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 */
73int
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 */
127int
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 */
178int
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