Asterisk - The Open Source Telephony Project  GIT-master-e8cda4b
bt_search.c
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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 
37 #if defined(LIBC_SCCS) && !defined(lint)
38 static char sccsid[] = "@(#)bt_search.c 8.8 (Berkeley) 7/31/94";
39 #endif /* LIBC_SCCS and not lint */
40 
41 #include <sys/types.h>
42 
43 #include <stdio.h>
44 
45 #include "../include/db.h"
46 #include "btree.h"
47 
48 static int __bt_snext __P((BTREE *, PAGE *, const DBT *, int *));
49 static int __bt_sprev __P((BTREE *, PAGE *, const DBT *, int *));
50 
51 /*
52  * __bt_search --
53  * 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;
72  indx_t base, index, lim;
73  pgno_t pg;
74  int cmp;
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, we're almost done. If no duplicates
100  * are allowed, or we have an exact match, we're done. Else,
101  * it's possible that there were matching keys on this page,
102  * which later deleted, and we're on a page with no matches
103  * while there are matches on other pages. If at the start or
104  * end of a page, check the adjacent page.
105  */
106  if (h->flags & P_BLEAF) {
107  if (!F_ISSET(t, B_NODUPS)) {
108  if (base == 0 &&
109  h->prevpg != P_INVALID &&
110  __bt_sprev(t, h, key, exactp))
111  return (&t->bt_cur);
112  if (base == NEXTINDEX(h) &&
113  h->nextpg != P_INVALID &&
114  __bt_snext(t, h, key, exactp))
115  return (&t->bt_cur);
116  }
117  *exactp = 0;
118  t->bt_cur.index = base;
119  return (&t->bt_cur);
120  }
121 
122  /*
123  * No match found. Base is the smallest index greater than
124  * key and may be zero or a last + 1 index. If it's non-zero,
125  * decrement by one, and record the internal page which should
126  * be a parent page for the key. If a split later occurs, the
127  * inserted page will be to the right of the saved page.
128  */
129  index = base ? base - 1 : base;
130 
131 next: BT_PUSH(t, h->pgno, index);
132  pg = GETBINTERNAL(h, index)->pgno;
133  mpool_put(t->bt_mp, h, 0);
134  }
135 }
136 
137 /*
138  * __bt_snext --
139  * Check for an exact match after the key.
140  *
141  * Parameters:
142  * t: tree
143  * h: current page
144  * key: key
145  * exactp: pointer to exact match flag
146  *
147  * Returns:
148  * If an exact match found.
149  */
150 static int
151 __bt_snext(t, h, key, exactp)
152  BTREE *t;
153  PAGE *h;
154  const DBT *key;
155  int *exactp;
156 {
157  EPG e;
158 
159  /*
160  * Get the next page. The key is either an exact
161  * match, or not as good as the one we already have.
162  */
163  if ((e.page = mpool_get(t->bt_mp, h->nextpg, 0)) == NULL)
164  return (0);
165  e.index = 0;
166  if (__bt_cmp(t, key, &e) == 0) {
167  mpool_put(t->bt_mp, h, 0);
168  t->bt_cur = e;
169  *exactp = 1;
170  return (1);
171  }
172  mpool_put(t->bt_mp, e.page, 0);
173  return (0);
174 }
175 
176 /*
177  * __bt_sprev --
178  * Check for an exact match before the key.
179  *
180  * Parameters:
181  * t: tree
182  * h: current page
183  * key: key
184  * exactp: pointer to exact match flag
185  *
186  * Returns:
187  * If an exact match found.
188  */
189 static int
190 __bt_sprev(t, h, key, exactp)
191  BTREE *t;
192  PAGE *h;
193  const DBT *key;
194  int *exactp;
195 {
196  EPG e;
197 
198  /*
199  * Get the previous page. The key is either an exact
200  * match, or not as good as the one we already have.
201  */
202  if ((e.page = mpool_get(t->bt_mp, h->prevpg, 0)) == NULL)
203  return (0);
204  e.index = NEXTINDEX(e.page) - 1;
205  if (__bt_cmp(t, key, &e) == 0) {
206  mpool_put(t->bt_mp, h, 0);
207  t->bt_cur = e;
208  *exactp = 1;
209  return (1);
210  }
211  mpool_put(t->bt_mp, e.page, 0);
212  return (0);
213 }
Definition: btree.h:75
#define NEXTINDEX(p)
Definition: btree.h:98
pgno_t pgno
Definition: btree.h:76
#define F_ISSET(p, f)
Definition: btree.h:42
#define BT_PUSH(t, p, i)
Definition: btree.h:322
EPG bt_cur
Definition: btree.h:317
int mpool_put(MPOOL *mp, void *page, u_int flags)
Definition: mpool.c:251
static int __bt_snext __P((BTREE *, PAGE *, const DBT *, int *))
Definition: btree.h:254
Definition: db.h:85
static int __bt_sprev(BTREE *t, PAGE *h, const DBT *key, int *exactp)
Definition: bt_search.c:190
#define NULL
Definition: resample.c:96
u_int16_t indx_t
Definition: db.h:80
#define GETBINTERNAL(pg, indx)
Definition: btree.h:138
Definition: btree.h:312
static int __bt_snext(BTREE *t, PAGE *h, const DBT *key, int *exactp)
Definition: bt_search.c:151
void * mpool_get(MPOOL *mp, pgno_t pgno, u_int flags)
Definition: mpool.c:165
u_int32_t flags
Definition: btree.h:87
PAGE * page
Definition: btree.h:255
MPOOL * bt_mp
Definition: btree.h:313
int __bt_cmp(BTREE *t, const DBT *k1, EPG *e)
Definition: bt_utils.c:153
#define B_NODUPS
Definition: btree.h:374
u_int32_t pgno_t
Definition: db.h:78
pgno_t nextpg
Definition: btree.h:78
indx_t index
Definition: btree.h:256
pgno_t prevpg
Definition: btree.h:77
#define P_ROOT
Definition: btree.h:65
#define P_INVALID
Definition: btree.h:63
EPG * __bt_search(BTREE *t, const DBT *key, int *exactp)
Definition: bt_search.c:66
#define BT_CLR(t)
Definition: btree.h:328
#define P_BLEAF
Definition: btree.h:81