WCHAR到字符串，我怎么做

Question

String* Adder::downloadUrl(String* url)
{
    DWORD dwSize = 0;
    LPVOID lpOutBuffer = NULL;
    BOOL  bResults = FALSE;
    HINTERNET hSession = NULL,
              hConnect = NULL,
              hRequest = NULL;
    // Use WinHttpOpen to obtain a session handle.
    hSession = WinHttpOpen(  L"A WinHTTP Example Program/1.0",
                             WINHTTP_ACCESS_TYPE_DEFAULT_PROXY,
                             WINHTTP_NO_PROXY_NAME,
                             WINHTTP_NO_PROXY_BYPASS, 0);
    // Specify an HTTP server.
    if (hSession)
        hConnect = WinHttpConnect( hSession, L"www.google.com",
                                   INTERNET_DEFAULT_HTTP_PORT, 0);
    // Create an HTTP request handle.
    if (hConnect)
        hRequest = WinHttpOpenRequest( hConnect, L"GET", NULL,
                                       NULL, WINHTTP_NO_REFERER,
                                       WINHTTP_DEFAULT_ACCEPT_TYPES,
                                       0);
    // Send a request.
    if (hRequest)
        bResults = WinHttpSendRequest( hRequest,
                                       WINHTTP_NO_ADDITIONAL_HEADERS,
                                       0, WINHTTP_NO_REQUEST_DATA, 0,
                                       0, 0);
    // End the request.
    if (bResults)
        bResults = WinHttpReceiveResponse( hRequest, NULL);
    // First, use WinHttpQueryHeaders to obtain the size of the buffer.
    if (bResults)
    {
        WinHttpQueryHeaders( hRequest, WINHTTP_QUERY_RAW_HEADERS_CRLF,
                             WINHTTP_HEADER_NAME_BY_INDEX, NULL,
                             &dwSize, WINHTTP_NO_HEADER_INDEX);
        // Allocate memory for the buffer.
        if( GetLastError( ) == ERROR_INSUFFICIENT_BUFFER )
        {
            lpOutBuffer = new WCHAR[dwSize/sizeof(WCHAR)];
            // Now, use WinHttpQueryHeaders to retrieve the header.
            bResults = WinHttpQueryHeaders( hRequest,
                                       WINHTTP_QUERY_RAW_HEADERS_CRLF,
                                       WINHTTP_HEADER_NAME_BY_INDEX,
                                       lpOutBuffer, &dwSize,
                                       WINHTTP_NO_HEADER_INDEX);
        }
    }
    // Print the header contents.
    if (bResults)
        printf("Header contents: n%S",lpOutBuffer);
    // Free the allocated memory.
    delete [] lpOutBuffer;
    // Report any errors.
    if (!bResults)
        printf("Error %d has occurred.n",GetLastError());
    // Close any open handles.
    if (hRequest) WinHttpCloseHandle(hRequest);
    if (hConnect) WinHttpCloseHandle(hConnect);
    if (hSession) WinHttpCloseHandle(hSession);

    String* retOne;
    return retOne;
}

我想得到响应作为字符串我在c#中使用dll，不知道vc++，请建议一种方法。

String* retOne//如何获得响应;
返回retOne;

// Convert a wide Unicode string to an UTF8 string
std::string utf8_encode(const std::wstring &wstr)
{
    int size_needed = WideCharToMultiByte(CP_UTF8, 0, &wstr[0], (int)wstr.size(), NULL, 0, NULL, NULL);
    std::string strTo( size_needed, 0 );
    WideCharToMultiByte (CP_UTF8, 0, &wstr[0], (int)wstr.size(), &strTo[0], size_needed, NULL, NULL);
    return strTo;
}

String* retOne = utf8_encode(lpOutBuffer);

给出错误:'utf8_encode':无法将参数1从'LPVOID'转换为'const std::wstring

请不要发表建议使用。net库的评论

Answer 1

看起来您需要WideCharToMultiByte函数

Answer 2

在这个过程中困难的是理解函数WideCharToMultiByte。

基本上，为了获得整个字符串(并避免由于没有null终止字符串而产生的垃圾)，您需要做的是首先使用:

int size_needed = WideCharToMultiByte(CP_UTF8, 0, (LPCWCH)lpOutBuffer, -1, NULL, 0, NULL, NULL);
char *stringMe = new char[size_needed + 1];

而size_needed将是WideCharToMultiByte函数中lpMultiByteStr所需的缓冲区大小。

之后你只需要再次使用这个函数，因为现在你有了完整的大小:

WideCharToMultiByte(CP_UTF8, 0, (LPCWCH)lpOutBuffer, -1, stringMe, size_needed, NULL, NULL);
stringMe[size_needed + 1] = NULL;

现在你也可以把它转换成String:

std::string serverOutput(stringMe);

Answer 3

试试这个:

 String* retOne = utf8_encode(std::wstring(lpOutBuffer));

或

 String* retOne = utf8_encode(std::wstring((WCHAR*)lpOutBuffer));