1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
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_ */
|
