| // 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.base.Preconditions; |
| import com.google.protobuf.CodedInputStream; |
| import com.google.protobuf.CodedOutputStream; |
| import java.io.IOException; |
| import java.nio.ByteBuffer; |
| import java.nio.charset.StandardCharsets; |
| import java.util.Arrays; |
| |
| /** |
| * Specialized {@link ObjectCodec} for storing singleton values. Values serialize to a supplied |
| * representation, which is useful for debugging and is used to verify the serialized representation |
| * during deserialization. |
| */ |
| public class SingletonCodec<T> implements ObjectCodec<T> { |
| |
| /** |
| * Create instance wrapping the singleton {@code value}. Will serialize to the byte array |
| * representation of {@code mnemonic}. On deserialization if {@code mnemonic} matches the |
| * serialized data then {@code value} is returned. |
| */ |
| public static <T> SingletonCodec<T> of(T value, String mnemonic) { |
| return new SingletonCodec<T>(value, mnemonic); |
| } |
| |
| private final T value; |
| private final byte[] mnemonic; |
| |
| private SingletonCodec(T value, String mnemonic) { |
| this.value = Preconditions.checkNotNull(value, "SingletonCodec cannot represent null"); |
| this.mnemonic = mnemonic.getBytes(StandardCharsets.UTF_8); |
| } |
| |
| @SuppressWarnings("unchecked") |
| @Override |
| public Class<T> getEncodedClass() { |
| return (Class<T>) value.getClass(); |
| } |
| |
| @Override |
| public void serialize(SerializationContext context, T t, CodedOutputStream codedOut) |
| throws IOException { |
| // TODO(michajlo): See how usefully mnemonic actually winds up being for debugging, we may |
| // want to just toss it and trust that the classifier for this value is good enough. |
| codedOut.writeByteArrayNoTag(mnemonic); |
| } |
| |
| @Override |
| public T deserialize(DeserializationContext context, CodedInputStream codedIn) |
| throws SerializationException, IOException { |
| // Get ByteBuffer instead of raw bytes, as it may be a direct view of the data and not a copy, |
| // which is much more efficient. |
| ByteBuffer readMnemonic = codedIn.readByteBuffer(); |
| if (!bytesEqual(mnemonic, readMnemonic)) { |
| throw new SerializationException( |
| "Failed to decode singleton " + value + " expected " + Arrays.toString(mnemonic)); |
| } |
| return value; |
| } |
| |
| private static boolean bytesEqual(byte[] expected, ByteBuffer buffer) { |
| if (buffer.remaining() != expected.length) { |
| return false; |
| } |
| |
| for (int i = 0; i < expected.length; i++) { |
| if (expected[i] != buffer.get(i)) { |
| return false; |
| } |
| } |
| |
| return true; |
| } |
| } |
| |