sys/src/libc/port/strstr.c

   1 #include <u.h>
   2 #include <libc.h>
   3
   4 /*
   5  * Return pointer to first occurrence of s2 in s1,
   6  * 0 if none
   7  */
   8 char*
   9 strstr(char *s1, char *s2)
  10 {
  11         char *p, *pa, *pb;
  12         int c0, c;
  13
  14         c0 = *s2;
  15         if(c0 == 0)
  16                 return s1;
  17         s2++;
  18         for(p=strchr(s1, c0); p; p=strchr(p+1, c0)) {
  19                 pa = p;
  20                 for(pb=s2;; pb++) {
  21                         c = *pb;
  22                         if(c == 0)
  23                                 return p;
  24                         if(c != *++pa)
  25                                 break;
  26                 }
  27         }
  28         return 0;
  29 }