lib/libc/stdlib/tdelete.c

   1 /*      $NetBSD: tdelete.c,v 1.6 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: tdelete.c,v 1.6 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
  25 /* find a node with key "vkey" in tree "vrootp" */
  26 void *
  27 tdelete(const void *vkey, void **vrootp,
  28     int (*compar)(const void *, const void *))
  29 {
  30         node_t **rootp = (node_t **)vrootp;
  31         node_t *p, *q, *r;
  32         int  cmp;
  33
  34         _DIAGASSERT(vkey != NULL);
  35         _DIAGASSERT(compar != NULL);
  36
  37         if (rootp == NULL || (p = *rootp) == NULL)
  38                 return NULL;
  39
  40         while ((cmp = (*compar)(vkey, (*rootp)->key)) != 0) {
  41                 p = *rootp;
  42                 rootp = (cmp < 0) ?
  43                     &(*rootp)->llink :          /* follow llink branch */
  44                     &(*rootp)->rlink;           /* follow rlink branch */
  45                 if (*rootp == NULL)
  46                         return NULL;            /* key not found */
  47         }
  48         r = (*rootp)->rlink;                    /* D1: */
  49         if ((q = (*rootp)->llink) == NULL)      /* Left NULL? */
  50                 q = r;
  51         else if (r != NULL) {                   /* Right link is NULL? */
  52                 if (r->llink == NULL) {         /* D2: Find successor */
  53                         r->llink = q;
  54                         q = r;
  55                 } else {                        /* D3: Find NULL link */
  56                         for (q = r->llink; q->llink != NULL; q = r->llink)
  57                                 r = q;
  58                         r->llink = q->rlink;
  59                         q->llink = (*rootp)->llink;
  60                         q->rlink = (*rootp)->rlink;
  61                 }
  62         }
  63         if (p != *rootp)
  64                 free(*rootp);                   /* D4: Free node */
  65         *rootp = q;                             /* link parent to new node */
  66         return p;
  67 }