/*
* 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 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.
*
* <p>This class assists the implementation of collection classes. Do not use
* this class to serialize collections that are defined elsewhere.
*
* @author Jared Levy
*/
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)}.
*
* <p>The returned count may be used to construct an empty collection of the
* appropriate capacity before calling any of the {@code populate} methods.
*/
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.
*
* <p>The serialized output consists of the number of entries, first key,
* first value, second key, second value, and so on.
*/
static <K, V> void writeMap(Map<K, V> map, ObjectOutputStream stream)
throws IOException {
stream.writeInt(map.size());
for (Map.Entry<K, V> 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 <K, V> void populateMap(Map<K, V> 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 <K, V> void populateMap(Map<K, V> 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.
*
* <p>The serialized output consists of the number of distinct elements, the
* first element, its count, the second element, its count, and so on.
*/
static <E> void writeMultiset(
Multiset<E> multiset, ObjectOutputStream stream) throws IOException {
int entryCount = multiset.entrySet().size();
stream.writeInt(entryCount);
for (Multiset.Entry<E> 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 <E> void populateMultiset(
Multiset<E> 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 <E> void populateMultiset(
Multiset<E> 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.
*
* <p>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 <K, V> void writeMultimap(
Multimap<K, V> multimap, ObjectOutputStream stream) throws IOException {
stream.writeInt(multimap.asMap().size());
for (Map.Entry<K, Collection<V>> 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 <K, V> void populateMultimap(
Multimap<K, V> 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 <K, V> void populateMultimap(
Multimap<K, V> 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<V> 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 <T> FieldSetter<T> getFieldSetter(
final Class<T> clazz, String fieldName) {
try {
Field field = clazz.getDeclaredField(fieldName);
return new FieldSetter<T>(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<T> {
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);
}
}
}
}