org.apache.giraph.block_app.framework.block.RepeatUntilBlock.java Source code

Introduction

Here is the source code for org.apache.giraph.block_app.framework.block.RepeatUntilBlock.java

Source

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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 org.apache.giraph.block_app.framework.block;

import java.util.Collections;
import java.util.Iterator;

import org.apache.giraph.block_app.framework.piece.AbstractPiece;
import org.apache.giraph.function.Consumer;
import org.apache.giraph.function.Supplier;

import com.google.common.collect.AbstractIterator;
import com.google.common.collect.Iterables;

/**
 * Block that repeats another block until toQuit supplier returns true,
 * but at most given number of times.
 *
 * If toQuit returns true on first run, block is not going
 * to be executed at all.
 */
@SuppressWarnings("rawtypes")
public final class RepeatUntilBlock implements Block {
    private final Block block;
    private final int repeatTimes;
    private final Supplier<Boolean> toQuit;

    public RepeatUntilBlock(int repeatTimes, Block block, Supplier<Boolean> toQuit) {
        this.block = block;
        this.repeatTimes = repeatTimes;
        this.toQuit = toQuit;
    }

    /**
     * Repeat unlimited number of times, until toQuit supplier returns true.
     */
    public static Block unlimited(Block block, Supplier<Boolean> toQuit) {
        return new RepeatUntilBlock(Integer.MAX_VALUE, block, toQuit);
    }

    @Override
    public Iterator<AbstractPiece> iterator() {
        // nCopies uses constant memory, creating a looped list with single element
        final Iterator<AbstractPiece> repeatIterator = Iterables.concat(Collections.nCopies(repeatTimes, block))
                .iterator();
        return new AbstractIterator<AbstractPiece>() {
            @Override
            protected AbstractPiece computeNext() {
                if (Boolean.TRUE.equals(toQuit.get()) || !repeatIterator.hasNext()) {
                    return endOfData();
                }

                return repeatIterator.next();
            }
        };
    }

    @Override
    public void forAllPossiblePieces(Consumer<AbstractPiece> consumer) {
        block.forAllPossiblePieces(consumer);
    }

    @Override
    public String toString() {
        return "RepeatUntilBlock(" + repeatTimes + " * " + block + ")";
    }
}