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This source file includes following definitions.
- __bt_search
- __bt_snext
- __bt_sprev
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. Neither the name of the University nor the names of its contributors
17 * may be used to endorse or promote products derived from this software
18 * without specific prior written permission.
19 *
20 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
23 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
30 * SUCH DAMAGE.
31 */
32
33 #if defined(LIBC_SCCS) && !defined(lint)
34 static char sccsid[] = "@(#)bt_search.c 8.8 (Berkeley) 7/31/94";
35 #endif /* LIBC_SCCS and not lint */
36
37 #ifdef HAVE_CONFIG_H
38 #include <config.h>
39 #endif
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 * @param[in] t tree to search
55 * @param[in] key key to find
56 * @param[out] exactp pointer to exact match flag
57 *
58 * @return
59 * The #EPG for matching record, if any, or the #EPG for the location
60 * of the key, if it were inserted into the tree, is entered into
61 * the BTREE::bt_cur field of the tree. A pointer to the field is returned.
62 */
63 EPG *
64 __bt_search(t, key, exactp)
65 BTREE *t;
66 const DBT *key;
67 int *exactp;
68 {
69 PAGE *h;
70 indx_t base, index, lim;
71 pgno_t pg;
72 int cmp;
73
74 BT_CLR(t);
75 for (pg = P_ROOT;;) {
76 if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL)
77 return (NULL);
78
79 /* Do a binary search on the current page. */
80 t->bt_cur.page = h;
81 for (base = 0, lim = NEXTINDEX(h); lim; lim >>= 1) {
82 t->bt_cur.index = index = base + (lim >> 1);
83 if ((cmp = __bt_cmp(t, key, &t->bt_cur)) == 0) {
84 if (h->flags & P_BLEAF) {
85 *exactp = 1;
86 return (&t->bt_cur);
87 }
88 goto next;
89 }
90 if (cmp > 0) {
91 base = index + 1;
92 --lim;
93 }
94 }
95
96 /*
97 * If it's a leaf page, we're almost done. If no duplicates
98 * are allowed, or we have an exact match, we're done. Else,
99 * it's possible that there were matching keys on this page,
100 * which later deleted, and we're on a page with no matches
101 * while there are matches on other pages. If at the start or
102 * end of a page, check the adjacent page.
103 */
104 if (h->flags & P_BLEAF) {
105 if (!F_ISSET(t, B_NODUPS)) {
106 if (base == 0 &&
107 h->prevpg != P_INVALID &&
108 __bt_sprev(t, h, key, exactp))
109 return (&t->bt_cur);
110 if (base == NEXTINDEX(h) &&
111 h->nextpg != P_INVALID &&
112 __bt_snext(t, h, key, exactp))
113 return (&t->bt_cur);
114 }
115 *exactp = 0;
116 t->bt_cur.index = base;
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: BT_PUSH(t, h->pgno, index);
130 pg = GETBINTERNAL(h, index)->pgno;
131 mpool_put(t->bt_mp, h, 0);
132 }
133 }
134
135 /**
136 * __bt_snext --
137 * Check for an exact match after the @a key.
138 *
139 * @param[in] t tree
140 * @param[in] h current page
141 * @param[in] key key
142 * @param[out] exactp pointer to exact match flag
143 *
144 * @return
145 * @VAR{TRUE} (1) if an exact match found, else @VAR{FALSE} (0).
146 */
147 static int
148 __bt_snext(t, h, key, exactp)
149 BTREE *t;
150 PAGE *h;
151 const DBT *key;
152 int *exactp;
153 {
154 EPG e;
155
156 /*
157 * Get the next page. The key is either an exact
158 * match, or not as good as the one we already have.
159 */
160 if ((e.page = mpool_get(t->bt_mp, h->nextpg, 0)) == NULL)
161 return (0);
162 e.index = 0;
163 if (__bt_cmp(t, key, &e) == 0) {
164 mpool_put(t->bt_mp, h, 0);
165 t->bt_cur = e;
166 *exactp = 1;
167 return (1);
168 }
169 mpool_put(t->bt_mp, e.page, 0);
170 return (0);
171 }
172
173 /**
174 * __bt_sprev --
175 * Check for an exact match before the @a key.
176 *
177 * @param[in] t tree
178 * @param[in] h current page
179 * @param[in] key key
180 * @param[out] exactp pointer to exact match flag
181 *
182 * @return
183 * @VAR{TRUE} (1) if an exact match found, else @VAR{FALSE} (0).
184 */
185 static int
186 __bt_sprev(t, h, key, exactp)
187 BTREE *t;
188 PAGE *h;
189 const DBT *key;
190 int *exactp;
191 {
192 EPG e;
193
194 /*
195 * Get the previous page. The key is either an exact
196 * match, or not as good as the one we already have.
197 */
198 if ((e.page = mpool_get(t->bt_mp, h->prevpg, 0)) == NULL)
199 return (0);
200 e.index = NEXTINDEX(e.page) - 1;
201 if (__bt_cmp(t, key, &e) == 0) {
202 mpool_put(t->bt_mp, h, 0);
203 t->bt_cur = e;
204 *exactp = 1;
205 return (1);
206 }
207 mpool_put(t->bt_mp, e.page, 0);
208 return (0);
209 }
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