1 /* 2 * Tree search generalized from Knuth (6.2.2) Algorithm T just like 3 * the AT&T man page says. 4 * 5 * The node_t structure is for internal use only, lint doesn't grok it. 6 * 7 * Written by reading the System V Interface Definition, not the code. 8 * 9 * Totally public domain. 10 * 11 * $NetBSD: tdelete.c,v 1.2 1999/09/16 11:45:37 lukem Exp $ 12 * $FreeBSD: src/lib/libc/stdlib/tdelete.c,v 1.1.2.1 2000/08/17 07:38:39 jhb Exp $ 13 * $DragonFly: src/lib/libc/stdlib/tdelete.c,v 1.4 2005/11/20 12:37:49 swildner Exp $ 14 */ 15 16 #include <sys/cdefs.h> 17 18 #include <assert.h> 19 #define _SEARCH_PRIVATE 20 #include <search.h> 21 #include <stdlib.h> 22 23 24 /* delete node with given key */ 25 void * 26 tdelete(const void *vkey, /* key to be deleted */ 27 void **vrootp, /* address of the root of tree */ 28 int (*compar)(const void *, const void *)) 29 { 30 node_t **rootp = (node_t **)vrootp; 31 node_t *p, *q, *r; 32 int cmp; 33 34 if (rootp == NULL || (p = *rootp) == NULL) 35 return NULL; 36 37 while ((cmp = (*compar)(vkey, (*rootp)->key)) != 0) { 38 p = *rootp; 39 rootp = (cmp < 0) ? 40 &(*rootp)->llink : /* follow llink branch */ 41 &(*rootp)->rlink; /* follow rlink branch */ 42 if (*rootp == NULL) 43 return NULL; /* key not found */ 44 } 45 r = (*rootp)->rlink; /* D1: */ 46 if ((q = (*rootp)->llink) == NULL) /* Left NULL? */ 47 q = r; 48 else if (r != NULL) { /* Right link is NULL? */ 49 if (r->llink == NULL) { /* D2: Find successor */ 50 r->llink = q; 51 q = r; 52 } else { /* D3: Find NULL link */ 53 for (q = r->llink; q->llink != NULL; q = r->llink) 54 r = q; 55 r->llink = q->rlink; 56 q->llink = (*rootp)->llink; 57 q->rlink = (*rootp)->rlink; 58 } 59 } 60 free(*rootp); /* D4: Free node */ 61 *rootp = q; /* link parent to new node */ 62 return p; 63 } 64