lib/libc/db/hash/page.h

   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;