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  */
  14
  15 #define _SEARCH_PRIVATE
  16 #include <search.h>
  17 #include <stdlib.h>
  18
  19 /*
  20  * find or insert datum into search tree
  21  *
  22  * Parameters:
  23  *      vkey:   key to be located
  24  *      vrootp: address of tree root
  25  */
  26
  27 void *
  28 tsearch(const void *vkey, void **vrootp,
  29         int (*compar)(const void *, const void *))
  30 {
  31         node_t *q;
  32         node_t **rootp = (node_t **)vrootp;
  33
  34         if (rootp == NULL)
  35                 return NULL;
  36
  37         while (*rootp != NULL) {        /* Knuth's T1: */
  38                 int r;
  39
  40                 if ((r = (*compar)(vkey, (*rootp)->key)) == 0)  /* T2: */
  41                         return *rootp;          /* we found it! */
  42
  43                 rootp = (r < 0) ?
  44                     &(*rootp)->llink :          /* T3: follow left branch */
  45                     &(*rootp)->rlink;           /* T4: follow right branch */
  46         }
  47
  48         q = malloc(sizeof(node_t));             /* T5: key not found */
  49         if (q != NULL) {                        /* make new node */
  50                 *rootp = q;                     /* link new node to old */
  51                 /* LINTED const castaway ok */
  52                 q->key = __DECONST(void *, vkey); /* initialize new node */
  53                 q->llink = q->rlink = NULL;
  54         }
  55         return q;
  56 }