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