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Extended functionality for the Java driver.
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/*
 * Copyright DataStax, Inc.
 *
 * 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.datastax.driver.extras.codecs.arrays;

import static com.google.common.base.Preconditions.checkArgument;

import com.datastax.driver.core.CodecUtils;
import com.datastax.driver.core.DataType;
import com.datastax.driver.core.ProtocolVersion;
import com.datastax.driver.core.exceptions.InvalidTypeException;
import java.lang.reflect.Array;
import java.nio.ByteBuffer;

/**
 * Base class for all codecs dealing with Java primitive arrays. This class provides a more
 * efficient implementation of {@link #serialize(Object, ProtocolVersion)} and {@link
 * #deserialize(ByteBuffer, ProtocolVersion)} for primitive arrays.
 *
 * @param  The Java primitive array type this codec handles
 */
public abstract class AbstractPrimitiveArrayCodec extends AbstractArrayCodec {

  /**
   * @param cqlType The CQL type. Must be a list type.
   * @param javaClass The Java type. Must be an array class.
   */
  public AbstractPrimitiveArrayCodec(DataType.CollectionType cqlType, Class javaClass) {
    super(cqlType, javaClass);
    checkArgument(
        javaClass.getComponentType().isPrimitive(),
        "Expecting primitive array component type, got %s",
        javaClass.getComponentType());
  }

  @Override
  public ByteBuffer serialize(T array, ProtocolVersion protocolVersion)
      throws InvalidTypeException {
    if (array == null) return null;
    boolean isProtocolV3OrAbove = protocolVersion.compareTo(ProtocolVersion.V2) > 0;
    // native method
    int length = Array.getLength(array);
    checkArgument(
        isProtocolV3OrAbove || length < 65536,
        "Native protocol version %d supports up to 65535 elements in any collection - but collection contains %d elements",
        protocolVersion.toInt(),
        length);
    /*
     * Encoding of lists in the native protocol:
     * [size of list] [size of element 1][element1] [size of element 2][element2]...
     * Sizes are encoded on 2 bytes in protocol v1 and v2, 4 bytes otherwise.
     * (See native_protocol_v*.spec in https://github.com/apache/cassandra/blob/trunk/doc/)
     */
    // Number of bytes to encode sizes
    int sizeOfSize = isProtocolV3OrAbove ? 4 : 2;
    // Number of bytes to encode each element (preceded by its size)
    int sizeOfElement = sizeOfSize + sizeOfComponentType();
    // Number of bytes to encode the whole collection (size of collection + all elements)
    int totalSize = sizeOfSize + length * sizeOfElement;
    ByteBuffer output = ByteBuffer.allocate(totalSize);
    CodecUtils.writeSize(output, length, protocolVersion);
    for (int i = 0; i < length; i++) {
      CodecUtils.writeSize(output, sizeOfComponentType(), protocolVersion);
      serializeElement(output, array, i, protocolVersion);
    }
    output.flip();
    return output;
  }

  @Override
  public T deserialize(ByteBuffer bytes, ProtocolVersion protocolVersion)
      throws InvalidTypeException {
    if (bytes == null || bytes.remaining() == 0) return newInstance(0);
    boolean isProtocolV3OrAbove = protocolVersion.compareTo(ProtocolVersion.V2) > 0;
    int sizeOfSize = isProtocolV3OrAbove ? 4 : 2;
    ByteBuffer input = bytes.duplicate();
    int size = CodecUtils.readSize(input, protocolVersion);
    T array = newInstance(size);
    for (int i = 0; i < size; i++) {
      // Skip size (we know it will always be 4 since the elements are ints)
      input.position(input.position() + sizeOfSize);
      deserializeElement(input, array, i, protocolVersion);
    }
    return array;
  }

  /**
   * Return the size in bytes of the array component type.
   *
   * @return the size in bytes of the array component type.
   */
  protected abstract int sizeOfComponentType();

  /**
   * Write the {@code index}th element of {@code array} to {@code output}.
   *
   * @param output The ByteBuffer to write to.
   * @param array The array to read from.
   * @param index The element index.
   * @param protocolVersion The protocol version to use.
   */
  protected abstract void serializeElement(
      ByteBuffer output, T array, int index, ProtocolVersion protocolVersion);

  /**
   * Read the {@code index}th element of {@code array} from {@code input}.
   *
   * @param input The ByteBuffer to read from.
   * @param array The array to write to.
   * @param index The element index.
   * @param protocolVersion The protocol version to use.
   */
  protected abstract void deserializeElement(
      ByteBuffer input, T array, int index, ProtocolVersion protocolVersion);
}