Bitwise operators are rarely used in everyday swift programming
⚠️ : not to be confused by Logical Operators like “&&” and “||”
It’s mainly used to perform operations on individual bits, they are extremely useful and used in Flags, Graphics, Networking, Encryption…
| Operator | Description | |
| & | Binary AND | |
| | | Binary OR | |
| ^ | Binary XOR | |
| ~ | Binary One’s Complement | |
| << | Binary Shift Left | |
| >> | Binary Shift Right |
First, a refresher on the truth table of XOR, it gives True if both A and B are Different
| A | B | Result |
| TRUE | TRUE | FALSE |
| TRUE | FALSE | TRUE |
| FALSE | TRUE | TRUE |
| FALSE | FALSE | FALSE |
The basic code to represent integers as bits, and each operator and it’s result … 🧐
extension Int {
var binaryDescription: String {
var binaryString = ""
var internalNumber = self
for _ in (1...self.bitWidth) {
binaryString.insert(contentsOf: "\(internalNumber & 1)", at: binaryString.startIndex)
internalNumber >>= 1
}
return "0b " + binaryString
}
}
func bitwise_example() {
let x1 = 0x1
let x2 = 0x2
print("x1\t", x1.binaryDescription )
print("x2\t", x2.binaryDescription )
let binary_and = (x1 & x2)
let binary_or = (x1 | x2)
let binary_xor = (x1 ^ x2)
let binary_complement = (~x1)
let binary_shiftL = (x1 << 1)
let binary_shiftR = (x1 >> 1)
print("&\t", binary_and.binaryDescription )
print("|\t", binary_or.binaryDescription )
print("^\t", binary_xor.binaryDescription )
print("~\t", binary_complement.binaryDescription )
print("<<\t", binary_shiftL.binaryDescription )
print(">>\t", binary_shiftR.binaryDescription )
}Output
x1 0b 0000000000000000000000000000000000000000000000000000000000000001
x2 0b 0000000000000000000000000000000000000000000000000000000000000010
& 0b 0000000000000000000000000000000000000000000000000000000000000000
| 0b 0000000000000000000000000000000000000000000000000000000000000011
^ 0b 0000000000000000000000000000000000000000000000000000000000000011
~ 0b 1111111111111111111111111111111111111111111111111111111111111110
<< 0b 0000000000000000000000000000000000000000000000000000000000000010
>> 0b 0000000000000000000000000000000000000000000000000000000000000000Real Life Usage for them:
1- Color Format Conversion
Most probably, you would have such an extension in your boilerplate iOS app, it converts HEX colors into UIColor.
extension UIColor {
convenience init(red: Int, green: Int, blue: Int) {
assert(red >= 0 && red <= 255, "Invalid red component")
assert(green >= 0 && green <= 255, "Invalid green component")
assert(blue >= 0 && blue <= 255, "Invalid blue component")
self.init(red: CGFloat(red) / 255.0, green: CGFloat(green) / 255.0, blue: CGFloat(blue) / 255.0, alpha: 1.0)
}
convenience init(rgb: Int) {
self.init(
red: (rgb >> 16) & 0xFF,
green: (rgb >> 8) & 0xFF,
blue: rgb & 0xFF
)
}
}2- Quick & Dirty hashing
let a = 4012
let b = 8102
let c = 9101
func dirtyHash(a: Int, b: Int, c: Int) -> Int{
return ( a ^ b ^ c ^ 9999)
}3- Base64 Encoding
Base64 encoding converts a series of 8 bit bytes into 6 bit character lookup indexes. (SHIFT)ing, (AND)ing, (OR)ing, (NOT)ing are used for implementing the bit operations necessary for Base64 encode/decode.
4- Checking if a number is Odd/Even.
func isEven(number: Int) -> Bool{
return ((number & 0x1) == 0)
}
func isOdd(number: Int) -> Bool{
return ((number & 0x1) > 0)
}5- Solving Problems efficiently and in a performant way.
Write a program to swap the value of two variable.
Using temporary variable
c = a; a = b; b = c;
Without using temporary variable
a = a+b; b = a-b; a = a-b;
Using bitwise operator
a = a^b; b = a^b; a = a^b;
6- Calculating valid network addresses for a subnet
7- Calculating Permission in Role-based access control systems, RBAC.
8- Calculating Inverse Square Root very fastly
http://h14s.p5r.org/2012/09/0x5f3759df.html
Also:
Some people use bitwise operators to handle multiple error code together, each bit can hold a separate value.
N-bitmap can be a really cool and compact data structure.
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