lib/libc/stdlib/tsearch.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: tsearch.c,v 1.3 1999/09/16 11:45:37 lukem Exp $
  12  * $FreeBSD: src/lib/libc/stdlib/tsearch.c,v 1.1.2.1 2000/08/17 07:38:39 jhb Exp $
  13  * $DragonFly: src/lib/libc/stdlib/tsearch.c,v 1.6 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 <search.h>
  21 #include <stdlib.h>
  22
  23 /* find or insert datum into search tree
  24  *
  25  * Parameters:
  26  *      vkey:   key to be located
  27  *      vrootp: address of tree root
  28  */
  29 void *
  30 tsearch(const void *vkey, void **vrootp,
  31         int (*compar)(const void *, const void *))
  32 {
  33         node_t *q;
  34         node_t **rootp = (node_t **)vrootp;
  35
  36         if (rootp == NULL)
  37                 return NULL;
  38
  39         while (*rootp != NULL) {        /* Knuth's T1: */
  40                 int r;
  41
  42                 if ((r = (*compar)(vkey, (*rootp)->key)) == 0)  /* T2: */
  43                         return *rootp;          /* we found it! */
  44
  45                 rootp = (r < 0) ?
  46                     &(*rootp)->llink :          /* T3: follow left branch */
  47                     &(*rootp)->rlink;           /* T4: follow right branch */
  48         }
  49
  50         q = malloc(sizeof(node_t));             /* T5: key not found */
  51         if (q != 0) {                           /* make new node */
  52                 *rootp = q;                     /* link new node to old */
  53                 /* LINTED const castaway ok */
  54                 q->key = __DECONST(void *, vkey); /* initialize new node */
  55                 q->llink = q->rlink = NULL;
  56         }
  57         return q;
  58 }