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// Protocol Buffers - Google's data interchange format
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// https://developers.google.com/protocol-buffers/
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package io.prestosql.orc.protobuf;

import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import java.util.Set;

/**
 * Internal representation of map fields in generated messages.
 *
 * This class supports accessing the map field as a {@link Map} to be used in
 * generated API and also supports accessing the field as a {@link List} to be
 * used in reflection API. It keeps track of where the data is currently stored
 * and do necessary conversions between map and list.
 *
 * This class is a protobuf implementation detail. Users shouldn't use this
 * class directly.
 *
 * THREAD-SAFETY NOTE: Read-only access is thread-safe. Users can call getMap()
 * and getList() concurrently in multiple threads. If write-access is needed,
 * all access must be synchronized.
 */
public class MapField implements MutabilityOracle {
  /**
   * Indicates where the data of this map field is currently stored.
   *
   * MAP: Data is stored in mapData.
   * LIST: Data is stored in listData.
   * BOTH: mapData and listData have the same data.
   *
   * When the map field is accessed (through generated API or reflection API),
   * it will shift between these 3 modes:
   *
   *          getMap()   getList()   getMutableMap()   getMutableList()
   *   MAP      MAP        BOTH          MAP               LIST
   *   LIST     BOTH       LIST          MAP               LIST
   *   BOTH     BOTH       BOTH          MAP               LIST
   *
   * As the map field changes its mode, the list/map reference returned in a
   * previous method call may be invalidated.
   */
  private enum StorageMode {MAP, LIST, BOTH}

  private volatile boolean isMutable;
  private volatile StorageMode mode;
  private MutatabilityAwareMap mapData;
  private List listData;

  // Convert between a map entry Message and a key-value pair.
  private static interface Converter {
    Message convertKeyAndValueToMessage(K key, V value);
    void convertMessageToKeyAndValue(Message message, Map map);

    Message getMessageDefaultInstance();
  }

  private static class ImmutableMessageConverter implements Converter {
    private final MapEntry defaultEntry;
    public ImmutableMessageConverter(MapEntry defaultEntry) {
      this.defaultEntry = defaultEntry;
    }

    @Override
    public Message convertKeyAndValueToMessage(K key, V value) {
      return defaultEntry.newBuilderForType().setKey(key).setValue(value).buildPartial();
    }

    @Override
    public void convertMessageToKeyAndValue(Message message, Map map) {
      MapEntry entry = (MapEntry) message;
      map.put(entry.getKey(), entry.getValue());
    }

    @Override
    public Message getMessageDefaultInstance() {
      return defaultEntry;
    }
  }


  private final Converter converter;

  private MapField(
      Converter converter,
      StorageMode mode,
      Map mapData) {
    this.converter = converter;
    this.isMutable = true;
    this.mode = mode;
    this.mapData = new MutatabilityAwareMap(this, mapData);
    this.listData = null;
  }

  private MapField(
      MapEntry defaultEntry,
      StorageMode mode,
      Map mapData) {
    this(new ImmutableMessageConverter(defaultEntry), mode, mapData);
  }


  /** Returns an immutable empty MapField. */
  public static  MapField emptyMapField(
      MapEntry defaultEntry) {
    return new MapField(
        defaultEntry, StorageMode.MAP, Collections.emptyMap());
  }


  /** Creates a new mutable empty MapField. */
  public static  MapField newMapField(MapEntry defaultEntry) {
    return new MapField(
        defaultEntry, StorageMode.MAP, new LinkedHashMap());
  }


  private Message convertKeyAndValueToMessage(K key, V value) {
    return converter.convertKeyAndValueToMessage(key, value);
  }

  @SuppressWarnings("unchecked")
  private void convertMessageToKeyAndValue(Message message, Map map) {
    converter.convertMessageToKeyAndValue(message, map);
  }

  private List convertMapToList(MutatabilityAwareMap mapData) {
    List listData = new ArrayList();
    for (Map.Entry entry : mapData.entrySet()) {
      listData.add(
          convertKeyAndValueToMessage(
              entry.getKey(), entry.getValue()));
    }
    return listData;
  }

  private MutatabilityAwareMap convertListToMap(List listData) {
    Map mapData = new LinkedHashMap();
    for (Message item : listData) {
      convertMessageToKeyAndValue(item, mapData);
    }
    return new MutatabilityAwareMap(this, mapData);
  }

  /** Returns the content of this MapField as a read-only Map. */
  public Map getMap() {
    if (mode == StorageMode.LIST) {
      synchronized (this) {
        if (mode == StorageMode.LIST) {
          mapData = convertListToMap(listData);
          mode = StorageMode.BOTH;
        }
      }
    }
    return Collections.unmodifiableMap(mapData);
  }

  /** Gets a mutable Map view of this MapField. */
  public Map getMutableMap() {
    if (mode != StorageMode.MAP) {
      if (mode == StorageMode.LIST) {
        mapData = convertListToMap(listData);
      }
      listData = null;
      mode = StorageMode.MAP;
    }
    return mapData;
  }

  public void mergeFrom(MapField other) {
    getMutableMap().putAll(MapFieldLite.copy(other.getMap()));
  }

  public void clear() {
    mapData = new MutatabilityAwareMap(this, new LinkedHashMap());
    mode = StorageMode.MAP;
  }

  @SuppressWarnings("unchecked")
  @Override
  public boolean equals(Object object) {
    if (!(object instanceof MapField)) {
      return false;
    }
    MapField other = (MapField) object;
    return MapFieldLite.equals(getMap(), other.getMap());
  }

  @Override
  public int hashCode() {
    return MapFieldLite.calculateHashCodeForMap(getMap());
  }

  /** Returns a deep copy of this MapField. */
  public MapField copy() {
    return new MapField(
        converter, StorageMode.MAP, MapFieldLite.copy(getMap()));
  }

  /** Gets the content of this MapField as a read-only List. */
  List getList() {
    if (mode == StorageMode.MAP) {
      synchronized (this) {
        if (mode == StorageMode.MAP) {
          listData = convertMapToList(mapData);
          mode = StorageMode.BOTH;
        }
      }
    }
    return Collections.unmodifiableList(listData);
  }

  /** Gets a mutable List view of this MapField. */
  List getMutableList() {
    if (mode != StorageMode.LIST) {
      if (mode == StorageMode.MAP) {
        listData = convertMapToList(mapData);
      }
      mapData = null;
      mode = StorageMode.LIST;
    }
    return listData;
  }

  /**
   * Gets the default instance of the message stored in the list view of this
   * map field.
   */
  Message getMapEntryMessageDefaultInstance() {
    return converter.getMessageDefaultInstance();
  }

  /**
   * Makes this list 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;
  }

  /* (non-Javadoc)
   * @see io.prestosql.orc.protobuf.MutabilityOracle#ensureMutable()
   */
  @Override
  public void ensureMutable() {
    if (!isMutable()) {
      throw new UnsupportedOperationException();
    }
  }

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

    MutatabilityAwareMap(MutabilityOracle mutabilityOracle, Map 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 m) {
      mutabilityOracle.ensureMutable();
      delegate.putAll(m);
    }

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

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

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

    @Override
    public Set> entrySet() {
      return new MutatabilityAwareSet>(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 implements Collection {
      private final MutabilityOracle mutabilityOracle;
      private final Collection delegate;

      MutatabilityAwareCollection(MutabilityOracle mutabilityOracle, Collection 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 iterator() {
        return new MutatabilityAwareIterator(mutabilityOracle, delegate.iterator());
      }

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

      @Override
      public  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 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 implements Set {
      private final MutabilityOracle mutabilityOracle;
      private final Set delegate;

      MutatabilityAwareSet(MutabilityOracle mutabilityOracle, Set 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 iterator() {
        return new MutatabilityAwareIterator(mutabilityOracle, delegate.iterator());
      }

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

      @Override
      public  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 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 implements Iterator {
      private final MutabilityOracle mutabilityOracle;
      private final Iterator delegate;

      MutatabilityAwareIterator(MutabilityOracle mutabilityOracle, Iterator 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();
      }
    }
  }
}




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