newlib/libc/string/strncasecmp.c

   1 /*
   2 FUNCTION
   3         <<strncasecmp>>---case-insensitive character string compare
   4
   5 INDEX
   6         strncasecmp
   7
   8 SYNOPSIS
   9         #include <strings.h>
  10         int strncasecmp(const char *<[a]>, const char * <[b]>, size_t <[length]>);
  11
  12 DESCRIPTION
  13         <<strncasecmp>> compares up to <[length]> characters
  14         from the string at <[a]> to the string at <[b]> in a
  15         case-insensitive manner.
  16
  17 RETURNS
  18
  19         If <<*<[a]>>> sorts lexicographically after <<*<[b]>>> (after
  20         both are converted to lowercase), <<strncasecmp>> returns a
  21         number greater than zero.  If the two strings are equivalent,
  22         <<strncasecmp>> returns zero.  If <<*<[a]>>> sorts
  23         lexicographically before <<*<[b]>>>, <<strncasecmp>> returns a
  24         number less than zero.
  25
  26 PORTABILITY
  27 <<strncasecmp>> is in the Berkeley Software Distribution.
  28
  29 <<strncasecmp>> requires no supporting OS subroutines. It uses
  30 tolower() from elsewhere in this library.
  31
  32 QUICKREF
  33         strncasecmp
  34 */
  35
  36 #include <strings.h>
  37 #include <ctype.h>
  38
  39 int
  40 strncasecmp (const char *s1,
  41         const char *s2,
  42         size_t n)
  43 {
  44   int d = 0;
  45   for ( ; n != 0; n--)
  46     {
  47       const int c1 = tolower(*s1++);
  48       const int c2 = tolower(*s2++);
  49       if (((d = c1 - c2) != 0) || (c2 == '\0'))
  50         break;
  51     }
  52   return d;
  53 }