1 /*- 2 * SPDX-License-Identifier: BSD-2-Clause 3 * 4 * Copyright (c) 2005-2008 Poul-Henning Kamp 5 * All rights reserved. 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 1. Redistributions of source code must retain the above copyright 11 * notice, this list of conditions and the following disclaimer. 12 * 2. Redistributions in binary form must reproduce the above copyright 13 * notice, this list of conditions and the following disclaimer in the 14 * documentation and/or other materials provided with the distribution. 15 * 16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 17 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 20 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26 * SUCH DAMAGE. 27 * 28 * $FreeBSD$ 29 */ 30 31 #ifndef __LOCAL_FIFOLOG_H_ 32 #define __LOCAL_FIFOLOG_H_ 33 34 /* 35 * Definitions for fifolog "protocol": the on-media layout. 36 * 37 * The fifolog on-media record has three layers: 38 * The outer timestamping and synchronization layer. 39 * The zlib implemented data compression. 40 * The inner sequencing and identification layer. 41 * 42 * All three layers are synchronized at a subset of the outer layer 43 * record boundaries, from where reading can be initiated. 44 * 45 * 46 * The outer layer: 47 * ----------------- 48 * The first record in a fifolog contains a magic string and version 49 * information along with a 32be encoded recordsize for all records 50 * in the fifolog, including the first. 51 * The recordsize is explicit to avoid ambiguities when a media is 52 * moved from one machine to another. 53 * 54 * Each record in the fifolog has the following contents: 55 * offset type contents 56 * -------------------------------------------------------------- 57 * 0 32be sequence_number 58 * The sequence number is randomly chosen for the 59 * fifolog and increments once for each record written. 60 * It's presence allow quick identification of the next 61 * record to be written using a binary search for the 62 * first place where a discontinuity in the sequence 63 * numbers occur. 64 * 4 8 flags (FIFOLOG_FLG_*) 65 * 66 * If (flags & (FIFOLOG_FLG_SYNC)) the record is a synchronization point 67 * at which the inner layers are aligned so that reading can be started 68 * at this point. 69 * To enable seeks into the file based on timestamps, a third field is 70 * present in these records as well: 71 * 5 32be time_t containing POSIX's understanding of UTC. 72 * 73 * These fields are immediately followed by the inner layer payload as 74 * described below, which has variable length. 75 * 76 * If the inner layer payload is shorter than the available space in 77 * the record, it is padded with zero bytes, and the number of unused 78 * bytes, including the encoded length thereof is recorded at the end 79 * of the record as follows: 80 * 81 * If (flags & FIFOLOG_FLG_1BYTE) 82 * n-1 8 number of unused bytes 83 * else if (flags & FIFOLOG_FLG_4BYTE) 84 * n-4 32be number of unused bytes 85 * 86 * 87 * The gzip layer 88 * -------------- 89 * Is just output from zlib, nothing special here. FIFOLOG_FLG_SYNC 90 * corresponds to Z_FINISH flags to zlib. 91 * In most cases, the timer will expire before zlib has filled an entire 92 * record in which case Z_SYNC_FLUSH will be used to force as much as 93 * possible into the buffer before it is written. This is not marked 94 * in outer layer (apart from a natural correlation with padding) since 95 * zlibs data stream handles this without help. 96 * 97 * 98 * The inner layer: 99 * ---------------- 100 * The inner layer contains data identification and to the second 101 * timestamping (the timestamp in the outer layer only marks the 102 * first possible timestamp for content in the SYNC record). 103 * 104 * offset type contents 105 * -------------------------------------------------------------- 106 * 0 32be ident 107 * 108 * The bottom 30 bits of the identification word are application defined, 109 * presently unused in the stand-alone fifolog tools, but used in the 110 * original "measured" application that originated the fifolog format. 111 * Should for instance syslogd(8) grow native support for fifolog format, 112 * it could store the message priority here. 113 * 114 * If (ident & FIFOLOG_TIMESTAMP) the record is prefixed by: 115 * 4 32be time_t containing POSIX's understanding of UTC. 116 * 117 * Then follows the content, either as a NUL terminated string or as 118 * a length encoded binary sequence: 119 * 120 * If (ident & FIFOLOG_LENGTH) the record is prefixed by: 121 * {0|4} 8 length of binary data 122 * 123 */ 124 125 /* Magic identification string */ 126 #define FIFOLOG_FMT_MAGIC "Measured FIFOLOG Ver 1.01\n" 127 128 /* Offset of the 32be encoded recordsize in the first sector */ 129 #define FIFOLOG_OFF_BS 0x20 130 131 #define FIFOLOG_FLG_1BYTE 0x01 132 #define FIFOLOG_FLG_4BYTE 0x02 133 #define FIFOLOG_FLG_RESTART 0x40 134 #define FIFOLOG_FLG_SYNC 0x80 135 136 #define FIFOLOG_TIMESTAMP 0x80000000 137 #define FIFOLOG_LENGTH 0x40000000 138 #define FIFOLOG_IDENT 0x3fffffff 139 140 #endif /* __LOCAL_FIFOLOG_H_ */ 141