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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.devtools.build.lib.skyframe.serialization.strings.StringCodecs;
import com.google.protobuf.CodedInputStream;
import com.google.protobuf.CodedOutputStream;
import java.io.IOException;
import java.lang.reflect.Field;
import java.util.Optional;
import javax.annotation.Nullable;
/** Helper methods for polymorphic codecs using reflection. */
public class PolymorphicHelper {
private PolymorphicHelper() {}
/**
* Serializes a polymorphic type.
*
* @param dependency if null, it means that the parent, polymorphic type, provides no dependency.
* It is valid for dependency to be non-null, with an enclosed null value. This means that
* dependency itself is null (as opposed to non-existent).
*/
@SuppressWarnings("unchecked")
public static void serialize(
Object input, CodedOutputStream codedOut, @Nullable Optional<?> dependency)
throws IOException, SerializationException {
if (input != null) {
Class<?> clazz = input.getClass();
try {
Object codec = getCodec(clazz);
codedOut.writeBoolNoTag(true);
StringCodecs.asciiOptimized().serialize(clazz.getName(), codedOut);
if (codec instanceof ObjectCodec) {
((ObjectCodec) codec).serialize(input, codedOut);
} else if (codec instanceof InjectingObjectCodec) {
if (dependency == null) {
throw new SerializationException(
clazz.getCanonicalName() + " serialize parent class lacks required dependency.");
}
((InjectingObjectCodec) codec).serialize(dependency.orElse(null), input, codedOut);
} else {
throw new SerializationException(
clazz.getCanonicalName()
+ ".CODEC has unexpected type "
+ codec.getClass().getCanonicalName());
}
} catch (ReflectiveOperationException e) {
throw new SerializationException(input.getClass().getName(), e);
}
} else {
codedOut.writeBoolNoTag(false);
}
}
/**
* Deserializes a polymorphic type.
*
* @param dependency if null, it means that the parent, polymorphic type, provides no dependency.
* It is valid for dependency to be non-null, with an enclosed null value. This means the
* dependency itself is null (as opposed to non-existent).
*/
@SuppressWarnings("unchecked")
public static Object deserialize(CodedInputStream codedIn, @Nullable Optional<?> dependency)
throws IOException, SerializationException {
Object deserialized = null;
if (codedIn.readBool()) {
String className = StringCodecs.asciiOptimized().deserialize(codedIn);
try {
Object codec = getCodec(Class.forName(className));
if (codec instanceof ObjectCodec) {
return ((ObjectCodec) codec).deserialize(codedIn);
} else if (codec instanceof InjectingObjectCodec) {
if (dependency == null) {
throw new SerializationException(
className + " deserialize parent class lacks required dependency.");
}
return ((InjectingObjectCodec) codec).deserialize(dependency.orElse(null), codedIn);
} else {
throw new SerializationException(
className + ".CODEC has unexpected type " + codec.getClass().getCanonicalName());
}
} catch (ReflectiveOperationException e) {
throw new SerializationException(className, e);
}
}
return deserialized;
}
/** Returns the static CODEC instance for {@code clazz}. */
private static Object getCodec(Class<?> clazz)
throws NoSuchFieldException, IllegalAccessException {
Field codecField = clazz.getDeclaredField("CODEC");
codecField.setAccessible(true);
return codecField.get(null);
}
}
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