xref: /freebsd/lib/libc/db/btree/bt_utils.c (revision 0ac22237f12015101ffe02a37786a092603c1f03)
1 /*-
2  * Copyright (c) 1990, 1993, 1994
3  *	The Regents of the University of California.  All rights reserved.
4  *
5  * This code is derived from software contributed to Berkeley by
6  * Mike Olson.
7  *
8  * Redistribution and use in source and binary forms, with or without
9  * modification, are permitted provided that the following conditions
10  * are met:
11  * 1. Redistributions of source code must retain the above copyright
12  *    notice, this list of conditions and the following disclaimer.
13  * 2. Redistributions in binary form must reproduce the above copyright
14  *    notice, this list of conditions and the following disclaimer in the
15  *    documentation and/or other materials provided with the distribution.
16  * 4. Neither the name of the University nor the names of its contributors
17  *    may be used to endorse or promote products derived from this software
18  *    without specific prior written permission.
19  *
20  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
21  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
22  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
23  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
24  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
25  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
26  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
27  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
28  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
29  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
30  * SUCH DAMAGE.
31  */
32 
33 #if defined(LIBC_SCCS) && !defined(lint)
34 static char sccsid[] = "@(#)bt_utils.c	8.8 (Berkeley) 7/20/94";
35 #endif /* LIBC_SCCS and not lint */
36 #include <sys/cdefs.h>
37 __FBSDID("$FreeBSD$");
38 
39 #include <sys/param.h>
40 
41 #include <stdio.h>
42 #include <stdlib.h>
43 #include <string.h>
44 
45 #include <db.h>
46 #include "btree.h"
47 
48 /*
49  * __bt_ret --
50  *	Build return key/data pair.
51  *
52  * Parameters:
53  *	t:	tree
54  *	e:	key/data pair to be returned
55  *	key:	user's key structure (NULL if not to be filled in)
56  *	rkey:	memory area to hold key
57  *	data:	user's data structure (NULL if not to be filled in)
58  *	rdata:	memory area to hold data
59  *       copy:	always copy the key/data item
60  *
61  * Returns:
62  *	RET_SUCCESS, RET_ERROR.
63  */
64 int
65 __bt_ret(BTREE *t, EPG *e, DBT *key, DBT *rkey, DBT *data, DBT *rdata, int copy)
66 {
67 	BLEAF *bl;
68 	void *p;
69 
70 	bl = GETBLEAF(e->page, e->index);
71 
72 	/*
73 	 * We must copy big keys/data to make them contigous.  Otherwise,
74 	 * leave the page pinned and don't copy unless the user specified
75 	 * concurrent access.
76 	 */
77 	if (key == NULL)
78 		goto dataonly;
79 
80 	if (bl->flags & P_BIGKEY) {
81 		if (__ovfl_get(t, bl->bytes,
82 		    &key->size, &rkey->data, &rkey->size))
83 			return (RET_ERROR);
84 		key->data = rkey->data;
85 	} else if (copy || F_ISSET(t, B_DB_LOCK)) {
86 		if (bl->ksize > rkey->size) {
87 			p = (void *)(rkey->data == NULL ?
88 			    malloc(bl->ksize) : realloc(rkey->data, bl->ksize));
89 			if (p == NULL)
90 				return (RET_ERROR);
91 			rkey->data = p;
92 			rkey->size = bl->ksize;
93 		}
94 		memmove(rkey->data, bl->bytes, bl->ksize);
95 		key->size = bl->ksize;
96 		key->data = rkey->data;
97 	} else {
98 		key->size = bl->ksize;
99 		key->data = bl->bytes;
100 	}
101 
102 dataonly:
103 	if (data == NULL)
104 		return (RET_SUCCESS);
105 
106 	if (bl->flags & P_BIGDATA) {
107 		if (__ovfl_get(t, bl->bytes + bl->ksize,
108 		    &data->size, &rdata->data, &rdata->size))
109 			return (RET_ERROR);
110 		data->data = rdata->data;
111 	} else if (copy || F_ISSET(t, B_DB_LOCK)) {
112 		/* Use +1 in case the first record retrieved is 0 length. */
113 		if (bl->dsize + 1 > rdata->size) {
114 			p = (void *)(rdata->data == NULL ?
115 			    malloc(bl->dsize + 1) :
116 			    realloc(rdata->data, bl->dsize + 1));
117 			if (p == NULL)
118 				return (RET_ERROR);
119 			rdata->data = p;
120 			rdata->size = bl->dsize + 1;
121 		}
122 		memmove(rdata->data, bl->bytes + bl->ksize, bl->dsize);
123 		data->size = bl->dsize;
124 		data->data = rdata->data;
125 	} else {
126 		data->size = bl->dsize;
127 		data->data = bl->bytes + bl->ksize;
128 	}
129 
130 	return (RET_SUCCESS);
131 }
132 
133 /*
134  * __BT_CMP -- Compare a key to a given record.
135  *
136  * Parameters:
137  *	t:	tree
138  *	k1:	DBT pointer of first arg to comparison
139  *	e:	pointer to EPG for comparison
140  *
141  * Returns:
142  *	< 0 if k1 is < record
143  *	= 0 if k1 is = record
144  *	> 0 if k1 is > record
145  */
146 int
147 __bt_cmp(BTREE *t, const DBT *k1, EPG *e)
148 {
149 	BINTERNAL *bi;
150 	BLEAF *bl;
151 	DBT k2;
152 	PAGE *h;
153 	void *bigkey;
154 
155 	/*
156 	 * The left-most key on internal pages, at any level of the tree, is
157 	 * guaranteed by the following code to be less than any user key.
158 	 * This saves us from having to update the leftmost key on an internal
159 	 * page when the user inserts a new key in the tree smaller than
160 	 * anything we've yet seen.
161 	 */
162 	h = e->page;
163 	if (e->index == 0 && h->prevpg == P_INVALID && !(h->flags & P_BLEAF))
164 		return (1);
165 
166 	bigkey = NULL;
167 	if (h->flags & P_BLEAF) {
168 		bl = GETBLEAF(h, e->index);
169 		if (bl->flags & P_BIGKEY)
170 			bigkey = bl->bytes;
171 		else {
172 			k2.data = bl->bytes;
173 			k2.size = bl->ksize;
174 		}
175 	} else {
176 		bi = GETBINTERNAL(h, e->index);
177 		if (bi->flags & P_BIGKEY)
178 			bigkey = bi->bytes;
179 		else {
180 			k2.data = bi->bytes;
181 			k2.size = bi->ksize;
182 		}
183 	}
184 
185 	if (bigkey) {
186 		if (__ovfl_get(t, bigkey,
187 		    &k2.size, &t->bt_rdata.data, &t->bt_rdata.size))
188 			return (RET_ERROR);
189 		k2.data = t->bt_rdata.data;
190 	}
191 	return ((*t->bt_cmp)(k1, &k2));
192 }
193 
194 /*
195  * __BT_DEFCMP -- Default comparison routine.
196  *
197  * Parameters:
198  *	a:	DBT #1
199  *	b: 	DBT #2
200  *
201  * Returns:
202  *	< 0 if a is < b
203  *	= 0 if a is = b
204  *	> 0 if a is > b
205  */
206 int
207 __bt_defcmp(const DBT *a, const DBT *b)
208 {
209 	size_t len;
210 	u_char *p1, *p2;
211 
212 	/*
213 	 * XXX
214 	 * If a size_t doesn't fit in an int, this routine can lose.
215 	 * What we need is an integral type which is guaranteed to be
216 	 * larger than a size_t, and there is no such thing.
217 	 */
218 	len = MIN(a->size, b->size);
219 	for (p1 = a->data, p2 = b->data; len--; ++p1, ++p2)
220 		if (*p1 != *p2)
221 			return ((int)*p1 - (int)*p2);
222 	return ((int)a->size - (int)b->size);
223 }
224 
225 /*
226  * __BT_DEFPFX -- Default prefix routine.
227  *
228  * Parameters:
229  *	a:	DBT #1
230  *	b: 	DBT #2
231  *
232  * Returns:
233  *	Number of bytes needed to distinguish b from a.
234  */
235 size_t
236 __bt_defpfx(const DBT *a, const DBT *b)
237 {
238 	u_char *p1, *p2;
239 	size_t cnt, len;
240 
241 	cnt = 1;
242 	len = MIN(a->size, b->size);
243 	for (p1 = a->data, p2 = b->data; len--; ++p1, ++p2, ++cnt)
244 		if (*p1 != *p2)
245 			return (cnt);
246 
247 	/* a->size must be <= b->size, or they wouldn't be in this order. */
248 	return (a->size < b->size ? a->size + 1 : a->size);
249 }
250