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 #include <sys/types.h> 36 37 #include <stdio.h> 38 39 #include <db.h> 40 #include "btree.h" 41 42 static int __bt_snext(BTREE *, PAGE *, const DBT *, int *); 43 static int __bt_sprev(BTREE *, PAGE *, const DBT *, int *); 44 45 /* 46 * __bt_search -- 47 * Search a btree for a key. 48 * 49 * Parameters: 50 * t: tree to search 51 * key: key to find 52 * exactp: pointer to exact match flag 53 * 54 * Returns: 55 * The EPG for matching record, if any, or the EPG for the location 56 * of the key, if it were inserted into the tree, is entered into 57 * the bt_cur field of the tree. A pointer to the field is returned. 58 */ 59 EPG * 60 __bt_search(BTREE *t, const DBT *key, int *exactp) 61 { 62 PAGE *h; 63 indx_t base, idx, lim; 64 pgno_t pg; 65 int cmp; 66 67 BT_CLR(t); 68 for (pg = P_ROOT;;) { 69 if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL) 70 return (NULL); 71 72 /* Do a binary search on the current page. */ 73 t->bt_cur.page = h; 74 for (base = 0, lim = NEXTINDEX(h); lim; lim >>= 1) { 75 t->bt_cur.index = idx = base + (lim >> 1); 76 if ((cmp = __bt_cmp(t, key, &t->bt_cur)) == 0) { 77 if (h->flags & P_BLEAF) { 78 *exactp = 1; 79 return (&t->bt_cur); 80 } 81 goto next; 82 } 83 if (cmp > 0) { 84 base = idx + 1; 85 --lim; 86 } 87 } 88 89 /* 90 * If it's a leaf page, we're almost done. If no duplicates 91 * are allowed, or we have an exact match, we're done. Else, 92 * it's possible that there were matching keys on this page, 93 * which later deleted, and we're on a page with no matches 94 * while there are matches on other pages. If at the start or 95 * end of a page, check the adjacent page. 96 */ 97 if (h->flags & P_BLEAF) { 98 if (!F_ISSET(t, B_NODUPS)) { 99 if (base == 0 && 100 h->prevpg != P_INVALID && 101 __bt_sprev(t, h, key, exactp)) 102 return (&t->bt_cur); 103 if (base == NEXTINDEX(h) && 104 h->nextpg != P_INVALID && 105 __bt_snext(t, h, key, exactp)) 106 return (&t->bt_cur); 107 } 108 *exactp = 0; 109 t->bt_cur.index = base; 110 return (&t->bt_cur); 111 } 112 113 /* 114 * No match found. Base is the smallest index greater than 115 * key and may be zero or a last + 1 index. If it's non-zero, 116 * decrement by one, and record the internal page which should 117 * be a parent page for the key. If a split later occurs, the 118 * inserted page will be to the right of the saved page. 119 */ 120 idx = base ? base - 1 : base; 121 122 next: BT_PUSH(t, h->pgno, idx); 123 pg = GETBINTERNAL(h, idx)->pgno; 124 mpool_put(t->bt_mp, h, 0); 125 } 126 } 127 128 /* 129 * __bt_snext -- 130 * Check for an exact match after the key. 131 * 132 * Parameters: 133 * t: tree 134 * h: current page 135 * key: key 136 * exactp: pointer to exact match flag 137 * 138 * Returns: 139 * If an exact match found. 140 */ 141 static int 142 __bt_snext(BTREE *t, PAGE *h, const DBT *key, int *exactp) 143 { 144 EPG e; 145 146 /* 147 * Get the next page. The key is either an exact 148 * match, or not as good as the one we already have. 149 */ 150 if ((e.page = mpool_get(t->bt_mp, h->nextpg, 0)) == NULL) 151 return (0); 152 e.index = 0; 153 if (__bt_cmp(t, key, &e) == 0) { 154 mpool_put(t->bt_mp, h, 0); 155 t->bt_cur = e; 156 *exactp = 1; 157 return (1); 158 } 159 mpool_put(t->bt_mp, e.page, 0); 160 return (0); 161 } 162 163 /* 164 * __bt_sprev -- 165 * Check for an exact match before the key. 166 * 167 * Parameters: 168 * t: tree 169 * h: current page 170 * key: key 171 * exactp: pointer to exact match flag 172 * 173 * Returns: 174 * If an exact match found. 175 */ 176 static int 177 __bt_sprev(BTREE *t, PAGE *h, const DBT *key, int *exactp) 178 { 179 EPG e; 180 181 /* 182 * Get the previous page. The key is either an exact 183 * match, or not as good as the one we already have. 184 */ 185 if ((e.page = mpool_get(t->bt_mp, h->prevpg, 0)) == NULL) 186 return (0); 187 e.index = NEXTINDEX(e.page) - 1; 188 if (__bt_cmp(t, key, &e) == 0) { 189 mpool_put(t->bt_mp, h, 0); 190 t->bt_cur = e; 191 *exactp = 1; 192 return (1); 193 } 194 mpool_put(t->bt_mp, e.page, 0); 195 return (0); 196 } 197