1 /*- 2 * SPDX-License-Identifier: BSD-3-Clause 3 * 4 * Copyright (c) 1990, 1993, 1994 5 * The Regents of the University of California. All rights reserved. 6 * 7 * This code is derived from software contributed to Berkeley by 8 * Mike Olson. 9 * 10 * Redistribution and use in source and binary forms, with or without 11 * modification, are permitted provided that the following conditions 12 * are met: 13 * 1. Redistributions of source code must retain the above copyright 14 * notice, this list of conditions and the following disclaimer. 15 * 2. Redistributions in binary form must reproduce the above copyright 16 * notice, this list of conditions and the following disclaimer in the 17 * documentation and/or other materials provided with the distribution. 18 * 3. Neither the name of the University nor the names of its contributors 19 * may be used to endorse or promote products derived from this software 20 * without specific prior written permission. 21 * 22 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 23 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 25 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 27 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 28 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 29 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 30 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 31 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32 * SUCH DAMAGE. 33 */ 34 35 #if defined(LIBC_SCCS) && !defined(lint) 36 static char sccsid[] = "@(#)bt_search.c 8.8 (Berkeley) 7/31/94"; 37 #endif /* LIBC_SCCS and not lint */ 38 #include <sys/cdefs.h> 39 __FBSDID("$FreeBSD$"); 40 41 #include <sys/types.h> 42 43 #include <stdio.h> 44 45 #include <db.h> 46 #include "btree.h" 47 48 static int __bt_snext(BTREE *, PAGE *, const DBT *, int *); 49 static int __bt_sprev(BTREE *, PAGE *, const DBT *, int *); 50 51 /* 52 * __bt_search -- 53 * Search a btree for a key. 54 * 55 * Parameters: 56 * t: tree to search 57 * key: key to find 58 * exactp: pointer to exact match flag 59 * 60 * Returns: 61 * The EPG for matching record, if any, or the EPG for the location 62 * of the key, if it were inserted into the tree, is entered into 63 * the bt_cur field of the tree. A pointer to the field is returned. 64 */ 65 EPG * 66 __bt_search(BTREE *t, const DBT *key, int *exactp) 67 { 68 PAGE *h; 69 indx_t base, idx, lim; 70 pgno_t pg; 71 int cmp; 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 = idx = 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 = idx + 1; 91 --lim; 92 } 93 } 94 95 /* 96 * If it's a leaf page, we're almost done. If no duplicates 97 * are allowed, or we have an exact match, we're done. Else, 98 * it's possible that there were matching keys on this page, 99 * which later deleted, and we're on a page with no matches 100 * while there are matches on other pages. If at the start or 101 * end of a page, check the adjacent page. 102 */ 103 if (h->flags & P_BLEAF) { 104 if (!F_ISSET(t, B_NODUPS)) { 105 if (base == 0 && 106 h->prevpg != P_INVALID && 107 __bt_sprev(t, h, key, exactp)) 108 return (&t->bt_cur); 109 if (base == NEXTINDEX(h) && 110 h->nextpg != P_INVALID && 111 __bt_snext(t, h, key, exactp)) 112 return (&t->bt_cur); 113 } 114 *exactp = 0; 115 t->bt_cur.index = base; 116 return (&t->bt_cur); 117 } 118 119 /* 120 * No match found. Base is the smallest index greater than 121 * key and may be zero or a last + 1 index. If it's non-zero, 122 * decrement by one, and record the internal page which should 123 * be a parent page for the key. If a split later occurs, the 124 * inserted page will be to the right of the saved page. 125 */ 126 idx = base ? base - 1 : base; 127 128 next: BT_PUSH(t, h->pgno, idx); 129 pg = GETBINTERNAL(h, idx)->pgno; 130 mpool_put(t->bt_mp, h, 0); 131 } 132 } 133 134 /* 135 * __bt_snext -- 136 * Check for an exact match after the key. 137 * 138 * Parameters: 139 * t: tree 140 * h: current page 141 * key: key 142 * exactp: pointer to exact match flag 143 * 144 * Returns: 145 * If an exact match found. 146 */ 147 static int 148 __bt_snext(BTREE *t, PAGE *h, const DBT *key, int *exactp) 149 { 150 EPG e; 151 152 /* 153 * Get the next page. The key is either an exact 154 * match, or not as good as the one we already have. 155 */ 156 if ((e.page = mpool_get(t->bt_mp, h->nextpg, 0)) == NULL) 157 return (0); 158 e.index = 0; 159 if (__bt_cmp(t, key, &e) == 0) { 160 mpool_put(t->bt_mp, h, 0); 161 t->bt_cur = e; 162 *exactp = 1; 163 return (1); 164 } 165 mpool_put(t->bt_mp, e.page, 0); 166 return (0); 167 } 168 169 /* 170 * __bt_sprev -- 171 * Check for an exact match before the key. 172 * 173 * Parameters: 174 * t: tree 175 * h: current page 176 * key: key 177 * exactp: pointer to exact match flag 178 * 179 * Returns: 180 * If an exact match found. 181 */ 182 static int 183 __bt_sprev(BTREE *t, PAGE *h, const DBT *key, int *exactp) 184 { 185 EPG e; 186 187 /* 188 * Get the previous page. The key is either an exact 189 * match, or not as good as the one we already have. 190 */ 191 if ((e.page = mpool_get(t->bt_mp, h->prevpg, 0)) == NULL) 192 return (0); 193 e.index = NEXTINDEX(e.page) - 1; 194 if (__bt_cmp(t, key, &e) == 0) { 195 mpool_put(t->bt_mp, h, 0); 196 t->bt_cur = e; 197 *exactp = 1; 198 return (1); 199 } 200 mpool_put(t->bt_mp, e.page, 0); 201 return (0); 202 } 203