/*- * 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 *)(void *)((u_int8_t *)(void *)(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
