How to set low and high bytes of a wchar_t ?
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Thread: How to set low and high bytes of a wchar_t ?

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  1. #1
    Join Date
    May 2002
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    How to set low and high bytes of a wchar_t ?

    I have a method of converting a wide char array to an unsigned char array. Now I need to be able to convert back (from unsigned char array to wide char array) but cannot figure out how to do that.

    Here's my wc2uc method which uses built in macros (BTW, where do these come from? Are they unique to Windows API or are they part of C standard ?):
    Code:
    int wcstoucs(wchar_t wcs[], int nsz, unsigned char uc[] )
    {
    	//uc = new unsigned char [ 2 * nsz + 1 ];
    	//memset(uc, 0x00, 2 * nsz + 1);
    	wchar_t wch = ' ';
    	int wdx = 0;
    	for(size_t i = 0; i < 2 * nsz; i+=2)
    	{
    		wch = wcs[wdx];
    		//pb[i] = LOBYTE(wch);      // bigEndian
    		//pb[i+1] = HIBYTE(wch);
    		uc[i] = HIBYTE(wch);		// littleEndian (x86)
    		uc[i+1] = LOBYTE(wch);
    		wdx++;
    	}
    	return 2 * nsz;
    
    }// wcstoucs(wchar_t wcs[], int nsz, unsigned char uc[] )
    And here's a method that only depends upon what I am certain is native 'C':
    Code:
    	// given a wchar_t get the low and the hi order bytes
    	wchar_t wch;
    	byte lobyte, hibyte;
    
    	wch = 0xABCD;
    	lobyte  = wch &0xff;
    	hibyte = wch >> 8;
    
    	printf("wch = %0.4X\n", wch);     // ABCD
    	printf("lobyte =: %0.2X\n", lobyte);   // CD
    	printf("hibyte =: %0.2X\n", hibyte);   // AB
    But we run into an lvalue problem if we try to inverse the operation:
    Code:
    	wchar_t wch = 0x0000;
    	unsigned char ucb = 0x94;
    	// set the low byte
    	LOBYTE(wch) = ucb;  // Error: Expression must be a modifiable lvalue
    So how to set the hi and lo bytes of a wchar_t ?
    Last edited by Mike Pliam; June 24th, 2013 at 02:28 AM.
    mpliam

  2. #2
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    Re: How to set low and high bytes of a wchar_t ?

    Code:
    #include <wchar.h>
    #include <stdio.h>
    
    int main()
    {
    wchar_t	wct;
    
    unsigned char lb, ub;
    
    	lb = 0x17;
    	ub = 0x15;
    
    	wct = (ub << 8) + lb;
    
    	printf("0x%04x", wct);
    	return 0;
    }
    This prints 0x1517. I hope this is what you wanted.
    All advice is offered in good faith only. You are ultimately responsible for effects of your programs and the integrity of the machines they run on.

  3. #3
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    Re: How to set low and high bytes of a wchar_t ?

    This prints 0x1517. I hope this is what you wanted.
    Exactly! Thanks very much.
    mpliam

  4. #4
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    Re: How to set low and high bytes of a wchar_t ?

    Quote Originally Posted by Mike Pliam View Post
    Exactly! Thanks very much.
    Are you trying to re-invent MultiByteToWideChar function?
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  5. #5
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    Re: How to set low and high bytes of a wchar_t ?

    Quote Originally Posted by VladimirF View Post
    Are you trying to re-invent MultiByteToWideChar function?
    doesn't loook like it, since he's not converting anything codepage wise...

    it looks more like he's trying to reinvent a typecast from a wchar_t* to char*, but doing it by copying rather than casting the buffer.

  6. #6
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    Re: How to set low and high bytes of a wchar_t ?

    >> And here's a method that only depends upon what I am certain is native 'C'
    The size of wchar_t is implementation defined. On most *nix's it is 4 bytes as UTF32 in native byte-order. On all Windows platforms it's 2 bytes as UTF16LE.

    >> wcstoucs
    That's name confused me because UCS is an encoding

    gg

  7. #7
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    Re: How to set low and high bytes of a wchar_t ?

    Quote Originally Posted by Codeplug View Post
    On all Windows platforms it's 2 bytes as UTF16LE.
    This isn't correct.
    On Windows NT it's UCS2
    On Windows XP it's technically UTF16 but none of the fonts support a codepoint above 0xFFFF

    Win95/98/ME has only partial support for wide character API's which was then also UCS2.

    When dealing with networks/file systems UTF16 (even UCS2) has been flaky in the past, it wasn't until recently that a lot of the issues got cleaned up.

  8. #8
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    Re: How to set low and high bytes of a wchar_t ?

    >> This isn't correct.
    I'm sure readers can google if they are interested in the level-of-support for surrogate pairs in each historical platform - and even then support varies among the modules/apps in each platform:
    http://www.i18nguy.com/surrogates.html
    http://msdn.microsoft.com/en-us/goglobal/bb688099.aspx
    http://msdn.microsoft.com/en-us/libr...(v=vs.85).aspx

    In the end, it's just easier to say "Windows is UTF16LE".

    gg

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