gonzui

    1: /*      $OpenBSD: page.h,v 1.6 2003/06/02 20:18:34 millert 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(u_int16_t) + (K)->size + (D)->size)
   75: #define BIGOVERHEAD     (4*sizeof(u_int16_t))
   76: #define KEYSIZE(K)      (4*sizeof(u_int16_t) + (K)->size);
   77: #define OVFLSIZE        (2*sizeof(u_int16_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(u_int16_t))
   84: 
   85: typedef struct {
   86:         BUFHEAD *newp;
   87:         BUFHEAD *oldp;
   88:         BUFHEAD *nextp;
   89:         u_int16_t next_addr;
   90: }       SPLIT_RETURN;