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