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package moe.nea.firmament.util.collections
import java.lang.ref.ReferenceQueue
import java.lang.ref.WeakReference
import moe.nea.firmament.features.debug.DebugLogger
/**
* Cache class that uses [WeakReferences][WeakReference] to only cache values while there is still a life reference to
* the key. Each key can have additional extra data that is used to look up values. That extra data is not required to
* be a life reference. The main Key is compared using strict reference equality. This map is not synchronized.
*/
open class WeakCache<Key : Any, ExtraKey : Any, Value : Any>(val name: String) {
private val queue = object : ReferenceQueue<Key>() {}
private val map = mutableMapOf<Ref, Value>()
val size: Int
get() {
clearOldReferences()
return map.size
}
fun clearOldReferences() {
var successCount = 0
var totalCount = 0
while (true) {
val reference = queue.poll() as WeakCache<*, *, *>.Ref? ?: break
totalCount++
if (reference.shouldBeEvicted() && map.remove(reference) != null)
successCount++
}
if (totalCount > 0)
logger.log("Cleared $successCount/$totalCount references from queue")
}
open fun mkRef(key: Key, extraData: ExtraKey): Ref {
return Ref(key, extraData)
}
fun get(key: Key, extraData: ExtraKey): Value? {
clearOldReferences()
return map[mkRef(key, extraData)]
}
fun put(key: Key, extraData: ExtraKey, value: Value) {
clearOldReferences()
map[mkRef(key, extraData)] = value
}
fun getOrPut(key: Key, extraData: ExtraKey, value: (Key, ExtraKey) -> Value): Value {
clearOldReferences()
return map.getOrPut(mkRef(key, extraData)) { value(key, extraData) }
}
fun clear() {
map.clear()
}
init {
allInstances.add(this)
}
companion object {
val allInstances = InstanceList<WeakCache<*, *, *>>("WeakCaches")
private val logger = DebugLogger("WeakCache")
fun <Key : Any, Value : Any> memoize(name: String, function: (Key) -> Value):
CacheFunction.NoExtraData<Key, Value> {
return CacheFunction.NoExtraData(WeakCache(name), function)
}
fun <Key : Any, ExtraKey : Any, Value : Any> dontMemoize(name: String, function: (Key, ExtraKey) -> Value) = function
fun <Key : Any, ExtraKey : Any, Value : Any> memoize(name: String, function: (Key, ExtraKey) -> Value):
CacheFunction.WithExtraData<Key, ExtraKey, Value> {
return CacheFunction.WithExtraData(WeakCache(name), function)
}
}
open inner class Ref(
weakInstance: Key,
val extraData: ExtraKey,
) : WeakReference<Key>(weakInstance, queue) {
open fun shouldBeEvicted() = true
val hashCode = System.identityHashCode(weakInstance) * 31 + extraData.hashCode()
override fun equals(other: Any?): Boolean {
if (other !is WeakCache<*, *, *>.Ref) return false
return other.hashCode == this.hashCode
&& other.get() === this.get()
&& other.extraData == this.extraData
}
override fun hashCode(): Int {
return hashCode
}
}
interface CacheFunction {
val cache: WeakCache<*, *, *>
data class NoExtraData<Key : Any, Value : Any>(
override val cache: WeakCache<Key, Unit, Value>,
val wrapped: (Key) -> Value,
) : CacheFunction, (Key) -> Value {
override fun invoke(p1: Key): Value {
return cache.getOrPut(p1, Unit, { a, _ -> wrapped(a) })
}
}
data class WithExtraData<Key : Any, ExtraKey : Any, Value : Any>(
override val cache: WeakCache<Key, ExtraKey, Value>,
val wrapped: (Key, ExtraKey) -> Value,
) : CacheFunction, (Key, ExtraKey) -> Value {
override fun invoke(p1: Key, p2: ExtraKey): Value {
return cache.getOrPut(p1, p2, wrapped)
}
}
}
}
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