001/**
002 * The MIT License (MIT)
003 *
004 * Copyright (c) 2019 nobark (tools4j), Marco Terzer, Anton Anufriev
005 *
006 * Permission is hereby granted, free of charge, to any person obtaining a copy
007 * of this software and associated documentation files (the "Software"), to deal
008 * in the Software without restriction, including without limitation the rights
009 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
010 * copies of the Software, and to permit persons to whom the Software is
011 * furnished to do so, subject to the following conditions:
012 *
013 * The above copyright notice and this permission notice shall be included in all
014 * copies or substantial portions of the Software.
015 *
016 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
017 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
018 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
019 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
020 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
021 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
022 * SOFTWARE.
023 */
024package org.tools4j.nobark.loop;
025
026/**
027 * Handler to define strategy in idle loops when no work is performed.  Some applications may want to busy spin in a
028 * loop, others prefer to back off and release the CPU core to perform more useful work.
029 */
030@FunctionalInterface
031public interface IdleStrategy {
032
033    /** Invoked if no work was done */
034    void idle();
035
036    /**
037     * Invoked with boolean flag indicating whether work was done or not.  Delegates to {@link #reset()} when work was
038     * done and to {@link #idle()} if not.
039     *
040     * @param  workDone true if some work was performed
041     */
042    default void idle(final boolean workDone) {
043        if (workDone) {
044            reset();
045        } else {
046            idle();
047        }
048    }
049
050    /** Invoked if some work was performed and an idle strategy should reset to prepare for the next idle phase */
051    default void reset() {}
052
053    /**
054     * Idle strategy that performs a no-OP, that is, an idle loop will essentially become a busy-spin loop.
055     */
056    IdleStrategy NO_OP = new IdleStrategy() {
057        @Override
058        public void idle() {
059            //no op
060        }
061
062        @Override
063        public void idle(final boolean workDone) {
064            //no op
065        }
066    };
067}