skikoMain.androidx.compose.ui.text.Cache.skiko.kt Maven / Gradle / Ivy

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/*
 * Copyright 2023 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.compose.ui.text

import org.jetbrains.skiko.currentNanoTime

// Extremely simple Cache interface which is enough for ui.text needs
internal interface Cache {
    // get a value for [key] or load it by [loader] if it doesn't exist
    fun get(key: K, loader: (K) -> V): V
}

/**
 * Cache with weak keys.
 */
internal expect class WeakKeysCache() : Cache

/**
 * Cache with expiring entries after `expireAfter` after last access.
 */
internal class ExpireAfterAccessCache(
    val expireAfterNanos: Long,
    val currentNanos: () -> Long = ::currentNanoTime
) : Cache {
    internal val map = HashMap()
    internal val accessTime = LinkedHashMap()

    override fun get(key: K, loader: (K) -> V): V {
        accessTime.remove(key)
        return map.getOrPut(key) {
            loader(key)
        }.also {
            val now = currentNanos()
            accessTime[key] = now
            checkEvicted(now)
        }
    }

    private fun checkEvicted(now: Long) {
        val expireTime = now - expireAfterNanos
        accessTime.keys.takeWhile {
            accessTime[it]!! < expireTime
        }.forEach {
            map.remove(it)
            accessTime.remove(it)
        }
    }
}