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lognestmonster / a99593f

A general-purpose single-header C logging library and parser for event-based logs. (Incomplete)

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1<img src="/static/logo.png" height="200px"/>
2
3_Multilevel logging for advanced programs._
4
51. [lognestmonster](#lognestmonster)
62. [Library Class Structure](#library-class-structure)
7 1. [Semantics](#semantics)
83. [Serialization Format](#serialization-format)
9 1. [Events](#events)
10 2. [Statements](#statements)
11 1. [Verbosity Level Enumeration](#verbosity-level-enumeration)
12 3. [Example](#example)
134. [Temporary Data Saving](#temporary-data-saving)
145. [Copyright](#copyright)
15
16# lognestmonster
17
18## Library Class Structure
19This is subject to future change over security concerns regarding pointers and memory allocation.
20```
21class lognestmonster
22
23 enum VerbosityLevels {INFO, DEBUG, VERBOSE, VERYVERBOSE, WARNING, ERROR}
24
25 struct QueueConfig
26 char * out_dir // directory to output log files
27
28 virtual void * alloc(size_t size) // implementation defaults to cstd malloc()
29 virtual void free(void * block) // implementation defaults to cstd free()
30 virtual void * serialize(LogObject * obj) // implementation defaults to manual serialization of standard LogObject to allocated block
31 virtual bool write(void * serialized, size_t size, std::ostream stream, bool append) // implementation defaults to writing entire serialized block to stream
32 virtual int delete(char * file_name) // implementation defaults to cstd remove()
33
34 interface LogObject
35 Pushable * parent
36 char * temp_file
37 virtual bool save_temp()
38 virtual bool delete_temp()
39
40 interface Pushable
41 protected:
42 std::vector<LogObject *> pushed
43 public:
44 push(LogObject * obj)
45 push(int verbosity, char * tag, char * message) // implicitly creates a Statement and then pushes
46
47 class Queue : Pushable
48 public:
49 struct QueueConfig * _config
50 constructor (struct QueueConfig * config)
51 write() // serializes, writes, and clears pushed LogObjects
52 write(LogObject * obj) // implicit push(), then write()
53 write(int verbosity, char * tag, char * message) // implicit Statement creation, push(), then write()
54
55 class Event : LogObject, Pushable
56 public:
57 constructor (LogObject * obj) // implicit push()
58 constructor (int verbosity, char * tag, char * message) // implicit Statement creation, then push()
59
60 class Statement : LogObject
61 public:
62 int verbosity
63 int timestamp
64 std::string * tag
65 std::string * message
66 constructor (int verbosity, char * tag, char * message)
67```
68### Semantics
69A `Queue` handles data serialization and file writing to the main logtree file. Queue writing refers to sending serialized logtree data to the outstream. Queue pushing refers to adding an Event or Statement to the queue for future writing.
70
71An `Event` is a pushable list of statements or events, or the "nest". Event pushing refers to adding an Event or Statement to the parent's list.
72
73A `Statement` is the data-containing log item with a timestamp, verbosity level, tag/invoker, and message.
74
75In reference to data serialization, `parser` as used here is just a deserializer.
76
77## Serialization Format
78
79By default the library serializes log tree information in a special format. This can be overriden by anybody that uses the library.
80
81### Metadata
82
83All saved files should begin with an `unsigned char` version number and an `unsigned long long` millisecond timestamp.
84```
85unsigned char version
86unsigned long long timestamp
87```
88
89### Events
90Open event with `0x2` and close with `0x3`. Statements or more events can be written inbetween these tags.
91```
920x2 // open event
93 // more events or statements
940x3 // close event
95```
96
97### Statements
98Open statement with `0x0` and close `0x1`.
99
1001. 1 byte for an open statement tag
1012. 1 byte for a predefined verbosity level enum
1023. 4 bytes for an unsigned integer timestamp
1034. 1 byte for the length of the tag string
1045. 0-255 bytes for the tag string
1056. 2 bytes for the length of the message string
1067. 0-65535 bytes for the message string
1078. 1 byte for a close statement tag
108
109```
1100x0
111 unsigned char verbosity
112 unsigned long long timestamp
113 unsigned char tag_size
114 unsigned char[] tag
115 unsigned short message_size
116 unsigned char[] message
1170x1
118```
119A close statement tag is always needed in case the serializer method is overriden and provides extra data/metadata. If a close statement tag isn't written, a parser/deserializer won't be able to read a serialized logtree with extra data.
120
121#### Verbosity Level Enumeration
122The 6 verbosity level enums and their byte values are:
123```
124INFO = 0
125DEBUG = 1
126VERBOSE = 2
127VERYVERBOSE = 3
128WARNING = 4
129ERROR = 5
130```
131
132### Example
1331 statement inside one 1 event:
134```
1351565561768719 // timestamp 8*
1360x2 // open event 1
1370x0 // open statement 1
1381565561768752 // timestamp 8*
1390 // verbosity 1
1404 // tag_size 1
141"INIT" // tag 4*
1425 // message_size 2
143"HELLO" // message 5*
1440x1 // close statement 1
1450x3 // close event 1
146 // 33 total bytes for this log tree
147```
148With the sample log tree used here, the raw byte file totals 25 bytes. In use, a parser/deserializer could take this file and create output similar to the following:
149```
150lognestmonster - log_folder/
151Size: 33 bytes | Timestamp: 1565561768719
1521 Statement | 1 Event | 0 Unsaved Data Trees
153::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
154
155v 1 ITEM
156 1565561768752 - INFO - INIT - HELLO
157
158
159
160::::::::::: press q to exit | arrow keys to move, expand, collapse :::::::::::
161```
162
163## Temporary Data Saving
164
165By the nature of a push-write logging library, there's a chance that some created Statements and Events might not be pushed and written before the program's exit, whether it hangs, crashes, throws a runtime exception, is SIGKILLed, or anything else. Seeing as the point of logging is to find and diagnose errors with ease, it'd be frustrating to lose critical last-second information like this. The solution: save temporary serialized data for every creation or change to Statements or Events. Every logtree that ends in a Statement will have its own temporary data file; when a Statement is pushed to an Event, the Statement's file will be deleted and replaced into the greater Event file. See the following example for how data is separated into files:
166
167```
168Queue queue;
169Event event;
170Statement state1;
171Statement state2;
172
173// Existing files:
174// statement1.raw
175// statement2.raw
176
177event.push(state1)
178
179// Existing files:
180// event.raw
181// statement2.raw
182
183queue.push(event)
184
185// Existing files:
186// event.raw
187// statement2.raw
188
189event.push(state2)
190
191// Existing files:
192// event.raw (all log items now exist inside the event, in the queue)
193
194queue.write()
195
196// Existing files:
197// log12345.raw (consists of 2 statements inside 1 event)
198```
199
200In reality, file names will likely contain timestamps, hashes, UUIDs, or some other form of identifiable metadata.
201
202## Copyright
203
204lognestmonster Copyright (c) 2019 Joshua 'joshuas3' Stockin under the [GNU General Public License v3](LICENSE).
205
206The following should be present in each file.
207```
208lognestmonster Copyright (c) 2019 Joshua 'joshuas3' Stockin
209<https://github.com/JoshuaS3/lognestmonster/>.
210
211
212This file is part of lognestmonster.
213
214lognestmonster is free software: you can redistribute it and/or modify
215it under the terms of the GNU General Public License as published by
216the Free Software Foundation, either version 3 of the License, or
217(at your option) any later version.
218
219lognestmonster is distributed in the hope that it will be useful,
220but WITHOUT ANY WARRANTY; without even the implied warranty of
221MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
222GNU General Public License for more details.
223
224You should have received a copy of the GNU General Public License
225along with lognestmonster. If not, see <https://www.gnu.org/licenses/>.
226```
227