toolchain/gcc/newlib/libc/string/strncasecmp.c

   1 /*
   2 FUNCTION
   3         <<strncasecmp>>---case insensitive character string compare
   4
   5 INDEX
   6         strncasecmp
   7
   8 ANSI_SYNOPSIS
   9         #include <string.h>
  10         int strncasecmp(const char *<[a]>, const char * <[b]>, size_t <[length]>);
  11
  12 TRAD_SYNOPSIS
  13         #include <string.h>
  14         int strncasecmp(<[a]>, <[b]>, <[length]>)
  15         char *<[a]>;
  16         char *<[b]>;
  17         size_t <[length]>
  18
  19 DESCRIPTION
  20         <<strncasecmp>> compares up to <[length]> characters
  21         from the string at <[a]> to the string at <[b]> in a
  22         case-insensitive manner.
  23
  24 RETURNS
  25
  26         If <<*<[a]>>> sorts lexicographically after <<*<[b]>>> (after
  27         both are converted to upper case), <<strncasecmp>> returns a
  28         number greater than zero.  If the two strings are equivalent,
  29         <<strncasecmp>> returns zero.  If <<*<[a]>>> sorts
  30         lexicographically before <<*<[b]>>>, <<strncasecmp>> returns a
  31         number less than zero.
  32
  33 PORTABILITY
  34 <<strncasecmp>> is in the Berkeley Software Distribution.
  35
  36 <<strncasecmp>> requires no supporting OS subroutines. It uses
  37 tolower() from elsewhere in this library.
  38
  39 QUICKREF
  40         strncasecmp
  41 */
  42
  43 #include <string.h>
  44 #include <ctype.h>
  45
  46 int
  47 _DEFUN (strncasecmp, (s1, s2, n),
  48         _CONST char *s1 _AND
  49         _CONST char *s2 _AND
  50         size_t n)
  51 {
  52   if (n == 0)
  53     return 0;
  54
  55   while (n-- != 0 && tolower(*s1) == tolower(*s2))
  56     {
  57       if (n == 0 || *s1 == '\0' || *s2 == '\0')
  58         break;
  59       s1++;
  60       s2++;
  61     }
  62
  63   return tolower(*(unsigned char *) s1) - tolower(*(unsigned char *) s2);
  64 }