1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
|
/*-
* Copyright (c) 1990, 1993
* The Regents of the University of California. All rights reserved.
*
* This code is derived from software contributed to Berkeley by
* Mike Olson.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by the University of
* California, Berkeley and its contributors.
* 4. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#if defined(LIBC_SCCS) && !defined(lint)
static char sccsid[] = "@(#)bt_get.c 8.2 (Berkeley) 9/7/93";
#endif /* LIBC_SCCS and not lint */
#include <sys/types.h>
#include <errno.h>
#include <stddef.h>
#include <stdio.h>
#include <db.h>
#include "btree.h"
/*
* __BT_GET -- Get a record from the btree.
*
* Parameters:
* dbp: pointer to access method
* key: key to find
* data: data to return
* flag: currently unused
*
* Returns:
* RET_ERROR, RET_SUCCESS and RET_SPECIAL if the key not found.
*/
int
__bt_get(dbp, key, data, flags)
const DB *dbp;
const DBT *key;
DBT *data;
u_int flags;
{
BTREE *t;
EPG *e;
int exact, status;
t = dbp->internal;
/* Toss any page pinned across calls. */
if (t->bt_pinned != NULL) {
mpool_put(t->bt_mp, t->bt_pinned, 0);
t->bt_pinned = NULL;
}
/* Get currently doesn't take any flags. */
if (flags) {
errno = EINVAL;
return (RET_ERROR);
}
if ((e = __bt_search(t, key, &exact)) == NULL)
return (RET_ERROR);
if (!exact) {
mpool_put(t->bt_mp, e->page, 0);
return (RET_SPECIAL);
}
/*
* A special case is if we found the record but it's flagged for
* deletion. In this case, we want to find another record with the
* same key, if it exists. Rather than look around the tree we call
* __bt_first and have it redo the search, as __bt_first will not
* return keys marked for deletion. Slow, but should never happen.
*/
if (ISSET(t, B_DELCRSR) && e->page->pgno == t->bt_bcursor.pgno &&
e->index == t->bt_bcursor.index) {
mpool_put(t->bt_mp, e->page, 0);
if ((e = __bt_first(t, key, &exact)) == NULL)
return (RET_ERROR);
if (!exact)
return (RET_SPECIAL);
}
status = __bt_ret(t, e, NULL, data);
/*
* If the user is doing concurrent access, we copied the
* key/data, toss the page.
*/
if (ISSET(t, B_DB_LOCK))
mpool_put(t->bt_mp, e->page, 0);
else
t->bt_pinned = e->page;
return (status);
}
/*
* __BT_FIRST -- Find the first entry.
*
* Parameters:
* t: the tree
* key: the key
*
* Returns:
* The first entry in the tree greater than or equal to key.
*/
EPG *
__bt_first(t, key, exactp)
BTREE *t;
const DBT *key;
int *exactp;
{
register PAGE *h;
register EPG *e;
EPG save;
pgno_t cpgno, pg;
indx_t cindex;
int found;
/*
* Find any matching record; __bt_search pins the page. Only exact
* matches are tricky, otherwise just return the location of the key
* if it were to be inserted into the tree.
*/
if ((e = __bt_search(t, key, exactp)) == NULL)
return (NULL);
if (!*exactp)
return (e);
if (ISSET(t, B_DELCRSR)) {
cpgno = t->bt_bcursor.pgno;
cindex = t->bt_bcursor.index;
} else {
cpgno = P_INVALID;
cindex = 0; /* GCC thinks it's uninitialized. */
}
/*
* Walk backwards, skipping empty pages, as long as the entry matches
* and there are keys left in the tree. Save a copy of each match in
* case we go too far. A special case is that we don't return a match
* on records that the cursor references that have already been flagged
* for deletion.
*/
save = *e;
h = e->page;
found = 0;
do {
if (cpgno != h->pgno || cindex != e->index) {
if (save.page->pgno != e->page->pgno) {
mpool_put(t->bt_mp, save.page, 0);
save = *e;
} else
save.index = e->index;
found = 1;
}
/*
* Make a special effort not to unpin the page the last (or
* original) match was on, but also make sure it's unpinned
* if an error occurs.
*/
while (e->index == 0) {
if (h->prevpg == P_INVALID)
goto done1;
if (h->pgno != save.page->pgno)
mpool_put(t->bt_mp, h, 0);
if ((h = mpool_get(t->bt_mp, h->prevpg, 0)) == NULL) {
if (h->pgno == save.page->pgno)
mpool_put(t->bt_mp, save.page, 0);
return (NULL);
}
e->page = h;
e->index = NEXTINDEX(h);
}
--e->index;
} while (__bt_cmp(t, key, e) == 0);
/*
* Reach here with the last page that was looked at pinned, which may
* or may not be the same as the last (or original) match page. If
* it's not useful, release it.
*/
done1: if (h->pgno != save.page->pgno)
mpool_put(t->bt_mp, h, 0);
/*
* If still haven't found a record, the only possibility left is the
* next one. Move forward one slot, skipping empty pages and check.
*/
if (!found) {
h = save.page;
if (++save.index == NEXTINDEX(h)) {
do {
pg = h->nextpg;
mpool_put(t->bt_mp, h, 0);
if (pg == P_INVALID) {
*exactp = 0;
return (e);
}
if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL)
return (NULL);
} while ((save.index = NEXTINDEX(h)) == 0);
save.page = h;
}
if (__bt_cmp(t, key, &save) != 0) {
*exactp = 0;
return (e);
}
}
*e = save;
*exactp = 1;
return (e);
}
|
