tsearch/tfind.c

   1 /*      $NetBSD: tfind.c,v 1.3.18.2 2005/03/23 11:12:21 tron Exp $      */
   2
   3 /*
   4  * Tree search generalized from Knuth (6.2.2) Algorithm T just like
   5  * the AT&T man page says.
   6  *
   7  * The node_t structure is for internal use only, lint doesn't grok it.
   8  *
   9  * Written by reading the System V Interface Definition, not the code.
  10  *
  11  * Totally public domain.
  12  */
  13
  14 #include <assert.h>
  15 #define _SEARCH_PRIVATE
  16 #include <stdlib.h>
  17 #include <tsearch/search.h>
  18
  19
  20 /* find a node, or return 0 */
  21 void *
  22 tfind(const void *vkey,
  23       void * const *vrootp,
  24       int (*compar) (const void *, const void *))
  25 {
  26         node_t * const *rootp = (node_t * const*)vrootp;
  27
  28         if (rootp == NULL)
  29                 return NULL;
  30
  31         while (*rootp != NULL) {                /* T1: */
  32                 int r;
  33
  34                 if ((r = (*compar)(vkey, (*rootp)->key)) == 0)  /* T2: */
  35                         return *rootp;          /* key found */
  36                 rootp = (r < 0) ?
  37                     &(*rootp)->llink :          /* T3: follow left branch */
  38                     &(*rootp)->rlink;           /* T4: follow right branch */
  39         }
  40         return NULL;
  41 }