db/hash/FreeBSD/page.h

   1 /*-
   2  * Copyright (c) 1990, 1993, 1994
   3  *      The Regents of the University of California.  All rights reserved.
   4  *
   5  * This code is derived from software contributed to Berkeley by
   6  * Margo Seltzer.
   7  *
   8  * Redistribution and use in source and binary forms, with or without
   9  * modification, are permitted provided that the following conditions
  10  * are met:
  11  * 1. Redistributions of source code must retain the above copyright
  12  *    notice, this list of conditions and the following disclaimer.
  13  * 2. Redistributions in binary form must reproduce the above copyright
  14  *    notice, this list of conditions and the following disclaimer in the
  15  *    documentation and/or other materials provided with the distribution.
  16  * 4. Neither the name of the University nor the names of its contributors
  17  *    may be used to endorse or promote products derived from this software
  18  *    without specific prior written permission.
  19  *
  20  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  21  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  22  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  23  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  24  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  25  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  26  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  27  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  28  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  29  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  30  * SUCH DAMAGE.
  31  *
  32  *      @(#)page.h      8.2 (Berkeley) 5/31/94
  33  * $FreeBSD: src/lib/libc/db/hash/page.h,v 1.4 2009/03/04 00:58:04 delphij Exp $
  34  */
  35
  36 /*
  37  * Definitions for hashing page file format.
  38  */
  39
  40 /*
  41  * routines dealing with a data page
  42  *
  43  * page format:
  44  *      +------------------------------+
  45  * p    | n | keyoff | datoff | keyoff |
  46  *      +------------+--------+--------+
  47  *      | datoff | free  |  ptr  | --> |
  48  *      +--------+---------------------+
  49  *      |        F R E E A R E A       |
  50  *      +--------------+---------------+
  51  *      |  <---- - - - | data          |
  52  *      +--------+-----+----+----------+
  53  *      |  key   | data     | key      |
  54  *      +--------+----------+----------+
  55  *
  56  * Pointer to the free space is always:  p[p[0] + 2]
  57  * Amount of free space on the page is:  p[p[0] + 1]
  58  */
  59
  60 /*
  61  * How many bytes required for this pair?
  62  *      2 shorts in the table at the top of the page + room for the
  63  *      key and room for the data
  64  *
  65  * We prohibit entering a pair on a page unless there is also room to append
  66  * an overflow page. The reason for this it that you can get in a situation
  67  * where a single key/data pair fits on a page, but you can't append an
  68  * overflow page and later you'd have to split the key/data and handle like
  69  * a big pair.
  70  * You might as well do this up front.
  71  */
  72
  73 #define PAIRSIZE(K,D)   (2*sizeof(u_int16_t) + (K)->size + (D)->size)
  74 #define BIGOVERHEAD     (4*sizeof(u_int16_t))
  75 #define KEYSIZE(K)      (4*sizeof(u_int16_t) + (K)->size);
  76 #define OVFLSIZE        (2*sizeof(u_int16_t))
  77 #define FREESPACE(P)    ((P)[(P)[0]+1])
  78 #define OFFSET(P)       ((P)[(P)[0]+2])
  79 #define PAIRFITS(P,K,D) \
  80         (((P)[2] >= REAL_KEY) && \
  81             (PAIRSIZE((K),(D)) + OVFLSIZE) <= FREESPACE((P)))
  82 #define PAGE_META(N)    (((N)+3) * sizeof(u_int16_t))
  83
  84 typedef struct {
  85         BUFHEAD *newp;
  86         BUFHEAD *oldp;
  87         BUFHEAD *nextp;
  88         u_int16_t next_addr;
  89 }       SPLIT_RETURN;