| /* |
| * 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.map; |
| |
| import org.apache.tinkerpop.gremlin.process.traversal.Traversal; |
| import org.apache.tinkerpop.gremlin.process.traversal.Traverser; |
| import org.apache.tinkerpop.gremlin.process.traversal.traverser.TraverserRequirement; |
| import org.apache.tinkerpop.gremlin.process.traversal.util.FastNoSuchElementException; |
| import org.apache.tinkerpop.gremlin.structure.util.StringFactory; |
| |
| import java.util.*; |
| |
| /** |
| * @author Daniel Kuppitz (http://gremlin.guru) |
| */ |
| public final class RangeLocalStep<S> extends MapStep<S, S> { |
| |
| private final long low; |
| private final long high; |
| |
| public RangeLocalStep(final Traversal.Admin traversal, final long low, final long high) { |
| super(traversal); |
| if (low != -1 && high != -1 && low > high) { |
| throw new IllegalArgumentException("Not a legal range: [" + low + ", " + high + ']'); |
| } |
| this.low = low; |
| this.high = high; |
| } |
| |
| @Override |
| protected S map(final Traverser.Admin<S> traverser) { |
| final S start = traverser.get(); |
| return applyRange(start, this.low, this.high); |
| } |
| |
| /** |
| * Extracts the specified range of elements from a collection. |
| * Return type depends on dynamic type of start. |
| * <ul> |
| * <li> |
| * Map becomes Map (order-preserving) |
| * </li> |
| * <li> |
| * Set becomes Set (order-preserving) |
| * </li> |
| * <li> |
| * Other Collection types become List |
| * </li> |
| * </ul> |
| */ |
| static <S> S applyRange(final S start, final long low, final long high) { |
| if (start instanceof Map) { |
| return (S) applyRangeMap((Map) start, low, high); |
| } else if (start instanceof Iterable) { |
| return (S) applyRangeIterable((Iterable) start, low, high); |
| } |
| return start; |
| } |
| |
| /** |
| * Extracts specified range of elements from a Map. |
| */ |
| private static Map applyRangeMap(final Map map, final long low, final long high) { |
| final long capacity = (high != -1 ? high : map.size()) - low; |
| final Map result = new LinkedHashMap((int) Math.min(capacity, map.size())); |
| long c = 0L; |
| for (final Object obj : map.entrySet()) { |
| final Map.Entry entry = (Map.Entry) obj; |
| if (c >= low) { |
| if (c < high || high == -1) { |
| result.put(entry.getKey(), entry.getValue()); |
| } else break; |
| } |
| c++; |
| } |
| return result; |
| } |
| |
| /** |
| * Extracts specified range of elements from a Collection. |
| */ |
| private static Object applyRangeIterable(final Iterable<Object> iterable, final long low, final long high) { |
| // See if we only want a single item. It is also possible that we will allow more than one item, but that the |
| // incoming container is only capable of producing a single item. In that case, we will still emit a |
| // container. This allows the result type to be predictable based on the step arguments. It also allows us to |
| // avoid creating the result container for the single case. |
| boolean single = high != -1 ? (high - low == 1) : false; |
| |
| final Collection resultCollection = |
| single ? null : (iterable instanceof Set) ? new LinkedHashSet() : new LinkedList(); |
| Object result = single ? null : resultCollection; |
| long c = 0L; |
| for (final Object item : iterable) { |
| if (c >= low) { |
| if (c < high || high == -1) { |
| if (single) { |
| result = item; |
| break; |
| } else { |
| resultCollection.add(item); |
| } |
| } else break; |
| } |
| c++; |
| } |
| if (null == result) |
| // We have nothing to emit, so stop traversal. |
| throw FastNoSuchElementException.instance(); |
| return result; |
| } |
| |
| @Override |
| public String toString() { |
| return StringFactory.stepString(this, this.low, this.high); |
| } |
| |
| @Override |
| public int hashCode() { |
| return super.hashCode() ^ Long.hashCode(this.high) ^ Long.hashCode(this.low); |
| } |
| |
| @Override |
| public Set<TraverserRequirement> getRequirements() { |
| return Collections.singleton(TraverserRequirement.OBJECT); |
| } |
| } |