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 * 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 * @(#)bt_search.c 8.8 (Berkeley) 7/31/94 37 * $DragonFly: src/lib/libc/db/btree/bt_search.c,v 1.4 2003/11/12 20:21:22 eirikn Exp $ 38 */ 39 40 #include <sys/types.h> 41 42 #include <stdio.h> 43 44 #include <db.h> 45 #include "btree.h" 46 47 static int __bt_snext (BTREE *, PAGE *, const DBT *, int *); 48 static int __bt_sprev (BTREE *, PAGE *, const DBT *, int *); 49 50 /* 51 * __bt_search -- 52 * Search a btree for a key. 53 * 54 * Parameters: 55 * t: tree to search 56 * key: key to find 57 * exactp: pointer to exact match flag 58 * 59 * Returns: 60 * The EPG for matching record, if any, or the EPG for the location 61 * of the key, if it were inserted into the tree, is entered into 62 * the bt_cur field of the tree. A pointer to the field is returned. 63 */ 64 EPG * 65 __bt_search(t, key, exactp) 66 BTREE *t; 67 const DBT *key; 68 int *exactp; 69 { 70 PAGE *h; 71 indx_t base, index, lim; 72 pgno_t pg; 73 int cmp; 74 75 BT_CLR(t); 76 for (pg = P_ROOT;;) { 77 if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL) 78 return (NULL); 79 80 /* Do a binary search on the current page. */ 81 t->bt_cur.page = h; 82 for (base = 0, lim = NEXTINDEX(h); lim; lim >>= 1) { 83 t->bt_cur.index = index = base + (lim >> 1); 84 if ((cmp = __bt_cmp(t, key, &t->bt_cur)) == 0) { 85 if (h->flags & P_BLEAF) { 86 *exactp = 1; 87 return (&t->bt_cur); 88 } 89 goto next; 90 } 91 if (cmp > 0) { 92 base = index + 1; 93 --lim; 94 } 95 } 96 97 /* 98 * If it's a leaf page, we're almost done. If no duplicates 99 * are allowed, or we have an exact match, we're done. Else, 100 * it's possible that there were matching keys on this page, 101 * which later deleted, and we're on a page with no matches 102 * while there are matches on other pages. If at the start or 103 * end of a page, check the adjacent page. 104 */ 105 if (h->flags & P_BLEAF) { 106 if (!F_ISSET(t, B_NODUPS)) { 107 if (base == 0 && 108 h->prevpg != P_INVALID && 109 __bt_sprev(t, h, key, exactp)) 110 return (&t->bt_cur); 111 if (base == NEXTINDEX(h) && 112 h->nextpg != P_INVALID && 113 __bt_snext(t, h, key, exactp)) 114 return (&t->bt_cur); 115 } 116 *exactp = 0; 117 t->bt_cur.index = base; 118 return (&t->bt_cur); 119 } 120 121 /* 122 * No match found. Base is the smallest index greater than 123 * key and may be zero or a last + 1 index. If it's non-zero, 124 * decrement by one, and record the internal page which should 125 * be a parent page for the key. If a split later occurs, the 126 * inserted page will be to the right of the saved page. 127 */ 128 index = base ? base - 1 : base; 129 130 next: BT_PUSH(t, h->pgno, index); 131 pg = GETBINTERNAL(h, index)->pgno; 132 mpool_put(t->bt_mp, h, 0); 133 } 134 } 135 136 /* 137 * __bt_snext -- 138 * Check for an exact match after the key. 139 * 140 * Parameters: 141 * t: tree 142 * h: current page 143 * key: key 144 * exactp: pointer to exact match flag 145 * 146 * Returns: 147 * If an exact match found. 148 */ 149 static int 150 __bt_snext(t, h, key, exactp) 151 BTREE *t; 152 PAGE *h; 153 const DBT *key; 154 int *exactp; 155 { 156 EPG e; 157 158 /* 159 * Get the next page. The key is either an exact 160 * match, or not as good as the one we already have. 161 */ 162 if ((e.page = mpool_get(t->bt_mp, h->nextpg, 0)) == NULL) 163 return (0); 164 e.index = 0; 165 if (__bt_cmp(t, key, &e) == 0) { 166 mpool_put(t->bt_mp, h, 0); 167 t->bt_cur = e; 168 *exactp = 1; 169 return (1); 170 } 171 mpool_put(t->bt_mp, e.page, 0); 172 return (0); 173 } 174 175 /* 176 * __bt_sprev -- 177 * Check for an exact match before the key. 178 * 179 * Parameters: 180 * t: tree 181 * h: current page 182 * key: key 183 * exactp: pointer to exact match flag 184 * 185 * Returns: 186 * If an exact match found. 187 */ 188 static int 189 __bt_sprev(t, h, key, exactp) 190 BTREE *t; 191 PAGE *h; 192 const DBT *key; 193 int *exactp; 194 { 195 EPG e; 196 197 /* 198 * Get the previous page. The key is either an exact 199 * match, or not as good as the one we already have. 200 */ 201 if ((e.page = mpool_get(t->bt_mp, h->prevpg, 0)) == NULL) 202 return (0); 203 e.index = NEXTINDEX(e.page) - 1; 204 if (__bt_cmp(t, key, &e) == 0) { 205 mpool_put(t->bt_mp, h, 0); 206 t->bt_cur = e; 207 *exactp = 1; 208 return (1); 209 } 210 mpool_put(t->bt_mp, e.page, 0); 211 return (0); 212 } 213