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// 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} (intented 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;
}
}
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