Safe JSON

A JSON library made for config files.

This library provides a parser, serializer and needed data structures to safely read and write config files,
by replacing missing or malformed data with provided default values.
For convenience the library also contains a dynamic parser that can deal with unknown JSON data.

Example

#include <sstream>
#include <iostream>
#include "../safe_json.hpp"

namespace jss = ztu::json::safe;

namespace my_object_builder {
	using namespace jss::literals;

	using my_default_object_t = object<
		set<"boolean", true_B>{},
		set<"integer", -1_I>{},
		set<"unsigned", 6_U>{},
		set<"floating", 3.5_N>{},
		set<"string", "test"_S>{},
		set<"enum",
			enumeration<"two",
				"one", "two", "three"
			>{}
		>{},
		set<"array",
			array<1_I,
				1_I, 2_I, 3_I
			>{}
		>{},
		set<"variant",
			variant<"one",
				holds<"one",
					set<"b", true_B>{}
				>{},
				holds<"two",
					set<"i", 1_I>{}
				>{},
				holds<"three",
					set<"f", 1.0_N>{}
				>{}
			>{}
		>{}
	>;
}

constexpr my_object_builder::my_default_object_t my_default_object{};

int main() {

	auto is = std::stringstream(
		"{\n"
		"	\"boolean\": true,\n"
		"	\"integer\": -3.33,\n"
		"	\"unsigned\": -345,\n"
		"	\"floating\": 2.0,\n"
		"	\"string\": \"test\",\n"
		"	\"enum\": \"one\",\n"
		"	\"numbers\": \"not-a-number\",\n"
		"	\"array\": {\n"
		"		\"test\": \"some-string\"\n"
		"	},\n"
		"	\"variant\": {\n"
		"      \"_type\": \"two\",\n"
		"      \"i\": 2\n"
		"    }\n"
		"}"
	);

	auto parser = jss::parser(is);
	auto value = parser.parse<my_default_object>();

	auto serializer = jss::serializer(std::cout);
	serializer.serialize<my_default_object>(value);
	std::cout << std::endl;
}

More examples can be found in the examples directory.

Testing

The parser implementation is tested for correctness using the JSON Parsing Test Suite test_parsing tests, with the following exceptions:

• Tests for "trailing garbage" have been removed as this parser is based on a data stream and should not parse past the first JSON data structure.
• Tests that limit the floating point number representation to less than the C++ standard

Performance

Performance is not the main focus of this library, but here is a small list, comparing the parsing and serialization speed to other implementations. These numbers represent the average time taken to parse the twitter.json file from a string buffer and serializing to a new string across 100 runs.
(Benchmarking is only provided for a basic overview and does not represent scientifically sound data)

node benchamrk.js ./implementations ../twitter.json 100

Implementation	avg parse time (us)	avg serialize time (us)
simd_json	243.78	703.01
node_json	4487.61	4504.89
python_json	4463.91	14890.70
dynamic_json	12508.96	8813.86
java_json	55500.71	30942.80