lib/libc/stdlib/tsearch.c

   1 /*      $NetBSD: tsearch.c,v 1.4 1999/09/20 04:39:43 lukem 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: tsearch.c,v 1.4 1999/09/20 04:39:43 lukem Exp $");
  17 #endif /* LIBC_SCCS and not lint */
  18
  19 #include <assert.h>
  20 #define _SEARCH_PRIVATE
  21 #include <search.h>
  22 #include <stdlib.h>
  23
  24 /* find or insert datum into search tree */
  25 void *
  26 tsearch(vkey, vrootp, compar)
  27         const void *vkey;               /* key to be located */
  28         void **vrootp;                  /* address of tree root */
  29         int (*compar) __P((const void *, const void *));
  30 {
  31         node_t *q;
  32         node_t **rootp = (node_t **)vrootp;
  33
  34         _DIAGASSERT(vkey != NULL);
  35         _DIAGASSERT(compar != NULL);
  36
  37         if (rootp == NULL)
  38                 return NULL;
  39
  40         while (*rootp != NULL) {        /* Knuth's T1: */
  41                 int r;
  42
  43                 if ((r = (*compar)(vkey, (*rootp)->key)) == 0)  /* T2: */
  44                         return *rootp;          /* we found it! */
  45
  46                 rootp = (r < 0) ?
  47                     &(*rootp)->llink :          /* T3: follow left branch */
  48                     &(*rootp)->rlink;           /* T4: follow right branch */
  49         }
  50
  51         q = malloc(sizeof(node_t));             /* T5: key not found */
  52         if (q != 0) {                           /* make new node */
  53                 *rootp = q;                     /* link new node to old */
  54                 q->key = __UNCONST(vkey);       /* initialize new node */
  55                 q->llink = q->rlink = NULL;
  56         }
  57         return q;
  58 }