stdlib/FreeBSD/tdelete.c

   1 /*      $NetBSD: tdelete.c,v 1.2 1999/09/16 11:45:37 lukem 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 0
  16 #if defined(LIBC_SCCS) && !defined(lint)
  17 __RCSID("$NetBSD: tdelete.c,v 1.2 1999/09/16 11:45:37 lukem Exp $");
  18 #endif /* LIBC_SCCS and not lint */
  19 #endif
  20 __FBSDID("$FreeBSD: src/lib/libc/stdlib/tdelete.c,v 1.6 2003/01/05 02:43:18 tjr Exp $");
  21
  22 #define _SEARCH_PRIVATE
  23 #include <search.h>
  24 #include <stdlib.h>
  25
  26
  27 /*
  28  * delete node with given key
  29  *
  30  * vkey:   key to be deleted
  31  * vrootp: address of the root of the tree
  32  * compar: function to carry out node comparisons
  33  */
  34 void *
  35 tdelete(const void * __restrict vkey, void ** __restrict vrootp,
  36     int (*compar)(const void *, const void *))
  37 {
  38         node_t **rootp = (node_t **)vrootp;
  39         node_t *p, *q, *r;
  40         int cmp;
  41
  42         if (rootp == NULL || (p = *rootp) == NULL)
  43                 return NULL;
  44
  45         while ((cmp = (*compar)(vkey, (*rootp)->key)) != 0) {
  46                 p = *rootp;
  47                 rootp = (cmp < 0) ?
  48                     &(*rootp)->llink :          /* follow llink branch */
  49                     &(*rootp)->rlink;           /* follow rlink branch */
  50                 if (*rootp == NULL)
  51                         return NULL;            /* key not found */
  52         }
  53         r = (*rootp)->rlink;                    /* D1: */
  54         if ((q = (*rootp)->llink) == NULL)      /* Left NULL? */
  55                 q = r;
  56         else if (r != NULL) {                   /* Right link is NULL? */
  57                 if (r->llink == NULL) {         /* D2: Find successor */
  58                         r->llink = q;
  59                         q = r;
  60                 } else {                        /* D3: Find NULL link */
  61                         for (q = r->llink; q->llink != NULL; q = r->llink)
  62                                 r = q;
  63                         r->llink = q->rlink;
  64                         q->llink = (*rootp)->llink;
  65                         q->rlink = (*rootp)->rlink;
  66                 }
  67         }
  68         free(*rootp);                           /* D4: Free node */
  69         *rootp = q;                             /* link parent to new node */
  70         return p;
  71 }