1 /* $NetBSD: tdelete.c,v 1.1 1999/02/22 10:33:15 christos 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 1.1 1999/02/22 10:33:15 christos Exp $"); 17 #endif /* LIBC_SCCS and not lint */ 18 19 #define _SEARCH_PRIVATE 20 #include <search.h> 21 #include <stdlib.h> 22 23 24 /* delete node with given key */ 25 void * 26 tdelete(vkey, vrootp, compar) 27 const void *vkey; /* key to be deleted */ 28 void **vrootp; /* address of the root of tree */ 29 int (*compar) __P((const void *, const void *)); 30 { 31 node_t **rootp = (node_t **)vrootp; 32 node_t *p, *q, *r; 33 int cmp; 34 35 if (rootp == NULL || (p = *rootp) == NULL) 36 return NULL; 37 38 while ((cmp = (*compar)(vkey, (*rootp)->key)) != 0) { 39 p = *rootp; 40 rootp = (cmp < 0) ? 41 &(*rootp)->llink : /* follow llink branch */ 42 &(*rootp)->rlink; /* follow rlink branch */ 43 if (*rootp == NULL) 44 return NULL; /* key not found */ 45 } 46 r = (*rootp)->rlink; /* D1: */ 47 if ((q = (*rootp)->llink) == NULL) /* Left NULL? */ 48 q = r; 49 else if (r != NULL) { /* Right link is NULL? */ 50 if (r->llink == NULL) { /* D2: Find successor */ 51 r->llink = q; 52 q = r; 53 } else { /* D3: Find NULL link */ 54 for (q = r->llink; q->llink != NULL; q = r->llink) 55 r = q; 56 r->llink = q->rlink; 57 q->llink = (*rootp)->llink; 58 q->rlink = (*rootp)->rlink; 59 } 60 } 61 free(*rootp); /* D4: Free node */ 62 *rootp = q; /* link parent to new node */ 63 return p; 64 } 65