lib/libc/stdlib/tfind.c

   1 /*
   2  * Tree search generalized from Knuth (6.2.2) Algorithm T just like
   3  * the AT&T man page says.
   4  *
   5  * The node_t structure is for internal use only, lint doesn't grok it.
   6  *
   7  * Written by reading the System V Interface Definition, not the code.
   8  *
   9  * Totally public domain.
  10  *
  11  * $NetBSD: tfind.c,v 1.2 1999/09/16 11:45:37 lukem Exp $
  12  * $FreeBSD: src/lib/libc/stdlib/tfind.c,v 1.5 2003/01/05 02:43:18 tjr Exp $
  13  * $DragonFly: src/lib/libc/stdlib/tsearch.c,v 1.6 2005/11/24 17:18:30 swildner Exp $
  14  */
  15
  16 #define _SEARCH_PRIVATE
  17 #include <stdlib.h>
  18 #include <search.h>
  19
  20 /*
  21  * find a node, or return 0
  22  *
  23  * Parameters:
  24  *      vkey:   key to be found
  25  *      vrootp: address of the tree root
  26  */
  27 void *
  28 tfind(const void *vkey, void * const *vrootp,
  29       int (*compar)(const void *, const void *))
  30 {
  31         node_t **rootp = (node_t **)vrootp;
  32
  33         if (rootp == NULL)
  34                 return NULL;
  35
  36         while (*rootp != NULL) {                /* T1: */
  37                 int r;
  38
  39                 if ((r = (*compar)(vkey, (*rootp)->key)) == 0)  /* T2: */
  40                         return *rootp;          /* key found */
  41                 rootp = (r < 0) ?
  42                     &(*rootp)->llink :          /* T3: follow left branch */
  43                     &(*rootp)->rlink;           /* T4: follow right branch */
  44         }
  45         return NULL;
  46 }