lib/libc/stdlib/tdelete.c

   1 /*      $NetBSD: tdelete.c,v 1.3 1999/09/20 04:39:43 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 defined(LIBC_SCCS) && !defined(lint)
  16 __RCSID("$NetBSD: tdelete.c,v 1.3 1999/09/20 04:39:43 lukem 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 /* delete node with given key */
  26 void *
  27 tdelete(vkey, vrootp, compar)
  28         const void *vkey;       /* key to be deleted */
  29         void      **vrootp;     /* address of the root of tree */
  30         int       (*compar) __P((const void *, const void *));
  31 {
  32         node_t **rootp = (node_t **)vrootp;
  33         node_t *p, *q, *r;
  34         int  cmp;
  35
  36         _DIAGASSERT(vkey != NULL);
  37         _DIAGASSERT(compar != NULL);
  38
  39         if (rootp == NULL || (p = *rootp) == NULL)
  40                 return NULL;
  41
  42         while ((cmp = (*compar)(vkey, (*rootp)->key)) != 0) {
  43                 p = *rootp;
  44                 rootp = (cmp < 0) ?
  45                     &(*rootp)->llink :          /* follow llink branch */
  46                     &(*rootp)->rlink;           /* follow rlink branch */
  47                 if (*rootp == NULL)
  48                         return NULL;            /* key not found */
  49         }
  50         r = (*rootp)->rlink;                    /* D1: */
  51         if ((q = (*rootp)->llink) == NULL)      /* Left NULL? */
  52                 q = r;
  53         else if (r != NULL) {                   /* Right link is NULL? */
  54                 if (r->llink == NULL) {         /* D2: Find successor */
  55                         r->llink = q;
  56                         q = r;
  57                 } else {                        /* D3: Find NULL link */
  58                         for (q = r->llink; q->llink != NULL; q = r->llink)
  59                                 r = q;
  60                         r->llink = q->rlink;
  61                         q->llink = (*rootp)->llink;
  62                         q->rlink = (*rootp)->rlink;
  63                 }
  64         }
  65         if (p != *rootp)
  66                 free(*rootp);                   /* D4: Free node */
  67         *rootp = q;                             /* link parent to new node */
  68         return p;
  69 }