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Prototyping a Flags/Bitmasks implementation in Kotlin 1.1.1
class BitMask(val value: Long)
interface Flags {
val bit: Long
fun toBitMask(): BitMask = BitMask(bit)
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): 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): BitMask = BitMask(value or other.value)
operator infix fun 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)
fun main(args : Array<String>){
val mask: BitMask = ParameterFeature.Path +
ParameterFeature.Query +
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}")
enum class ParameterFeature(override val bit: Long) : Flags {
Path(1 shl 0),
Query(1 shl 1),
Header(1 shl 2),
Body(1 shl 3),
FormUnencoded(1 shl 4),
FormMultipart(1 shl 5);
#!/usr/bin/env bash
kotlinc {BitMask,Flags,globals,ParameterFeature,main}.kt && kotlin MainKt
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mochadwi commented Feb 24, 2019

Thank you very much for this awesome example @jimschubert

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fabriciovergara commented Aug 23, 2021

Hidden gem

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jimschubert commented Aug 24, 2021

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

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