lib/libc/stdlib/tsearch.c

   1 /*      $NetBSD: tsearch.c,v 1.7 2012/06/25 22:32:45 abs 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 1.7 2012/06/25 22:32:45 abs 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(const void *vkey, void **vrootp,
  27     int (*compar)(const void *, const void *))
  28 {
  29         node_t *q;
  30         node_t **rootp = (node_t **)vrootp;
  31
  32         _DIAGASSERT(vkey != NULL);
  33         _DIAGASSERT(compar != NULL);
  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                 q->key = __UNCONST(vkey);       /* initialize new node */
  53                 q->llink = q->rlink = NULL;
  54         }
  55         return q;
  56 }