C programming help ....

[Vu Pham]

I think gcc will take care of the big/little endian accordingly. Your
solution is correct, too.

I also see somebody use something like : 
#define INT(x)  (x[3]<<24) + (x[2]<<16) + (x[1])<<8) + x[0]
 int a = INT("ABCD");

Sorry for the top post, but  Outlook is out of my control :)
________________________________

From: linux-users-bounces at linux-sxs.org
[mailto:linux-users-bounces at linux-sxs.org] On Behalf Of Kevin O'Gorman
Sent: Friday, May 19, 2006 12:05 PM
To: Linux tips and tricks
Subject: Re: C programming help ....


Vu Pham's solution depends on the specifics of your C compiler.
Mine won't allow multi-character constants in that way, at least
not without a warning.  It doesn't like his main() function parameters
either.
A more portable way (though still subject to differences of endianness):

typedef union {
    char bytes[4];
    int code;
} code_t;

int main( int argc, char *argv[] )
{   
    code_t b = {'A', 'B', 'C', 'D'};

    printf(" %02x", (b.code >> 24) & 0xFF);
    printf(" %02x", (b.code >> 16) & 0xFF);
    printf(" %02x", (b.code >> 8) & 0xFF);
    printf(" %02x\n", (b.code ) & 0xFF);

    return 0;
}



On 5/19/06, Vu Pham <vu at sivell.com> wrote: 

	You can use something like
	
	Var = 'LNDE';
	
	And the compiler will pack it in accordingly;
	
	int main( int c, char *args )
	{
	int a = (int)'XYZT';
	        printf( "%02x ", (a&0xFF000000) >> 24 ); 
	        printf( "%02x ", (a&0x00FF0000) >> 16 );
	        printf( "%02x ", (a&0x0000FF00) >> 8  );
	        printf( "%02x \n", (a&0xFF)  );
	
	}
	[vu at cvs vu]$ ./t
	58 59 5a 54
	[vu at cvs vu]$
	
	
	-----Original Message-----
	From: linux-users-bounces at linux-sxs.org
	[mailto: linux-users-bounces at linux-sxs.org
<mailto:linux-users-bounces at linux-sxs.org> ] On Behalf Of Ben Duncan
	Sent: Friday, May 19, 2006 10:52 AM
	To: Linux tips and tricks
	Subject: C programming help ....
	
	Ok, I am trying to figure out how to "pack" hex strings a 32 bit
integer. 
	What I need to do is code the following characters.
	"LNDE", "INDE", "RNDE", "DATA", "DEAD" each into a integer.
	
	is the correct way to do this (on a 32 bit machine) thus: 
	
	int LNDE_int = 0x4C4E4445 ;         /* Pack 'LNDE' into LNDE_int */
	
	.. and so on and so on ....
	
	Thanks ...
	
	
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-- 
Kevin O'Gorman, PhD