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