Secure LibCurl Wrapper in C++ for HTTP(S) API Calls with Nlohmann Json Support

This project uses 2 simple files to create the wrapper with SecureLibCurlJson.h containing the definitions and SecureLibCurlJson.cpp containing all the implementaions.

This repository has 2 branches:

1. Windows
2. Linux

Table of Contents

• Windows (Visual Studio 2022)
• Linux (Tested on Ubuntu 22.04 LTS)
• Usage

---

Windows (Visual Studio 2022)

The entire Visual Studio 2022 Project is contained in the Windows Branch

Project Settings for Libcurl

Note : These steps have already been performed in the visual studio project included in this repo, but, they are documented if you need to setup a new project.

• Download Curl for Windows
• Extract:
  • The include and lib folders and keep them in a new folder called [your-curl-dir] (it is named curl-8.4.0_3-win64-mingw in this repo's case)
  • The bin/libcurl-x64.dll file inside and keep it in your project directory.
• Download CA certificate extracted from Mozilla cacert.pem and place it inside your project directory.
• Add {your-curl-dir}/include to Configuration Properties -> VC++ Directories -> Include Directories.
• Add {your-curl-dir}/lib to Configuration Properties -> VC++ Directories -> Library Directories.
• In Configuration Properties -> Linker -> Input -> Additional Dependencies, add these followings lines:

{your-curl-dir}/lib/libcurl_a.lib
Ws2_32.lib
Wldap32.lib
Crypt32.lib
Normaliz.lib

• In Configuration Properties -> Build Events -> Post-Build Event -> Command Line add the following lines to copy necessary files when the .exe is generated:

copy "libcurl-x64.dll" "$(SolutionDir)$(Platform)\$(Configuration)\libcurl-x64.dll"
copy "cacert.pem" "$(SolutionDir)$(Platform)\$(Configuration)\cacert.pem"

Project Settings for Nlohmann Json

• Download json.hpp from Nlohmann Json and keep it in a folder called nlohmann in your project directory
• You can now use the library as follows:

#include "nlohmann/json.hpp"

using json = nlohmann::json;

Directory Structure

This is what the directory structure should look like after setting up

.
├── curl-8.4.0_3-win64-mingw/
│   ├── include/
│   │   └── [all the files inside include as-is]
│   └── lib/
│       └── [all the files inside lib as-is]
├── nlohmann/
│   └── json.hpp
├── cacert.pem
├── libcurl-x64.dll
├── SecureLibCurlJson.h
├── SecureLibCurlJson.cpp
└── Source.cpp

---

Linux (Tested on Ubuntu 22.04 LTS)

The Linux code is contained in the Linux Branch

Install Prerequisites (Libcurl and Nlohmann JSON)

Run the following commands in the terminal

sudo apt update
sudo apt upgrade
sudo apt install libcurl4-openssl-dev
sudo apt install nlohmann-json3-dev

Download the updated CA certificate extracted from Mozilla

Run the following command in the terminal from inside the directory with the source code

curl --etag-compare etag.txt --etag-save etag.txt --remote-name https://curl.se/ca/cacert.pem

Directory Structure

This is what the directory structure should look like

.
├── cacert.pem
├── etag.txt
├── SecureLibCurlJson.h
├── SecureLibCurlJson.cpp
└── Source.cpp

Compile

g++ -o SLCJ.out Source.cpp SecureLibCurlJson.cpp -lcurl

Run the program

./SLCJ.out

---

Usage

Example usage is provided in Source.cpp

  SecureLibCurlJson curlLib(true);

  std::string apiUrl = "https://api.publicapis.org/entries";
  std::string requestType = "GET";

  std::map<std::string, std::string> queryParameters;
  /*  EXAMPLE USAGE OF QUERY PARAMETERS
  *   queryParameters["key"] = "abcxyz123";
  *   queryParameters["query"] = "helloworld";
  */

  json bodyParameters;
  /*  EXAMPLE USAGE OF BODY PARAMETERS
  *   bodyParameters["value1"] = "one";
  *   bodyParameters["value2"] = "two";
  *   -- if json objects need to be nested --
  *   json nestedValues;
  *   nestedValues["nestedValue1"] = "n_one";
  *   nestedValues["nestedValue2"] = "n_two";
  *   bodyParameters["nested"] = nestedValues;
  */

  json responseData = curlLib.MakeApiRequest(apiUrl, requestType, queryParameters, bodyParameters);

  if (!responseData.empty())
  {
      std::cout << "Response Data: " << responseData.dump(2) << std::endl;
  }
  else
  {
      std::cerr << "API request failed." << std::endl;
  }

---