jvm.io.realm.kotlin.internal.interop.gc.NativeObjectReference.kt Maven / Gradle / Ivy
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Wrapper for interacting with Realm Kotlin native code. This artifact is not supposed to be consumed directly, but through 'io.realm.kotlin:gradle-plugin:1.13.0' instead.
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/*
* Copyright 2021 Realm Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package io.realm.kotlin.internal.interop.gc
import io.realm.kotlin.internal.interop.LongPointerWrapper
import io.realm.kotlin.internal.interop.realmc
import java.lang.ref.PhantomReference
import java.lang.ref.ReferenceQueue
/**
* This class is used for holding the reference to the native pointers present in NativeObjects.
* This is required as phantom references cannot access the original objects for this value.
* The phantom references will be stored in a double linked list to avoid the reference itself gets GCed. When the
* referent get GCed, the reference will be added to the ReferenceQueue. Loop in the daemon thread will retrieve the
* phantom reference from the ReferenceQueue then dealloc the referent and remove the reference from the double linked
* list. See [FinalizerRunnable] for more implementation details.
*/
internal class NativeObjectReference(
private val context: NativeContext,
referent: LongPointerWrapper<*>,
referenceQueue: ReferenceQueue>?
) :
PhantomReference>(referent, referenceQueue) {
private val isReleased = referent.released
private val ptr: Long = referent.ptr
private var prev: NativeObjectReference? = null
private var next: NativeObjectReference? = null
companion object {
private val referencePool = ReferencePool()
}
init {
referencePool.add(this)
}
/**
* To dealloc native resources.
*/
fun cleanup() {
synchronized(context) {
if (isReleased.compareAndSet(false, true)) {
realmc.realm_release(ptr)
}
}
// Remove the PhantomReference from the pool to free it.
referencePool.remove(this)
}
// Linked list to keep the reference of the PhantomReference
private class ReferencePool {
var head: NativeObjectReference? = null
@Synchronized
fun add(ref: NativeObjectReference) {
ref.prev = null
ref.next = head
if (head != null) {
head!!.prev = ref
}
head = ref
}
@Synchronized
fun remove(ref: NativeObjectReference) {
val next = ref.next
val prev = ref.prev
ref.next = null
ref.prev = null
if (prev != null) {
prev.next = next
} else {
head = next
}
if (next != null) {
next.prev = prev
}
}
}
}
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