Stephen Mwangi

Bitmasks in Go

 Feb 3, 2025    2 min. read

 · bitmasks · flags · golang ·

This code demonstrates how to use bitwise operations to manipulate flags in Go.

Defining Flags

You can define flags this way:

type Flags uint8

const (
	Read    Flags = 1 << iota // 1
	Write                     // 2
	Execute                   // 4
)

const (
	All Flags = Read | Write | Execute
)
  • An 8-bit unsigned integer (uint8) is used to represent flags
  • iota is used to automatically increment values
  • Flags are defined using left shift, creating powers of 2:
    • Read = 00000001 $(2^0 = 1)$
    • Write = 00000010 $(2^1 = 2)$
    • Execute = 00000100 $(2^2 = 4)$

Bitwise Operations

  1. Set Operation: Combine flags
func Set(a, b Flags) Flags {
	return a | b
}
  1. Clear Operation: Remove specific flags
func Clear(a, b Flags) Flags {
	return a &^ b
}
  1. Toggle Operation: Flip specific flags
func Toggle(a, b Flags) Flags {
	return a ^ b
}
  1. Check Operation: Verify if any flag is set
func Has(a, b Flags) bool {
	return a&b != 0
}
  1. Check All Operation: Verify if all flags are set
func HasAll(a, b Flags) bool {
	return a&b == b
}

Usage

Sample usage:

func main() {
	perms := Read | Write
	fmt.Println("has read:", Has(perms, Read))       // true
	fmt.Println("has execute:", Has(perms, Execute)) // false
	fmt.Println("has any flag:", Has(perms, All))    // true

	perms = Set(perms, Execute)
	perms = Clear(perms, Write)

	fmt.Println("has read and write:", HasAll(perms, Read|Write))     // false
	fmt.Println("has read and execute:", HasAll(perms, Execute|Read)) // true

	perms = Toggle(perms, Execute)
	fmt.Println("has execute:", Has(perms, Execute)) // false
}