/* ![[previous]](../icons/n_left.png)
![[next]](../icons/n_right.png)
![[first]](../icons/first.png)
![[last]](../icons/last.png)
![[top]](../icons/n_top.png)
![[bottom]](../icons/bottom.png)
![[index]](../icons/index.png)
![[help]](../icons/help.png)
*/
This source file includes following definitions.
- __ovfl_get
- __ovfl_put
- __ovfl_delete
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_overflow.c 8.5 (Berkeley) 7/16/94";
35 #endif /* LIBC_SCCS and not lint */
36
37 #ifdef HAVE_CONFIG_H
38 #include <config.h>
39 #endif
40 #include <stdio.h>
41 #ifdef STDC_HEADERS
42 #include <stdlib.h>
43 #endif
44 #ifdef HAVE_STRING_H
45 #include <string.h>
46 #else
47 #include <strings.h>
48 #endif
49
50 #include "db.h"
51 #include "btree.h"
52
53 /**
54 * @file
55 * Big key/data code.
56 *
57 * Big key and data entries are stored on linked lists of pages. The initial
58 * reference is byte string stored with the key or data and is the page number
59 * and size. The actual record is stored in a chain of pages linked by the
60 * nextpg field of the #PAGE header.
61 *
62 * The first page of the chain has a special property. If the record is used
63 * by an internal page, it cannot be deleted and the #P_PRESERVE bit will be set
64 * in the header.
65 *
66 * @par XXX
67 * A single #DBT is written to each chain, so a lot of space on the last page
68 * is wasted. This is a fairly major bug for some data sets.
69 */
70
71 /**
72 * __OVFL_GET -- Get an overflow key/data item.
73 *
74 * @param t tree
75 * @param p pointer to {#pgno_t, @CODE{u_int32_t}}
76 * @param ssz
77 * @param buf storage address
78 * @param bufsz storage size
79 *
80 * @return #RET_ERROR, #RET_SUCCESS
81 */
82 int
83 __ovfl_get(t, p, ssz, buf, bufsz)
84 BTREE *t;
85 void *p;
86 size_t *ssz;
87 void **buf;
88 size_t *bufsz;
89 {
90 PAGE *h;
91 pgno_t pg;
92 size_t nb, plen;
93 u_int32_t sz;
94
95 memmove(&pg, p, sizeof(pgno_t));
96 memmove(&sz, (char *)p + sizeof(pgno_t), sizeof(u_int32_t));
97 *ssz = sz;
98
99 #ifdef DEBUG
100 if (pg == P_INVALID || sz == 0)
101 abort();
102 #endif
103 /* Make the buffer bigger as necessary. */
104 if (*bufsz < sz) {
105 *buf = (char *)(*buf == NULL ? malloc(sz) : realloc(*buf, sz));
106 if (*buf == NULL)
107 return (RET_ERROR);
108 *bufsz = sz;
109 }
110
111 /*
112 * Step through the linked list of pages, copying the data on each one
113 * into the buffer. Never copy more than the data's length.
114 */
115 plen = t->bt_psize - BTDATAOFF;
116 for (p = *buf;; p = (char *)p + nb, pg = h->nextpg) {
117 if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL)
118 return (RET_ERROR);
119
120 nb = MIN(sz, plen);
121 memmove(p, (char *)h + BTDATAOFF, nb);
122 mpool_put(t->bt_mp, h, 0);
123
124 if ((sz -= nb) == 0)
125 break;
126 }
127 return (RET_SUCCESS);
128 }
129
130 /**
131 * __OVFL_PUT -- Store an overflow key/data item.
132 *
133 * @param t tree
134 * @param dbt #DBT to store
135 * @param pg storage page number
136 *
137 * @return #RET_ERROR, #RET_SUCCESS
138 */
139 int
140 __ovfl_put(t, dbt, pg)
141 BTREE *t;
142 const DBT *dbt;
143 pgno_t *pg;
144 {
145 PAGE *h, *last;
146 void *p;
147 pgno_t npg;
148 size_t nb, plen;
149 u_int32_t sz;
150
151 /*
152 * Allocate pages and copy the key/data record into them. Store the
153 * number of the first page in the chain.
154 */
155 plen = t->bt_psize - BTDATAOFF;
156 for (last = NULL, p = dbt->data, sz = dbt->size;;
157 p = (char *)p + plen, last = h) {
158 if ((h = __bt_new(t, &npg)) == NULL)
159 return (RET_ERROR);
160
161 h->pgno = npg;
162 h->nextpg = h->prevpg = P_INVALID;
163 h->flags = P_OVERFLOW;
164 h->lower = h->upper = 0;
165
166 nb = MIN(sz, plen);
167 memmove((char *)h + BTDATAOFF, p, nb);
168
169 if (last) {
170 last->nextpg = h->pgno;
171 mpool_put(t->bt_mp, last, MPOOL_DIRTY);
172 } else
173 *pg = h->pgno;
174
175 if ((sz -= nb) == 0) {
176 mpool_put(t->bt_mp, h, MPOOL_DIRTY);
177 break;
178 }
179 }
180 return (RET_SUCCESS);
181 }
182
183 /**
184 * __OVFL_DELETE -- Delete an overflow chain.
185 *
186 * @param t tree
187 * @param p pointer to {#pgno_t, @CODE{u_int32_t}}
188 *
189 * @return #RET_ERROR, #RET_SUCCESS
190 */
191 int
192 __ovfl_delete(t, p)
193 BTREE *t;
194 void *p;
195 {
196 PAGE *h;
197 pgno_t pg;
198 size_t plen;
199 u_int32_t sz;
200
201 memmove(&pg, p, sizeof(pgno_t));
202 memmove(&sz, (char *)p + sizeof(pgno_t), sizeof(u_int32_t));
203
204 #ifdef DEBUG
205 if (pg == P_INVALID || sz == 0)
206 abort();
207 #endif
208 if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL)
209 return (RET_ERROR);
210
211 /* Don't delete chains used by internal pages. */
212 if (h->flags & P_PRESERVE) {
213 mpool_put(t->bt_mp, h, 0);
214 return (RET_SUCCESS);
215 }
216
217 /* Step through the chain, calling the free routine for each page. */
218 for (plen = t->bt_psize - BTDATAOFF;; sz -= plen) {
219 pg = h->nextpg;
220 __bt_free(t, h);
221 if (sz <= plen)
222 break;
223 if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL)
224 return (RET_ERROR);
225 }
226 return (RET_SUCCESS);
227 }
/* ![[top]](../icons/top.png)
![[bottom]](../icons/n_bottom.png)
*/