Reverse the bits of an integer in Swift

bitreverse.swift

func reverse <T: FixedWidthInteger> ( word: T ) -> T {
    
    var word = word
    var rev : T = 0
    
    for _ in (0..<word.bitWidth) {
        rev = (rev << 1) + (word & 0b1)
        word >>= 1
    }
    return rev
}