converting narrow string to wide string

Question

How can i convert a narrow string to a wide string ?

I have tried this method :

string myName;
getline( cin , myName );
wst         


        

Answer 1

You should do this :

inline std::wstring convert( const std::string& as )
{
            // deal with trivial case of empty string
    if( as.empty() )    return std::wstring();

            // determine required length of new string
    size_t reqLength = ::MultiByteToWideChar( CP_UTF8, 0, as.c_str(), (int)as.length(), 0, 0 );

            // construct new string of required length
    std::wstring ret( reqLength, L'\0' );

            // convert old string to new string
    ::MultiByteToWideChar( CP_UTF8, 0, as.c_str(), (int)as.length(), &ret[0], (int)ret.length() );

            // return new string ( compiler should optimize this away )
    return ret;
}

This expects the std::string to be UTF-8 (CP_UTF8), when you have another encoding replace the codepage.

Another way could be :

inline std::wstring convert( const std::string& as )
{
    wchar_t* buf = new wchar_t[as.size() * 2 + 2];
    swprintf( buf, L"%S", as.c_str() );
    std::wstring rval = buf;
    delete[] buf;
    return rval;
}

Answer 2

This article published on the MSDN Magazine 2016 September issue discusses the conversion in details using Win32 APIs.

Note that using MultiByteToWideChar() is much faster than using the std:: stuff on Windows.

Answer 3

Here are two functions that can be used: mbstowcs_s and wcstombs_s.

mbstowcs_s: Converts a sequence of multibyte characters to a corresponding sequence of wide characters. wcstombs_s: Converts a sequence of wide characters to a corresponding sequence of multibyte characters.

errno_t wcstombs_s(
   size_t *pReturnValue,
   char *mbstr,
   size_t sizeInBytes,
   const wchar_t *wcstr,
   size_t count 
);

errno_t mbstowcs_s(
   size_t *pReturnValue,
   wchar_t *wcstr,
   size_t sizeInWords,
   const char *mbstr,
   size_t count 

);

See http://msdn.microsoft.com/en-us/library/eyktyxsx.aspx and http://msdn.microsoft.com/en-us/library/s7wzt4be.aspx.

Answer 4

Use mbtowc():

string myName;
wchar_t wstr[BUFFER_SIZE];

getline( cin , myName );
mbtowc(wstr, myName, BUFFER_SIZE);

Answer 5

If the source is ASCII encoded, you can just do this:

wstring printerName;
printerName.assign( myName.begin(), myName.end() );

Answer 6

I found this while googling the problem. I have pasted the code for reference. Author of this post is Paul McKenzie.

std::string str = "Hello";
std::wstring str2(str.length(), L' '); // Make room for characters

// Copy string to wstring.
std::copy(str.begin(), str.end(), str2.begin());