How to write a constant time function to copy the most significant bit to all bits

Question

I\'d like to write a function, in C, which takes the MSB of uint8_t, and if it\'s set, returns 0xFF and if not 0x00. In short, which retur

Answer 1

What about

- (x >> 7)

?

Only the MSB is retained and math negation is used to replicate it to all bits.