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tsearch.c

/*    $NetBSD: tsearch.c,v 1.4 1999/09/20 04:39:43 lukem Exp $    */

/*
 * Tree search generalized from Knuth (6.2.2) Algorithm T just like
 * the AT&T man page says.
 *
 * The node_t structure is for internal use only, lint doesn't grok it.
 *
 * Written by reading the System V Interface Definition, not the code.
 *
 * Totally public domain.
 */

#include <assert.h>
#define _SEARCH_PRIVATE
#include <search.h>
#include <stdlib.h>


/* find or insert datum into search tree */
void *
tsearch(const void * __restrict__ vkey,         /* key to be located */
      void ** __restrict__ vrootp,        /* address of tree root */
      int (*compar) (const void *, const void *))
{
      node_t *q;
      node_t **rootp = (node_t **)vrootp;

      if (rootp == NULL)
            return NULL;

      while (*rootp != NULL) {      /* Knuth's T1: */
            int r;

            if ((r = (*compar)(vkey, (*rootp)->key)) == 0)  /* T2: */
                  return *rootp;          /* we found it! */

            rootp = (r < 0) ?
                &(*rootp)->llink :        /* T3: follow left branch */
                &(*rootp)->rlink;         /* T4: follow right branch */
      }

      q = malloc(sizeof(node_t));         /* T5: key not found */
      if (q != 0) {                       /* make new node */
            *rootp = q;             /* link new node to old */
            /* LINTED const castaway ok */
            q->key = (void *)vkey;        /* initialize new node */
            q->llink = q->rlink = NULL;
      }
      return q;
}

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