WCHAR to String, how do i do it? - c++

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;
}
I want to get response as string i am using dll in C#, dont know vc++ at all, please suggest a way.
String* retOne //how to get response;
return retOne;
UPDATE
// 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);
Gives error: 'utf8_encode' : cannot convert parameter 1 from 'LPVOID' to 'const std::wstring
Please don't post comments suggesting use of .net libraries.

Answer 1

Looks like you need the WideCharToMultiByte function

Answer 2

Whats hard in this process is to understand the function WideCharToMultiByte.
Basically what you need to do in order to get the whole string (and avoid garbage as a result of not having a null terminating string) is first use:
int size_needed = WideCharToMultiByte(CP_UTF8, 0, (LPCWCH)lpOutBuffer, -1, NULL, 0, NULL, NULL);
char *stringMe = new char[size_needed + 1];
While size_needed will be the required buffer size for lpMultiByteStr in the WideCharToMultiByte function.
Afterwards you just need to use that function again, since now you have the complete size:
WideCharToMultiByte(CP_UTF8, 0, (LPCWCH)lpOutBuffer, -1, stringMe, size_needed, NULL, NULL);
stringMe[size_needed + 1] = NULL;
Now you can also convert it to String:
std::string serverOutput(stringMe);

Answer 3

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