Re: WCHAR conversion problem

"I?aki" <Iaki@discussions.microsoft.com> ha scritto nel messaggio
news:E3DC8B26-374D-4000-A3BB-055B83C9B663@microsoft.com...


In modern C++ I would not use this malloc() stuff: you have new,
std::vector, robust string classes like CString[A|W], these are better tools
to build quality code, IMHO.

You may try this function Utf16ToAnsi(), like this:

 CStringA filename = Utf16ToAnsi(
     Cache_detail->fileName, // UTF-16 string
     Cache_detail->fileNameLength // length in *bytes*
   );

Note that it is unusual in Windows programming to have length of string
expressed in bytes. Usually length of strings are expressed in TCHARs (which
equals bytes only for ANSI strings, not for Unicode UTF-16 strings...).

Here's the commented code of Utf16ToAnsi()'s body:

<code>

//------------------------------------------------------------------
// Converts a string from Unicode (UTF-16) to ANSI.
// The input string length is specified in bytes (8 bits),
// and the input string could be not NUL terminated.
//------------------------------------------------------------------
CStringA Utf16ToAnsi( const WCHAR * utf16String, ULONG lengthInBytes )
{
    // Convert length from bytes to WCHAR count
    const int lengthInWChars = lengthInBytes / sizeof(WCHAR);

    // Get the size, in bytes, of destination buffer
    // (to store ANSI string)
    int ansiBufferSize = ::WideCharToMultiByte(
        CP_ACP, // current system Windows ANSI code page
        0, // default flags
        utf16String, // pointer to UTF-16 string to convert
        lengthInWChars, // length in wide chars
        NULL, // destination buffer (unused)
        0, // request size (in bytes) for dest. buffer
        NULL, NULL // do not use default char
    );
    if ( ansiBufferSize == 0 )
    {
        // Error occurred...
        // Throw an exception with GetLastError() or something...
        AtlThrowLastWin32();
    }

    // Allocate destination buffer with proper size
    std::vector< char > ansiBuffer( ansiBufferSize );

    // Do the conversion
    int result = ::WideCharToMultiByte(
        CP_ACP, // current system Windows ANSI code page
        0, // default flags
        utf16String, // pointer to UTF-16 string to convert
        lengthInWChars, // length in wide chars
        &ansiBuffer[0], // destination buffer
        ansiBufferSize, // size (in bytes) of destination buffer
        NULL, NULL // do not use default char
    );
    if ( result == 0 )
    {
        // Error
        AtlThrowLastWin32();
    }

    // Return a copy of the string
    return CStringA( &ansiBuffer[0], ansiBufferSize );
}

</code>

HTH,
Giovanni