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Contents
  1. 1. Json Format
  2. 2. Json for Modern C++
  3. 3. Reference
  • json format and C++ support

Json Format

Data could be classified as

  • scalar: a variable
  • sequence: a list or array
  • mapping: key/value, hash or dictionary

Data expression

  • same kind of data could be seprated by “,”
  • mapping uses “:”
  • array(list) uses “[]”
  • mapping set uses “{}”

Example

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{
    "version": 0.2,
    "vc_kernel_args": [
        [0, "float"],
        [1, "float"],
        [2, "float"],
        [3, "int"],
        [4, "int"]
    ],
    "hsaco_kernel_obj": {
        "symbol"           : "vector_add",
        "dim"              : 1,
        "workgroup_size_x" : 16,
        "workgroup_size_y" : 1,
        "workgroup_size_z" : 1,
        "grid_size_x"      : 16,
        "grid_size_y"      : 1,
        "grid_size_z"      : 1
    }
}

Json for Modern C++

  • download release from page nlohmann json release

  • include the header

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    #include "json.hpp"

  • Parse json file

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    #include <fstream>
    #include "json.hpp"

    using json = nlohmann::json;

    std::ifstream f(jsonFile);
    if (!f.is_open()) {
       std::cout << "Failed to open " << jsonFile << std::endl;
       return;
    }

    json j = json::parse(f);

    std::cout << j["version"] << std::endl;
    std::cout << j["vc_kernel_args"].size() << std::endl;

    // dump the string
    std::string str = j["vc_kernel_args"][0][1].dump(); // it has "", this is "float"
    str.substr(1, str.size() - 2); // remove the "" at the beginning and end

Reference

Contents
  1. 1. Json Format
  2. 2. Json for Modern C++
  3. 3. Reference