/*
    *
    * 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.hadoop.hbase.filter;
  
  import com.google.protobuf.InvalidProtocolBufferException;
  import org.apache.hadoop.hbase.classification.InterfaceAudience;
  import org.apache.hadoop.hbase.classification.InterfaceStability;
  import org.apache.hadoop.hbase.exceptions.DeserializationException;
  import org.apache.hadoop.hbase.protobuf.generated.ComparatorProtos;
  
  /**
   * A bit comparator which performs the specified bitwise operation on each of the bytes
   * with the specified byte array. Then returns whether the result is non-zero.
   */
  @InterfaceAudience.Public
  @InterfaceStability.Stable
  public class BitComparator extends ByteArrayComparable {
  
    /** Bit operators. */
    @InterfaceAudience.Public
    @InterfaceStability.Stable
    public enum BitwiseOp {
      /** and */
      AND,
      /** or */
      OR,
      /** xor */
      XOR
    }
    protected BitwiseOp bitOperator;
  
    /**
     * Constructor
     * @param value value
     * @param bitOperator operator to use on the bit comparison
     */
    public BitComparator(byte[] value, BitwiseOp bitOperator) {
      super(value);
      this.bitOperator = bitOperator;
    }
  
    /**
     * @return the bitwise operator
     */
    public BitwiseOp getOperator() {
      return bitOperator;
    }
  
    /**
     * @return The comparator serialized using pb
     */
    public byte [] toByteArray() {
      ComparatorProtos.BitComparator.Builder builder =
        ComparatorProtos.BitComparator.newBuilder();
      builder.setComparable(super.convert());
      ComparatorProtos.BitComparator.BitwiseOp bitwiseOpPb =
        ComparatorProtos.BitComparator.BitwiseOp.valueOf(bitOperator.name());
      builder.setBitwiseOp(bitwiseOpPb);
      return builder.build().toByteArray();
    }
  
    /**
     * @param pbBytes A pb serialized {@link BitComparator} instance
     * @return An instance of {@link BitComparator} made from <code>bytes</code>
     * @throws DeserializationException
     * @see #toByteArray
     */
    public static BitComparator parseFrom(final byte [] pbBytes)
    throws DeserializationException {
      ComparatorProtos.BitComparator proto;
      try {
        proto = ComparatorProtos.BitComparator.parseFrom(pbBytes);
      } catch (InvalidProtocolBufferException e) {
        throw new DeserializationException(e);
      }
      BitwiseOp bitwiseOp = BitwiseOp.valueOf(proto.getBitwiseOp().name());
      return new BitComparator(proto.getComparable().getValue().toByteArray(),bitwiseOp);
    }
  
    /**
     * @param other
     * @return true if and only if the fields of the comparator that are serialized
    * are equal to the corresponding fields in other.  Used for testing.
    */
   boolean areSerializedFieldsEqual(ByteArrayComparable other) {
     if (other == this) return true;
     if (!(other instanceof BitComparator)) return false;
 
     BitComparator comparator = (BitComparator)other;
     return super.areSerializedFieldsEqual(other)
       && this.getOperator().equals(comparator.getOperator());
   }
 
   @Override
   public int compareTo(byte[] value, int offset, int length) {
     if (length != this.value.length) {
       return 1;
     }
     int b = 0;
     //Iterating backwards is faster because we can quit after one non-zero byte.
     for (int i = length - 1; i >= 0 && b == 0; i--) {
       switch (bitOperator) {
         case AND:
           b = (this.value[i] & value[i+offset]) & 0xff;
           break;
         case OR:
           b = (this.value[i] | value[i+offset]) & 0xff;
           break;
         case XOR:
           b = (this.value[i] ^ value[i+offset]) & 0xff;
           break;
       }
     }
     return b == 0 ? 1 : 0;
   }
 }