net.sandius.rembulan.impl.SchedulingContexts Maven / Gradle / Ivy
/*
* Copyright 2016 Miroslav Janíček
*
* 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 net.sandius.rembulan.impl;
import net.sandius.rembulan.runtime.SchedulingContext;
import net.sandius.rembulan.runtime.SchedulingContextFactory;
import net.sandius.rembulan.util.Check;
/**
* Static factory for instantiating scheduling contexts.
*/
public final class SchedulingContexts {
private SchedulingContexts() {
// not to be instantiated
}
private static final SchedulingContext NEVER_INSTANCE = new NeverPausingSchedulingContext();
private static final SchedulingContext ALWAYS_INSTANCE = new AlwaysPausingSchedulingContext();
/**
* Returns a scheduling context that always returns {@code false} from
* {@link SchedulingContext#shouldPause()}, i.e., that never indicates
* that the caller should yield.
*
* @return a scheduling context that never indicates that the caller should yield
*/
public static SchedulingContext neverPause() {
return NEVER_INSTANCE;
}
/**
* Returns a scheduling context that always returns {@code true} from
* {@link SchedulingContext#shouldPause()}, i.e., that always indicates
* that the caller should yield.
*
* @return a scheduling context that always indicates that the caller should yield
*/
public static SchedulingContext alwaysPause() {
return ALWAYS_INSTANCE;
}
/**
* Returns a scheduling context with an internal tick counter (initialised to
* {@code max}).
*
* Every call to {@link SchedulingContext#registerTicks(int)} with a positive argument
* decreases the counter accordingly (calls with non-positive arguments are ignored).
* The scheduling context returns {@code true} from {@link SchedulingContext#shouldPause()}
* if and only if counter is lesser than or equal to 0.
*
* @param max the initial counter value, must be non-negative
* @return a scheduling context that starts indicating that the caller should yield
* once the counter is lesser than or equal to 0
*
* @throws IllegalArgumentException when {@code max} is negative
*/
public static SchedulingContext newCountDownContext(long max) {
return new CountDownSchedulingContext(max);
}
private static class NeverPausingSchedulingContext implements SchedulingContext {
@Override
public void registerTicks(int ticks) {
// no-op
}
@Override
public boolean shouldPause() {
return false;
}
}
private static class AlwaysPausingSchedulingContext implements SchedulingContext {
@Override
public void registerTicks(int ticks) {
// no-op
}
@Override
public boolean shouldPause() {
return true;
}
}
private static class CountDownSchedulingContext implements SchedulingContext {
private long allowance;
public CountDownSchedulingContext(long max) {
Check.nonNegative(max);
this.allowance = max;
}
@Override
public void registerTicks(int ticks) {
allowance -= Math.max(0, ticks);
}
@Override
public boolean shouldPause() {
return allowance <= 0;
}
}
private static final SchedulingContextFactory NEVER_FACTORY = new SchedulingContextFactory() {
@Override
public SchedulingContext newInstance() {
return neverPause();
}
};
private static final SchedulingContextFactory ALWAYS_FACTORY = new SchedulingContextFactory() {
@Override
public SchedulingContext newInstance() {
return alwaysPause();
}
};
/**
* Returns a scheduling context factory that always returns {@link #neverPause()}.
*
* @return a scheduling context factory for never-pausing scheduling contexts
*/
public static SchedulingContextFactory neverPauseFactory() {
return NEVER_FACTORY;
}
/**
* Returns a scheduling context factory that always returns {@link #alwaysPause()}.
*
* @return a scheduling context factory for always-pausing scheduling contexts
*/
public static SchedulingContextFactory alwaysPauseFactory() {
return ALWAYS_FACTORY;
}
/**
* Returns a scheduling context factory that always returns {@link #newCountDownContext(long)}
* with the argument {@code max}.
*
* @param max the initial counter value, must be non-negative
* @return a scheduling context factory that returns tick-capped scheduling contexts
*
* @throws IllegalArgumentException when {@code max} is negative
*/
public static SchedulingContextFactory countDownContextFactory(final long max) {
Check.nonNegative(max);
return new SchedulingContextFactory() {
@Override
public SchedulingContext newInstance() {
return newCountDownContext(max);
}
};
}
}