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 21 #include <assert.h> 22 #define _SEARCH_PRIVATE 23 #include <search.h> 24 #include <stdlib.h> 25 26 27 /* delete node with given key */ 28 void * 29 _DEFUN(tdelete, (vkey, vrootp, compar), 30 const void *vkey _AND /* key to be deleted */ 31 void **vrootp _AND /* address of the root of tree */ 32 int (*compar)(const void *, const void *)) 33 { 34 node_t **rootp = (node_t **)vrootp; 35 node_t *p, *q, *r; 36 int cmp; 37 38 if (rootp == NULL || (p = *rootp) == NULL) 39 return NULL; 40 41 while ((cmp = (*compar)(vkey, (*rootp)->key)) != 0) { 42 p = *rootp; 43 rootp = (cmp < 0) ? 44 &(*rootp)->llink : /* follow llink branch */ 45 &(*rootp)->rlink; /* follow rlink branch */ 46 if (*rootp == NULL) 47 return NULL; /* key not found */ 48 } 49 r = (*rootp)->rlink; /* D1: */ 50 if ((q = (*rootp)->llink) == NULL) /* Left NULL? */ 51 q = r; 52 else if (r != NULL) { /* Right link is NULL? */ 53 if (r->llink == NULL) { /* D2: Find successor */ 54 r->llink = q; 55 q = r; 56 } else { /* D3: Find NULL link */ 57 for (q = r->llink; q->llink != NULL; q = r->llink) 58 r = q; 59 r->llink = q->rlink; 60 q->llink = (*rootp)->llink; 61 q->rlink = (*rootp)->rlink; 62 } 63 } 64 free(*rootp); /* D4: Free node */ 65 *rootp = q; /* link parent to new node */ 66 return p; 67 } 68