1 /*- 2 * Copyright (c) 1990, 1993, 1994 3 * The Regents of the University of California. All rights reserved. 4 * 5 * This code is derived from software contributed to Berkeley by 6 * Margo Seltzer. 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in the 15 * documentation and/or other materials provided with the distribution. 16 * 3. Neither the name of the University nor the names of its contributors 17 * may be used to endorse or promote products derived from this software 18 * without specific prior written permission. 19 * 20 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30 * SUCH DAMAGE. 31 * 32 * @(#)page.h 8.2 (Berkeley) 5/31/94 33 * $FreeBSD: head/lib/libc/db/hash/page.h 189327 2009-03-04 00:58:04Z delphij $ 34 */ 35 36 /* 37 * Definitions for hashing page file format. 38 */ 39 40 /* 41 * routines dealing with a data page 42 * 43 * page format: 44 * +------------------------------+ 45 * p | n | keyoff | datoff | keyoff | 46 * +------------+--------+--------+ 47 * | datoff | free | ptr | --> | 48 * +--------+---------------------+ 49 * | F R E E A R E A | 50 * +--------------+---------------+ 51 * | <---- - - - | data | 52 * +--------+-----+----+----------+ 53 * | key | data | key | 54 * +--------+----------+----------+ 55 * 56 * Pointer to the free space is always: p[p[0] + 2] 57 * Amount of free space on the page is: p[p[0] + 1] 58 */ 59 60 /* 61 * How many bytes required for this pair? 62 * 2 shorts in the table at the top of the page + room for the 63 * key and room for the data 64 * 65 * We prohibit entering a pair on a page unless there is also room to append 66 * an overflow page. The reason for this it that you can get in a situation 67 * where a single key/data pair fits on a page, but you can't append an 68 * overflow page and later you'd have to split the key/data and handle like 69 * a big pair. 70 * You might as well do this up front. 71 */ 72 73 #define PAIRSIZE(K,D) (2*sizeof(uint16_t) + (K)->size + (D)->size) 74 #define BIGOVERHEAD (4*sizeof(uint16_t)) 75 #define KEYSIZE(K) (4*sizeof(uint16_t) + (K)->size); 76 #define OVFLSIZE (2*sizeof(uint16_t)) 77 #define FREESPACE(P) ((P)[(P)[0]+1]) 78 #define OFFSET(P) ((P)[(P)[0]+2]) 79 #define PAIRFITS(P,K,D) \ 80 (((P)[2] >= REAL_KEY) && \ 81 (PAIRSIZE((K),(D)) + OVFLSIZE) <= FREESPACE((P))) 82 #define PAGE_META(N) (((N)+3) * sizeof(uint16_t)) 83 84 typedef struct { 85 BUFHEAD *newp; 86 BUFHEAD *oldp; 87 BUFHEAD *nextp; 88 uint16_t next_addr; 89 } SPLIT_RETURN; 90