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 * @(#)bt_overflow.c 8.5 (Berkeley) 7/16/94
33 * $FreeBSD: head/lib/libc/db/btree/bt_overflow.c 189387 2009-03-05 00:57:01Z delphij $
34 */
35
36 #include <sys/param.h>
37
38 #include <stdio.h>
39 #include <stdlib.h>
40 #include <string.h>
41
42 #include <db.h>
43 #include "btree.h"
44
45 /*
46 * Big key/data code.
47 *
48 * Big key and data entries are stored on linked lists of pages. The initial
49 * reference is byte string stored with the key or data and is the page number
50 * and size. The actual record is stored in a chain of pages linked by the
51 * nextpg field of the PAGE header.
52 *
53 * The first page of the chain has a special property. If the record is used
54 * by an internal page, it cannot be deleted and the P_PRESERVE bit will be set
55 * in the header.
56 *
57 * XXX
58 * A single DBT is written to each chain, so a lot of space on the last page
59 * is wasted. This is a fairly major bug for some data sets.
60 */
61
62 /*
63 * __OVFL_GET -- Get an overflow key/data item.
64 *
65 * Parameters:
66 * t: tree
67 * p: pointer to { pgno_t, uint32_t }
68 * buf: storage address
69 * bufsz: storage size
70 *
71 * Returns:
72 * RET_ERROR, RET_SUCCESS
73 */
74 int
__ovfl_get(BTREE * t,void * p,size_t * ssz,void ** buf,size_t * bufsz)75 __ovfl_get(BTREE *t, void *p, size_t *ssz, void **buf, size_t *bufsz)
76 {
77 PAGE *h;
78 pgno_t pg;
79 size_t nb, plen;
80 uint32_t sz;
81
82 memmove(&pg, p, sizeof(pgno_t));
83 memmove(&sz, (char *)p + sizeof(pgno_t), sizeof(uint32_t));
84 *ssz = sz;
85
86 #ifdef DEBUG
87 if (pg == P_INVALID || sz == 0)
88 abort();
89 #endif
90 /* Make the buffer bigger as necessary. */
91 if (*bufsz < sz) {
92 *buf = reallocf(*buf, sz);
93 if (*buf == NULL)
94 return (RET_ERROR);
95 *bufsz = sz;
96 }
97
98 /*
99 * Step through the linked list of pages, copying the data on each one
100 * into the buffer. Never copy more than the data's length.
101 */
102 plen = t->bt_psize - BTDATAOFF;
103 for (p = *buf;; p = (char *)p + nb, pg = h->nextpg) {
104 if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL)
105 return (RET_ERROR);
106
107 nb = MIN(sz, plen);
108 memmove(p, (char *)h + BTDATAOFF, nb);
109 mpool_put(t->bt_mp, h, 0);
110
111 if ((sz -= nb) == 0)
112 break;
113 }
114 return (RET_SUCCESS);
115 }
116
117 /*
118 * __OVFL_PUT -- Store an overflow key/data item.
119 *
120 * Parameters:
121 * t: tree
122 * data: DBT to store
123 * pgno: storage page number
124 *
125 * Returns:
126 * RET_ERROR, RET_SUCCESS
127 */
128 int
__ovfl_put(BTREE * t,const DBT * dbt,pgno_t * pg)129 __ovfl_put(BTREE *t, const DBT *dbt, pgno_t *pg)
130 {
131 PAGE *h, *last;
132 void *p;
133 pgno_t npg;
134 size_t nb, plen;
135 uint32_t sz;
136
137 /*
138 * Allocate pages and copy the key/data record into them. Store the
139 * number of the first page in the chain.
140 */
141 plen = t->bt_psize - BTDATAOFF;
142 for (last = NULL, p = dbt->data, sz = dbt->size;;
143 p = (char *)p + plen, last = h) {
144 if ((h = __bt_new(t, &npg)) == NULL)
145 return (RET_ERROR);
146
147 h->pgno = npg;
148 h->nextpg = h->prevpg = P_INVALID;
149 h->flags = P_OVERFLOW;
150 h->lower = h->upper = 0;
151
152 nb = MIN(sz, plen);
153 memmove((char *)h + BTDATAOFF, p, nb);
154
155 if (last) {
156 last->nextpg = h->pgno;
157 mpool_put(t->bt_mp, last, MPOOL_DIRTY);
158 } else
159 *pg = h->pgno;
160
161 if ((sz -= nb) == 0) {
162 mpool_put(t->bt_mp, h, MPOOL_DIRTY);
163 break;
164 }
165 }
166 return (RET_SUCCESS);
167 }
168
169 /*
170 * __OVFL_DELETE -- Delete an overflow chain.
171 *
172 * Parameters:
173 * t: tree
174 * p: pointer to { pgno_t, uint32_t }
175 *
176 * Returns:
177 * RET_ERROR, RET_SUCCESS
178 */
179 int
__ovfl_delete(BTREE * t,void * p)180 __ovfl_delete(BTREE *t, void *p)
181 {
182 PAGE *h;
183 pgno_t pg;
184 size_t plen;
185 uint32_t sz;
186
187 memmove(&pg, p, sizeof(pgno_t));
188 memmove(&sz, (char *)p + sizeof(pgno_t), sizeof(uint32_t));
189
190 #ifdef DEBUG
191 if (pg == P_INVALID || sz == 0)
192 abort();
193 #endif
194 if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL)
195 return (RET_ERROR);
196
197 /* Don't delete chains used by internal pages. */
198 if (h->flags & P_PRESERVE) {
199 mpool_put(t->bt_mp, h, 0);
200 return (RET_SUCCESS);
201 }
202
203 /* Step through the chain, calling the free routine for each page. */
204 for (plen = t->bt_psize - BTDATAOFF;; sz -= plen) {
205 pg = h->nextpg;
206 __bt_free(t, h);
207 if (sz <= plen)
208 break;
209 if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL)
210 return (RET_ERROR);
211 }
212 return (RET_SUCCESS);
213 }
214