db/hash/page.h

   1 /*
   2  * Copyright (c) 1999 Apple Computer, Inc. All rights reserved.
   3  *
   4  * @APPLE_LICENSE_HEADER_START@
   5  *
   6  * Copyright (c) 1999-2003 Apple Computer, Inc.  All Rights Reserved.
   7  *
   8  * This file contains Original Code and/or Modifications of Original Code
   9  * as defined in and that are subject to the Apple Public Source License
  10  * Version 2.0 (the 'License'). You may not use this file except in
  11  * compliance with the License. Please obtain a copy of the License at
  12  * http://www.opensource.apple.com/apsl/ and read it before using this
  13  * file.
  14  *
  15  * The Original Code and all software distributed under the License are
  16  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  17  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  18  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  19  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  20  * Please see the License for the specific language governing rights and
  21  * limitations under the License.
  22  *
  23  * @APPLE_LICENSE_HEADER_END@
  24  */
  25 /*
  26  * Copyright (c) 1990, 1993
  27  *      The Regents of the University of California.  All rights reserved.
  28  *
  29  * This code is derived from software contributed to Berkeley by
  30  * Margo Seltzer.
  31  *
  32  * Redistribution and use in source and binary forms, with or without
  33  * modification, are permitted provided that the following conditions
  34  * are met:
  35  * 1. Redistributions of source code must retain the above copyright
  36  *    notice, this list of conditions and the following disclaimer.
  37  * 2. Redistributions in binary form must reproduce the above copyright
  38  *    notice, this list of conditions and the following disclaimer in the
  39  *    documentation and/or other materials provided with the distribution.
  40  * 3. All advertising materials mentioning features or use of this software
  41  *    must display the following acknowledgement:
  42  *      This product includes software developed by the University of
  43  *      California, Berkeley and its contributors.
  44  * 4. Neither the name of the University nor the names of its contributors
  45  *    may be used to endorse or promote products derived from this software
  46  *    without specific prior written permission.
  47  *
  48  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  49  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  50  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  51  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  52  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  53  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  54  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  55  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  56  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  57  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  58  * SUCH DAMAGE.
  59  */
  60
  61 /*
  62  * Definitions for hashing page file format.
  63  */
  64
  65 /*
  66  * routines dealing with a data page
  67  *
  68  * page format:
  69  *      +------------------------------+
  70  * p    | n | keyoff | datoff | keyoff |
  71  *      +------------+--------+--------+
  72  *      | datoff | free  |  ptr  | --> |
  73  *      +--------+---------------------+
  74  *      |        F R E E A R E A       |
  75  *      +--------------+---------------+
  76  *      |  <---- - - - | data          |
  77  *      +--------+-----+----+----------+
  78  *      |  key   | data     | key      |
  79  *      +--------+----------+----------+
  80  *
  81  * Pointer to the free space is always:  p[p[0] + 2]
  82  * Amount of free space on the page is:  p[p[0] + 1]
  83  */
  84
  85 /*
  86  * How many bytes required for this pair?
  87  *      2 shorts in the table at the top of the page + room for the
  88  *      key and room for the data
  89  *
  90  * We prohibit entering a pair on a page unless there is also room to append
  91  * an overflow page. The reason for this it that you can get in a situation
  92  * where a single key/data pair fits on a page, but you can't append an
  93  * overflow page and later you'd have to split the key/data and handle like
  94  * a big pair.
  95  * You might as well do this up front.
  96  */
  97
  98 #define PAIRSIZE(K,D)   (2*sizeof(u_short) + (K)->size + (D)->size)
  99 #define BIGOVERHEAD     (4*sizeof(u_short))
 100 #define KEYSIZE(K)      (4*sizeof(u_short) + (K)->size);
 101 #define OVFLSIZE        (2*sizeof(u_short))
 102 #define FREESPACE(P)    ((P)[(P)[0]+1])
 103 #define OFFSET(P)       ((P)[(P)[0]+2])
 104 #define PAIRFITS(P,K,D) \
 105         (((P)[2] >= REAL_KEY) && \
 106             (PAIRSIZE((K),(D)) + OVFLSIZE) <= FREESPACE((P)))
 107 #define PAGE_META(N)    (((N)+3) * sizeof(u_short))
 108
 109 typedef struct {
 110         BUFHEAD *newp;
 111         BUFHEAD *oldp;
 112         BUFHEAD *nextp;
 113         u_short next_addr;
 114 }       SPLIT_RETURN;