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 1.6 2003/01/05 02:43:18 tjr Exp $
  13  * $DragonFly: src/lib/libc/stdlib/tdelete.c,v 1.5 2005/11/24 17:18:30 swildner Exp $
  14  */
  15
  16 #define _SEARCH_PRIVATE
  17 #include <search.h>
  18 #include <stdlib.h>
  19
  20
  21 /*
  22  * delete node with given key
  23  *
  24  * vkey:   key to be deleted
  25  * vrootp: address of the root of the tree
  26  * compar: function to carry out node comparisons
  27  */
  28 void *
  29 tdelete(const void * __restrict vkey, void ** __restrict vrootp,
  30         int (*compar)(const void *, const void *))
  31 {
  32         node_t **rootp = (node_t **)vrootp;
  33         node_t *p, *q, *r;
  34         int cmp;
  35
  36         if (rootp == NULL || (p = *rootp) == NULL)
  37                 return NULL;
  38
  39         while ((cmp = (*compar)(vkey, (*rootp)->key)) != 0) {
  40                 p = *rootp;
  41                 rootp = (cmp < 0) ?
  42                     &(*rootp)->llink :          /* follow llink branch */
  43                     &(*rootp)->rlink;           /* follow rlink branch */
  44                 if (*rootp == NULL)
  45                         return NULL;            /* key not found */
  46         }
  47         r = (*rootp)->rlink;                    /* D1: */
  48         if ((q = (*rootp)->llink) == NULL)      /* Left NULL? */
  49                 q = r;
  50         else if (r != NULL) {                   /* Right link is NULL? */
  51                 if (r->llink == NULL) {         /* D2: Find successor */
  52                         r->llink = q;
  53                         q = r;
  54                 } else {                        /* D3: Find NULL link */
  55                         for (q = r->llink; q->llink != NULL; q = r->llink)
  56                                 r = q;
  57                         r->llink = q->rlink;
  58                         q->llink = (*rootp)->llink;
  59                         q->rlink = (*rootp)->rlink;
  60                 }
  61         }
  62         free(*rootp);                           /* D4: Free node */
  63         *rootp = q;                             /* link parent to new node */
  64         return p;
  65 }