C++爬虫模板3.1(winhttp)

由于原始代码已经是一个很好的示例，下面提供的代码是一个简化版本，去除了原始代码中的一些复杂性，并添加了必要的注释。

#include <iostream>
#include <string>
#include <winhttp.h>
 
#pragma comment(lib, "winhttp.lib")
 
bool GetHttpFile(const std::wstring& url, const std::wstring& filename) {
    HINTERNET hSession = ::WinHttpOpen(L"Crawler/3.1", WINHTTP_ACCESS_TYPE_DEFAULT_PROXY, WINHTTP_NO_PROXY_NAME, WINHTTP_NO_PROXY_BYPASS, 0);
    if (!hSession) {
        std::cerr << "WinHttpOpen failed: " << GetLastError() << std::endl;
        return false;
    }
 
    HINTERNET hConnect = ::WinHttpConnect(hSession, L"www.example.com", INTERNET_DEFAULT_HTTP_PORT, 0);
    if (!hConnect) {
        std::cerr << "WinHttpConnect failed: " << GetLastError() << std::endl;
        ::WinHttpCloseHandle(hSession);
        return false;
    }
 
    HINTERNET hRequest = ::WinHttpOpenRequest(hConnect, L"GET", url.c_str(), NULL, WINHTTP_NO_REFERER, WINHTTP_DEFAULT_ACCEPT_TYPES, 0);
    if (!hRequest) {
        std::cerr << "WinHttpOpenRequest failed: " << GetLastError() << std::endl;
        ::WinHttpCloseHandle(hConnect);
        ::WinHttpCloseHandle(hSession);
        return false;
    }
 
    if (!::WinHttpSendRequest(hRequest, WINHTTP_NO_ADDITIONAL_HEADERS, 0, WINHTTP_NO_REQUEST_DATA, 0, 0, 0)) {
        std::cerr << "WinHttpSendRequest failed: " << GetLastError() << std::endl;
        ::WinHttpCloseHandle(hRequest);
        ::WinHttpCloseHandle(hConnect);
        ::WinHttpCloseHandle(hSession);
        return false;
    }
 
    if (!::WinHttpReceiveResponse(hRequest, NULL)) {
        std::cerr << "WinHttpReceiveResponse failed: " << GetLastError() << std::endl;
        ::WinHttpCloseHandle(hRequest);
        ::WinHttpCloseHandle(hConnect);
        ::WinHttpCloseHandle(hSession);
        return false;
    }
 
    DWORD dwSize = 0;
    DWORD dwDownloaded = 0;
    std::ofstream outfile(filename, std::ios::out | std::ios::binary);
    if (outfile) {
        do {
            char buffer[4096];
            if (!::WinHttpQueryDataAvailable(hRequest, &dwSize)) {
                std::cerr << "WinHttpQueryDataAvailable failed: " << GetLastError() << std::endl;
                ::WinHttpCloseHandle(hRequest);
                ::WinHttpCloseHandle(hConnect);
                ::WinHttpCloseHandle(hSession);
                return false;
            }
 
            if (!dwSize) {
                break;
            }
 
            if (!::WinHttpReadDa