src/string/strverscmp.c

   1 #define _GNU_SOURCE
   2 #include <ctype.h>
   3 #include <string.h>
   4
   5 int strverscmp(const char *l0, const char *r0)
   6 {
   7         const unsigned char *l = (const void *)l0;
   8         const unsigned char *r = (const void *)r0;
   9         size_t i, dp, j;
  10         int z = 1;
  11
  12         /* Find maximal matching prefix and track its maximal digit
  13          * suffix and whether those digits are all zeros. */
  14         for (dp=i=0; l[i]==r[i]; i++) {
  15                 int c = l[i];
  16                 if (!c) return 0;
  17                 if (!isdigit(c)) dp=i+1, z=1;
  18                 else if (c!='0') z=0;
  19         }
  20
  21         if (l[dp]!='0' && r[dp]!='0') {
  22                 /* If we're not looking at a digit sequence that began
  23                  * with a zero, longest digit string is greater. */
  24                 for (j=i; isdigit(l[j]); j++)
  25                         if (!isdigit(r[j])) return 1;
  26                 if (isdigit(r[j])) return -1;
  27         } else if (z && dp<i && (isdigit(l[i]) || isdigit(r[i]))) {
  28                 /* Otherwise, if common prefix of digit sequence is
  29                  * all zeros, digits order less than non-digits. */
  30                 return (unsigned char)(l[i]-'0') - (unsigned char)(r[i]-'0');
  31         }
  32
  33         return l[i] - r[i];
  34 }