return (void *)p;
 802 }
 803 EXPORT_SYMBOL(memscan);
 804 #endif
 805
 806 #ifndef __HAVE_ARCH_STRSTR
 807 /**
 808  * strstr - Find the first substring in a %NUL terminated string
 809  * @s1: The string to be searched
 810  * @s2: The string to search for
 811  */
 812 char *strstr(const char *s1, const char *s2)
 813 {
 814         size_t l1, l2;
 815
 816         l2 = strlen(s2);
 817         if (!l2)
 818                 return (char *)s1;
 819         l1 = strlen(s1);
 820         while (l1 >= l2) {
 821                 l1--;
 822                 if (!memcmp(s1, s2, l2))
 823                         return (char *)s1;
 824                 s1++;
 825         }
 826         return NULL;
 827 }
 828 EXPORT_SYMBOL(strstr);
 829 #endif
 830
 831 #ifndef __HAVE_ARCH_STRNSTR
 832 /**
 833  * strnstr - Find the first substring in a length-limited string
 834  * @s1: The string to be searched
 835  * @s2: The string to search for
 836  * @len: the maximum number of characters to search
 837  */
 838 char *strnstr(const char *s1, const char *s2, size_t len)
 839 {
 840         size_t l2;
 841
 842         l2 = strlen(s2);
 843         if (!l2)
 844                 return (char *)s1;
 845         while (len >= l2) {
 846                 len--;
 847                 if (!memcmp(s1, s2, l2))
 848                         return (char *)s1;
 849                 s1++;
 850         }
 851         return NULL;
 852 }
 853 EXPORT_SYMBOL(strnstr);
 854 #endif
 855
 856 #ifndef __HAVE_ARCH_MEMCHR
 857 /**
 858  * memchr - Find a character in an area of memory.
 859  * @s: The memory area
 860  * @c: The byte to search for
 861  * @n: The size of the area.
 862  *
 863  * returns the address of the first occurrence of @c, or %NULL
 864  * if @c is not found
 865  */
 866 void *memchr(const void *s, int c, size_t n)
 867 {
 868         const unsigned char *p = s;
 869         while (n-- != 0) {
 870                 if ((unsigned char)c == *p++) {
 871                         return (void *)(p - 1);
 872                 }
 873         }
 874         return NULL;
 875 }
 876 EXPORT_SYMBOL(memchr);
 877 #endif
 878
 879 static void *check_bytes8(const u8 *start, u8 value, unsigned int bytes)
 880 {
 881         while (bytes) {
 882                 if (*start != value)
 883                         return (void *)start;
 884                 start++;
 885                 bytes--;
 886         }
 887         return NULL;
 888 }
 889
 890 /**
 891  * memchr_inv - Find an unmatching character in an area of memory.
 892  * @start: The memory area
 893  * @c: Find a character other than c
 894  * @bytes: The size of the area.
 895  *
 896  * returns the address of the first character other than @c, or %NULL
 897  * if the whole buffer contains just @c.
 898  */
 899 void *memchr_inv(const void *start, int c, size_t bytes)
 900 {
 901         u8 value = c;
 902         u64 value64;
 903         unsigned int words, prefix;
 904
 905         if (bytes <= 16)
 906                 return check_bytes8(start, value, bytes);
 907
 908         value64 = value;
 909 #if defined(CONFIG_ARCH_HAS_FAST_MULTIPLIER) && BITS_PER_LONG == 64
 910         value64 *= 0x0101010101010101;
 911 #elif defined(CONFIG_ARCH_HAS_FAST_MULTIPLIER)
 912         value64 *= 0x01010101;
 913         value64 |= value64 << 32;
 914 #else
 915         value64 |= value64 << 8;
 916         value64 |= value64 << 16;
 917         value64 |= value64 << 32;
 918 #endif
 919
 920         prefix = (unsigned long)start % 8;
 921         if (prefix) {
 922                 u8 *r;
 923
 924                 prefix = 8 - prefix;
 925                 r = check_bytes8(start, value, prefix);
 926                 if (r)
 927                         return r;
 928                 start += prefix;
 929                 bytes -= prefix;
 930         }
 931
 932         words = bytes / 8;
 933
 934         while (words) {
 935                 if (*(u64 *)start != value64)
 936                         return check_bytes8(start, value, 8);
 937                 start += 8;
 938                 words--;
 939         }
 940
 941         return check_bytes8(start, value, bytes % 8);
 942 }
 943 EXPORT_SYMBOL(memchr_inv);