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 *
__bt_search(BTREE * t,const DBT * key,int * exactp)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
__bt_snext(BTREE * t,PAGE * h,const DBT * key,int * exactp)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
__bt_sprev(BTREE * t,PAGE * h,const DBT * key,int * exactp)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