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/types.h> 39 40 #include <stdio.h> 41 42 #include <db.h> 43 #include "btree.h" 44 45 static int __bt_snext(BTREE *, PAGE *, const DBT *, int *); 46 static int __bt_sprev(BTREE *, PAGE *, const DBT *, int *); 47 48 /* 49 * __bt_search -- 50 * 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(BTREE *t, const DBT *key, int *exactp) 64 { 65 PAGE *h; 66 indx_t base, idx, lim; 67 pgno_t pg; 68 int cmp; 69 70 BT_CLR(t); 71 for (pg = P_ROOT;;) { 72 if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL) 73 return (NULL); 74 75 /* Do a binary search on the current page. */ 76 t->bt_cur.page = h; 77 for (base = 0, lim = NEXTINDEX(h); lim; lim >>= 1) { 78 t->bt_cur.index = idx = base + (lim >> 1); 79 if ((cmp = __bt_cmp(t, key, &t->bt_cur)) == 0) { 80 if (h->flags & P_BLEAF) { 81 *exactp = 1; 82 return (&t->bt_cur); 83 } 84 goto next; 85 } 86 if (cmp > 0) { 87 base = idx + 1; 88 --lim; 89 } 90 } 91 92 /* 93 * If it's a leaf page, we're almost done. If no duplicates 94 * are allowed, or we have an exact match, we're done. Else, 95 * it's possible that there were matching keys on this page, 96 * which later deleted, and we're on a page with no matches 97 * while there are matches on other pages. If at the start or 98 * end of a page, check the adjacent page. 99 */ 100 if (h->flags & P_BLEAF) { 101 if (!F_ISSET(t, B_NODUPS)) { 102 if (base == 0 && 103 h->prevpg != P_INVALID && 104 __bt_sprev(t, h, key, exactp)) 105 return (&t->bt_cur); 106 if (base == NEXTINDEX(h) && 107 h->nextpg != P_INVALID && 108 __bt_snext(t, h, key, exactp)) 109 return (&t->bt_cur); 110 } 111 *exactp = 0; 112 t->bt_cur.index = base; 113 return (&t->bt_cur); 114 } 115 116 /* 117 * No match found. Base is the smallest index greater than 118 * key and may be zero or a last + 1 index. If it's non-zero, 119 * decrement by one, and record the internal page which should 120 * be a parent page for the key. If a split later occurs, the 121 * inserted page will be to the right of the saved page. 122 */ 123 idx = base ? base - 1 : base; 124 125 next: BT_PUSH(t, h->pgno, idx); 126 pg = GETBINTERNAL(h, idx)->pgno; 127 mpool_put(t->bt_mp, h, 0); 128 } 129 } 130 131 /* 132 * __bt_snext -- 133 * Check for an exact match after the key. 134 * 135 * Parameters: 136 * t: tree 137 * h: current page 138 * key: key 139 * exactp: pointer to exact match flag 140 * 141 * Returns: 142 * If an exact match found. 143 */ 144 static int 145 __bt_snext(BTREE *t, PAGE *h, const DBT *key, int *exactp) 146 { 147 EPG e; 148 149 /* 150 * Get the next page. The key is either an exact 151 * match, or not as good as the one we already have. 152 */ 153 if ((e.page = mpool_get(t->bt_mp, h->nextpg, 0)) == NULL) 154 return (0); 155 e.index = 0; 156 if (__bt_cmp(t, key, &e) == 0) { 157 mpool_put(t->bt_mp, h, 0); 158 t->bt_cur = e; 159 *exactp = 1; 160 return (1); 161 } 162 mpool_put(t->bt_mp, e.page, 0); 163 return (0); 164 } 165 166 /* 167 * __bt_sprev -- 168 * Check for an exact match before the key. 169 * 170 * Parameters: 171 * t: tree 172 * h: current page 173 * key: key 174 * exactp: pointer to exact match flag 175 * 176 * Returns: 177 * If an exact match found. 178 */ 179 static int 180 __bt_sprev(BTREE *t, PAGE *h, const DBT *key, int *exactp) 181 { 182 EPG e; 183 184 /* 185 * Get the previous page. The key is either an exact 186 * match, or not as good as the one we already have. 187 */ 188 if ((e.page = mpool_get(t->bt_mp, h->prevpg, 0)) == NULL) 189 return (0); 190 e.index = NEXTINDEX(e.page) - 1; 191 if (__bt_cmp(t, key, &e) == 0) { 192 mpool_put(t->bt_mp, h, 0); 193 t->bt_cur = e; 194 *exactp = 1; 195 return (1); 196 } 197 mpool_put(t->bt_mp, e.page, 0); 198 return (0); 199 } 200