qjson

A fast, efficient JSON parsing and serialization library designed for modern C++ applications.

Features

🚀Ultra-Fast Performance

• 6x faster parsing than nlohmann/json
• Nearly 3x faster serialization than nlohmann/json
• Zero-copy view mode provides additional 2x performance boost

⚡ Memory Efficient

• Two memory policies: copy and view modes
• View mode eliminates unnecessary string copying
• Compact internal storage reduces memory footprint

🛠 Modern C++ Design

• Fully utilizes C++17 features
• Template-based design with type safety
• constexpr optimizations for compile-time computation
• Exception-safe design

Performance Benchmarks

Performance comparison with popular JSON libraries on the same hardware:

• Test environment: Intel i7-12700H @ 2.68GHz, 100,000 Iterations

JSON File Structure Statistics

---

Filename	Size(bytes)	elementCount	objectCount	arrayCount	numberCount	stringCount	trueCount	falseCount	nullCount
canana.json	2251051	167170	4	56045	111126	12	0	0	0
citm_catalog.json	1727204	11908	10937	10451	14392	26604	0	0	1263
twitter.json	631514	568	1264	1050	2109	18099	345	2446	1946

---

1. Parsing Performance (Parse, in MB/s)

JSON Library	canada.json	citmcatalog.json	twitter.json
Nlohmann (C++11)	103.945	368.416	181.022
QJson (View+Pool)	807.360	1574.752	1387.693
QJson (Copy+Pool)	695.873	1232.005	1073.545
QJson (View)	731.189	1030.138	930.848
QJson (Copy)	377.089	612.111	431.727
RapidJSON_AutoUTF	387.924	394.442	262.079
RapidJSON_FullPrec	246.698	1344.645	525.990
RapidJSON_Insitu	564.049	1597.663	751.883
RapidJSON_Iterative	550.454	1138.348	520.085
RapidJSON	593.850	1574.752	564.971

---

2. Stringification Performance (Stringify, in MB/s)

JSON Library	canada.json	citmcatalog.json	twitter.json
Nlohmann (C++11)	48.947	517.821	306.805
QJson (View+Pool)	2172.844	4666.261	3811.764
QJson (Copy+Pool)	1953.384	4653.079	3717.646
QJson (View)	2036.783	4887.804	3885.540
QJson (Copy)	1984.075	4692.849	3885.540
RapidJSON_AutoUTF	190.688	1359.068	562.333
RapidJSON_FullPrec	287.462	2549.830	1123.617
RapidJSON_Insitu	300.416	2278.271	965.158
RapidJSON_Iterative	299.870	2541.960	1129.941
RapidJSON	302.022	2569.719	1229.099

---

3. Statistics Performance (Statistics, in MB/s)

JSON Library	canada.json	citmcatalog.json	twitter.json
Nlohmann (C++11)	4923.783	4537.714	1942.770
QJson (View+Pool)	5740.025	10359.686	3717.646
QJson (Copy+Pool)	5261.690	9863.414	3672.309
QJson (View)	6925.063	11850.288	2448.206
QJson (Copy)	5590.546	10981.267	2448.206
RapidJSON_AutoUTF	6446.755	14707.054	13383.526
RapidJSON_FullPrec	6168.878	13959.238	12547.056
RapidJSON_Insitu	6446.755	14839.550	13383.526
RapidJSON_Iterative	6389.195	14323.392	13092.580
RapidJSON	6408.267	14323.392	12814.015

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Summary & Observations

• Parsing Performance:
  QJson View and RapidJSONInsitu deliver the best parsing speeds across most files. Nlohmann is consistently slower.
• Stringification Performance:
  QJson and RapidJSONFullPrec perform best on complex files like twitter.json. simdjson and SonicJSON show impressive speeds on citmcatalog.json.
• Statistics Performance:
  The RapidJSON family dominates, especially on citmcatalog.json, reaching speeds above 15,000 MB/s.

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Quick Start

Building from Source

git clone git@github.com:qinyonghang/json.git
cd json
mkdir build && cd build
cmake ..
make
make install

Using CMake

find_package(qjson REQUIRED)
target_link_libraries(${TARGET_NAME} PRIVATE qlib::json)

Parsing JSON

#include "qlib/json.h"

using namespace qlib;
json_view_t json;
result = json::parse(&json, begin, end);
if (0 != result) {
    std::cout << "json::parse return " << result << std::endl;
    break;
}

// get string
auto name = json["name"].get<string_t>();
std::cout << "name: " << name << std::endl;

// get array
auto& array = json["array"].array();
for (auto& item : array) {
    std::cout << item.get<string_t>() << std::endl;
}

// get object
auto& object = json["object"].object();
for (auto& [key, value] : object) {
    std::cout << key << ": " << value.get<string_t>() << std::endl;
}

Memory Policies

Copy Mode(json_t)

using namespace qlib;
json_t json;
result = json::parse(&json, begin, end);
if (0 != result) {
    std::cout << "json::parse return " << result << std::endl;
    break;
}

• Creates data copies
• Suitable for scenarios requiring JSON data modification
• Data independent with safe lifetime

View Mode(json_view_t)

using namespace qlib;
json_view_t json;
result = json::parse(&json, begin, end);
if (0 != result) {
    std::cout << "json::parse return " << result << std::endl;
    break;
}

• Zero-copy, references original data
• Up to 2x performance improvement
• Suitable for read-only scenarios, requires original data lifetime management

High-Performance Usage Tips

1. Prefer view mode: Use json_view_t for read-only operations for optimal performance
2. Avoid deep copying: Use move semantics std::move() when possible

Dependencies

• C++14
• Standard library only (no external dependencies)

Designed for C++ developers who demand ultimate performance