/*
* Copyright 2017 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 javax.annotation.Nonnegative;
import javax.annotation.Nonnull;
import javax.annotation.concurrent.ThreadSafe;
/**
* Calculates when cache entries expire. A single expiration time is retained so that the lifetime
* of an entry may be extended or reduced by subsequent evaluations.
*
* @author ben.manes@gmail.com (Ben Manes)
*/
@ThreadSafe
public interface Expiry<K, V> {
/**
* Specifies that the entry should be automatically removed from the cache once the duration has
* elapsed after the entry's creation. To indicate no expiration an entry may be given an
* excessively long period, such as {@code Long#MAX_VALUE}.
* <p>
* <b>Note:</b> The {@code currentTime} is supplied by the configured {@link Ticker} and by
* default does not relate to system or wall-clock time. When calculating the duration based on a
* time stamp, the current time should be obtained independently.
*
* @param key the key represented by this entry
* @param value the value represented by this entry
* @param currentTime the current time, in nanoseconds
* @return the length of time before the entry expires, in nanoseconds
*/
long expireAfterCreate(@Nonnull K key, @Nonnull V value, long currentTime);
/**
* Specifies that the entry should be automatically removed from the cache once the duration has
* elapsed after the replacement of its value. To indicate no expiration an entry may be given an
* excessively long period, such as {@code Long#MAX_VALUE}. The {@code currentDuration} may be
* returned to not modify the expiration time.
* <p>
* <b>Note:</b> The {@code currentTime} is supplied by the configured {@link Ticker} and by
* default does not relate to system or wall-clock time. When calculating the duration based on a
* time stamp, the current time should be obtained independently.
*
* @param key the key represented by this entry
* @param value the value represented by this entry
* @param currentTime the current time, in nanoseconds
* @param currentDuration the current duration, in nanoseconds
* @return the length of time before the entry expires, in nanoseconds
*/
long expireAfterUpdate(@Nonnull K key, @Nonnull V value,
long currentTime, @Nonnegative long currentDuration);
/**
* Specifies that the entry should be automatically removed from the cache once the duration has
* elapsed after its last read. To indicate no expiration an entry may be given an excessively
* long period, such as {@code Long#MAX_VALUE}. The {@code currentDuration} may be returned to not
* modify the expiration time.
* <p>
* <b>Note:</b> The {@code currentTime} is supplied by the configured {@link Ticker} and by
* default does not relate to system or wall-clock time. When calculating the duration based on a
* time stamp, the current time should be obtained independently.
*
* @param key the key represented by this entry
* @param value the value represented by this entry
* @param currentTime the current time, in nanoseconds
* @param currentDuration the current duration, in nanoseconds
* @return the length of time before the entry expires, in nanoseconds
*/
long expireAfterRead(@Nonnull K key, @Nonnull V value,
long currentTime, @Nonnegative long currentDuration);
}