XTypeElementStore.kt
/*
* Copyright 2020 The Android Open Source Project
*
* 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 androidx.room.compiler.processing.javac
import androidx.room.compiler.processing.XTypeElement
import java.lang.ref.WeakReference
/**
* Utility class to cache type element wrappers.
*/
internal class XTypeElementStore<BackingType, T : XTypeElement>(
private val findElement: (qName: String) -> BackingType?,
private val getQName: (BackingType) -> String?,
private val wrap: (type: BackingType) -> T
) {
// instead of something like a Guava cache, we use a map of weak references here because our
// main goal is avoiding to re-parse type elements as we go up & down in the hierarchy while
// not necessarily wanting to preserve type elements after we are done with them. Doing that
// could possibly hold a lot more information than we desire.
private val typeCache = mutableMapOf<String, WeakReference<T>>()
operator fun get(backingType: BackingType): T {
val qName = getQName(backingType)
@Suppress("FoldInitializerAndIfToElvis")
if (qName == null) {
// just wrap without caching, likely an error or local type in kotlin
return wrap(backingType)
}
typeCache[qName]?.get()?.let {
return it
}
val wrapped = wrap(backingType)
return cache(qName, wrapped)
}
operator fun get(qName: String): T? {
typeCache[qName]?.get()?.let {
return it
}
val result = findElement(qName)?.let(wrap) ?: return null
return cache(qName, result)
}
private fun cache(qName: String, element: T): T {
typeCache[qName] = WeakReference(element)
return element
}
internal fun clear() {
typeCache.clear()
}
}