Re: Conversion of byte array to cstring

From:
 HItz <hitesh_impossible@yahoo.co.in>
Newsgroups:
microsoft.public.vc.mfc
Date:
Thu, 23 Aug 2007 21:33:17 -0700
Message-ID:
<1187929997.986932.139500@i38g2000prf.googlegroups.com>
On Aug 24, 6:25 am, Joseph M. Newcomer <newco...@flounder.com> wrote:

This code assumes the CByteArray does not have a NUL character

        CString Buffer((LPCSTR)Array.GetBuffer());

while this relies on a "feature" that many disapprove of, it works very well. The
"feature" is that there is a CString constructor that will accept an 8-bit character
string and create an initialized CString, even if the CString is actually a Unicode
string.

It does not need a concatenation, which can get you into the "exponential growth cost"
problem if the string is very long.

Another approach would be

        CByteArray Array;
        ...
        CString Buffer = A2T((LPCSTR)Array.GetBuffer());
On Fri, 24 Aug 2007 01:06:33 +0200, "Giovanni Dicanio" <giovanni.dica...@invalid.it>
wrote:

"AliR (VC++ MVP)" <A...@online.nospam> ha scritto nel messaggio
news:SFhzi.4581$LL7.4217@nlpi069.nbdc.sbc.com...

What kind of conversion are we talking about, what is the byte array
representing? Does the byte array have 0 anywhere in it?

Here is one way

CString Buffer;
for (int i = 0; i < Array.Length();i++)
{
   Buffer += (TCHAR)Array.GetAt(i);
}


Hello Alir,

I don't want to be picky, but I don't like very much the above TCHAR cast...

I think that the above code could be OK *without the TCHAR cast*, if Array
stores BYTEs, which are the ANSI characters to be put in the CString.
But if the input array stores bytes for Unicode UTF-16 strings, I think that
it would not be correct.

I think that a code like the following could be OK, with two separate
branches for ANSI and Unicode (UTF-16):

<code>
///////////////////////////////////////////////////////////
// An array storing BYTEs
///////////////////////////////////////////////////////////
typedef std::vector< BYTE > ByteArray;

///////////////////////////////////////////////////////////
// Build a ANSI string from characters stored into a
// byte array
///////////////////////////////////////////////////////////
CStringA BuildAnsiString( const ByteArray & chars )
{
   if ( chars.empty() )
       return "";

   const int charsCount = static_cast<int>( chars.size() );
   CStringA str( ' ', charsCount );
   for ( int i = 0; i < charsCount; i++ )
   {
       str.SetAt( i, chars[ i ] );
   }

   return str;
}


****
This seems to be an unnecessarily complicated way to deal with this. Given that it can be
written in a single line of code using the constructor, the entire body could be

return CStringA((LPCSTR)chars.GetBuffer());

and it would also be faster, particularly in debug mode.
                                        joe
****

///////////////////////////////////////////////////////////
// Build a Unicode UTF-16 string from characters stored
// into a byte array
///////////////////////////////////////////////////////////
CStringW BuildUnicodeString( const ByteArray & chars )
{
   if ( chars.empty() )
       return L"";

   // Unicode chars count
   const int charsCount = static_cast<int>( chars.size() ) / 2;

   CStringW str( ' ', charsCount );
   const BYTE * pBytes = &chars[0];
   for ( int i = 0; i < charsCount; i++ )
   {
       // Build the Unicode UTF-16 code-point
       WCHAR wch = MAKEWORD( *pBytes, *(pBytes+1) );

       // Point to next WCHAR in source array
       pBytes += 2;

       // Update string character
       str.SetAt( i, wch );
   }

   return str;
}


****
But the body could be

return CStringW((LPCSTR)chars.GetBuffer());

which is a lot simpler to write.
                                joe

****

//
// TEST
//
void Test()
{

   //
   // ANSI Test
   //
   ByteArray ansiChars;
   ansiChars.push_back( 0x48 ); // H
   ansiChars.push_back( 0x49 ); // I

   CStringA strAnsi = BuildAnsiString( ansiChars );
   CA2W s( strAnsi );
   AfxMessageBox( s );

   //
   // Unicode Test
   //
   ByteArray charsUnicode;
   charsUnicode.push_back( 0xB1 ); // alpha
   charsUnicode.push_back( 0x03 );

   charsUnicode.push_back( 0xB4 ); // delta
   charsUnicode.push_back( 0x03 );

   CStringW strUnicode = BuildUnicodeString( charsUnicode );
   AfxMessageBox( strUnicode );
}

</code>

Maybe the OP was not very clear about the content of his byte-array...

Giovanni


Joseph M. Newcomer [MVP]
email: newco...@flounder.com
Web:http://www.flounder.com
MVP Tips:http://www.flounder.com/mvp_tips.htm


Is there any function in MFC which can convert a byte array like BYTE
bt_Array[260]; to CString.

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