google/protobuf/MapFieldLite.java

// Protocol Buffers - Google's data interchange format
// Copyright 2008 Google Inc.  All rights reserved.
// https://developers.google.com/protocol-buffers/
//
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// modification, are permitted provided that the following conditions are
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//
//     * Redistributions of source code must retain the above copyright
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// in the documentation and/or other materials provided with the
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// contributors may be used to endorse or promote products derived from
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package com.google.protobuf;

import com.google.protobuf.Internal.EnumLite;

import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.Map;
import java.util.Set;

/**
 * Internal representation of map fields in generated lite-runtime messages.
 *
 * This class is a protobuf implementation detail. Users shouldn't use this
 * class directly.
 */
public final class MapFieldLite<K, V> implements MutabilityOracle {
  private MutatabilityAwareMap<K, V> mapData;
  private boolean isMutable;

  private MapFieldLite(Map<K, V> mapData) {
    this.mapData = new MutatabilityAwareMap<K, V>(this, mapData);
    this.isMutable = true;
  }

  @SuppressWarnings({"rawtypes", "unchecked"})
  private static final MapFieldLite EMPTY_MAP_FIELD =
      new MapFieldLite(Collections.emptyMap());
  static {
    EMPTY_MAP_FIELD.makeImmutable();
  }

  /** Returns an singleton immutable empty MapFieldLite instance. */
  @SuppressWarnings({"unchecked", "cast"})
  public static <K, V> MapFieldLite<K, V> emptyMapField() {
    return (MapFieldLite<K, V>) EMPTY_MAP_FIELD;
  }

  /** Creates a new MapFieldLite instance. */
  public static <K, V> MapFieldLite<K, V> newMapField() {
    return new MapFieldLite<K, V>(new LinkedHashMap<K, V>());
  }

  /** Gets the content of this MapField as a read-only Map. */
  public Map<K, V> getMap() {
    return Collections.unmodifiableMap(mapData);
  }

  /** Gets a mutable Map view of this MapField. */
  public Map<K, V> getMutableMap() {
    return mapData;
  }

  public void mergeFrom(MapFieldLite<K, V> other) {
    mapData.putAll(copy(other.mapData));
  }

  public void clear() {
    mapData.clear();
  }

  private static boolean equals(Object a, Object b) {
    if (a instanceof byte[] && b instanceof byte[]) {
      return Arrays.equals((byte[]) a, (byte[]) b);
    }
    return a.equals(b);
  }

  /**
   * Checks whether two {@link Map}s are equal. We don't use the default equals
   * method of {@link Map} because it compares by identity not by content for
   * byte arrays.
   */
  static <K, V> boolean equals(Map<K, V> a, Map<K, V> b) {
    if (a == b) {
      return true;
    }
    if (a.size() != b.size()) {
      return false;
    }
    for (Map.Entry<K, V> entry : a.entrySet()) {
      if (!b.containsKey(entry.getKey())) {
        return false;
      }
      if (!equals(entry.getValue(), b.get(entry.getKey()))) {
        return false;
      }
    }
    return true;
  }

  /**
   * Checks whether two map fields are equal.
   */
  @SuppressWarnings("unchecked")
  @Override
  public boolean equals(Object object) {
    if (!(object instanceof MapFieldLite)) {
      return false;
    }
    MapFieldLite<K, V> other = (MapFieldLite<K, V>) object;
    return equals(mapData, other.mapData);
  }

  private static int calculateHashCodeForObject(Object a) {
    if (a instanceof byte[]) {
      return Internal.hashCode((byte[]) a);
    }
    // Enums should be stored as integers internally.
    if (a instanceof EnumLite) {
      throw new UnsupportedOperationException();
    }
    return a.hashCode();
  }

  /**
   * Calculates the hash code for a {@link Map}. We don't use the default hash
   * code method of {@link Map} because for byte arrays and protobuf enums it
   * use {@link Object#hashCode()}.
   */
  static <K, V> int calculateHashCodeForMap(Map<K, V> a) {
    int result = 0;
    for (Map.Entry<K, V> entry : a.entrySet()) {
      result += calculateHashCodeForObject(entry.getKey())
          ^ calculateHashCodeForObject(entry.getValue());
    }
    return result;
  }

  @Override
  public int hashCode() {
    return calculateHashCodeForMap(mapData);
  }

  private static Object copy(Object object) {
    if (object instanceof byte[]) {
      byte[] data = (byte[]) object;
      return Arrays.copyOf(data, data.length);
    }
    return object;
  }

  /**
   * Makes a deep copy of a {@link Map}. Immutable objects in the map will be
   * shared (e.g., integers, strings, immutable messages) and mutable ones will
   * have a copy (e.g., byte arrays, mutable messages).
   */
  @SuppressWarnings("unchecked")
  static <K, V> Map<K, V> copy(Map<K, V> map) {
    Map<K, V> result = new LinkedHashMap<K, V>();
    for (Map.Entry<K, V> entry : map.entrySet()) {
      result.put(entry.getKey(), (V) copy(entry.getValue()));
    }
    return result;
  }

  /** Returns a deep copy of this map field. */
  public MapFieldLite<K, V> copy() {
    return new MapFieldLite<K, V>(copy(mapData));
  }

  /**
   * Makes this field immutable. All subsequent modifications will throw an
   * {@link UnsupportedOperationException}.
   */
  public void makeImmutable() {
    isMutable = false;
  }

  /**
   * Returns whether this field can be modified.
   */
  public boolean isMutable() {
    return isMutable;
  }

  @Override
  public void ensureMutable() {
    if (!isMutable()) {
      throw new UnsupportedOperationException();
    }
  }

  /**
   * An internal map that checks for mutability before delegating.
   */
  static class MutatabilityAwareMap<K, V> implements Map<K, V> {
    private final MutabilityOracle mutabilityOracle;
    private final Map<K, V> delegate;

    MutatabilityAwareMap(MutabilityOracle mutabilityOracle, Map<K, V> delegate) {
      this.mutabilityOracle = mutabilityOracle;
      this.delegate = delegate;
    }

    @Override
    public int size() {
      return delegate.size();
    }

    @Override
    public boolean isEmpty() {
      return delegate.isEmpty();
    }

    @Override
    public boolean containsKey(Object key) {
      return delegate.containsKey(key);
    }

    @Override
    public boolean containsValue(Object value) {
      return delegate.containsValue(value);
    }

    @Override
    public V get(Object key) {
      return delegate.get(key);
    }

    @Override
    public V put(K key, V value) {
      mutabilityOracle.ensureMutable();
      return delegate.put(key, value);
    }

    @Override
    public V remove(Object key) {
      mutabilityOracle.ensureMutable();
      return delegate.remove(key);
    }

    @Override
    public void putAll(Map<? extends K, ? extends V> m) {
      mutabilityOracle.ensureMutable();
      delegate.putAll(m);
    }

    @Override
    public void clear() {
      mutabilityOracle.ensureMutable();
      delegate.clear();
    }

    @Override
    public Set<K> keySet() {
      return new MutatabilityAwareSet<K>(mutabilityOracle, delegate.keySet());
    }

    @Override
    public Collection<V> values() {
      return new MutatabilityAwareCollection<V>(mutabilityOracle, delegate.values());
    }

    @Override
    public Set<java.util.Map.Entry<K, V>> entrySet() {
      return new MutatabilityAwareSet<Entry<K, V>>(mutabilityOracle, delegate.entrySet());
    }

    @Override
    public boolean equals(Object o) {
      return delegate.equals(o);
    }

    @Override
    public int hashCode() {
      return delegate.hashCode();
    }

    @Override
    public String toString() {
      return delegate.toString();
    }
  }

  /**
   * An internal collection that checks for mutability before delegating.
   */
  private static class MutatabilityAwareCollection<E> implements Collection<E> {
    private final MutabilityOracle mutabilityOracle;
    private final Collection<E> delegate;

    MutatabilityAwareCollection(MutabilityOracle mutabilityOracle, Collection<E> delegate) {
      this.mutabilityOracle = mutabilityOracle;
      this.delegate = delegate;
    }

    @Override
    public int size() {
      return delegate.size();
    }

    @Override
    public boolean isEmpty() {
      return delegate.isEmpty();
    }

    @Override
    public boolean contains(Object o) {
      return delegate.contains(o);
    }

    @Override
    public Iterator<E> iterator() {
      return new MutatabilityAwareIterator<E>(mutabilityOracle, delegate.iterator());
    }

    @Override
    public Object[] toArray() {
      return delegate.toArray();
    }

    @Override
    public <T> T[] toArray(T[] a) {
      return delegate.toArray(a);
    }

    @Override
    public boolean add(E e) {
      // Unsupported operation in the delegate.
      throw new UnsupportedOperationException();
    }

    @Override
    public boolean remove(Object o) {
      mutabilityOracle.ensureMutable();
      return delegate.remove(o);
    }

    @Override
    public boolean containsAll(Collection<?> c) {
      return delegate.containsAll(c);
    }

    @Override
    public boolean addAll(Collection<? extends E> c) {
      // Unsupported operation in the delegate.
      throw new UnsupportedOperationException();
    }

    @Override
    public boolean removeAll(Collection<?> c) {
      mutabilityOracle.ensureMutable();
      return delegate.removeAll(c);
    }

    @Override
    public boolean retainAll(Collection<?> c) {
      mutabilityOracle.ensureMutable();
      return delegate.retainAll(c);
    }

    @Override
    public void clear() {
      mutabilityOracle.ensureMutable();
      delegate.clear();
    }

    @Override
    public boolean equals(Object o) {
      return delegate.equals(o);
    }

    @Override
    public int hashCode() {
      return delegate.hashCode();
    }

    @Override
    public String toString() {
      return delegate.toString();
    }
  }

  /**
   * An internal set that checks for mutability before delegating.
   */
  private static class MutatabilityAwareSet<E> implements Set<E> {
    private final MutabilityOracle mutabilityOracle;
    private final Set<E> delegate;

    MutatabilityAwareSet(MutabilityOracle mutabilityOracle, Set<E> delegate) {
      this.mutabilityOracle = mutabilityOracle;
      this.delegate = delegate;
    }

    @Override
    public int size() {
      return delegate.size();
    }

    @Override
    public boolean isEmpty() {
      return delegate.isEmpty();
    }

    @Override
    public boolean contains(Object o) {
      return delegate.contains(o);
    }

    @Override
    public Iterator<E> iterator() {
      return new MutatabilityAwareIterator<E>(mutabilityOracle, delegate.iterator());
    }

    @Override
    public Object[] toArray() {
      return delegate.toArray();
    }

    @Override
    public <T> T[] toArray(T[] a) {
      return delegate.toArray(a);
    }

    @Override
    public boolean add(E e) {
      mutabilityOracle.ensureMutable();
      return delegate.add(e);
    }

    @Override
    public boolean remove(Object o) {
      mutabilityOracle.ensureMutable();
      return delegate.remove(o);
    }

    @Override
    public boolean containsAll(Collection<?> c) {
      return delegate.containsAll(c);
    }

    @Override
    public boolean addAll(Collection<? extends E> c) {
      mutabilityOracle.ensureMutable();
      return delegate.addAll(c);
    }

    @Override
    public boolean retainAll(Collection<?> c) {
      mutabilityOracle.ensureMutable();
      return delegate.retainAll(c);
    }

    @Override
    public boolean removeAll(Collection<?> c) {
      mutabilityOracle.ensureMutable();
      return delegate.removeAll(c);
    }

    @Override
    public void clear() {
      mutabilityOracle.ensureMutable();
      delegate.clear();
    }

    @Override
    public boolean equals(Object o) {
      return delegate.equals(o);
    }

    @Override
    public int hashCode() {
      return delegate.hashCode();
    }

    @Override
    public String toString() {
      return delegate.toString();
    }
  }

  /**
   * An internal iterator that checks for mutability before delegating.
   */
  private static class MutatabilityAwareIterator<E> implements Iterator<E> {
    private final MutabilityOracle mutabilityOracle;
    private final Iterator<E> delegate;

    MutatabilityAwareIterator(MutabilityOracle mutabilityOracle, Iterator<E> delegate) {
      this.mutabilityOracle = mutabilityOracle;
      this.delegate = delegate;
    }

    @Override
    public boolean hasNext() {
      return delegate.hasNext();
    }

    @Override
    public E next() {
      return delegate.next();
    }

    @Override
    public void remove() {
      mutabilityOracle.ensureMutable();
      delegate.remove();
    }

    @Override
    public boolean equals(Object obj) {
      return delegate.equals(obj);
    }

    @Override
    public int hashCode() {
      return delegate.hashCode();
    }

    @Override
    public String toString() {
      return delegate.toString();
    }
  }
}