prism/util/pm_strncasecmp.c

   1 #include "prism/util/pm_strncasecmp.h"
   2
   3 /**
   4  * A locale-insensitive version of `tolower(3)`
   5  */
   6 static inline int
   7 pm_tolower(int c)
   8 {
   9     if ('A' <= c && c <= 'Z') {
  10         return c | 0x20;
  11     }
  12     return c;
  13 }
  14
  15 /**
  16  * Compare two strings, ignoring case, up to the given length. Returns 0 if the
  17  * strings are equal, a negative number if string1 is less than string2, or a
  18  * positive number if string1 is greater than string2.
  19  *
  20  * Note that this is effectively our own implementation of strncasecmp, but it's
  21  * not available on all of the platforms we want to support so we're rolling it
  22  * here.
  23  */
  24 int
  25 pm_strncasecmp(const uint8_t *string1, const uint8_t *string2, size_t length) {
  26     size_t offset = 0;
  27     int difference = 0;
  28
  29     while (offset < length && string1[offset] != '\0') {
  30         if (string2[offset] == '\0') return string1[offset];
  31         if ((difference = pm_tolower(string1[offset]) - pm_tolower(string2[offset])) != 0) return difference;
  32         offset++;
  33     }
  34
  35     return difference;
  36 }