1 /*- 2 * Copyright (c) 1990, 1993 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 37 #if defined(LIBC_SCCS) && !defined(lint) 38 /* from: static char sccsid[] = "@(#)bt_search.c 8.4 (Berkeley) 12/10/93"; */ 39 static char *rcsid = "$Id: bt_search.c,v 1.5 1994/01/24 03:59:45 cgd Exp $"; 40 #endif /* LIBC_SCCS and not lint */ 41 42 #include <sys/types.h> 43 44 #include <stdio.h> 45 46 #include <db.h> 47 #include "btree.h" 48 49 static int bt_snext __P((BTREE *, PAGE *, const DBT *, int *)); 50 static int bt_sprev __P((BTREE *, PAGE *, const DBT *, int *)); 51 52 /* 53 * __BT_SEARCH -- 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(t, key, exactp) 67 BTREE *t; 68 const DBT *key; 69 int *exactp; 70 { 71 PAGE *h, *n; 72 indx_t index; 73 pgno_t pg; 74 int base, cmp, lim; 75 76 BT_CLR(t); 77 for (pg = P_ROOT;;) { 78 if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL) 79 return (NULL); 80 81 /* Do a binary search on the current page. */ 82 t->bt_cur.page = h; 83 for (base = 0, lim = NEXTINDEX(h); lim; lim >>= 1) { 84 t->bt_cur.index = index = base + (lim >> 1); 85 if ((cmp = __bt_cmp(t, key, &t->bt_cur)) == 0) { 86 if (h->flags & P_BLEAF) { 87 *exactp = 1; 88 return (&t->bt_cur); 89 } 90 goto next; 91 } 92 if (cmp > 0) { 93 base = index + 1; 94 --lim; 95 } 96 } 97 98 /* 99 * If it's a leaf page, and duplicates aren't allowed, we're 100 * done. If duplicates are allowed, it's possible that there 101 * were duplicate keys on duplicate pages, and they were later 102 * deleted, so we could be on a page with no matches while 103 * there are matches on other pages. If we're at the start or 104 * end of a page, check on both sides. 105 */ 106 if (h->flags & P_BLEAF) { 107 t->bt_cur.index = base; 108 *exactp = 0; 109 if (!ISSET(t, B_NODUPS)) { 110 if (base == 0 && 111 bt_sprev(t, h, key, exactp)) 112 return (&t->bt_cur); 113 if (base == NEXTINDEX(h) && 114 bt_snext(t, h, key, exactp)) 115 return (&t->bt_cur); 116 } 117 return (&t->bt_cur); 118 } 119 120 /* 121 * No match found. Base is the smallest index greater than 122 * key and may be zero or a last + 1 index. If it's non-zero, 123 * decrement by one, and record the internal page which should 124 * be a parent page for the key. If a split later occurs, the 125 * inserted page will be to the right of the saved page. 126 */ 127 index = base ? base - 1 : base; 128 129 next: if (__bt_push(t, h->pgno, index) == RET_ERROR) 130 return (NULL); 131 pg = GETBINTERNAL(h, index)->pgno; 132 mpool_put(t->bt_mp, h, 0); 133 } 134 } 135 136 /* 137 * BT_SNEXT -- Check for an exact match after the key. 138 * 139 * Parameters: 140 * t: tree to search 141 * h: current page. 142 * key: key to find 143 * exactp: pointer to exact match flag 144 * 145 * Returns: 146 * If an exact match found. 147 */ 148 static int 149 bt_snext(t, h, key, exactp) 150 BTREE *t; 151 PAGE *h; 152 const DBT *key; 153 int *exactp; 154 { 155 EPG e; 156 PAGE *tp; 157 pgno_t pg; 158 159 /* Skip until reach the end of the tree or a key. */ 160 for (pg = h->nextpg; pg != P_INVALID;) { 161 if ((tp = mpool_get(t->bt_mp, pg, 0)) == NULL) { 162 mpool_put(t->bt_mp, h, 0); 163 return (NULL); 164 } 165 if (NEXTINDEX(tp) != 0) 166 break; 167 pg = tp->prevpg; 168 mpool_put(t->bt_mp, tp, 0); 169 } 170 /* 171 * The key is either an exact match, or not as good as 172 * the one we already have. 173 */ 174 if (pg != P_INVALID) { 175 e.page = tp; 176 e.index = NEXTINDEX(tp) - 1; 177 if (__bt_cmp(t, key, &e) == 0) { 178 mpool_put(t->bt_mp, h, 0); 179 t->bt_cur = e; 180 *exactp = 1; 181 return (1); 182 } 183 } 184 return (0); 185 } 186 187 /* 188 * BT_SPREV -- Check for an exact match before the key. 189 * 190 * Parameters: 191 * t: tree to search 192 * h: current page. 193 * key: key to find 194 * exactp: pointer to exact match flag 195 * 196 * Returns: 197 * If an exact match found. 198 */ 199 static int 200 bt_sprev(t, h, key, exactp) 201 BTREE *t; 202 PAGE *h; 203 const DBT *key; 204 int *exactp; 205 { 206 EPG e; 207 PAGE *tp; 208 pgno_t pg; 209 210 /* Skip until reach the beginning of the tree or a key. */ 211 for (pg = h->prevpg; pg != P_INVALID;) { 212 if ((tp = mpool_get(t->bt_mp, pg, 0)) == NULL) { 213 mpool_put(t->bt_mp, h, 0); 214 return (NULL); 215 } 216 if (NEXTINDEX(tp) != 0) 217 break; 218 pg = tp->prevpg; 219 mpool_put(t->bt_mp, tp, 0); 220 } 221 /* 222 * The key is either an exact match, or not as good as 223 * the one we already have. 224 */ 225 if (pg != P_INVALID) { 226 e.page = tp; 227 e.index = NEXTINDEX(tp) - 1; 228 if (__bt_cmp(t, key, &e) == 0) { 229 mpool_put(t->bt_mp, h, 0); 230 t->bt_cur = e; 231 *exactp = 1; 232 return (1); 233 } 234 } 235 return (0); 236 } 237