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