UInt64 and UInt16 extensions to mask the bits and convert to String

StdLibExtensions.swift

//
//  StdLibExtensions.swift
//
//  Created by Bill Morrison on 1/19/19.
//

import Foundation

extension UInt64 {
    
    enum Mask: UInt64 {
        case bits_00_16 = 0x000000000000ffff
        case bits_17_32 = 0x00000000ffff0000
        case bits_33_48 = 0x0000ffff00000000
        case bits_49_64 = 0xffff000000000000
    }
    
    func get16bits(_ mask: UInt64) -> UInt16 {
        switch mask {
        case 0x000000000000ffff:
            return UInt16(self & 0x000000000000ffff)
        case 0x00000000ffff0000:
            return UInt16((self & 0x00000000ffff0000) >> 16)
        case 0x0000ffff00000000:
            return UInt16((self & 0x0000ffff00000000) >> 32)
        case 0xffff000000000000:
            return UInt16((self & 0xffff000000000000) >> 48)
        default:
            return UInt16(self & mask)
        }
    }
    
    func toBitString(_ ch: String = "_") -> String {
        return
            get16bits(0xffff000000000000).toBitString()
                + ch + get16bits(0x0000ffff00000000).toBitString()
                + ch + get16bits(0x00000000ffff0000).toBitString()
                + ch + get16bits(0x000000000000ffff).toBitString()
        
    }
}

extension UInt16 {
    
    func toBitString(_ ch: String = "_") -> String {
        var result =  String(String("0000000000000000" + String(self, radix: 2)).suffix(16))
        for ix in 0 ... 2 {
            result.insert(contentsOf: ch, at:result.index(result.startIndex, offsetBy: ( (4 * (ix+1)) + ix)))
        }
        return result
        
    }
}