Download a file with curl 7.43.0

HttpDownload.cpp

#include <cstdint>
#include <string>
#include <vector>
#include <iostream>
#include <fstream>
#include <cassert>

#include <curl/curl.h>


/*
 first of all, initialize curl lib.
 in main function, call it.
 curl_global_init(CURL_GLOBAL_ALL);
 
 call clean up function on program termination 
 curl_global_cleanup();
 */

////////////////////////////////////////////////////////////////////////////////
class CHttpDownload
{
public:
    CHttpDownload() : m_curl(nullptr)
    {
        
    }
    
    ~CHttpDownload();
    
    bool Initialize(const std::string & url, const std::string fileName = "");
    bool Run();
    
    auto & GetData() const
    {
        return m_buffer;
    }
    
private:
    
    static size_t WriteBufferCallback(
        char * ptr,
        size_t size,
        size_t nmemb,
        void * userdata
    );
    
private:
    CURL * m_curl;
    std::vector<uint8_t> m_buffer;
    std::string m_fileName;
    std::ofstream m_file;
};

////////////////////////////////////////////////////////////////////////////////
CHttpDownload::~CHttpDownload()
{
    curl_easy_cleanup(m_curl);
    
    if (m_file.is_open())
    {
        m_file.close();
    }
}

////////////////////////////////////////////////////////////////////////////////
bool CHttpDownload::Initialize(
    const std::string & url,
    const std::string fileName
)
{
    m_fileName = fileName;
    
    m_curl = curl_easy_init();
    if (!m_curl)
    {
        return false;
    }
    
    if (curl_easy_setopt(m_curl, CURLOPT_URL, url.c_str()) != CURLE_OK)
    {
        return false;
    }
    
    if (curl_easy_setopt(m_curl, CURLOPT_SSL_VERIFYPEER, 0L) != CURLE_OK)
    {
        return false;
    }
    
    if (curl_easy_setopt(m_curl, CURLOPT_TIMEOUT, 30) != CURLE_OK)
    {
        return false;
    }
    
    if (curl_easy_setopt(m_curl, CURLOPT_CONNECTTIMEOUT, 30) != CURLE_OK)
    {
        return false;
    }
    
    auto callback = &CHttpDownload::WriteBufferCallback;
    if (curl_easy_setopt(m_curl, CURLOPT_WRITEFUNCTION, callback) != CURLE_OK)
    {
        return false;
    }
    
    auto data = static_cast<void *>(this);
    if (curl_easy_setopt(m_curl, CURLOPT_WRITEDATA, data) != CURLE_OK)
    {
        return false;
    }
    
    return true;
}
   
////////////////////////////////////////////////////////////////////////////////
bool CHttpDownload::Run()
{
    assert(m_curl);
    if (!m_curl)
    {
        return false;
    }
    
    if (!m_fileName.empty())
    {
        m_file.open(
            m_fileName,
            std::ios::out | std::ios::trunc | std::ios::binary
        );
    }
    
    auto code = curl_easy_perform(m_curl);
    
    if (m_file.is_open())
    {
        m_file.close();
    }
    
    if (CURLE_OK != code)
    {
        std::cout << curl_easy_strerror(code) << std::endl;
        return false;
    }
    
    return true;
}

////////////////////////////////////////////////////////////////////////////////
size_t CHttpDownload::WriteBufferCallback(
    char * ptr,
    size_t size,
    size_t nmemb,
    void * userdata
)
{
    assert(1 == size);
    
    auto bytes = size * nmemb;
    
    auto http = static_cast<CHttpDownload *>(userdata);
    
    if (http->m_file.is_open())
    {
        http->m_file.write(ptr, bytes);
        return bytes;
    }
    
    auto & buffer = http->m_buffer;
    
    auto bufferSize = buffer.size();
    buffer.resize(bufferSize + bytes);
    
    std::copy(ptr, ptr + bytes, buffer.begin() + bufferSize);
    
    return bytes;
}