lib/libc/stdlib/tdelete.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: tdelete.c,v 1.2 1999/09/16 11:45:37 lukem Exp $
  12  * $FreeBSD: src/lib/libc/stdlib/tdelete.c,v 1.1.2.1 2000/08/17 07:38:39 jhb Exp $
  13  * $DragonFly: src/lib/libc/stdlib/tdelete.c,v 1.4 2005/11/20 12:37:49 swildner Exp $
  14  */
  15
  16 #include <sys/cdefs.h>
  17
  18 #include <assert.h>
  19 #define _SEARCH_PRIVATE
  20 #include <search.h>
  21 #include <stdlib.h>
  22
  23
  24 /* delete node with given key */
  25 void *
  26 tdelete(const void *vkey,                               /* key to be deleted */
  27         void **vrootp,                                  /* address of the root of tree */
  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         if (rootp == NULL || (p = *rootp) == NULL)
  35                 return NULL;
  36
  37         while ((cmp = (*compar)(vkey, (*rootp)->key)) != 0) {
  38                 p = *rootp;
  39                 rootp = (cmp < 0) ?
  40                     &(*rootp)->llink :          /* follow llink branch */
  41                     &(*rootp)->rlink;           /* follow rlink branch */
  42                 if (*rootp == NULL)
  43                         return NULL;            /* key not found */
  44         }
  45         r = (*rootp)->rlink;                    /* D1: */
  46         if ((q = (*rootp)->llink) == NULL)      /* Left NULL? */
  47                 q = r;
  48         else if (r != NULL) {                   /* Right link is NULL? */
  49                 if (r->llink == NULL) {         /* D2: Find successor */
  50                         r->llink = q;
  51                         q = r;
  52                 } else {                        /* D3: Find NULL link */
  53                         for (q = r->llink; q->llink != NULL; q = r->llink)
  54                                 r = q;
  55                         r->llink = q->rlink;
  56                         q->llink = (*rootp)->llink;
  57                         q->rlink = (*rootp)->rlink;
  58                 }
  59         }
  60         free(*rootp);                           /* D4: Free node */
  61         *rootp = q;                             /* link parent to new node */
  62         return p;
  63 }