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