1/*	$OpenBSD: page.h,v 1.6 2003/06/02 20:18:34 millert 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 * Margo Seltzer.
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 *	@(#)page.h	8.2 (Berkeley) 5/31/94
35 */
36
37/*
38 * Definitions for hashing page file format.
39 */
40
41/*
42 * routines dealing with a data page
43 *
44 * page format:
45 *	+------------------------------+
46 * p	| n | keyoff | datoff | keyoff |
47 * 	+------------+--------+--------+
48 *	| datoff | free  |  ptr  | --> |
49 *	+--------+---------------------+
50 *	|	 F R E E A R E A       |
51 *	+--------------+---------------+
52 *	|  <---- - - - | data	       |
53 *	+--------+-----+----+----------+
54 *	|  key   | data     | key      |
55 *	+--------+----------+----------+
56 *
57 * Pointer to the free space is always:  p[p[0] + 2]
58 * Amount of free space on the page is:  p[p[0] + 1]
59 */
60
61/*
62 * How many bytes required for this pair?
63 *	2 shorts in the table at the top of the page + room for the
64 *	key and room for the data
65 *
66 * We prohibit entering a pair on a page unless there is also room to append
67 * an overflow page. The reason for this it that you can get in a situation
68 * where a single key/data pair fits on a page, but you can't append an
69 * overflow page and later you'd have to split the key/data and handle like
70 * a big pair.
71 * You might as well do this up front.
72 */
73
74#define	PAIRSIZE(K,D)	(2*sizeof(u_int16_t) + (K)->size + (D)->size)
75#define BIGOVERHEAD	(4*sizeof(u_int16_t))
76#define KEYSIZE(K)	(4*sizeof(u_int16_t) + (K)->size);
77#define OVFLSIZE	(2*sizeof(u_int16_t))
78#define FREESPACE(P)	((P)[(P)[0]+1])
79#define	OFFSET(P)	((P)[(P)[0]+2])
80#define PAIRFITS(P,K,D) \
81	(((P)[2] >= REAL_KEY) && \
82	    (PAIRSIZE((K),(D)) + OVFLSIZE) <= FREESPACE((P)))
83#define PAGE_META(N)	(((N)+3) * sizeof(u_int16_t))
84
85typedef struct {
86	BUFHEAD *newp;
87	BUFHEAD *oldp;
88	BUFHEAD *nextp;
89	u_int16_t next_addr;
90}       SPLIT_RETURN;
91