C++ :: Formatting Iostream For Readable Hex

My problem is that the setfill('0') doesn't affect the output; I want four columns of 64bit numbers in hex which I read in binary mode from a file.

Here is the problem:

fffffff2 f1040000 fff10000 780000
76000d 11740000 0 5f
5f40405f 50636853 796d5f40 30304055
66687669 68556867 76657655 776c7866

and the code to produce it:

cout << hex << setw(4) << setfill('0') ;
unsigned long test,inc,grp;
grp = 0;
for (int i = 0; i < size; i += 4){
test = buffer[i];

[Code] .....