oshi.util.Memoizer Maven / Gradle / Ivy
/**
* MIT License
*
* Copyright (c) 2010 - 2020 The OSHI Project Contributors: https://github.com/oshi/oshi/graphs/contributors
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in all
* copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
* SOFTWARE.
*/
package oshi.util;
import java.util.concurrent.TimeUnit;
import java.util.function.Supplier;
import oshi.annotation.concurrent.ThreadSafe;
/**
* A memoized function stores the output corresponding to some set of specific
* inputs. Subsequent calls with remembered inputs return the remembered result
* rather than recalculating it.
*/
@ThreadSafe
public final class Memoizer {
private static final Supplier defaultExpirationNanos = memoize(Memoizer::queryExpirationConfig,
TimeUnit.MINUTES.toNanos(1));
private Memoizer() {
}
private static long queryExpirationConfig() {
return TimeUnit.MILLISECONDS.toNanos(GlobalConfig.get("oshi.util.memoizer.expiration", 300));
}
/**
* Default exipiration of memoized values in nanoseconds, which will refresh
* after this time elapses. Update by setting {@link GlobalConfig} property
* oshi.util.memoizer.expiration to a value in milliseconds.
*
* @return The number of nanoseconds to keep memoized values before refreshing
*/
public static long defaultExpiration() {
return defaultExpirationNanos.get();
}
/**
* Store a supplier in a delegate function to be computed once, and only again
* after time to live (ttl) has expired.
*
* @param
* The type of object supplied
* @param original
* The {@link java.util.function.Supplier} to memoize
* @param ttlNanos
* Time in nanoseconds to retain calculation. If negative, retain
* indefinitely.
* @return A memoized version of the supplier
*/
public static Supplier memoize(Supplier original, long ttlNanos) {
// Adapted from Guava's ExpiringMemoizingSupplier
return new Supplier() {
final Supplier delegate = original;
volatile T value; // NOSONAR squid:S3077
volatile long expirationNanos;
@Override
public T get() {
long nanos = expirationNanos;
long now = System.nanoTime();
if (nanos == 0 || (ttlNanos >= 0 && now - nanos >= 0)) {
synchronized (this) {
if (nanos == expirationNanos) { // recheck for lost race
T t = delegate.get();
value = t;
nanos = now + ttlNanos;
expirationNanos = (nanos == 0) ? 1 : nanos;
return t;
}
}
}
return value;
}
};
}
/**
* Store a supplier in a delegate function to be computed only once.
*
* @param
* The type of object supplied
* @param original
* The {@link java.util.function.Supplier} to memoize
* @return A memoized version of the supplier
*/
public static Supplier memoize(Supplier original) {
return memoize(original, -1L);
}
}