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
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
|
/**
\mainpage
\section _intro Introduction
<a HREF="http://www.json.org/">JSON (JavaScript Object Notation)</a>
is a lightweight data-interchange format.
Here is an example of JSON data:
\verbatim
{
"encoding" : "UTF-8",
"plug-ins" : [
"python",
"c++",
"ruby"
],
"indent" : { "length" : 3, "use_space": true }
}
\endverbatim
<b>JsonCpp</b> supports comments as <i>meta-data</i>:
\code
// Configuration options
{
// Default encoding for text
"encoding" : "UTF-8",
// Plug-ins loaded at start-up
"plug-ins" : [
"python",
"c++", // trailing comment
"ruby"
],
// Tab indent size
// (multi-line comment)
"indent" : { /*embedded comment*/ "length" : 3, "use_space": true }
}
\endcode
\section _features Features
- read and write JSON document
- attach C++ style comments to element during parsing
- rewrite JSON document preserving original comments
Notes: Comments used to be supported in JSON but were removed for
portability (C like comments are not supported in Python). Since
comments are useful in configuration/input file, this feature was
preserved.
\section _example Code example
\code
Json::Value root; // 'root' will contain the root value after parsing.
std::cin >> root;
// You can also read into a particular sub-value.
std::cin >> root["subtree"];
// Get the value of the member of root named 'encoding',
// and return 'UTF-8' if there is no such member.
std::string encoding = root.get("encoding", "UTF-8" ).asString();
// Get the value of the member of root named 'plug-ins'; return a 'null' value if
// there is no such member.
const Json::Value plugins = root["plug-ins"];
// Iterate over the sequence elements.
for ( int index = 0; index < plugins.size(); ++index )
loadPlugIn( plugins[index].asString() );
// Try other datatypes. Some are auto-convertible to others.
foo::setIndentLength( root["indent"].get("length", 3).asInt() );
foo::setIndentUseSpace( root["indent"].get("use_space", true).asBool() );
// Since Json::Value has an implicit constructor for all value types, it is not
// necessary to explicitly construct the Json::Value object.
root["encoding"] = foo::getCurrentEncoding();
root["indent"]["length"] = foo::getCurrentIndentLength();
root["indent"]["use_space"] = foo::getCurrentIndentUseSpace();
// If you like the defaults, you can insert directly into a stream.
std::cout << root;
// Of course, you can write to `std::ostringstream` if you prefer.
// If desired, remember to add a linefeed and flush.
std::cout << std::endl;
\endcode
\section _advanced Advanced usage
Configure *builders* to create *readers* and *writers*. For
configuration, we use our own `Json::Value` (rather than
standard setters/getters) so that we can add
features without losing binary-compatibility.
\code
// For convenience, use `writeString()` with a specialized builder.
Json::StreamWriterBuilder wbuilder;
wbuilder["indentation"] = "\t";
std::string document = Json::writeString(wbuilder, root);
// Here, using a specialized Builder, we discard comments and
// record errors as we parse.
Json::CharReaderBuilder rbuilder;
rbuilder["collectComments"] = false;
std::string errs;
bool ok = Json::parseFromStream(rbuilder, std::cin, &root, &errs);
\endcode
Yes, compile-time configuration-checking would be helpful,
but `Json::Value` lets you
write and read the builder configuration, which is better! In other words,
you can configure your JSON parser using JSON.
CharReaders and StreamWriters are not thread-safe, but they are re-usable.
\code
Json::CharReaderBuilder rbuilder;
cfg >> rbuilder.settings_;
std::unique_ptr<Json::CharReader> const reader(rbuilder.newCharReader());
reader->parse(start, stop, &value1, &errs);
// ...
reader->parse(start, stop, &value2, &errs);
// etc.
\endcode
\section _pbuild Build instructions
The build instructions are located in the file
<a HREF="https://github.com/open-source-parsers/jsoncpp/blob/master/README.md">README.md</a> in the top-directory of the project.
The latest version of the source is available in the project's GitHub repository:
<a HREF="https://github.com/open-source-parsers/jsoncpp/">
jsoncpp</a>
\section _news What's New?
The description of latest changes can be found in
<a HREF="https://github.com/open-source-parsers/jsoncpp/wiki/NEWS">
the NEWS wiki
</a>.
\section _rlinks Related links
- <a HREF="http://www.json.org/">JSON</a> Specification and alternate language implementations.
- <a HREF="http://www.yaml.org/">YAML</a> A data format designed for human readability.
- <a HREF="http://www.cl.cam.ac.uk/~mgk25/unicode.html">UTF-8 and Unicode FAQ</a>.
\section _plinks Old project links
- <a href="https://sourceforge.net/projects/jsoncpp/">https://sourceforge.net/projects/jsoncpp/</a>
- <a href="http://jsoncpp.sourceforge.net">http://jsoncpp.sourceforge.net</a>
- <a href="http://sourceforge.net/projects/jsoncpp/files/">http://sourceforge.net/projects/jsoncpp/files/</a>
- <a href="http://jsoncpp.svn.sourceforge.net/svnroot/jsoncpp/trunk/">http://jsoncpp.svn.sourceforge.net/svnroot/jsoncpp/trunk/</a>
- <a href="http://jsoncpp.sourceforge.net/old.html">http://jsoncpp.sourceforge.net/old.html</a>
\section _license License
See file <a href="https://github.com/open-source-parsers/jsoncpp/blob/master/LICENSE"><code>LICENSE</code></a> in the top-directory of the project.
Basically JsonCpp is licensed under MIT license, or public domain if desired
and recognized in your jurisdiction.
\author Baptiste Lepilleur <blep@users.sourceforge.net> (originator)
\author Christopher Dunn <cdunn2001@gmail.com> (primary maintainer)
\version \include version
We make strong guarantees about binary-compatibility, consistent with
<a href="http://apr.apache.org/versioning.html">the Apache versioning scheme</a>.
\sa version.h
*/
|
