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Diffstat (limited to 'usr.sbin/fifolog/lib/fifolog.h')
| -rw-r--r-- | usr.sbin/fifolog/lib/fifolog.h | 138 |
1 files changed, 138 insertions, 0 deletions
diff --git a/usr.sbin/fifolog/lib/fifolog.h b/usr.sbin/fifolog/lib/fifolog.h new file mode 100644 index 0000000..0575a46 --- /dev/null +++ b/usr.sbin/fifolog/lib/fifolog.h @@ -0,0 +1,138 @@ +/*- + * 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. + * + * $FreeBSD$ + */ + +#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_ */ |
