/*
* Copyright 2016 Ben Manes. All Rights Reserved.
*
* 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 com.github.benmanes.caffeine.cache;
import java.lang.reflect.Field;
import com.google.common.base.Throwables;
/**
* A hook to enforce a predictable random seed is used by Caffeine's caches.
*
* @author ben.manes@gmail.com (Ben Manes)
*/
public final class RandomSeedEnforcer {
static final int RANDOM_SEED = 1033096058;
private RandomSeedEnforcer() {}
/** Force the random seed to a predictable value. */
public static void ensureRandomSeed(Cache<?, ?> cache) {
if (!(cache.asMap() instanceof BoundedLocalCache<?, ?>)) {
return;
}
BoundedLocalCache<?, ?> map = (BoundedLocalCache<?, ?>) cache.asMap();
if (map.evicts()) {
ensureRandomSeed(map.frequencySketch());
}
}
/** Force the random seed to a predictable value. */
public static void ensureRandomSeed(FrequencySketch<?> sketch) {
try {
Field field = FrequencySketch.class.getDeclaredField("randomSeed");
field.setAccessible(true);
field.setInt(sketch, RANDOM_SEED);
} catch (Exception e) {
Throwables.throwIfUnchecked(e);
throw new RuntimeException(e);
}
}
}