lib/libc/stdlib/tfind.c

   1 /*      $NetBSD: tfind.c,v 1.5 2005/03/23 08:16:53 kleink 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 <sys/cdefs.h>
  15 #if defined(LIBC_SCCS) && !defined(lint)
  16 __RCSID("$NetBSD: tfind.c,v 1.5 2005/03/23 08:16:53 kleink Exp $");
  17 #endif /* LIBC_SCCS and not lint */
  18
  19 #include <assert.h>
  20 #define _SEARCH_PRIVATE
  21 #include <stdlib.h>
  22 #include <search.h>
  23
  24 /* find a node, or return 0 */
  25 void *
  26 tfind(vkey, vrootp, compar)
  27         const void *vkey;               /* key to be found */
  28         void * const *vrootp;           /* address of the tree root */
  29         int (*compar) __P((const void *, const void *));
  30 {
  31         node_t * const *rootp = (node_t * const*)vrootp;
  32
  33         _DIAGASSERT(vkey != NULL);
  34         _DIAGASSERT(compar != NULL);
  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 }