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 */
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	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 */
129int
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 */
180int
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