page.h (3558B)
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. ***REMOVED*** - see 17 * ftp://ftp.cs.berkeley.edu/pub/4bsd/README.Impt.License.Change 18 * 4. 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 #ifndef PAGE_H 74 #define PAGE_H 75 76 #define PAIRSIZE(K, D) (2 * sizeof(uint16) + (K)->size + (D)->size) 77 #define BIGOVERHEAD (4 * sizeof(uint16)) 78 #define KEYSIZE(K) (4 * sizeof(uint16) + (K)->size); 79 #define OVFLSIZE (2 * sizeof(uint16)) 80 #define FREESPACE(P) ((P)[(P)[0] + 1]) 81 #define OFFSET(P) ((P)[(P)[0] + 2]) 82 #define PAIRFITS(P, K, D) \ 83 (((P)[2] >= REAL_KEY) && \ 84 (PAIRSIZE((K), (D)) + OVFLSIZE) <= FREESPACE((P))) 85 #define PAGE_META(N) (((N) + 3) * sizeof(uint16)) 86 87 typedef struct { 88 BUFHEAD *newp; 89 BUFHEAD *oldp; 90 BUFHEAD *nextp; 91 uint16 next_addr; 92 } SPLIT_RETURN; 93 #endif