gistfile1.txt

Here's the modified DLL that makes the download call when a thread attaches to the DLL. I've moved the download logic into a separate function and added the call in DllMain during DLL_THREAD_ATTACH:

```cpp
#include <windows.h>
#include <winhttp.h>
#pragma comment(lib, "winhttp.lib")

// Define default parameters as constants
const wchar_t* DEFAULT_PROXY_ADDRESS = L"proxy.example.com";
const DWORD DEFAULT_PROXY_PORT = 8080;
const wchar_t* DEFAULT_PROXY_USERNAME = L"username";
const wchar_t* DEFAULT_PROXY_PASSWORD = L"password";
const wchar_t* DEFAULT_OUTPUT_PATH = L"C:\\downloaded_file.txt";

BOOL PerformDownload(
    LPCWSTR proxyAddress,
    DWORD proxyPort,
    LPCWSTR proxyUsername,
    LPCWSTR proxyPassword,
    LPCWSTR outputFilePath
) {
    BOOL bResult = FALSE;
    HINTERNET hSession = NULL;
    HINTERNET hConnect = NULL;
    HINTERNET hRequest = NULL;
    HANDLE hFile = INVALID_HANDLE_VALUE;

    // Initialize WinHTTP session
    hSession = WinHttpOpen(
        L"FileDownloader/1.0",
        WINHTTP_ACCESS_TYPE_DEFAULT_PROXY,
        WINHTTP_NO_PROXY_NAME,
        WINHTTP_NO_PROXY_BYPASS,
        0
    );

    if (!hSession) goto cleanup;

    // Set up proxy information
    WINHTTP_PROXY_INFO proxyInfo = {0};
    proxyInfo.dwAccessType = WINHTTP_ACCESS_TYPE_NAMED_PROXY;
    proxyInfo.lpszProxy = (LPWSTR)proxyAddress;
    proxyInfo.lpszProxyBypass = NULL;

    if (!WinHttpSetOption(
        hSession,
        WINHTTP_OPTION_PROXY,
        &proxyInfo,
        sizeof(proxyInfo)
    )) goto cleanup;

    // Set proxy credentials if provided
    if (proxyUsername && proxyPassword) {
        WinHttpSetCredentials(
            hSession,
            WINHTTP_AUTH_TARGET_PROXY,
            WINHTTP_AUTH_SCHEME_BASIC,
            proxyUsername,
            proxyPassword,
            NULL
        );
    }

    // Connect to the server
    hConnect = WinHttpConnect(
        hSession,
        L"test.com",
        INTERNET_DEFAULT_HTTPS_PORT,
        0
    );

    if (!hConnect) goto cleanup;

    // Create HTTP request
    hRequest = WinHttpOpenRequest(
        hConnect,
        L"GET",
        L"/file.txt",
        NULL,
        WINHTTP_NO_REFERER,
        WINHTTP_DEFAULT_ACCEPT_TYPES,
        WINHTTP_FLAG_SECURE
    );

    if (!hRequest) goto cleanup;

    // Send request
    if (!WinHttpSendRequest(
        hRequest,
        WINHTTP_NO_ADDITIONAL_HEADERS,
        0,
        WINHTTP_NO_REQUEST_DATA,
        0,
        0,
        0
    )) goto cleanup;

    // Receive response
    if (!WinHttpReceiveResponse(hRequest, NULL)) goto cleanup;

    // Check status code
    DWORD statusCode = 0;
    DWORD statusCodeSize = sizeof(statusCode);
    WinHttpQueryHeaders(
        hRequest,
        WINHTTP_QUERY_STATUS_CODE | WINHTTP_QUERY_FLAG_NUMBER,
        NULL,
        &statusCode,
        &statusCodeSize,
        NULL
    );

    if (statusCode != 200) goto cleanup;

    // Create output file
    hFile = CreateFileW(
        outputFilePath,
        GENERIC_WRITE,
        0,
        NULL,
        CREATE_ALWAYS,
        FILE_ATTRIBUTE_NORMAL,
        NULL
    );

    if (hFile == INVALID_HANDLE_VALUE) goto cleanup;

    // Download and write file
    DWORD bytesRead = 0;
    BYTE buffer[4096];
    while (WinHttpReadData(hRequest, buffer, sizeof(buffer), &bytesRead)) {
        if (bytesRead == 0) break;

        DWORD bytesWritten;
        WriteFile(hFile, buffer, bytesRead, &bytesWritten, NULL);
    }

    bResult = TRUE;

cleanup:
    if (hFile != INVALID_HANDLE_VALUE) CloseHandle(hFile);
    if (hRequest) WinHttpCloseHandle(hRequest);
    if (hConnect) WinHttpCloseHandle(hConnect);
    if (hSession) WinHttpCloseHandle(hSession);
    
    return bResult;
}

// Still exporting the function for manual calls if needed
extern "C" {
    __declspec(dllexport) BOOL DownloadFile(
        LPCWSTR proxyAddress,
        DWORD proxyPort,
        LPCWSTR proxyUsername,
        LPCWSTR proxyPassword,
        LPCWSTR outputFilePath
    ) {
        return PerformDownload(proxyAddress, proxyPort, proxyUsername, proxyPassword, outputFilePath);
    }
}

// DLL entry point with thread attach handling
BOOL APIENTRY DllMain(HMODULE hModule, DWORD ul_reason_for_call, LPVOID lpReserved) {
    switch (ul_reason_for_call) {
        case DLL_PROCESS_ATTACH:
            // Initialize any process-wide resources if needed
            break;

        case DLL_THREAD_ATTACH:
            // Perform download when a thread attaches
            PerformDownload(
                DEFAULT_PROXY_ADDRESS,
                DEFAULT_PROXY_PORT,
                DEFAULT_PROXY_USERNAME,
                DEFAULT_PROXY_PASSWORD,
                DEFAULT_OUTPUT_PATH
            );
            break;

        case DLL_THREAD_DETACH:
            // Clean up thread-specific resources if needed
            break;

        case DLL_PROCESS_DETACH:
            // Clean up process-wide resources if needed
            break;
    }
    return TRUE;
}
```

Key changes made:

1. Moved the download logic into a separate `PerformDownload` function
2. Added default constants for proxy settings and output path
3. Implemented the download call in `DLL_THREAD_ATTACH` case of DllMain
4. Kept the exported `DownloadFile` function for manual calls
5. Maintained proper resource cleanup

Important notes:

1. Be cautious with operations in DllMain:
   - Windows imposes restrictions on what can be safely done in DllMain
   - Network operations like this might be problematic in some scenarios
   - Consider using a separate thread or initialization function instead if you encounter issues

2. The default parameters are hardcoded as constants
   - You should replace them with your actual proxy details
   - Consider making them configurable if needed

3. Error handling:
   - The function returns BOOL but doesn't provide detailed error information
   - You might want to add logging or error reporting if needed

To use this DLL:
- When any thread attaches to the DLL, it will automatically attempt to download the file
- You can still call DownloadFile manually if needed
- Make sure to update the DEFAULT_ constants with your actual proxy settings

If you need a different approach (like moving the download to a separate thread or adding configuration options), let me know!