1 /* $OpenBSD: bt_overflow.c,v 1.11 2015/01/16 16:48:51 deraadt Exp $ */
2
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 <stdio.h>
36 #include <stdlib.h>
37 #include <string.h>
38
39 #include <db.h>
40 #include "btree.h"
41
42 #define MINIMUM(a, b) (((a) < (b)) ? (a) : (b))
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 void *tp;
81
82 memmove(&pg, p, sizeof(pgno_t));
83 memmove(&sz, (char *)p + sizeof(pgno_t), sizeof(u_int32_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 tp = realloc(*buf, sz);
93 if (tp == NULL)
94 return (RET_ERROR);
95 *buf = tp;
96 *bufsz = sz;
97 }
98
99 /*
100 * Step through the linked list of pages, copying the data on each one
101 * into the buffer. Never copy more than the data's length.
102 */
103 plen = t->bt_psize - BTDATAOFF;
104 for (p = *buf;; p = (char *)p + nb, pg = h->nextpg) {
105 if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL)
106 return (RET_ERROR);
107
108 nb = MINIMUM(sz, plen);
109 memmove(p, (char *)h + BTDATAOFF, nb);
110 mpool_put(t->bt_mp, h, 0);
111
112 if ((sz -= nb) == 0)
113 break;
114 }
115 return (RET_SUCCESS);
116 }
117
118 /*
119 * __OVFL_PUT -- Store an overflow key/data item.
120 *
121 * Parameters:
122 * t: tree
123 * data: DBT to store
124 * pgno: storage page number
125 *
126 * Returns:
127 * RET_ERROR, RET_SUCCESS
128 */
129 int
__ovfl_put(BTREE * t,const DBT * dbt,pgno_t * pg)130 __ovfl_put(BTREE *t, const DBT *dbt, pgno_t *pg)
131 {
132 PAGE *h, *last;
133 void *p;
134 pgno_t npg;
135 size_t nb, plen;
136 u_int32_t sz;
137
138 /*
139 * Allocate pages and copy the key/data record into them. Store the
140 * number of the first page in the chain.
141 */
142 plen = t->bt_psize - BTDATAOFF;
143 for (last = NULL, p = dbt->data, sz = dbt->size;;
144 p = (char *)p + plen, last = h) {
145 if ((h = __bt_new(t, &npg)) == NULL)
146 return (RET_ERROR);
147
148 h->pgno = npg;
149 h->nextpg = h->prevpg = P_INVALID;
150 h->flags = P_OVERFLOW;
151 h->lower = h->upper = 0;
152
153 nb = MINIMUM(sz, plen);
154 memmove((char *)h + BTDATAOFF, p, nb);
155
156 if (last) {
157 last->nextpg = h->pgno;
158 mpool_put(t->bt_mp, last, MPOOL_DIRTY);
159 } else
160 *pg = h->pgno;
161
162 if ((sz -= nb) == 0) {
163 mpool_put(t->bt_mp, h, MPOOL_DIRTY);
164 break;
165 }
166 }
167 return (RET_SUCCESS);
168 }
169
170 /*
171 * __OVFL_DELETE -- Delete an overflow chain.
172 *
173 * Parameters:
174 * t: tree
175 * p: pointer to { pgno_t, u_int32_t }
176 *
177 * Returns:
178 * RET_ERROR, RET_SUCCESS
179 */
180 int
__ovfl_delete(BTREE * t,void * p)181 __ovfl_delete(BTREE *t, void *p)
182 {
183 PAGE *h;
184 pgno_t pg;
185 size_t plen;
186 u_int32_t sz;
187
188 memmove(&pg, p, sizeof(pgno_t));
189 memmove(&sz, (char *)p + sizeof(pgno_t), sizeof(u_int32_t));
190
191 #ifdef DEBUG
192 if (pg == P_INVALID || sz == 0)
193 abort();
194 #endif
195 if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL)
196 return (RET_ERROR);
197
198 /* Don't delete chains used by internal pages. */
199 if (h->flags & P_PRESERVE) {
200 mpool_put(t->bt_mp, h, 0);
201 return (RET_SUCCESS);
202 }
203
204 /* Step through the chain, calling the free routine for each page. */
205 for (plen = t->bt_psize - BTDATAOFF;; sz -= plen) {
206 pg = h->nextpg;
207 __bt_free(t, h);
208 if (sz <= plen)
209 break;
210 if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL)
211 return (RET_ERROR);
212 }
213 return (RET_SUCCESS);
214 }
215