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 1.6 2003/01/05 02:43:18 tjr Exp $ 13 * $DragonFly: src/lib/libc/stdlib/tdelete.c,v 1.5 2005/11/24 17:18:30 swildner Exp $ 14 */ 15 16 #define _SEARCH_PRIVATE 17 #include <search.h> 18 #include <stdlib.h> 19 20 21 /* 22 * delete node with given key 23 * 24 * vkey: key to be deleted 25 * vrootp: address of the root of the tree 26 * compar: function to carry out node comparisons 27 */ 28 void * 29 tdelete(const void * __restrict vkey, void ** __restrict vrootp, 30 int (*compar)(const void *, const void *)) 31 { 32 node_t **rootp = (node_t **)vrootp; 33 node_t *p, *q, *r; 34 int cmp; 35 36 if (rootp == NULL || (p = *rootp) == NULL) 37 return NULL; 38 39 while ((cmp = (*compar)(vkey, (*rootp)->key)) != 0) { 40 p = *rootp; 41 rootp = (cmp < 0) ? 42 &(*rootp)->llink : /* follow llink branch */ 43 &(*rootp)->rlink; /* follow rlink branch */ 44 if (*rootp == NULL) 45 return NULL; /* key not found */ 46 } 47 r = (*rootp)->rlink; /* D1: */ 48 if ((q = (*rootp)->llink) == NULL) /* Left NULL? */ 49 q = r; 50 else if (r != NULL) { /* Right link is NULL? */ 51 if (r->llink == NULL) { /* D2: Find successor */ 52 r->llink = q; 53 q = r; 54 } else { /* D3: Find NULL link */ 55 for (q = r->llink; q->llink != NULL; q = r->llink) 56 r = q; 57 r->llink = q->rlink; 58 q->llink = (*rootp)->llink; 59 q->rlink = (*rootp)->rlink; 60 } 61 } 62 free(*rootp); /* D4: Free node */ 63 *rootp = q; /* link parent to new node */ 64 return p; 65 } 66