While I know the process to set/unset a bit at a specific location - what is the most efficient way to do this operation over a range (say from position x to y)?
101011011011
n=12
x=3,y=7(from right)
Bit set: 101011111111
Bit unset: 101010000011
The mask has to be pushed dynamically as x and y will obviously be random.
Are we talking about C-like operations? If you want x and y to be variables, you can build two masks:
unsigned set(unsigned val, int x, int y) {
unsigned hi = ~0 << x; // 1's at position x and higher
unsigned lo = ~(~0 << y); // 1's at positions lower than y
return val | (lo & hi);
}
and
unsigned clear(unsigned val, int x, int y) {
unsigned hi = ~(~0 << x);
unsigned lo = ~0 << y;
return val & (lo | hi);
}
Note the end of the range is non-inclusive at the high end. So set(foo, 5, 9) sets bits 5 through 8, where each bit i is the one with value 2^i.