Net2/usr/src/lib/libc/db/hash/page.h

/*-
 * Copyright (c) 1990 The Regents of the University of California.
 * All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Margo Seltzer.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *	This product includes software developed by the University of
 *	California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 *	@(#)page.h	5.1 (Berkeley) 2/12/91
 */

/*
    Definitions for hashing page file format.
*/
extern	HTAB	*hashp;
/*
 * routines dealing with a data page
 *
 * page format:
 *	+------------------------------+
 * p	| n | keyoff | datoff | keyoff |
 * 	+------------+--------+--------+
 *	| datoff | free  |  ptr  | --> |
 *	+--------+---------------------+
 *	|	 F R E E A R E A       |
 *	+--------------+---------------+
 *	|  <---- - - - | data          |
 *	+--------+-----+----+----------+
 *	|  key   | data     | key      |
 *	+--------+----------+----------+
 *
 * Pointer to the free space is always:  p[p[0] + 2]
 * Amount of free space on the page is:  p[p[0] + 1]
 */

/*
    How many bytes required for this pair?
    2 shorts in the table at the top of the page +
    room for the key and room for the data

    We prohibit entering a pair on a page unless there is also
    room to append an overflow page. The reason for this it that
    you can get in a situation where a single key/data pair fits
    on a page, but you can't append an overflow page and later
    you'd have to split the key/data and handle like a big pair.
    You might as well do this up front.

*/
#define	PAIRSIZE(K,D)	(2*sizeof(u_short) + K->size + D->size)
#define BIGOVERHEAD	(4*sizeof(u_short))
#define KEYSIZE(K)	(4*sizeof(u_short) + K->size);
#define OVFLSIZE	(2*sizeof(u_short))
#define FREESPACE(P)	(P[P[0]+1])
#define	OFFSET(P)	(P[P[0]+2])
#define PAIRFITS(P,K,D)	((P[1] >= REAL_KEY) && \
			 (PAIRSIZE(K,D) + OVFLSIZE) <= FREESPACE(P))
#define PAGE_META(N)	((N+3) * sizeof(u_short))

typedef struct {
    BUFHEAD	*newp;
    BUFHEAD	*oldp;
    BUFHEAD	*nextp;
    u_short	next_addr;
} SPLIT_RETURN;