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// Copyright 2017 Yahoo Holdings. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
package com.yahoo.jdisc.handler;
import com.google.common.util.concurrent.Futures;
import com.google.common.util.concurrent.JdkFutureAdapters;
import com.google.common.util.concurrent.ListenableFuture;
import java.util.LinkedList;
import java.util.List;
import java.util.concurrent.*;
/**
* <p>This class implements a Future<Boolean> that is conjunction of zero or more other Future<Boolean>s,
* i.e. it evaluates to <tt>true</tt> if, and only if, all its operands evaluate to <tt>true</tt>. To use this class,
* simply create an instance of it and add operands to it using the {@link #addOperand(ListenableFuture)} method.</p>
* TODO: consider rewriting usage of FutureConjunction to use CompletableFuture instead.
*
* @author Simon Thoresen Hult
*/
public final class FutureConjunction implements ListenableFuture<Boolean> {
private final List<ListenableFuture<Boolean>> operands = new LinkedList<>();
/**
* <p>Adds a ListenableFuture<Boolean> to this conjunction. This can be called at any time, even after having called
* {@link #get()} previously.</p>
*
* @param operand The operand to add to this conjunction.
*/
public void addOperand(ListenableFuture<Boolean> operand) {
operands.add(operand);
}
@Override
public void addListener(Runnable listener, Executor executor) {
Futures.allAsList(operands).addListener(listener, executor);
}
@Override
public final boolean cancel(boolean mayInterruptIfRunning) {
boolean ret = true;
for (Future<Boolean> op : operands) {
if (!op.cancel(mayInterruptIfRunning)) {
ret = false;
}
}
return ret;
}
@Override
public final boolean isCancelled() {
for (Future<Boolean> op : operands) {
if (!op.isCancelled()) {
return false;
}
}
return true;
}
@Override
public final boolean isDone() {
for (Future<Boolean> op : operands) {
if (!op.isDone()) {
return false;
}
}
return true;
}
@Override
public final Boolean get() throws InterruptedException, ExecutionException {
Boolean ret = Boolean.TRUE;
for (Future<Boolean> op : operands) {
if (!op.get()) {
ret = Boolean.FALSE;
}
}
return ret;
}
@Override
public final Boolean get(long timeout, TimeUnit unit) throws InterruptedException, ExecutionException,
TimeoutException {
Boolean ret = Boolean.TRUE;
long nanos = unit.toNanos(timeout);
long lastTime = System.nanoTime();
for (Future<Boolean> op : operands) {
if (!op.get(nanos, TimeUnit.NANOSECONDS)) {
ret = Boolean.FALSE;
}
long now = System.nanoTime();
nanos -= now - lastTime;
lastTime = now;
}
return ret;
}
}
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