Prototyping a Flags/Bitmasks implementation in Kotlin 1.1.1

.gitignore

META-INF/
*.class

BitMask.kt

class BitMask(val value: Long)

Flags.kt

interface Flags  {
    val bit: Long

    fun toBitMask(): BitMask = BitMask(bit)
}

globals.kt

infix fun Flags.and(other: Long): BitMask = BitMask(bit and other)
infix fun <T: Flags> Flags.or(other: T): BitMask = BitMask(bit or other.bit)

operator infix fun Flags.plus(other: Flags): BitMask = BitMask(bit or other.bit)

inline fun <reified T> enabledValues(mask: BitMask) : List<T> where T : Enum<T>, T : Flags {
    return enumValues<T>().filter {
        mask hasFlag it
    }
}

infix fun BitMask.or(other: Flags): BitMask = BitMask(value or other.bit)

operator infix fun BitMask.plus(other: BitMask): BitMask = BitMask(value or other.value)
operator infix fun BitMask.plus(other: Flags): BitMask = BitMask(value or other.bit)

infix fun <T: Flags> BitMask.hasFlag(which: T): Boolean {
    // an Undefined flag is a special case.
    if(value == 0L || (value > 0L && which.bit == 0L)) return false

    return value and which.bit == which.bit
}

infix fun <T: Flags> BitMask.unset(which: T): BitMask = BitMask(value xor which.bit)

main.kt

fun main(args : Array<String>){
    val mask: BitMask = ParameterFeature.Path + 
        ParameterFeature.Query + 
        ParameterFeature.Header;
    
    val enabled = enabledValues<ParameterFeature>(mask)
    
    println("flags enabled: $enabled")
    println("flags disabled: ${enumValues<ParameterFeature>().filterNot { enabled.contains(it) } }")
    println("mask hasFlag ParameterFeature.Query: ${mask hasFlag ParameterFeature.Query}")
    println("mask hasFlag ParameterFeature.Body: ${mask hasFlag ParameterFeature.Body}")
}

ParameterFeature.kt

enum class ParameterFeature(override val bit: Long) : Flags {
    Undefined(0),
    Path(1 shl 0),
    Query(1 shl 1),
    Header(1 shl 2),
    Body(1 shl 3),
    FormUnencoded(1 shl 4),
    FormMultipart(1 shl 5);
}

run.sh

#!/usr/bin/env bash

kotlinc {BitMask,Flags,globals,ParameterFeature,main}.kt && kotlin MainKt

Thank you very much for this awesome example @jimschubert

Hidden gem

@fabriciovergara thanks! I'm glad you've found it useful.

nice work! very helpful for network physics

Great example, thank you