/*- * SPDX-License-Identifier: BSD-2-Clause * * Copyright (c) 2005-2008 Poul-Henning Kamp * All rights reserved. * * 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. * * THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 AUTHOR 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. */ #ifndef __LOCAL_FIFOLOG_H_ #define __LOCAL_FIFOLOG_H_ /* * Definitions for fifolog "protocol": the on-media layout. * * The fifolog on-media record has three layers: * The outer timestamping and synchronization layer. * The zlib implemented data compression. * The inner sequencing and identification layer. * * All three layers are synchronized at a subset of the outer layer * record boundaries, from where reading can be initiated. * * * The outer layer: * ----------------- * The first record in a fifolog contains a magic string and version * information along with a 32be encoded recordsize for all records * in the fifolog, including the first. * The recordsize is explicit to avoid ambiguities when a media is * moved from one machine to another. * * Each record in the fifolog has the following contents: * offset type contents * -------------------------------------------------------------- * 0 32be sequence_number * The sequence number is randomly chosen for the * fifolog and increments once for each record written. * It's presence allow quick identification of the next * record to be written using a binary search for the * first place where a discontinuity in the sequence * numbers occur. * 4 8 flags (FIFOLOG_FLG_*) * * If (flags & (FIFOLOG_FLG_SYNC)) the record is a synchronization point * at which the inner layers are aligned so that reading can be started * at this point. * To enable seeks into the file based on timestamps, a third field is * present in these records as well: * 5 32be time_t containing POSIX's understanding of UTC. * * These fields are immediately followed by the inner layer payload as * described below, which has variable length. * * If the inner layer payload is shorter than the available space in * the record, it is padded with zero bytes, and the number of unused * bytes, including the encoded length thereof is recorded at the end * of the record as follows: * * If (flags & FIFOLOG_FLG_1BYTE) * n-1 8 number of unused bytes * else if (flags & FIFOLOG_FLG_4BYTE) * n-4 32be number of unused bytes * * * The gzip layer * -------------- * Is just output from zlib, nothing special here. FIFOLOG_FLG_SYNC * corresponds to Z_FINISH flags to zlib. * In most cases, the timer will expire before zlib has filled an entire * record in which case Z_SYNC_FLUSH will be used to force as much as * possible into the buffer before it is written. This is not marked * in outer layer (apart from a natural correlation with padding) since * zlibs data stream handles this without help. * * * The inner layer: * ---------------- * The inner layer contains data identification and to the second * timestamping (the timestamp in the outer layer only marks the * first possible timestamp for content in the SYNC record). * * offset type contents * -------------------------------------------------------------- * 0 32be ident * * The bottom 30 bits of the identification word are application defined, * presently unused in the stand-alone fifolog tools, but used in the * original "measured" application that originated the fifolog format. * Should for instance syslogd(8) grow native support for fifolog format, * it could store the message priority here. * * If (ident & FIFOLOG_TIMESTAMP) the record is prefixed by: * 4 32be time_t containing POSIX's understanding of UTC. * * Then follows the content, either as a NUL terminated string or as * a length encoded binary sequence: * * If (ident & FIFOLOG_LENGTH) the record is prefixed by: * {0|4} 8 length of binary data * */ /* Magic identification string */ #define FIFOLOG_FMT_MAGIC "Measured FIFOLOG Ver 1.01\n" /* Offset of the 32be encoded recordsize in the first sector */ #define FIFOLOG_OFF_BS 0x20 #define FIFOLOG_FLG_1BYTE 0x01 #define FIFOLOG_FLG_4BYTE 0x02 #define FIFOLOG_FLG_RESTART 0x40 #define FIFOLOG_FLG_SYNC 0x80 #define FIFOLOG_TIMESTAMP 0x80000000 #define FIFOLOG_LENGTH 0x40000000 #define FIFOLOG_IDENT 0x3fffffff #endif /* __LOCAL_FIFOLOG_H_ */
