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 defined(LIBC_SCCS) && !defined(lint) 16 __RCSID("$NetBSD: tdelete.c,v 1.2 1999/09/16 11:45:37 lukem Exp $"); 17 #endif /* LIBC_SCCS and not lint */ 18 19 #include <assert.h> 20 #define _SEARCH_PRIVATE 21 #include <search.h> 22 #include <stdlib.h> 23 24 25 /* delete node with given key */ 26 void * 27 tdelete(vkey, vrootp, compar) 28 const void *vkey; /* key to be deleted */ 29 void **vrootp; /* address of the root of tree */ 30 int (*compar) __P((const void *, const void *)); 31 { 32 node_t **rootp = (node_t **)vrootp; 33 node_t *p, *q, *r; 34 int cmp; 35 36 _DIAGASSERT(vkey != NULL); 37 _DIAGASSERT(compar != NULL); 38 #ifdef _DIAGNOSTIC 39 if (vkey == NULL || compar == NULL) 40 return (NULL); 41 #endif 42 43 if (rootp == NULL || (p = *rootp) == NULL) 44 return NULL; 45 46 while ((cmp = (*compar)(vkey, (*rootp)->key)) != 0) { 47 p = *rootp; 48 rootp = (cmp < 0) ? 49 &(*rootp)->llink : /* follow llink branch */ 50 &(*rootp)->rlink; /* follow rlink branch */ 51 if (*rootp == NULL) 52 return NULL; /* key not found */ 53 } 54 r = (*rootp)->rlink; /* D1: */ 55 if ((q = (*rootp)->llink) == NULL) /* Left NULL? */ 56 q = r; 57 else if (r != NULL) { /* Right link is NULL? */ 58 if (r->llink == NULL) { /* D2: Find successor */ 59 r->llink = q; 60 q = r; 61 } else { /* D3: Find NULL link */ 62 for (q = r->llink; q->llink != NULL; q = r->llink) 63 r = q; 64 r->llink = q->rlink; 65 q->llink = (*rootp)->llink; 66 q->rlink = (*rootp)->rlink; 67 } 68 } 69 free(*rootp); /* D4: Free node */ 70 *rootp = q; /* link parent to new node */ 71 return p; 72 } 73