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      1 /*	$NetBSD: page.h,v 1.8 2008/08/26 21:18:38 joerg 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(uint16_t) + (K)->size + (D)->size)
     75 #define BIGOVERHEAD	(4*sizeof(uint16_t))
     76 #define KEYSIZE(K)	(4*sizeof(uint16_t) + (K)->size);
     77 #define OVFLSIZE	(2*sizeof(uint16_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(uint16_t))
     84 
     85 typedef struct {
     86 	BUFHEAD *newp;
     87 	BUFHEAD *oldp;
     88 	BUFHEAD *nextp;
     89 	uint16_t next_addr;
     90 }       SPLIT_RETURN;
     91