com.google.devtools.build.lib.skyframe.serialization.ImmutableMapCodec.java Source code

Introduction

Here is the source code for com.google.devtools.build.lib.skyframe.serialization.ImmutableMapCodec.java

Source

// 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.ImmutableMap;
import com.google.common.collect.ImmutableSortedMap;
import com.google.common.collect.Ordering;
import com.google.protobuf.CodedInputStream;
import com.google.protobuf.CodedOutputStream;
import java.io.IOException;
import java.util.Comparator;
import java.util.Map;

/**
 * Encodes an {@link ImmutableMap}, which may be an {@link ImmutableSortedMap}. The iteration order
 * of the deserialized map is the same as the original map's.
 *
 * <p>We handle both {@link ImmutableMap} and {@link ImmutableSortedMap} here because we cannot
 * handle {@link ImmutableSortedMap} with any ordering other than the default, and so we degrade to
 * ImmutableMap in that case, hoping that the caller does not notice. Since the ordering is
 * preserved, the caller should not be sensitive to this change unless the caller's field is
 * declared to be an {@link ImmutableSortedMap}, in which case we will crash at runtime.
 *
 * <p>Any {@link SerializationException} or {@link IOException} that arises while serializing or
 * deserializing a map entry's value (not its key) will be wrapped in a new {@link
 * SerializationException} using {@link SerializationException#propagate}. (Note that this preserves
 * the type of {@link SerializationException.NoCodecException} exceptions.) The message will include
 * the {@code toString()} of the entry's key. For errors that occur while serializing, it will also
 * include the class name of the entry's value. Errors that occur while serializing an entry key are
 * not affected.
 *
 * <p>Because of the ambiguity around the key type (Comparable in the case of {@link
 * ImmutableSortedMap}, arbitrary otherwise, we avoid specifying the key type as a parameter.
 */
class ImmutableMapCodec<V> implements ObjectCodec<ImmutableMap<?, V>> {
    @SuppressWarnings("unchecked")
    @Override
    public Class<ImmutableMap<?, V>> getEncodedClass() {
        // Because Java disallows converting from Class<ImmutableMap> to Class<ImmutableMap<?, ?>>
        // directly.
        return (Class<ImmutableMap<?, V>>) ((Class<?>) ImmutableMap.class);
    }

    @Override
    public void serialize(SerializationContext context, ImmutableMap<?, V> map, CodedOutputStream codedOut)
            throws SerializationException, IOException {
        codedOut.writeInt32NoTag(map.size());
        boolean serializeAsSortedMap = false;
        if (map instanceof ImmutableSortedMap) {
            Comparator<?> comparator = ((ImmutableSortedMap<?, ?>) map).comparator();
            // In practice the comparator seems to always be Ordering.natural(), but be flexible.
            serializeAsSortedMap = comparator.equals(Ordering.natural())
                    || comparator.equals(Comparator.naturalOrder());
        }
        codedOut.writeBoolNoTag(serializeAsSortedMap);
        for (Map.Entry<?, ?> entry : map.entrySet()) {
            context.serialize(entry.getKey(), codedOut);
            try {
                context.serialize(entry.getValue(), codedOut);
            } catch (SerializationException | IOException e) {
                throw SerializationException
                        .propagate(String.format("Exception while serializing value of type %s for key '%s'",
                                entry.getValue().getClass().getName(), entry.getKey()), e);
            }
        }
    }

    @Override
    public ImmutableMap<?, V> deserialize(DeserializationContext context, CodedInputStream codedIn)
            throws SerializationException, IOException {
        int length = codedIn.readInt32();
        if (length < 0) {
            throw new SerializationException("Expected non-negative length: " + length);
        }
        if (codedIn.readBool()) {
            return buildMap(ImmutableSortedMap.naturalOrder(), length, context, codedIn);
        } else {
            return buildMap(ImmutableMap.builderWithExpectedSize(length), length, context, codedIn);
        }
    }

    private static <K, V> ImmutableMap<K, V> buildMap(ImmutableMap.Builder<K, V> builder, int length,
            DeserializationContext context, CodedInputStream codedIn) throws IOException, SerializationException {
        for (int i = 0; i < length; i++) {
            K key = context.deserialize(codedIn);
            V value;
            try {
                value = context.deserialize(codedIn);
            } catch (SerializationException | IOException e) {
                throw SerializationException
                        .propagate(String.format("Exception while deserializing value for key '%s'", key), e);
            }
            builder.put(key, value);
        }
        try {
            return builder.build();
        } catch (IllegalArgumentException e) {
            throw new SerializationException("Duplicate keys during ImmutableMapCodec deserialization", e);
        }
    }
}