| /** |
| * 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.apex.malhar.lib.state.spillable; |
| |
| import java.util.Set; |
| |
| import org.apache.hadoop.classification.InterfaceStability; |
| |
| import com.google.common.base.Preconditions; |
| import com.google.common.collect.Sets; |
| |
| /** |
| * This is an id generator that generates single byte ids for Spillable datastructures. |
| * |
| * @since 3.5.0 |
| */ |
| @InterfaceStability.Evolving |
| public class SequentialSpillableIdentifierGenerator implements SpillableIdentifierGenerator |
| { |
| private boolean nextCalled = false; |
| private boolean done = false; |
| private byte currentIdentifier = 0; |
| |
| private Set<Byte> registeredIdentifier = Sets.newHashSet(); |
| |
| @Override |
| public byte[] next() |
| { |
| Preconditions.checkState(!done); |
| |
| nextCalled = true; |
| |
| byte nextIndentifier = currentIdentifier; |
| seek(); |
| |
| return new byte[]{nextIndentifier}; |
| } |
| |
| @Override |
| public void register(byte[] identifierArray) |
| { |
| Preconditions.checkState(!nextCalled); |
| Preconditions.checkState(!done); |
| Preconditions.checkArgument(identifierArray.length == 1); |
| |
| byte identifier = identifierArray[0]; |
| |
| Preconditions.checkState(identifier >= currentIdentifier && |
| !registeredIdentifier.contains(identifier)); |
| |
| registeredIdentifier.add(identifier); |
| |
| if (currentIdentifier == identifier) { |
| seek(); |
| } |
| } |
| |
| private void seek() |
| { |
| if (currentIdentifier == Byte.MAX_VALUE) { |
| done = true; |
| } else { |
| do { |
| currentIdentifier++; |
| } while (registeredIdentifier.contains(currentIdentifier) && currentIdentifier < Byte.MAX_VALUE); |
| |
| done = currentIdentifier == Byte.MAX_VALUE && registeredIdentifier.contains(currentIdentifier); |
| } |
| } |
| } |