c - Finding n bit length 2s complement representation of a number -

i writing function parameters:

int nbit2s(long int x, long int n){  } 

i looking take in 64 bit number x, , find if 2 bit representation of n bit length possible. restricted using bitwise operators , excluded using operators such >= <=, , conditional statements

for example, nbit2s(5,3) returns 0 because representation impossible.

i'm not looking code ideas, far idea has been:

1. take in number n , convert it's binary representation.
2. left shift binary representation 64-n times msb , store in variable shift 3.shift right 64-n leading bit , store in shift
3. xor original number w, if 1 true, 0 false.

i feel along right lines, if explain perhaps better way or mistakes may have made, great.

if understanding question correctly, determine if integer x can represented binary number n or less bits.

an easy way test use bitwise , operator mask out bits above maximum value, , see if masked integer same original.

example:

bool nbit2s(uint64_t x, int n) {     return (x & (1ull << n) - 1) == x; }