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 free(*rootp); /* D4: Free node */ 66 *rootp = q; /* link parent to new node */ 67 return p; 68 } 69