1 #pragma ident "%Z%%M% %I% %E% SMI"
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. All advertising materials mentioning features or use of this software
19 * must display the following acknowledgement:
20 * This product includes software developed by the University of
21 * California, Berkeley and its contributors.
22 * 4. Neither the name of the University nor the names of its contributors
23 * may be used to endorse or promote products derived from this software
24 * without specific prior written permission.
25 *
26 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
27 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
28 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
29 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
30 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
31 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
32 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
33 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
34 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
35 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
36 * SUCH DAMAGE.
37 */
38
39 #if defined(LIBC_SCCS) && !defined(lint)
40 static char sccsid[] = "@(#)bt_overflow.c 8.5 (Berkeley) 7/16/94";
41 #endif /* LIBC_SCCS and not lint */
42
43 #include <sys/param.h>
44
45 #include <stdio.h>
46 #include <stdlib.h>
47 #include <string.h>
48
49 #include "db-int.h"
50 #include "btree.h"
51
52 /*
53 * Big key/data code.
54 *
55 * Big key and data entries are stored on linked lists of pages. The initial
56 * reference is byte string stored with the key or data and is the page number
57 * and size. The actual record is stored in a chain of pages linked by the
58 * nextpg field of the PAGE header.
59 *
60 * The first page of the chain has a special property. If the record is used
61 * by an internal page, it cannot be deleted and the P_PRESERVE bit will be set
62 * in the header.
63 *
64 * XXX
65 * A single DBT is written to each chain, so a lot of space on the last page
66 * is wasted. This is a fairly major bug for some data sets.
67 */
68
69 /*
70 * __OVFL_GET -- Get an overflow key/data item.
71 *
72 * Parameters:
73 * t: tree
74 * p: pointer to { db_pgno_t, u_int32_t }
75 * buf: storage address
76 * bufsz: storage size
77 *
78 * Returns:
79 * RET_ERROR, RET_SUCCESS
80 */
81 int
__ovfl_get(t,p,ssz,buf,bufsz)82 __ovfl_get(t, p, ssz, buf, bufsz)
83 BTREE *t;
84 void *p;
85 size_t *ssz;
86 void **buf;
87 size_t *bufsz;
88 {
89 PAGE *h;
90 db_pgno_t pg;
91 size_t nb, plen;
92 u_int32_t sz;
93
94 memmove(&pg, p, sizeof(db_pgno_t));
95 memmove(&sz, (char *)p + sizeof(db_pgno_t), sizeof(u_int32_t));
96 *ssz = sz;
97
98 #ifdef DEBUG
99 if (pg == P_INVALID || sz == 0)
100 abort();
101 #endif
102 /* Make the buffer bigger as necessary. */
103 if (*bufsz < sz) {
104 *buf = (char *)(*buf == NULL ? malloc(sz) : realloc(*buf, sz));
105 if (*buf == NULL)
106 return (RET_ERROR);
107 *bufsz = sz;
108 }
109
110 /*
111 * Step through the linked list of pages, copying the data on each one
112 * into the buffer. Never copy more than the data's length.
113 */
114 plen = t->bt_psize - BTDATAOFF;
115 for (p = *buf;; p = (char *)p + nb, pg = h->nextpg) {
116 if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL)
117 return (RET_ERROR);
118
119 nb = MIN(sz, plen);
120 memmove(p, (char *)h + BTDATAOFF, nb);
121 mpool_put(t->bt_mp, h, 0);
122
123 if ((sz -= nb) == 0)
124 break;
125 }
126 return (RET_SUCCESS);
127 }
128
129 /*
130 * __OVFL_PUT -- Store an overflow key/data item.
131 *
132 * Parameters:
133 * t: tree
134 * data: DBT to store
135 * pgno: storage page number
136 *
137 * Returns:
138 * RET_ERROR, RET_SUCCESS
139 */
140 int
__ovfl_put(t,dbt,pg)141 __ovfl_put(t, dbt, pg)
142 BTREE *t;
143 const DBT *dbt;
144 db_pgno_t *pg;
145 {
146 PAGE *h, *last;
147 void *p;
148 db_pgno_t npg;
149 size_t nb, plen;
150 u_int32_t sz;
151
152 /*
153 * Allocate pages and copy the key/data record into them. Store the
154 * number of the first page in the chain.
155 */
156 plen = t->bt_psize - BTDATAOFF;
157 for (last = NULL, p = dbt->data, sz = dbt->size;;
158 p = (char *)p + plen, last = h) {
159 if ((h = __bt_new(t, &npg)) == NULL)
160 return (RET_ERROR);
161
162 h->pgno = npg;
163 h->nextpg = h->prevpg = P_INVALID;
164 h->flags = P_OVERFLOW;
165 h->lower = h->upper = 0;
166
167 nb = MIN(sz, plen);
168 memmove((char *)h + BTDATAOFF, p, nb);
169
170 if (last) {
171 last->nextpg = h->pgno;
172 mpool_put(t->bt_mp, last, MPOOL_DIRTY);
173 } else
174 *pg = h->pgno;
175
176 if ((sz -= nb) == 0) {
177 mpool_put(t->bt_mp, h, MPOOL_DIRTY);
178 break;
179 }
180 }
181 return (RET_SUCCESS);
182 }
183
184 /*
185 * __OVFL_DELETE -- Delete an overflow chain.
186 *
187 * Parameters:
188 * t: tree
189 * p: pointer to { db_pgno_t, u_int32_t }
190 *
191 * Returns:
192 * RET_ERROR, RET_SUCCESS
193 */
194 int
__ovfl_delete(t,p)195 __ovfl_delete(t, p)
196 BTREE *t;
197 void *p;
198 {
199 PAGE *h;
200 db_pgno_t pg;
201 size_t plen;
202 u_int32_t sz;
203
204 memmove(&pg, p, sizeof(db_pgno_t));
205 memmove(&sz, (char *)p + sizeof(db_pgno_t), sizeof(u_int32_t));
206
207 #ifdef DEBUG
208 if (pg == P_INVALID || sz == 0)
209 abort();
210 #endif
211 if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL)
212 return (RET_ERROR);
213
214 /* Don't delete chains used by internal pages. */
215 if (h->flags & P_PRESERVE) {
216 mpool_put(t->bt_mp, h, 0);
217 return (RET_SUCCESS);
218 }
219
220 /* Step through the chain, calling the free routine for each page. */
221 for (plen = t->bt_psize - BTDATAOFF;; sz -= plen) {
222 pg = h->nextpg;
223 __bt_free(t, h);
224 if (sz <= plen)
225 break;
226 if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL)
227 return (RET_ERROR);
228 }
229 return (RET_SUCCESS);
230 }
231