Function int64 

pub fn int64(bits: &Bits) -> i64

Converts up to the first 64 bits of a bit string to a 64 bit signed integer.

If the length of the the bit string is less than 64, the result is sign-extended to 64 bits.

Example

let bits = Bits::new([0x10, 0x32, 0x54, 0x76]);
let long = bits_as::int64(&bits);

assert_eq!(long, 0x0000000076543210);

let bits = Bits::from([0x10, 0x32, 0x54, 0x76]);
let long = bits_as::int64(&bits);

assert_eq!(long, 0xFFFFFFFFF6543210u64 as i64);