1 /* $NetBSD: tdelete.c,v 1.2 1999/09/16 11:45:37 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 0 16 #if defined(LIBC_SCCS) && !defined(lint) 17 __RCSID("$NetBSD: tdelete.c,v 1.2 1999/09/16 11:45:37 lukem Exp $"); 18 #endif /* LIBC_SCCS and not lint */ 19 #endif 20 __FBSDID("$FreeBSD$"); 21 22 #define _SEARCH_PRIVATE 23 #include <search.h> 24 #include <stdlib.h> 25 26 27 /* 28 * delete node with given key 29 * 30 * vkey: key to be deleted 31 * vrootp: address of the root of the tree 32 * compar: function to carry out node comparisons 33 */ 34 void * 35 tdelete(const void * __restrict vkey, void ** __restrict vrootp, 36 int (*compar)(const void *, const void *)) 37 { 38 node_t **rootp = (node_t **)vrootp; 39 node_t *p, *q, *r; 40 int cmp; 41 42 if (rootp == NULL || (p = *rootp) == NULL) 43 return NULL; 44 45 while ((cmp = (*compar)(vkey, (*rootp)->key)) != 0) { 46 p = *rootp; 47 rootp = (cmp < 0) ? 48 &(*rootp)->llink : /* follow llink branch */ 49 &(*rootp)->rlink; /* follow rlink branch */ 50 if (*rootp == NULL) 51 return NULL; /* key not found */ 52 } 53 r = (*rootp)->rlink; /* D1: */ 54 if ((q = (*rootp)->llink) == NULL) /* Left NULL? */ 55 q = r; 56 else if (r != NULL) { /* Right link is NULL? */ 57 if (r->llink == NULL) { /* D2: Find successor */ 58 r->llink = q; 59 q = r; 60 } else { /* D3: Find NULL link */ 61 for (q = r->llink; q->llink != NULL; q = r->llink) 62 r = q; 63 r->llink = q->rlink; 64 q->llink = (*rootp)->llink; 65 q->rlink = (*rootp)->rlink; 66 } 67 } 68 free(*rootp); /* D4: Free node */ 69 *rootp = q; /* link parent to new node */ 70 return p; 71 } 72