Convert two's complement to sign-magnitude

Question

I need to convert from two\'s complement to sign-magnitude in C using only the operators

! ~ & ^ | + << >>

My approach is t

Answer 1

From http://graphics.stanford.edu/~seander/bithacks.html#IntegerAbs

int const mask = v >> 31;
unsigned int r = (v + mask) ^ mask;

Gives the absolute value (magnitude). If you wish to add the sign bit back simply mask and or the 32nd bit:

unsigned int s_M = r | (v & 0x80000000);

Or if you're looking for a one liner:

unsigned int s_M = ((v + (v >> 31)) ^ (v >> 31)) | (v & 0x80000000);