How do you check if a specific role is included in a bitmask using bitwise operations in Go?

Understanding Bitmasking and Bitwise Operations in Go

Bitmasking and bitwise operations are fundamental concepts in computer programming that allow manipulation of data at the binary level. In this example, we explore these concepts in Go:

<code class="go">package main

import (
    "fmt"
)

const (
    isAdmin = 1 << iota
    isHeadquarters
    canSeeFinancials

    canSeeAfrica
    canSeeAsia
    canSeeEurope
    canSeeNorthAmerica
    canSeeSouthAmerica
)

func main() {
    var roles byte = isAdmin | canSeeFinancials | canSeeEurope
    fmt.Printf("%b\n", roles)
    fmt.Printf("Is Admin? %v\n", isAdmin&roles == isAdmin)
}</code>

Bitmasking and Bitwise OR

The constants isAdmin, isHeadquarters, etc., represent role bitmasks, where each bit represents a specific role. Bitmasking involves shifting a single 1 bit to different positions, resulting in bit patterns with only one 1 bit. The bitwise OR operation (|) combines these bit patterns, creating a mask that activates any role included in the OR operation.

In the example above, roles is initialized using the bitwise OR operator:

<code class="go">var roles byte = isAdmin | canSeeFinancials | canSeeEurope</code>

This sets each bit corresponding to isAdmin, canSeeFinancials, and canSeeEurope to 1, while other bits remain 0.

Bitwise AND and Checking Roles

The expression isAdmin&roles == isAdmin checks whether roles includes the isAdmin role. Bitwise AND (&) performs a logical AND operation on each bit of the input bit patterns. The resulting bit pattern has 1 bits only where both input bits are 1.

In this case, isAdmin&roles produces a bit pattern with only one 1 bit, indicating the presence of the isAdmin role in roles. Comparing this result to isAdmin ensures that roles includes isAdmin.

Bitwise Equality and Single Role

In contrast, the expression roles == isAdmin checks if roles is equal to isAdmin. This is true only when roles exclusively contains the isAdmin role and no other roles.

Therefore, isAdmin&roles == isAdmin checks if roles contains the isAdmin role, while roles == isAdmin strictly checks if roles is solely the isAdmin role.

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