| /* |
| * 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.tinkerpop.gremlin.process.traversal.step.filter; |
| |
| import org.apache.tinkerpop.gremlin.process.computer.MemoryComputeKey; |
| import org.apache.tinkerpop.gremlin.process.traversal.Traversal; |
| import org.apache.tinkerpop.gremlin.process.traversal.Traverser; |
| import org.apache.tinkerpop.gremlin.process.traversal.step.Barrier; |
| import org.apache.tinkerpop.gremlin.process.traversal.step.Bypassing; |
| import org.apache.tinkerpop.gremlin.process.traversal.step.util.AbstractStep; |
| import org.apache.tinkerpop.gremlin.process.traversal.traverser.TraverserRequirement; |
| import org.apache.tinkerpop.gremlin.process.traversal.traverser.util.TraverserSet; |
| import org.apache.tinkerpop.gremlin.process.traversal.util.FastNoSuchElementException; |
| import org.apache.tinkerpop.gremlin.structure.util.StringFactory; |
| import org.apache.tinkerpop.gremlin.util.iterator.IteratorUtils; |
| |
| import java.util.ArrayDeque; |
| import java.util.Collections; |
| import java.util.Deque; |
| import java.util.NoSuchElementException; |
| import java.util.Set; |
| |
| /** |
| * @author Matt Frantz (http://github.com/mhfrantz) |
| */ |
| public final class TailGlobalStep<S> extends AbstractStep<S, S> implements Bypassing, Barrier<TraverserSet<S>> { |
| |
| private final long limit; |
| private Deque<Traverser.Admin<S>> tail; |
| private long tailBulk = 0L; |
| private boolean bypass = false; |
| |
| public TailGlobalStep(final Traversal.Admin traversal, final long limit) { |
| super(traversal); |
| this.limit = limit; |
| this.tail = new ArrayDeque<>((int) limit); |
| } |
| |
| public void setBypass(final boolean bypass) { |
| this.bypass = bypass; |
| } |
| |
| @Override |
| public Traverser.Admin<S> processNextStart() { |
| if (this.bypass) { |
| // If we are bypassing this step, let everything through. |
| return this.starts.next(); |
| } else { |
| // Pull everything available before we start delivering from the tail buffer. |
| if (this.starts.hasNext()) { |
| this.starts.forEachRemaining(this::addTail); |
| } |
| // Pull the oldest traverser from the tail buffer. |
| final Traverser.Admin<S> oldest = this.tail.pop(); |
| // Trim any excess from the oldest traverser. |
| final long excess = this.tailBulk - this.limit; |
| if (excess > 0) |
| oldest.setBulk(oldest.bulk() - excess); |
| // Account for the loss of bulk in the tail buffer as we emit the oldest traverser. |
| this.tailBulk -= oldest.bulk(); |
| return oldest; |
| } |
| } |
| |
| @Override |
| public void reset() { |
| super.reset(); |
| this.tail.clear(); |
| this.tailBulk = 0L; |
| } |
| |
| @Override |
| public String toString() { |
| return StringFactory.stepString(this, this.limit); |
| } |
| |
| @Override |
| public TailGlobalStep<S> clone() { |
| final TailGlobalStep<S> clone = (TailGlobalStep<S>) super.clone(); |
| clone.tail = new ArrayDeque<>((int) this.limit); |
| clone.tailBulk = 0L; |
| return clone; |
| } |
| |
| @Override |
| public int hashCode() { |
| return super.hashCode() ^ Long.hashCode(this.limit); |
| } |
| |
| @Override |
| public Set<TraverserRequirement> getRequirements() { |
| return Collections.singleton(TraverserRequirement.BULK); |
| } |
| |
| private void addTail(Traverser.Admin<S> start) { |
| // Calculate the tail bulk including this new start. |
| this.tailBulk += start.bulk(); |
| // Evict from the tail buffer until we have enough room. |
| while (!this.tail.isEmpty()) { |
| final Traverser.Admin<S> oldest = this.tail.getFirst(); |
| final long bulk = oldest.bulk(); |
| if (this.tailBulk - bulk < limit) |
| break; |
| this.tail.pop(); |
| this.tailBulk -= bulk; |
| } |
| this.tail.add(start); |
| } |
| |
| |
| @Override |
| public MemoryComputeKey<TraverserSet<S>> getMemoryComputeKey() { |
| return MemoryComputeKey.of(this.getId(), new RangeGlobalStep.RangeBiOperator<>(this.limit), false, true); |
| } |
| |
| @Override |
| public void processAllStarts() { |
| |
| } |
| |
| @Override |
| public boolean hasNextBarrier() { |
| return this.starts.hasNext(); |
| } |
| |
| @Override |
| public TraverserSet<S> nextBarrier() throws NoSuchElementException { |
| if (!this.starts.hasNext()) |
| throw FastNoSuchElementException.instance(); |
| final TraverserSet<S> barrier = new TraverserSet<>(); |
| while (this.starts.hasNext()) { |
| barrier.add(this.starts.next()); |
| } |
| return barrier; |
| } |
| |
| @Override |
| public void addBarrier(final TraverserSet<S> barrier) { |
| IteratorUtils.removeOnNext(barrier.iterator()).forEachRemaining(traverser -> { |
| traverser.setSideEffects(this.getTraversal().getSideEffects()); |
| this.addStart(traverser); |
| }); |
| } |
| } |