com.google.common.collect.Serialization Maven / Gradle / Ivy
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/*
* Copyright (C) 2008 The Guava Authors
*
* 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.common.collect;
import com.google.common.annotations.GwtIncompatible;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.lang.reflect.Field;
import java.util.Collection;
import java.util.Map;
/**
* Provides static methods for serializing collection classes.
*
* This class assists the implementation of collection classes. Do not use this class to
* serialize collections that are defined elsewhere.
*
* @author Jared Levy
*/
@GwtIncompatible
final class Serialization {
private Serialization() {}
/**
* Reads a count corresponding to a serialized map, multiset, or multimap. It returns the size of
* a map serialized by {@link #writeMap(Map, ObjectOutputStream)}, the number of distinct elements
* in a multiset serialized by {@link #writeMultiset(Multiset, ObjectOutputStream)}, or the number
* of distinct keys in a multimap serialized by {@link #writeMultimap(Multimap,
* ObjectOutputStream)}.
*/
static int readCount(ObjectInputStream stream) throws IOException {
return stream.readInt();
}
/**
* Stores the contents of a map in an output stream, as part of serialization. It does not support
* concurrent maps whose content may change while the method is running.
*
*
The serialized output consists of the number of entries, first key, first value, second key,
* second value, and so on.
*/
static void writeMap(Map map, ObjectOutputStream stream) throws IOException {
stream.writeInt(map.size());
for (Map.Entry entry : map.entrySet()) {
stream.writeObject(entry.getKey());
stream.writeObject(entry.getValue());
}
}
/**
* Populates a map by reading an input stream, as part of deserialization. See {@link #writeMap}
* for the data format.
*/
static void populateMap(Map map, ObjectInputStream stream)
throws IOException, ClassNotFoundException {
int size = stream.readInt();
populateMap(map, stream, size);
}
/**
* Populates a map by reading an input stream, as part of deserialization. See {@link #writeMap}
* for the data format. The size is determined by a prior call to {@link #readCount}.
*/
static void populateMap(Map map, ObjectInputStream stream, int size)
throws IOException, ClassNotFoundException {
for (int i = 0; i < size; i++) {
@SuppressWarnings("unchecked") // reading data stored by writeMap
K key = (K) stream.readObject();
@SuppressWarnings("unchecked") // reading data stored by writeMap
V value = (V) stream.readObject();
map.put(key, value);
}
}
/**
* Stores the contents of a multiset in an output stream, as part of serialization. It does not
* support concurrent multisets whose content may change while the method is running.
*
* The serialized output consists of the number of distinct elements, the first element, its
* count, the second element, its count, and so on.
*/
static void writeMultiset(Multiset multiset, ObjectOutputStream stream)
throws IOException {
int entryCount = multiset.entrySet().size();
stream.writeInt(entryCount);
for (Multiset.Entry entry : multiset.entrySet()) {
stream.writeObject(entry.getElement());
stream.writeInt(entry.getCount());
}
}
/**
* Populates a multiset by reading an input stream, as part of deserialization. See {@link
* #writeMultiset} for the data format.
*/
static void populateMultiset(Multiset multiset, ObjectInputStream stream)
throws IOException, ClassNotFoundException {
int distinctElements = stream.readInt();
populateMultiset(multiset, stream, distinctElements);
}
/**
* Populates a multiset by reading an input stream, as part of deserialization. See {@link
* #writeMultiset} for the data format. The number of distinct elements is determined by a prior
* call to {@link #readCount}.
*/
static void populateMultiset(
Multiset multiset, ObjectInputStream stream, int distinctElements)
throws IOException, ClassNotFoundException {
for (int i = 0; i < distinctElements; i++) {
@SuppressWarnings("unchecked") // reading data stored by writeMultiset
E element = (E) stream.readObject();
int count = stream.readInt();
multiset.add(element, count);
}
}
/**
* Stores the contents of a multimap in an output stream, as part of serialization. It does not
* support concurrent multimaps whose content may change while the method is running. The {@link
* Multimap#asMap} view determines the ordering in which data is written to the stream.
*
* The serialized output consists of the number of distinct keys, and then for each distinct
* key: the key, the number of values for that key, and the key's values.
*/
static void writeMultimap(Multimap multimap, ObjectOutputStream stream)
throws IOException {
stream.writeInt(multimap.asMap().size());
for (Map.Entry> entry : multimap.asMap().entrySet()) {
stream.writeObject(entry.getKey());
stream.writeInt(entry.getValue().size());
for (V value : entry.getValue()) {
stream.writeObject(value);
}
}
}
/**
* Populates a multimap by reading an input stream, as part of deserialization. See {@link
* #writeMultimap} for the data format.
*/
static void populateMultimap(Multimap multimap, ObjectInputStream stream)
throws IOException, ClassNotFoundException {
int distinctKeys = stream.readInt();
populateMultimap(multimap, stream, distinctKeys);
}
/**
* Populates a multimap by reading an input stream, as part of deserialization. See {@link
* #writeMultimap} for the data format. The number of distinct keys is determined by a prior call
* to {@link #readCount}.
*/
static void populateMultimap(
Multimap multimap, ObjectInputStream stream, int distinctKeys)
throws IOException, ClassNotFoundException {
for (int i = 0; i < distinctKeys; i++) {
@SuppressWarnings("unchecked") // reading data stored by writeMultimap
K key = (K) stream.readObject();
Collection values = multimap.get(key);
int valueCount = stream.readInt();
for (int j = 0; j < valueCount; j++) {
@SuppressWarnings("unchecked") // reading data stored by writeMultimap
V value = (V) stream.readObject();
values.add(value);
}
}
}
// Secret sauce for setting final fields; don't make it public.
static FieldSetter getFieldSetter(final Class clazz, String fieldName) {
try {
Field field = clazz.getDeclaredField(fieldName);
return new FieldSetter(field);
} catch (NoSuchFieldException e) {
throw new AssertionError(e); // programmer error
}
}
// Secret sauce for setting final fields; don't make it public.
static final class FieldSetter {
private final Field field;
private FieldSetter(Field field) {
this.field = field;
field.setAccessible(true);
}
void set(T instance, Object value) {
try {
field.set(instance, value);
} catch (IllegalAccessException impossible) {
throw new AssertionError(impossible);
}
}
void set(T instance, int value) {
try {
field.set(instance, value);
} catch (IllegalAccessException impossible) {
throw new AssertionError(impossible);
}
}
}
}