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