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/*-

 * Copyright (c) 1990, 1993, 1994

 *      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      8.2 (Berkeley) 5/31/94

 * $FreeBSD: src/lib/libc/db/hash/page.h,v 1.2 2002/03/22 23:41:40 obrien Exp $

 */

/*

 * Definitions for hashing page file format.

 */

/*

 * 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(__uint16_t) + (K)->size + (D)->size)

#define BIGOVERHEAD     (4*sizeof(__uint16_t))

#define KEYSIZE(K)      (4*sizeof(__uint16_t) + (K)->size);

#define OVFLSIZE        (2*sizeof(__uint16_t))

#define FREESPACE(P)    ((P)[(P)[0]+1])

#define OFFSET(P)       ((P)[(P)[0]+2])

#define PAIRFITS(P,K,D) \

        (((P)[2] >= REAL_KEY) && \

            (PAIRSIZE((K),(D)) + OVFLSIZE) <= FREESPACE((P)))

#define PAGE_META(N)    (((N)+3) * sizeof(__uint16_t))

typedef struct {

        BUFHEAD *newp;

        BUFHEAD *oldp;

        BUFHEAD *nextp;

        __uint16_t next_addr;

}       SPLIT_RETURN;