| /* $NetBSD: tdelete.c,v 1.3 1999/09/20 04:39:43 lukem Exp $ */ |
| |
| /* |
| * Tree search generalized from Knuth (6.2.2) Algorithm T just like |
| * the AT&T man page says. |
| * |
| * The node_t structure is for internal use only, lint doesn't grok it. |
| * |
| * Written by reading the System V Interface Definition, not the code. |
| * |
| * Totally public domain. |
| */ |
| |
| #include <assert.h> |
| #define _SEARCH_PRIVATE |
| #include <search.h> |
| #include <stdlib.h> |
| |
| #define _DIAGASSERT assert |
| |
| |
| |
| /* delete node with given key */ |
| void * |
| tdelete(const void *vkey, /* key to be deleted */ |
| void **vrootp, /* address of the root of tree */ |
| int (*compar)(const void *, const void *)) |
| { |
| node_t **rootp = (node_t **)vrootp; |
| node_t *p, *q, *r; |
| int cmp; |
| |
| _DIAGASSERT(compar != NULL); |
| |
| if (rootp == NULL || (p = *rootp) == NULL) |
| return NULL; |
| |
| while ((cmp = (*compar)(vkey, (*rootp)->key)) != 0) { |
| p = *rootp; |
| rootp = (cmp < 0) ? |
| &(*rootp)->llink : /* follow llink branch */ |
| &(*rootp)->rlink; /* follow rlink branch */ |
| if (*rootp == NULL) |
| return NULL; /* key not found */ |
| } |
| r = (*rootp)->rlink; /* D1: */ |
| if ((q = (*rootp)->llink) == NULL) /* Left NULL? */ |
| q = r; |
| else if (r != NULL) { /* Right link is NULL? */ |
| if (r->llink == NULL) { /* D2: Find successor */ |
| r->llink = q; |
| q = r; |
| } else { /* D3: Find NULL link */ |
| for (q = r->llink; q->llink != NULL; q = r->llink) |
| r = q; |
| r->llink = q->rlink; |
| q->llink = (*rootp)->llink; |
| q->rlink = (*rootp)->rlink; |
| } |
| } |
| free(*rootp); /* D4: Free node */ |
| *rootp = q; /* link parent to new node */ |
| return p; |
| } |