| // Copyright 2018 The Bazel Authors. All rights reserved. |
| // |
| // Licensed 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 com.google.devtools.build.lib.skyframe.serialization; |
| |
| import com.google.common.collect.ImmutableList; |
| import com.google.protobuf.CodedInputStream; |
| import com.google.protobuf.CodedOutputStream; |
| import java.io.IOException; |
| import java.util.AbstractList; |
| import java.util.ArrayList; |
| import java.util.Collections; |
| import java.util.LinkedList; |
| import java.util.List; |
| |
| /** |
| * Encodes a list of elements, each of which may be null. Unless explicitly specified as the codec, |
| * lists will only use this codec if they extend {@link AbstractList} or are one of {@link |
| * #RANDOM_ACCESS_TYPE} or {@link #SEQUENTIAL_ACCESS_TYPE} (intended to capture unmodifiable |
| * versions of normal lists). |
| */ |
| class NullableListCodec<T> implements ObjectCodec<List<T>> { |
| @SuppressWarnings("unchecked") |
| private static final Class<? extends List<?>> RANDOM_ACCESS_TYPE = |
| (Class<? extends List<?>>) Collections.unmodifiableList(new ArrayList<>()).getClass(); |
| // Need linked list to get sequential access class type. |
| @SuppressWarnings({"unchecked", "JdkObsolete"}) |
| private static final Class<? extends List<?>> SEQUENTIAL_ACCESS_TYPE = |
| (Class<? extends List<?>>) Collections.unmodifiableList(new LinkedList<>()).getClass(); |
| |
| // Needed due to generics / type erasure. |
| @SuppressWarnings("unchecked") |
| @Override |
| public Class<List<T>> getEncodedClass() { |
| // We return AbstractList here because List is an interface, so it will never be hit in the |
| // ancestor traversal of a concrete class. |
| return cast(AbstractList.class); |
| } |
| |
| @SuppressWarnings("unchecked") |
| @Override |
| public List<Class<? extends List<T>>> additionalEncodedClasses() { |
| return ImmutableList.of(cast(RANDOM_ACCESS_TYPE), cast(SEQUENTIAL_ACCESS_TYPE)); |
| } |
| |
| @Override |
| public void serialize(SerializationContext context, List<T> list, CodedOutputStream codedOut) |
| throws SerializationException, IOException { |
| codedOut.writeInt32NoTag(list.size()); |
| for (T item : list) { |
| context.serialize(item, codedOut); |
| } |
| } |
| |
| @Override |
| public List<T> deserialize(DeserializationContext context, CodedInputStream codedIn) |
| throws SerializationException, IOException { |
| int length = codedIn.readInt32(); |
| if (length < 0) { |
| throw new SerializationException("Expected non-negative length: " + length); |
| } |
| |
| ArrayList<T> list = new ArrayList<>(length); |
| for (int i = 0; i < length; i++) { |
| list.add(context.deserialize(codedIn)); |
| } |
| return maybeTransform(list); |
| } |
| |
| protected List<T> maybeTransform(ArrayList<T> startingList) { |
| return Collections.unmodifiableList(startingList); |
| } |
| |
| @SuppressWarnings({"unchecked", "rawtypes"}) // Raw List. |
| private Class<List<T>> cast(Class<? extends List> clazz) { |
| return (Class<List<T>>) clazz; |
| } |
| } |