db/hash/page.h

   1 /*
   2  * Copyright (c) 2003 Apple Computer, Inc. All rights reserved.
   3  *
   4  * @APPLE_LICENSE_HEADER_START@
   5  *
   6  * This file contains Original Code and/or Modifications of Original Code
   7  * as defined in and that are subject to the Apple Public Source License
   8  * Version 2.0 (the 'License'). You may not use this file except in
   9  * compliance with the License. Please obtain a copy of the License at
  10  * http://www.opensource.apple.com/apsl/ and read it before using this
  11  * file.
  12  *
  13  * The Original Code and all software distributed under the License are
  14  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  15  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  16  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  17  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  18  * Please see the License for the specific language governing rights and
  19  * limitations under the License.
  20  *
  21  * @APPLE_LICENSE_HEADER_END@
  22  */
  23 /*-
  24  * Copyright (c) 1990, 1993, 1994
  25  *      The Regents of the University of California.  All rights reserved.
  26  *
  27  * This code is derived from software contributed to Berkeley by
  28  * Margo Seltzer.
  29  *
  30  * Redistribution and use in source and binary forms, with or without
  31  * modification, are permitted provided that the following conditions
  32  * are met:
  33  * 1. Redistributions of source code must retain the above copyright
  34  *    notice, this list of conditions and the following disclaimer.
  35  * 2. Redistributions in binary form must reproduce the above copyright
  36  *    notice, this list of conditions and the following disclaimer in the
  37  *    documentation and/or other materials provided with the distribution.
  38  * 3. All advertising materials mentioning features or use of this software
  39  *    must display the following acknowledgement:
  40  *      This product includes software developed by the University of
  41  *      California, Berkeley and its contributors.
  42  * 4. Neither the name of the University nor the names of its contributors
  43  *    may be used to endorse or promote products derived from this software
  44  *    without specific prior written permission.
  45  *
  46  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  47  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  48  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  49  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  50  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  51  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  52  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  53  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  54  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  55  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  56  * SUCH DAMAGE.
  57  *
  58  *      @(#)page.h      8.2 (Berkeley) 5/31/94
  59  * $FreeBSD: src/lib/libc/db/hash/page.h,v 1.2 2002/03/22 23:41:40 obrien Exp $
  60  */
  61
  62 /*
  63  * Definitions for hashing page file format.
  64  */
  65
  66 /*
  67  * routines dealing with a data page
  68  *
  69  * page format:
  70  *      +------------------------------+
  71  * p    | n | keyoff | datoff | keyoff |
  72  *      +------------+--------+--------+
  73  *      | datoff | free  |  ptr  | --> |
  74  *      +--------+---------------------+
  75  *      |        F R E E A R E A       |
  76  *      +--------------+---------------+
  77  *      |  <---- - - - | data          |
  78  *      +--------+-----+----+----------+
  79  *      |  key   | data     | key      |
  80  *      +--------+----------+----------+
  81  *
  82  * Pointer to the free space is always:  p[p[0] + 2]
  83  * Amount of free space on the page is:  p[p[0] + 1]
  84  */
  85
  86 /*
  87  * How many bytes required for this pair?
  88  *      2 shorts in the table at the top of the page + room for the
  89  *      key and room for the data
  90  *
  91  * We prohibit entering a pair on a page unless there is also room to append
  92  * an overflow page. The reason for this it that you can get in a situation
  93  * where a single key/data pair fits on a page, but you can't append an
  94  * overflow page and later you'd have to split the key/data and handle like
  95  * a big pair.
  96  * You might as well do this up front.
  97  */
  98
  99 #define PAIRSIZE(K,D)   (2*sizeof(u_int16_t) + (K)->size + (D)->size)
 100 #define BIGOVERHEAD     (4*sizeof(u_int16_t))
 101 #define KEYSIZE(K)      (4*sizeof(u_int16_t) + (K)->size);
 102 #define OVFLSIZE        (2*sizeof(u_int16_t))
 103 #define FREESPACE(P)    ((P)[(P)[0]+1])
 104 #define OFFSET(P)       ((P)[(P)[0]+2])
 105 #define PAIRFITS(P,K,D) \
 106         (((P)[2] >= REAL_KEY) && \
 107             (PAIRSIZE((K),(D)) + OVFLSIZE) <= FREESPACE((P)))
 108 #define PAGE_META(N)    (((N)+3) * sizeof(u_int16_t))
 109
 110 typedef struct {
 111         BUFHEAD *newp;
 112         BUFHEAD *oldp;
 113         BUFHEAD *nextp;
 114         u_int16_t next_addr;
 115 }       SPLIT_RETURN;