import Foundation
/// Returns the zero-based position of the most significant set bit (MSB)
/// in an unsigned 32-bit integer.
///
/// Examples:
/// 1 -> 0
/// 2 -> 1
/// 8 -> 3
/// 15 -> 3
///
/// - Parameter value:
/// Unsigned integer to examine.
/// - Returns:
/// The zero-based position of the highest set bit,
/// or `nil` if the value is 0.
func msbPosition(of value: UInt32) -> Int? {
guard value != 0 else {
return nil
}
return UInt32.bitWidth - 1 - value.leadingZeroBitCount
}
func main() {
let testValues: [UInt32] = [
0,
1,
2,
8,
15,
0x1234,
0x8000_0000
]
for value in testValues {
if let position = msbPosition(of: value) {
print("Value: \(value), MSB position: \(position)")
} else {
print("Value: \(value), no bits are set")
}
}
}
main()
/*
run:
Value: 0, no bits are set
Value: 1, MSB position: 0
Value: 2, MSB position: 1
Value: 8, MSB position: 3
Value: 15, MSB position: 3
Value: 4660, MSB position: 12
Value: 2147483648, MSB position: 31
*/
