michael@0: /*-
michael@0:  * Copyright (c) 1990, 1993, 1994
michael@0:  *	The Regents of the University of California.  All rights reserved.
michael@0:  *
michael@0:  * This code is derived from software contributed to Berkeley by
michael@0:  * Margo Seltzer.
michael@0:  *
michael@0:  * Redistribution and use in source and binary forms, with or without
michael@0:  * modification, are permitted provided that the following conditions
michael@0:  * are met:
michael@0:  * 1. Redistributions of source code must retain the above copyright
michael@0:  *    notice, this list of conditions and the following disclaimer.
michael@0:  * 2. Redistributions in binary form must reproduce the above copyright
michael@0:  *    notice, this list of conditions and the following disclaimer in the
michael@0:  *    documentation and/or other materials provided with the distribution.
michael@0:  * 3. ***REMOVED*** - see 
michael@0:  *    ftp://ftp.cs.berkeley.edu/pub/4bsd/README.Impt.License.Change
michael@0:  * 4. Neither the name of the University nor the names of its contributors
michael@0:  *    may be used to endorse or promote products derived from this software
michael@0:  *    without specific prior written permission.
michael@0:  *
michael@0:  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
michael@0:  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
michael@0:  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
michael@0:  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
michael@0:  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
michael@0:  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
michael@0:  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
michael@0:  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
michael@0:  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
michael@0:  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
michael@0:  * SUCH DAMAGE.
michael@0:  *
michael@0:  *	@(#)page.h	8.2 (Berkeley) 5/31/94
michael@0:  */
michael@0: 
michael@0: /*
michael@0:  * Definitions for hashing page file format.
michael@0:  */
michael@0: 
michael@0: /*
michael@0:  * routines dealing with a data page
michael@0:  *
michael@0:  * page format:
michael@0:  *	+------------------------------+
michael@0:  * p	| n | keyoff | datoff | keyoff |
michael@0:  * 	+------------+--------+--------+
michael@0:  *	| datoff | free  |  ptr  | --> |
michael@0:  *	+--------+---------------------+
michael@0:  *	|	 F R E E A R E A       |
michael@0:  *	+--------------+---------------+
michael@0:  *	|  <---- - - - | data          |
michael@0:  *	+--------+-----+----+----------+
michael@0:  *	|  key   | data     | key      |
michael@0:  *	+--------+----------+----------+
michael@0:  *
michael@0:  * Pointer to the free space is always:  p[p[0] + 2]
michael@0:  * Amount of free space on the page is:  p[p[0] + 1]
michael@0:  */
michael@0: 
michael@0: /*
michael@0:  * How many bytes required for this pair?
michael@0:  *	2 shorts in the table at the top of the page + room for the
michael@0:  *	key and room for the data
michael@0:  *
michael@0:  * We prohibit entering a pair on a page unless there is also room to append
michael@0:  * an overflow page. The reason for this it that you can get in a situation
michael@0:  * where a single key/data pair fits on a page, but you can't append an
michael@0:  * overflow page and later you'd have to split the key/data and handle like
michael@0:  * a big pair.
michael@0:  * You might as well do this up front.
michael@0:  */
michael@0: #ifndef PAGE_H
michael@0: #define PAGE_H
michael@0: 
michael@0: #define	PAIRSIZE(K,D)	(2*sizeof(uint16) + (K)->size + (D)->size)
michael@0: #define BIGOVERHEAD	(4*sizeof(uint16))
michael@0: #define KEYSIZE(K)	(4*sizeof(uint16) + (K)->size);
michael@0: #define OVFLSIZE	(2*sizeof(uint16))
michael@0: #define FREESPACE(P)	((P)[(P)[0]+1])
michael@0: #define	OFFSET(P)	((P)[(P)[0]+2])
michael@0: #define PAIRFITS(P,K,D) \
michael@0: 	(((P)[2] >= REAL_KEY) && \
michael@0: 	    (PAIRSIZE((K),(D)) + OVFLSIZE) <= FREESPACE((P)))
michael@0: #define PAGE_META(N)	(((N)+3) * sizeof(uint16))
michael@0: 
michael@0: typedef struct {
michael@0: 	BUFHEAD *newp;
michael@0: 	BUFHEAD *oldp;
michael@0: 	BUFHEAD *nextp;
michael@0: 	uint16 next_addr;
michael@0: }       SPLIT_RETURN;
michael@0: #endif
michael@0: