1 /* $NetBSD: tdelete.c,v 1.2 1999/09/16 11:45:37 lukem Exp $ */ 2 /* $FreeBSD$ */ 3 4 /* 5 * Tree search generalized from Knuth (6.2.2) Algorithm T just like 6 * the AT&T man page says. 7 * 8 * The node_t structure is for internal use only, lint doesn't grok it. 9 * 10 * Written by reading the System V Interface Definition, not the code. 11 * 12 * Totally public domain. 13 */ 14 15 #include <sys/cdefs.h> 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 20 #include <assert.h> 21 #define _SEARCH_PRIVATE 22 #include <search.h> 23 #include <stdlib.h> 24 25 26 /* delete node with given key */ 27 void * 28 tdelete(vkey, vrootp, compar) 29 const void *vkey; /* key to be deleted */ 30 void **vrootp; /* address of the root of tree */ 31 int (*compar) __P((const void *, const void *)); 32 { 33 node_t **rootp = (node_t **)vrootp; 34 node_t *p, *q, *r; 35 int cmp; 36 37 if (rootp == NULL || (p = *rootp) == NULL) 38 return NULL; 39 40 while ((cmp = (*compar)(vkey, (*rootp)->key)) != 0) { 41 p = *rootp; 42 rootp = (cmp < 0) ? 43 &(*rootp)->llink : /* follow llink branch */ 44 &(*rootp)->rlink; /* follow rlink branch */ 45 if (*rootp == NULL) 46 return NULL; /* key not found */ 47 } 48 r = (*rootp)->rlink; /* D1: */ 49 if ((q = (*rootp)->llink) == NULL) /* Left NULL? */ 50 q = r; 51 else if (r != NULL) { /* Right link is NULL? */ 52 if (r->llink == NULL) { /* D2: Find successor */ 53 r->llink = q; 54 q = r; 55 } else { /* D3: Find NULL link */ 56 for (q = r->llink; q->llink != NULL; q = r->llink) 57 r = q; 58 r->llink = q->rlink; 59 q->llink = (*rootp)->llink; 60 q->rlink = (*rootp)->rlink; 61 } 62 } 63 free(*rootp); /* D4: Free node */ 64 *rootp = q; /* link parent to new node */ 65 return p; 66 } 67