newlib/libc/string/strncasecmp_l.c

   1 /*
   2 FUNCTION
   3         <<strncasecmp_l>>---case-insensitive character string compare
   4
   5 INDEX
   6         strncasecmp_l
   7
   8 SYNOPSIS
   9         #include <strings.h>
  10         int strncasecmp_l(const char *<[a]>, const char * <[b]>,
  11                           size_t <[length]>, locale_t <[locale]>);
  12
  13 DESCRIPTION
  14         <<strncasecmp_l>> compares up to <[length]> characters
  15         from the string at <[a]> to the string at <[b]> in a
  16         case-insensitive manner.
  17
  18         if <[locale]> is LC_GLOBAL_LOCALE or not a valid locale object, the
  19         behaviour is undefined.
  20
  21 RETURNS
  22
  23         If <<*<[a]>>> sorts lexicographically after <<*<[b]>>> (after
  24         both are converted to lowercase), <<strncasecmp_l>> returns a
  25         number greater than zero.  If the two strings are equivalent,
  26         <<strncasecmp_l>> returns zero.  If <<*<[a]>>> sorts
  27         lexicographically before <<*<[b]>>>, <<strncasecmp_l>> returns a
  28         number less than zero.
  29
  30 PORTABILITY
  31 <<strncasecmp_l>> is POSIX-1.2008.
  32
  33 <<strncasecmp_l>> requires no supporting OS subroutines. It uses
  34 tolower_l() from elsewhere in this library.
  35
  36 QUICKREF
  37         strncasecmp_l
  38 */
  39
  40 #include <strings.h>
  41 #include <ctype.h>
  42
  43 int
  44 strncasecmp_l (const char *s1, const char *s2, size_t n,
  45                struct __locale_t *locale)
  46 {
  47   int d = 0;
  48   for ( ; n != 0; n--)
  49     {
  50       const int c1 = tolower_l (*s1++, locale);
  51       const int c2 = tolower_l (*s2++, locale);
  52       if (((d = c1 - c2) != 0) || (c2 == '\0'))
  53         break;
  54     }
  55   return d;
  56 }