https://github.com/zenmumbler/krystal

A mighty fine C++11 JSON reader
https://github.com/zenmumbler/krystal

c-plus-plus c-plus-plus-11 header-only json library parser

Last synced: 2 days ago
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A mighty fine C++11 JSON reader

• Host: GitHub
• URL: https://github.com/zenmumbler/krystal
• Owner: zenmumbler
• Created: 2013-06-12T23:50:43.000Z (over 11 years ago)
• Default Branch: master
• Last Pushed: 2017-06-07T11:40:04.000Z (over 7 years ago)
• Last Synced: 2023-04-04T16:52:39.004Z (over 1 year ago)
• Topics: c-plus-plus, c-plus-plus-11, header-only, json, library, parser
• Language: C++
• Size: 702 KB
• Stars: 7
• Watchers: 4
• Forks: 1
• Open Issues: 0
• Metadata Files:
  • Readme: README.md

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README

        
krystal

=======

A C++11 JSON data reader with a simple but powerful API.


By Arthur Langereis ([@zenmumbler](http://twitter.com/zenmumbler/))

Design

------

- light-weight, clean codebase

	- a few classes and functions contained in a single `krystal` namespace

	- no macros or other global namespace pollution

	- depends on, and _only_ on the C++ standard library

- C++11 only

	- uses new language and library features to keep design simple

	- move-only semantics for `value` instances to avoid costly copies

- focus on ease of use

	- header-only framework

	- simple API with clear rules

	- integrated with language constructs (e.g. range for loop)

	- clear error messages in parser for syntax errors and in exceptions when using values

	- speed and memory usage limited by your std lib, but second only to rapidjson right now using clang & libc++

- fully conformant to JSON spec

	- correctly parses entire jsonchecker test suite

- UTF-8 only files and strings, [http://utf8everywhere.org/]()

- number values are doubles, limiting exact int values to +/- 2^53

- SAX and DOM style access

Examples

--------

Convenient parse calls generate a document in a single call.

	// from a stream

	auto file = std::ifstream{"game_data.json"};

	auto doc = krystal::parseStream(file);

	

	// or from a string

	std::string json { "...json data..." };

	auto doc = krystal::parseString(json);

	// you will always get a valid Value object

	// failed parse will yield a Null value, otherwise an Array or Object

	if (doc.isContainer())

		...; // succesfully parsed

Use subscripting for array and object values.

	auto delay = doc["levels"][0]["zombie spawn delay"].number();

	auto name = doc["levels"][0]["level name"].string();

Iterate over arrays or objects with normal range for syntax. Each loop yields a pair of `krystal::Value`s.

For arrays, `first` is a number value with the index, for objects, `first` is the key string value.

	for (auto kv : doc["levels"]) {

		auto levelIndex = kv.first.numberAs();

		auto& levelData = kv.second;

		...

	}

Usage

-----

krystal is a header-only library. Add the krystal directory to your include path and `#include`

the `krystal.hpp` umbrella header in your sources.

Status

------

/!\ Does not compile against stdlibc++, because krystal exploits UB by using an incomplete type

as the value of `vector` and `unordered_map`, the last of which stdlibc++ does not support

(legitimately) See:

[http://stackoverflow.com/questions/13089388/how-to-have-an-unordered-map-where-the-value-type-is-the-class-its-in]()

I was not aware of this when I started work on krystal and am currently looking into how to remedy this,

likely by wrapping the values in a `unique_ptr` as those explicitly allow incomplete types.

Does work with Clang 3.2, 3.3 and 3.4 compilers with the libc++ standard library.

Will not work on current (May 2014) MSVC compilers, even the CTP versions, because MSVC is not fully C++11 conformant yet.

JSON output is not yet supported.