content: /*
   * Licensed to the Apache Software Foundation (ASF) under one or more
   * contributor license agreements.  See the NOTICE file distributed with
   * this work for additional information regarding copyright ownership.
   * The ASF licenses this file to You 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 org.apache.spark.sql.catalyst.expressions;
  
  import java.nio.ByteBuffer;
  
  import org.apache.spark.sql.catalyst.util.MapData;
  import org.apache.spark.unsafe.Platform;
  
  /**
   * An Unsafe implementation of Map which is backed by raw memory instead of Java objects.
   *
   * Currently we just use 2 UnsafeArrayData to represent UnsafeMapData, with extra 8 bytes at head
   * to indicate the number of bytes of the unsafe key array.
   * [unsafe key array numBytes] [unsafe key array] [unsafe value array]
   */
  // TODO: Use a more efficient format which doesn't depend on unsafe array.
  public final class UnsafeMapData extends MapData {
  
    private Object baseObject;
    private long baseOffset;
  
    // The size of this map's backing data, in bytes.
    // The 4-bytes header of key array `numBytes` is also included, so it's actually equal to
    // 4 + key array numBytes + value array numBytes.
    private int sizeInBytes;
  
    public Object getBaseObject() { return baseObject; }
    public long getBaseOffset() { return baseOffset; }
    public int getSizeInBytes() { return sizeInBytes; }
  
    private final UnsafeArrayData keys;
    private final UnsafeArrayData values;
  
    /**
     * Construct a new UnsafeMapData. The resulting UnsafeMapData won't be usable until
     * `pointTo()` has been called, since the value returned by this constructor is equivalent
     * to a null pointer.
     */
    public UnsafeMapData() {
      keys = new UnsafeArrayData();
      values = new UnsafeArrayData();
    }
  
    /**
     * Update this UnsafeMapData to point to different backing data.
     *
     * @param baseObject the base object
     * @param baseOffset the offset within the base object
     * @param sizeInBytes the size of this map's backing data, in bytes
     */
    public void pointTo(Object baseObject, long baseOffset, int sizeInBytes) {
      // Read the numBytes of key array from the first 8 bytes.
      final long keyArraySize = Platform.getLong(baseObject, baseOffset);
      assert keyArraySize >= 0 : "keyArraySize (" + keyArraySize + ") should >= 0";
      assert keyArraySize <= Integer.MAX_VALUE : "keyArraySize (" + keyArraySize + ") should <= Integer.MAX_VALUE";
      final int valueArraySize = sizeInBytes - (int)keyArraySize - 8;
      assert valueArraySize >= 0 : "valueArraySize (" + valueArraySize + ") should >= 0";
  
      keys.pointTo(baseObject, baseOffset + 8, (int)keyArraySize);
      values.pointTo(baseObject, baseOffset + 8 + keyArraySize, valueArraySize);
  
      assert keys.numElements() == values.numElements();
  
      this.baseObject = baseObject;
      this.baseOffset = baseOffset;
      this.sizeInBytes = sizeInBytes;
    }
  
    @Override
    public int numElements() {
      return keys.numElements();
    }
  
    @Override
    public UnsafeArrayData keyArray() {
      return keys;
    }
  
    @Override
    public UnsafeArrayData valueArray() {
      return values;
    }
  
    public void writeToMemory(Object target, long targetOffset) {
      Platform.copyMemory(baseObject, baseOffset, target, targetOffset, sizeInBytes);
    }
  
    public void writeTo(ByteBuffer buffer) {
      assert(buffer.hasArray());
      byte[] target = buffer.array();
      int offset = buffer.arrayOffset();
      int pos = buffer.position();
      writeToMemory(target, Platform.BYTE_ARRAY_OFFSET + offset + pos);
      buffer.position(pos + sizeInBytes);
    }
  
    @Override
    public UnsafeMapData copy() {
      UnsafeMapData mapCopy = new UnsafeMapData();
      final byte[] mapDataCopy = new byte[sizeInBytes];
      Platform.copyMemory(
        baseObject, baseOffset, mapDataCopy, Platform.BYTE_ARRAY_OFFSET, sizeInBytes);
      mapCopy.pointTo(mapDataCopy, Platform.BYTE_ARRAY_OFFSET, sizeInBytes);
      return mapCopy;
    }
  }
  