Thread: Formatting Hex Output

SOLVED - Sort of, see edit

I'm trying to build a simple assembler and have now managed to get everything working except something rather trivial... the correct output format...

The format must be:

Address followed by a space followed by Operand and Opcode.

These must be two 32 bit values (as 8 hex characters). For the Operand/Opcode the first six bits are the Operand and the final two bits are the Opcode. EG:

00000001 0009D0A1

To generate this I am using:

Code:

printf ("%8.8X %6.6X%2.2X\n", printout, operand, opcode);

-----------

Solution involved a slightly roundabout and less than ideal way of doing it but am now using:

Code:

char test[7];
sprintf(test, "%X",-1);
printf ("%c%c%c%c%c%c\n",test[2],test[3],test[4],test[5],test[6],test[7]);

Which works fine. Will simply do a check to see if operand < 0 and if so use this style.

Which is all fine and lovely until the operand is a negative value at which point it will promptly ignore any attempts at following the format and print out 8 characters such as:

00000001 FFFFFFFF00

Any idea as for how to fix this?

man printf:

"The unsigned int argument is converted to ... unsigned hexadecimal (x and X) notation."

Unfortunately, I am not aware of any way to get printf to format a signed hexadecimal number, which, when you think about wouldn't make a lot of sense anyway.

One way to achieve what you are trying to do, would be to negate the operand and manually prefix a hyphen. Something along the lines of:

Code:

if(operand < 0)
    printf("-%X", -operand);

Basically for -1 it is required to print out:

FFFFFF

May not make much sense but just following the specification!


-----

Found a solution to the problem via a slightly roundabout way of doing it...

Code:

char test[7];
sprintf(test, "%X",-1);
printf ("%c%c%c%c%c%c\n",test[2],test[3],test[4],test[5],test[6],test[7]);

Originally Posted by mvtaylor

Basically for -1 it is required to print out:

FFFFFF

May not make much sense but just following the specification!

No can do. Printf only accepts length modifiers for the built-in types, none of which are 6 bytes. You'd have to write your own alternative.