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 1.1.2.1 2000/08/17 07:38:39 jhb Exp $
  13  * $DragonFly: src/lib/libc/stdlib/tfind.c,v 1.5 2005/11/24 17:18:30 swildner Exp $
  14  */
  15
  16 #include <sys/cdefs.h>
  17
  18 #include <assert.h>
  19 #define _SEARCH_PRIVATE
  20 #include <stdlib.h>
  21 #include <search.h>
  22
  23 /*
  24  * find a node, or return 0
  25  *
  26  * Parameters:
  27  *      vkey:   key to be found
  28  *      vrootp: address of the tree root
  29  */
  30 void *
  31 tfind(const void *vkey, void **vrootp,
  32       int (*compar)(const void *, const void *))
  33 {
  34         node_t **rootp = (node_t **)vrootp;
  35
  36         if (rootp == NULL)
  37                 return NULL;
  38
  39         while (*rootp != NULL) {                /* T1: */
  40                 int r;
  41
  42                 if ((r = (*compar)(vkey, (*rootp)->key)) == 0)  /* T2: */
  43                         return *rootp;          /* key found */
  44                 rootp = (r < 0) ?
  45                     &(*rootp)->llink :          /* T3: follow left branch */
  46                     &(*rootp)->rlink;           /* T4: follow right branch */
  47         }
  48         return NULL;
  49 }