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.asterix.dataflow.data.nontagged.hash;
  
  import java.io.IOException;
  
  import org.apache.asterix.om.types.ATypeTag;
  import org.apache.asterix.om.types.EnumDeserializer;
  import org.apache.hyracks.api.dataflow.value.IBinaryHashFunction;
  import org.apache.hyracks.api.dataflow.value.IBinaryHashFunctionFactory;
  import org.apache.hyracks.api.exceptions.HyracksDataException;
  import org.apache.hyracks.data.std.accessors.MurmurHash3BinaryHashFunctionFamily;
  import org.apache.hyracks.data.std.accessors.PointableBinaryHashFunctionFactory;
  import org.apache.hyracks.data.std.primitive.UTF8StringLowercasePointable;
  import org.apache.hyracks.data.std.util.GrowableArray;
  
  /**
   * This hash function factory is introduced to be able to hash heterogeneous list items.
   * The item type tag is also included in the hash computation to distinguish the different
   * types with the same raw bytes.
   */
  public class ListItemBinaryHashFunctionFactory implements IBinaryHashFunctionFactory {
  
      private static final long serialVersionUID = 1L;
  
      public static final ListItemBinaryHashFunctionFactory INSTANCE = new ListItemBinaryHashFunctionFactory();
  
      private ListItemBinaryHashFunctionFactory() {
      }
  
      @Override
      public IBinaryHashFunction createBinaryHashFunction() {
          return createBinaryHashFunction(ATypeTag.ANY, false);
      }
  
      public IBinaryHashFunction createBinaryHashFunction(final ATypeTag itemTypeTag, final boolean ignoreCase) {
          return new IBinaryHashFunction() {
  
              private IBinaryHashFunction lowerCaseStringHash =
                      new PointableBinaryHashFunctionFactory(UTF8StringLowercasePointable.FACTORY)
                              .createBinaryHashFunction();
              private IBinaryHashFunction genericBinaryHash =
                      MurmurHash3BinaryHashFunctionFamily.INSTANCE.createBinaryHashFunction(0);
              private GrowableArray taggedBytes = new GrowableArray();
  
              @Override
              public int hash(byte[] bytes, int offset, int length) throws HyracksDataException {
                  ATypeTag tag = itemTypeTag;
                  int skip = 0;
                  if (itemTypeTag == ATypeTag.ANY) {
                      tag = EnumDeserializer.ATYPETAGDESERIALIZER.deserialize(bytes[offset]);
                      skip = 1;
                  }
                  switch (tag) {
                      case STRING: {
                          if (ignoreCase) {
                              return lowerCaseStringHash.hash(bytes, offset + skip, length - skip);
                          }
                      }
                      default: {
                          if (itemTypeTag != ATypeTag.ANY) {
                              // add the itemTypeTag in front of the data
                              try {
                                  resetTaggedBytes(bytes, offset, length);
                                  return genericBinaryHash.hash(taggedBytes.getByteArray(), 0, length + 1);
                              } catch (IOException e) {
                                  throw HyracksDataException.create(e);
                              }
                          } else {
                              return genericBinaryHash.hash(bytes, offset, length);
                          }
                      }
                  }
              }
  
              private void resetTaggedBytes(byte[] data, int offset, int length) throws IOException {
                  taggedBytes.reset();
                  taggedBytes.getDataOutput().writeByte(itemTypeTag.serialize());
                  taggedBytes.getDataOutput().write(data, offset, length);
              }
          };
      }
  }
  