/* $NetBSD: tdelete.c,v 1.2 1999/09/16 11:45:37 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 <sys/cdefs.h> #if 0 #if defined(LIBC_SCCS) && !defined(lint) __RCSID("$NetBSD: tdelete.c,v 1.2 1999/09/16 11:45:37 lukem Exp $"); #endif /* LIBC_SCCS and not lint */ #endif #include <assert.h> #define _SEARCH_PRIVATE #include <search.h> #include <stdlib.h> /* delete node with given key */ void * tdelete (const void *__restrict vkey, /* key to be deleted */ void **__restrict 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; 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; }