Rapid builder allows you to create JSON in a nice and readable way, thanks to c++11 feature - std::initializer_list. You may create std::string, rapidjson::Document, or rapidjson::Value with three easy API calls: BuildJson, BuildValue, or BuildDocument. Rapid builder requires c++17 due to std::string_view usage.
Example json:
{
"password": "my_password",
"username": "my_username",
"validation-factors": [
{
"name": "remote_address",
"value": "127.0.0.1"
},
{
"name": "remote_port",
"value": 3333
}
]
}Rapid builder code:
const auto json = json::build(
{{"username", "my_username"},
{"password", "my_password"},
{"validation-factors", json::array({
{{"name", "remote_address"},
{"value", "127.0.0.1"}},
{{"name", "remote_port"},
{"value", 3333}}
})
}});The same json build code with regular rapidjson API:
rapidjson::Document doc;
auto& allocator = doc.GetAllocator();
doc.AddMember("username", "my_username", allocator);
doc.AddMember("password", "my_password", allocator);
rapidjson::Value arr(rapidjson::kArrayType);
rapidjson::Value valid_factor_addr(rapidjson::kObjectType);
valid_factor_addr.AddMember("name", "remote_address", allocator);
valid_factor_addr.AddMember("value", "127.0.0.1", allocator);
arr.PushBack(valid_factor_addr, allocator);
rapidjson::Value valid_factor_port(rapidjson::kObjectType);
valid_factor_port.AddMember("name", "remote_port", allocator);
valid_factor_port.AddMember("value", 3333, allocator);
arr.PushBack(valid_factor_port, allocator);
doc.AddMember("validation-factors", arr, allocator);
rapidjson::StringBuffer buffer;
rapidjson::Writer<rapidjson::StringBuffer> writer(buffer);
doc.Accept(writer);
const std::string json(buffer.GetString(), buffer.Size());The same json build code with writer rapidjson API:
rapidjson::StringBuffer string_buffer;
rapidjson::Writer<rapidjson::StringBuffer> writer(string_buffer);
writer.StartObject();
writer.Key("username");
writer.String("my_username");
writer.Key("password");
writer.String("my_password");
writer.Key("validation-factors");
writer.StartArray();
writer.StartObject();
writer.Key("name");
writer.String("remote_address");
writer.Key("value");
writer.String("127.0.0.1");
writer.EndObject();
writer.StartObject();
writer.Key("name");
writer.String("remote_port");
writer.Key("value");
writer.Int(3333);
writer.EndObject();
writer.EndArray();
const std::string json(string_buffer.GetString(), string_buffer.Size());So I think that you get the point of Rapid Builder. Nlohmann JSON library uses the same way to build JSON and I have added it to the benchmark section.
Even more complex things possible with Rapid Builder:
std::vector<int> values{1,2,3,4};
const auto rapid_json_object =
json::build({{"object", {{"some", "other"}, {"int", 0}}},
{"from vector", json::array(values)},
{"array of objects",
{{"string", json::array({string_field_name, json::array({0, 1, 2}), "2"}),
{{"name", "value"}, {"bool", false}}}}
}});Currently, you can use a container as JSON array source, but can't use rapidjson::Value in the same way. Another important limitation is about using temporal objects while building JSON documents or values - don't do that! Internally, this code uses StringRef() from rapidjson and value may die before it will be used.
Don't use temporary variables in the builder! Strings in the example below will be destroyed before building the JSON and you'll get garbage in result!
const auto bad_sample = json::build({{std::string("some field"), std::string("some value")}});Rapid builder can be modified to be used for almost any other JSON library internally.
Tested in Visual Studio 2019 (Open as Folder) and gcc under ubuntu. This project uses Conan as dependency manager and CMake as a build system. Build command:
cd repo_folder
cmake -DCMAKE_BUILD_TYPE=Release .
make
./bin/bench
./bin/tests
BM_RapidbuilderCreateJson - This builder, create json text.
BM_RapidjsonCreateJson - Regular rapidjson API, create json text.
BM_NlohmannCreateJson - Nlohmann JSON library, create json text.
BM_RapidjsonWriterCreateJson - Writer rapidjson API, create json text.
BM_RapidbuilderCreateDocument - This builder, create json object to continue work with.
BM_NlohmannCreateDocument - Nlohmann JSON library, create json object to continue work with.
BM_RapidjsonCreateDocument - Regular rapidjson API, create json object to continue work with.
2022-01-29T14:07:48+03:00
Running ./bench
Run on (20 X 3600 MHz CPU s)
Load Average: 0.52, 0.58, 0.59
------------------------------------------------------------------------
Benchmark Time CPU Iterations
------------------------------------------------------------------------
BM_RapidbuilderCreateJson 849 ns 837 ns 746667
BM_RapidjsonCreateJson 956 ns 963 ns 746667
BM_NlohmannCreateJson 4604 ns 4604 ns 149333
BM_RapidjsonWriterCreateJson 717 ns 715 ns 896000
BM_RapidbuilderCreateDocument 394 ns 392 ns 1792000
BM_NlohmannCreateDocument 3333 ns 3299 ns 203636
BM_RapidjsonCreateDocument 180 ns 180 ns 3733333
2022-01-29T14:10:11+03:00
Running bench.exe
Run on (20 X 3600 MHz CPU s)
CPU Caches:
L1 Data 32 KiB (x10)
L1 Instruction 32 KiB (x10)
L2 Unified 256 KiB (x10)
L3 Unified 20480 KiB (x1)
------------------------------------------------------------------------
Benchmark Time CPU Iterations
------------------------------------------------------------------------
BM_RapidbuilderCreateJson 1565 ns 1569 ns 448000
BM_RapidjsonCreateJson 2269 ns 2295 ns 320000
BM_NlohmannCreateJson 11585 ns 11719 ns 64000
BM_RapidjsonWriterCreateJson 1193 ns 1200 ns 560000
BM_RapidbuilderCreateDocument 1168 ns 1172 ns 640000
BM_NlohmannCreateDocument 9259 ns 9208 ns 74667
BM_RapidjsonCreateDocument 849 ns 837 ns 746667
Copy builder.h and builder.cpp into your project and use.
MIT License Copyright (c) 2022 pavel.sokolov@gmail.com / CEZEO software Ltd.. All rights reserved.
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