1/*- 2 * Copyright (c) 1990, 1993, 1994 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 * 4. Neither the name of the University nor the names of its contributors 17 * may be used to endorse or promote products derived from this software 18 * without specific prior written permission. 19 * 20 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30 * SUCH DAMAGE. 31 */ 32 33#if defined(LIBC_SCCS) && !defined(lint) 34static char sccsid[] = "@(#)bt_search.c 8.8 (Berkeley) 7/31/94"; 35#endif /* LIBC_SCCS and not lint */ 36#include <sys/cdefs.h> 37__FBSDID("$FreeBSD$"); 38 39#include <sys/types.h> 40 41#include <stdio.h> 42 43#include <db.h> 44#include "btree.h" 45 46static int __bt_snext(BTREE *, PAGE *, const DBT *, int *); 47static int __bt_sprev(BTREE *, PAGE *, const DBT *, int *); 48 49/* 50 * __bt_search -- 51 * Search a btree for a key. 52 * 53 * Parameters: 54 * t: tree to search 55 * key: key to find 56 * exactp: pointer to exact match flag 57 * 58 * Returns: 59 * The EPG for matching record, if any, or the EPG for the location 60 * of the key, if it were inserted into the tree, is entered into 61 * the bt_cur field of the tree. A pointer to the field is returned. 62 */ 63EPG * 64__bt_search(BTREE *t, const DBT *key, int *exactp) 65{ 66 PAGE *h; 67 indx_t base, idx, lim; 68 pgno_t pg; 69 int cmp; 70 71 BT_CLR(t); 72 for (pg = P_ROOT;;) { 73 if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL) 74 return (NULL); 75 76 /* Do a binary search on the current page. */ 77 t->bt_cur.page = h; 78 for (base = 0, lim = NEXTINDEX(h); lim; lim >>= 1) { 79 t->bt_cur.index = idx = base + (lim >> 1); 80 if ((cmp = __bt_cmp(t, key, &t->bt_cur)) == 0) { 81 if (h->flags & P_BLEAF) { 82 *exactp = 1; 83 return (&t->bt_cur); 84 } 85 goto next; 86 } 87 if (cmp > 0) { 88 base = idx + 1; 89 --lim; 90 } 91 } 92 93 /* 94 * If it's a leaf page, we're almost done. If no duplicates 95 * are allowed, or we have an exact match, we're done. Else, 96 * it's possible that there were matching keys on this page, 97 * which later deleted, and we're on a page with no matches 98 * while there are matches on other pages. If at the start or 99 * end of a page, check the adjacent page. 100 */ 101 if (h->flags & P_BLEAF) { 102 if (!F_ISSET(t, B_NODUPS)) { 103 if (base == 0 && 104 h->prevpg != P_INVALID && 105 __bt_sprev(t, h, key, exactp)) 106 return (&t->bt_cur); 107 if (base == NEXTINDEX(h) && 108 h->nextpg != P_INVALID && 109 __bt_snext(t, h, key, exactp)) 110 return (&t->bt_cur); 111 } 112 *exactp = 0; 113 t->bt_cur.index = base; 114 return (&t->bt_cur); 115 } 116 117 /* 118 * No match found. Base is the smallest index greater than 119 * key and may be zero or a last + 1 index. If it's non-zero, 120 * decrement by one, and record the internal page which should 121 * be a parent page for the key. If a split later occurs, the 122 * inserted page will be to the right of the saved page. 123 */ 124 idx = base ? base - 1 : base; 125 126next: BT_PUSH(t, h->pgno, idx); 127 pg = GETBINTERNAL(h, idx)->pgno; 128 mpool_put(t->bt_mp, h, 0); 129 } 130} 131 132/* 133 * __bt_snext -- 134 * Check for an exact match after the key. 135 * 136 * Parameters: 137 * t: tree 138 * h: current page 139 * key: key 140 * exactp: pointer to exact match flag 141 * 142 * Returns: 143 * If an exact match found. 144 */ 145static int 146__bt_snext(BTREE *t, PAGE *h, const DBT *key, int *exactp) 147{ 148 EPG e; 149 150 /* 151 * Get the next page. The key is either an exact 152 * match, or not as good as the one we already have. 153 */ 154 if ((e.page = mpool_get(t->bt_mp, h->nextpg, 0)) == NULL) 155 return (0); 156 e.index = 0; 157 if (__bt_cmp(t, key, &e) == 0) { 158 mpool_put(t->bt_mp, h, 0); 159 t->bt_cur = e; 160 *exactp = 1; 161 return (1); 162 } 163 mpool_put(t->bt_mp, e.page, 0); 164 return (0); 165} 166 167/* 168 * __bt_sprev -- 169 * Check for an exact match before the key. 170 * 171 * Parameters: 172 * t: tree 173 * h: current page 174 * key: key 175 * exactp: pointer to exact match flag 176 * 177 * Returns: 178 * If an exact match found. 179 */ 180static int 181__bt_sprev(BTREE *t, PAGE *h, const DBT *key, int *exactp) 182{ 183 EPG e; 184 185 /* 186 * Get the previous page. The key is either an exact 187 * match, or not as good as the one we already have. 188 */ 189 if ((e.page = mpool_get(t->bt_mp, h->prevpg, 0)) == NULL) 190 return (0); 191 e.index = NEXTINDEX(e.page) - 1; 192 if (__bt_cmp(t, key, &e) == 0) { 193 mpool_put(t->bt_mp, h, 0); 194 t->bt_cur = e; 195 *exactp = 1; 196 return (1); 197 } 198 mpool_put(t->bt_mp, e.page, 0); 199 return (0); 200} 201