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/*-
* Copyright (c) 1990, 1993, 1994
* The Regents of the University of California. All rights reserved.
*
* This code is derived from software contributed to Berkeley by
* Margo Seltzer.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by the University of
* California, Berkeley and its contributors.
* 4. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* @(#)page.h 8.4 (Berkeley) 11/7/95
*/
#define HI_MASK 0xFFFF0000
#define LO_MASK (~HI_MASK)
#define HI(N) ((u_int16_t)(((N) & HI_MASK) >> 16))
#define LO(N) ((u_int16_t)((N) & LO_MASK))
/* Constants for big key page overhead information. */
#define NUMSHORTS 0
#define KEYLEN 1
#define DATALEN 2
#define NEXTPAGE 3
/*
* Hash pages store meta-data beginning at the top of the page (offset 0)
* and key/data values beginning at the bottom of the page (offset pagesize).
* Fields are always accessed via macros so that we can change the page
* format without too much pain. The only changes that will require massive
* code changes are if we no longer store key/data offsets next to each
* other (since we use that fact to compute key lengths). In the accessor
* macros below, P means a pointer to the page, I means an index of the
* particular entry being accessed.
*
* Hash base page format
* BYTE ITEM NBYTES TYPE ACCESSOR MACRO
* ---- ------------------ ------ -------- --------------
* 0 previous page number 4 db_pgno_t PREV_PGNO(P)
* 4 next page number 4 db_pgno_t NEXT_PGNO(P)
* 8 # pairs on page 2 indx_t NUM_ENT(P)
* 10 page type 1 u_int8_t TYPE(P)
* 11 padding 1 u_int8_t none
* 12 highest free byte 2 indx_t OFFSET(P)
* 14 key offset 0 2 indx_t KEY_OFF(P, I)
* 16 data offset 0 2 indx_t DATA_OFF(P, I)
* 18 key offset 1 2 indx_t KEY_OFF(P, I)
* 20 data offset 1 2 indx_t DATA_OFF(P, I)
* ...etc...
*/
/* Indices (in bytes) of the beginning of each of these entries */
#define I_PREV_PGNO 0
#define I_NEXT_PGNO 4
#define I_ENTRIES 8
#define I_TYPE 10
#define I_HF_OFFSET 12
/* Overhead is everything prior to the first key/data pair. */
#define PAGE_OVERHEAD (I_HF_OFFSET + sizeof(indx_t))
/* To allocate a pair, we need room for one key offset and one data offset. */
#define PAIR_OVERHEAD ((sizeof(indx_t) << 1))
/* Use this macro to extract a value of type T from page P at offset O. */
#define REFERENCE(P, T, O) (((T *)((u_int8_t *)(P) + O))[0])
/*
* Use these macros to access fields on a page; P is a PAGE16 *.
*/
#define NUM_ENT(P) (REFERENCE((P), indx_t, I_ENTRIES))
#define PREV_PGNO(P) (REFERENCE((P), db_pgno_t, I_PREV_PGNO))
#define NEXT_PGNO(P) (REFERENCE((P), db_pgno_t, I_NEXT_PGNO))
#define TYPE(P) (REFERENCE((P), u_int8_t, I_TYPE))
#define OFFSET(P) (REFERENCE((P), indx_t, I_HF_OFFSET))
/*
* We need to store a page's own address on each page (unlike the Btree
* access method which needs the previous page). We use the PREV_PGNO
* field to store our own page number.
*/
#define ADDR(P) (PREV_PGNO((P)))
/* Extract key/data offsets and data for a given index. */
#define DATA_OFF(P, N) \
REFERENCE(P, indx_t, PAGE_OVERHEAD + N * PAIR_OVERHEAD + sizeof(indx_t))
#define KEY_OFF(P, N) \
REFERENCE(P, indx_t, PAGE_OVERHEAD + N * PAIR_OVERHEAD)
#define KEY(P, N) (((PAGE8 *)(P)) + KEY_OFF((P), (N)))
#define DATA(P, N) (((PAGE8 *)(P)) + DATA_OFF((P), (N)))
/*
* Macros used to compute various sizes on a page.
*/
#define PAIRSIZE(K, D) (PAIR_OVERHEAD + (K)->size + (D)->size)
#define BIGOVERHEAD (4 * sizeof(u_int16_t))
#define KEYSIZE(K) (4 * sizeof(u_int16_t) + (K)->size);
#define OVFLSIZE (2 * sizeof(u_int16_t))
#define BIGPAGEOVERHEAD (4 * sizeof(u_int16_t))
#define BIGPAGEOFFSET 4
#define BIGPAGESIZE(P) ((P)->BSIZE - BIGPAGEOVERHEAD)
#define PAGE_META(N) (((N) + 3) * sizeof(u_int16_t))
#define MINFILL 0.75
#define ISBIG(N, P) (((N) > ((P)->hdr.bsize * MINFILL)) ? 1 : 0)
#define ITEMSIZE(I) (sizeof(u_int16_t) + (I)->size)
/*
* Big key/data pages use a different page format. They have a single
* key/data "pair" containing the length of the key and data instead
* of offsets.
*/
#define BIGKEYLEN(P) (KEY_OFF((P), 0))
#define BIGDATALEN(P) (DATA_OFF((P), 0))
#define BIGKEY(P) (((PAGE8 *)(P)) + PAGE_OVERHEAD + PAIR_OVERHEAD)
#define BIGDATA(P) \
(((PAGE8 *)(P)) + PAGE_OVERHEAD + PAIR_OVERHEAD + KEY_OFF((P), 0))
#define OVFLPAGE 0
#define BIGPAIR 0
#define INVALID_PGNO 0xFFFFFFFF
typedef unsigned short PAGE16;
typedef unsigned char PAGE8;
#define A_BUCKET 0
#define A_OVFL 1
#define A_BITMAP 2
#define A_RAW 4
#define A_HEADER 5
#define PAIRFITS(P,K,D) ((PAIRSIZE((K),(D))) <= FREESPACE((P)))
#define BIGPAIRFITS(P) ((FREESPACE((P)) >= PAIR_OVERHEAD))
/*
* Since these are all unsigned, we need to guarantee that we never go
* negative. Offset values are 0-based and overheads are one based (i.e.
* one byte of overhead is 1, not 0), so we need to convert OFFSETs to
* 1-based counting before subtraction.
*/
#define FREESPACE(P) \
((OFFSET((P)) + 1 - PAGE_OVERHEAD - (NUM_ENT((P)) * PAIR_OVERHEAD)))
/*
* Overhead on header pages is just one word -- the length of the
* header info stored on that page.
*/
#define HEADER_OVERHEAD 4
#define HASH_PAGE 2
#define HASH_BIGPAGE 3
#define HASH_OVFLPAGE 4
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