1 /*- 2 * Copyright (c) 1990, 1993 3 * The Regents of the University of California. All rights reserved. 4 * 5 * This code is derived from software contributed to Berkeley by 6 * Mike Olson. 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in the 15 * documentation and/or other materials provided with the distribution. 16 * 3. All advertising materials mentioning features or use of this software 17 * must display the following acknowledgement: 18 * This product includes software developed by the University of 19 * California, Berkeley and its contributors. 20 * 4. Neither the name of the University nor the names of its contributors 21 * may be used to endorse or promote products derived from this software 22 * without specific prior written permission. 23 * 24 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 25 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 26 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 27 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 28 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 29 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 30 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 31 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 32 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 33 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 34 * SUCH DAMAGE. 35 */ 36 37 #if defined(LIBC_SCCS) && !defined(lint) 38 /* from: static char sccsid[] = "@(#)bt_search.c 8.2 (Berkeley) 9/14/93"; */ 39 static char *rcsid = "$Id: bt_search.c,v 1.4 1993/09/17 01:06:28 cgd Exp $"; 40 #endif /* LIBC_SCCS and not lint */ 41 42 #include <sys/types.h> 43 44 #include <stdio.h> 45 46 #include <db.h> 47 #include "btree.h" 48 49 /* 50 * __BT_SEARCH -- Search a btree for a key. 51 * 52 * Parameters: 53 * t: tree to search 54 * key: key to find 55 * exactp: pointer to exact match flag 56 * 57 * Returns: 58 * The EPG for matching record, if any, or the EPG for the location 59 * of the key, if it were inserted into the tree, is entered into 60 * the bt_cur field of the tree. A pointer to the field is returned. 61 */ 62 EPG * 63 __bt_search(t, key, exactp) 64 BTREE *t; 65 const DBT *key; 66 int *exactp; 67 { 68 register indx_t index; 69 register int base, cmp, lim; 70 register PAGE *h; 71 pgno_t pg; 72 73 BT_CLR(t); 74 for (pg = P_ROOT;;) { 75 if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL) 76 return (NULL); 77 78 /* Do a binary search on the current page. */ 79 t->bt_cur.page = h; 80 for (base = 0, lim = NEXTINDEX(h); lim; lim >>= 1) { 81 t->bt_cur.index = index = base + (lim >> 1); 82 if ((cmp = __bt_cmp(t, key, &t->bt_cur)) == 0) { 83 if (h->flags & P_BLEAF) { 84 *exactp = 1; 85 return (&t->bt_cur); 86 } 87 goto next; 88 } 89 if (cmp > 0) { 90 base = index + 1; 91 --lim; 92 } 93 } 94 95 /* If it's a leaf page, we're done. */ 96 if (h->flags & P_BLEAF) { 97 t->bt_cur.index = base; 98 *exactp = 0; 99 return (&t->bt_cur); 100 } 101 102 /* 103 * No match found. Base is the smallest index greater than 104 * key and may be zero or a last + 1 index. If it's non-zero, 105 * decrement by one, and record the internal page which should 106 * be a parent page for the key. If a split later occurs, the 107 * inserted page will be to the right of the saved page. 108 */ 109 index = base ? base - 1 : base; 110 111 next: if (__bt_push(t, h->pgno, index) == RET_ERROR) 112 return (NULL); 113 pg = GETBINTERNAL(h, index)->pgno; 114 mpool_put(t->bt_mp, h, 0); 115 } 116 } 117