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package me.bush.illnamethislater
import sun.misc.Unsafe
import java.lang.reflect.Modifier
import kotlin.reflect.KClass
import kotlin.reflect.KMutableProperty
import kotlin.reflect.full.declaredMembers
import kotlin.reflect.full.isSubclassOf
import kotlin.reflect.jvm.javaField
import kotlin.reflect.typeOf
/**
* A simple SAM interface for determining if an event (or any class) is cancellable.
*
* @author bush
* @since 1.0.0
*/
internal fun interface CancelledState {
/**
* Returns whether [event] is cancelled or not. [event] should only ever be of the type
* that was passed to [CancelledState.of], or this will cause an error.
*/
fun isCancelled(event: Any): Boolean
companion object {
private val UNSAFE = Unsafe::class.declaredMembers.single { it.name == "theUnsafe" }.handleCall() as Unsafe
private val CANCELLED_NAMES = arrayOf("canceled", "cancelled")
private val NOT_CANCELLABLE = CancelledState { false }
private val OFFSETS = hashMapOf<KClass<*>, Long>()
/**
* Creates a [CancelledState] object for events of class [type].
*/
fun of(type: KClass<*>, config: Config): CancelledState {
// Default impl for our event class.
if (type.isSubclassOf(Event::class)) return CancelledState { (it as Event).cancelled }
// If compat is disabled.
if (!config.thirdPartyCompatibility) return NOT_CANCELLABLE
// Find a field named "cancelled" or "canceled" that is a boolean, and has a backing field.
type.allMembers.filter { it.name in CANCELLED_NAMES && it.returnType == typeOf<Boolean>() }
.filterIsInstance<KMutableProperty<*>>().filter { it.javaField != null }.toList().let {
if (it.isEmpty()) return NOT_CANCELLABLE
if (it.size != 1) config.logger.warn("Multiple possible cancel fields found for event type $type")
it[0].javaField!!.let { field ->
if (Modifier.isStatic(field.modifiers)) OFFSETS[type] = UNSAFE.staticFieldOffset(field)
else OFFSETS[type] = UNSAFE.objectFieldOffset(field)
}
// This is the same speed as direct access, plus one JNI call and hashmap access.
// If you are familiar with C, this is essentially the same idea as pointers.
return CancelledState { event -> UNSAFE.getBoolean(event, OFFSETS[type]!!) }
}
}
}
}
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