lib/ansi/bsearch.c

   1 /*
   2  * (c) copyright 1987 by the Vrije Universiteit, Amsterdam, The Netherlands.
   3  * See the copyright notice in the ACK home directory, in the file "Copyright".
   4  */
   5 /* $Header$ */
   6
   7 #include        <stdlib.h>
   8
   9 void *
  10 bsearch(register const void *key, register const void *base,
  11         register size_t nmemb, register size_t size,
  12         int (*compar)(const void *, const void *))
  13 {
  14         register const void *mid_point;
  15         register int  cmp;
  16
  17         while (nmemb > 0) {
  18                 mid_point = (char *)base + size * (nmemb >> 1);
  19                 if ((cmp = (*compar)(key, mid_point)) == 0)
  20                         return (void *)mid_point;
  21                 if (cmp >= 0) {
  22                         base  = (char *)mid_point + size;
  23                         nmemb = (nmemb - 1) >> 1;
  24                 } else
  25                         nmemb >>= 1;
  26         }
  27         return (void *)NULL;
  28 }