curl desktop send request to website. объясните простыми словами..

[test2me]

#include <iostream>
#include <string>
#include <curl/curl.h>
#include <iostream>
using namespace std;


static size_t WriteCallback(void *contents, size_t size, size_t nmemb, void *userp)
{
    ((std::string*)userp)->append((char*)contents, size * nmemb);
    return size * nmemb;
}

int main(void)
{
  CURL *curl;
  CURLcode res;
  std::string readBuffer;

  curl = curl_easy_init();
  if(curl) {
    // url
    curl_easy_setopt(curl, CURLOPT_URL, "https://yandex.ru");
    // https
    curl_easy_setopt(curl, CURLOPT_HTTP_VERSION, (long)CURL_HTTP_VERSION_3);
    //create text from url
    curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, WriteCallback);
    //send string readbuffer as link to the callback function
    curl_easy_setopt(curl, CURLOPT_WRITEDATA, &readBuffer);
    //send request
    res = curl_easy_perform(curl);
    curl_easy_cleanup(curl);

    std::cout << readBuffer << std::endl;
  }
  return 0;
}

Объясните простыми словами, что делают эти функции?

  //create text from url
    curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, WriteCallback);
    //send string readbuffer as link to the callback function
    curl_easy_setopt(curl, CURLOPT_WRITEDATA, &readBuffer);

[p51x]

curl_easy_setopt

curl_easy_setopt is used to tell libcurl how to behave. By setting the appropriate options, the application can change libcurl's behavior. All options are set with an option followed by a parameter.

CURLOPT_WRITEFUNCTION

Callback for writing data. See CURLOPT_WRITEFUNCTION

Pass a pointer to your callback function, which should match the prototype shown above.

This callback function gets called by libcurl as soon as there is data received that needs to be saved. For most transfers, this callback gets called many times and each invoke delivers another chunk of data. ptr points to the delivered data, and the size of that data is nmemb; size is always 1.

The data passed to this function is not null-terminated.

CURLOPT_WRITEDATA

Data pointer to pass to the write callback. See CURLOPT_WRITEDATA

A data pointer to pass to the write callback. If you use the CURLOPT_WRITEFUNCTION option, this is the pointer you get in that callback's fourth and last argument. If you do not use a write callback, you must make pointer a 'FILE ' (cast to 'void ') as libcurl passes this to fwrite(3) when writing data.