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 * Margo Seltzer.
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 *	@(#)page.h	8.2 (Berkeley) 5/31/94
33 * $FreeBSD$
34 */
35
36/*
37 * Definitions for hashing page file format.
38 */
39
40/*
41 * routines dealing with a data page
42 *
43 * page format:
44 *	+------------------------------+
45 * p	| n | keyoff | datoff | keyoff |
46 * 	+------------+--------+--------+
47 *	| datoff | free  |  ptr  | --> |
48 *	+--------+---------------------+
49 *	|	 F R E E A R E A       |
50 *	+--------------+---------------+
51 *	|  <---- - - - | data	       |
52 *	+--------+-----+----+----------+
53 *	|  key   | data     | key      |
54 *	+--------+----------+----------+
55 *
56 * Pointer to the free space is always:  p[p[0] + 2]
57 * Amount of free space on the page is:  p[p[0] + 1]
58 */
59
60/*
61 * How many bytes required for this pair?
62 *	2 shorts in the table at the top of the page + room for the
63 *	key and room for the data
64 *
65 * We prohibit entering a pair on a page unless there is also room to append
66 * an overflow page. The reason for this it that you can get in a situation
67 * where a single key/data pair fits on a page, but you can't append an
68 * overflow page and later you'd have to split the key/data and handle like
69 * a big pair.
70 * You might as well do this up front.
71 */
72
73#define	PAIRSIZE(K,D)	(2*sizeof(u_int16_t) + (K)->size + (D)->size)
74#define BIGOVERHEAD	(4*sizeof(u_int16_t))
75#define KEYSIZE(K)	(4*sizeof(u_int16_t) + (K)->size);
76#define OVFLSIZE	(2*sizeof(u_int16_t))
77#define FREESPACE(P)	((P)[(P)[0]+1])
78#define	OFFSET(P)	((P)[(P)[0]+2])
79#define PAIRFITS(P,K,D) \
80	(((P)[2] >= REAL_KEY) && \
81	    (PAIRSIZE((K),(D)) + OVFLSIZE) <= FREESPACE((P)))
82#define PAGE_META(N)	(((N)+3) * sizeof(u_int16_t))
83
84typedef struct {
85	BUFHEAD *newp;
86	BUFHEAD *oldp;
87	BUFHEAD *nextp;
88	u_int16_t next_addr;
89}       SPLIT_RETURN;
90