/*
    * 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.
   *
   * The portion of this file denoted by 'Copied from com.google.protobuf.CodedInputStream'
   * is from Protocol Buffers v2.5.0 under the following license
   *
   * Copyright 2008 Google Inc.  All rights reserved.
   * http://code.google.com/p/protobuf/
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions are
   * met:
   *
   *     * Redistributions of source code must retain the above copyright
   * notice, this list of conditions and the following disclaimer.
   *     * Redistributions in binary form must reproduce the above
   * copyright notice, this list of conditions and the following disclaimer
   * in the documentation and/or other materials provided with the
   * distribution.
   *     * Neither the name of Google Inc. nor the names of its
   * contributors may be used to endorse or promote products derived from
   * this software without specific prior written permission.
   *
   * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
   * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
   * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
   * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
   * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
   * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
   * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
   * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
   * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
   * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
   * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
   *
   */
  package org.apache.hadoop.hbase.util;
  
  import org.apache.hadoop.hbase.classification.InterfaceAudience;
  import org.apache.hadoop.hbase.classification.InterfaceStability;
  
  /**
   * An abstract implementation of the ByteRange API
   */
  @InterfaceAudience.Private
  @InterfaceStability.Evolving
  public abstract class AbstractByteRange implements ByteRange {
    public static final int UNSET_HASH_VALUE = -1;
  
    // Note to maintainers: Do not make these final, as the intention is to
    // reuse objects of this class
  
    /**
     * The array containing the bytes in this range. It will be >= length.
     */
    protected byte[] bytes;
  
    /**
     * The index of the first byte in this range. {@code ByteRange.get(0)} will
     * return bytes[offset].
     */
    protected int offset;
  
    /**
     * The number of bytes in the range. Offset + length must be <= bytes.length
     */
    protected int length;
  
    /**
     * Variable for lazy-caching the hashCode of this range. Useful for frequently
     * used ranges, long-lived ranges, or long ranges.
     */
    protected int hash = UNSET_HASH_VALUE;
  
    //
    // methods for managing the backing array and range viewport
    //
    @Override
    public byte[] getBytes() {
      return bytes;
    }
  
    @Override
    public ByteRange set(int capacity) {
      return set(new byte[capacity]);
   }
 
   @Override
   public ByteRange set(byte[] bytes) {
     if (null == bytes) {
       return unset();
     }
 
     clearHashCache();
     this.bytes = bytes;
     this.offset = 0;
     this.length = bytes.length;
     return this;
   }
 
   @Override
   public ByteRange set(byte[] bytes, int offset, int length) {
     if (null == bytes) {
       return unset();
     }
 
     clearHashCache();
     this.bytes = bytes;
     this.offset = offset;
     this.length = length;
     return this;
   }
 
   @Override
   public int getOffset() {
     return offset;
   }
 
   @Override
   public ByteRange setOffset(int offset) {
     clearHashCache();
     this.offset = offset;
     return this;
   }
 
   @Override
   public int getLength() {
     return length;
   }
 
   @Override
   public ByteRange setLength(int length) {
     clearHashCache();
     this.length = length;
     return this;
   }
 
   @Override
   public boolean isEmpty() {
     return isEmpty(this);
   }
 
   /**
    * @return true when {@code range} is of zero length, false otherwise.
    */
   public static boolean isEmpty(ByteRange range) {
     return range == null || range.getLength() == 0;
   }
 
   //
   // methods for retrieving data
   //
 
   @Override
   public byte get(int index) {
     return bytes[offset + index];
   }
 
   @Override
   public ByteRange get(int index, byte[] dst) {
     if (0 == dst.length) {
       return this;
     }
 
     return get(index, dst, 0, dst.length);
   }
 
   @Override
   public ByteRange get(int index, byte[] dst, int offset, int length) {
     if (0 == length) {
       return this;
     }
 
     System.arraycopy(this.bytes, this.offset + index, dst, offset, length);
     return this;
   }
 
   @Override
   public short getShort(int index) {
     int offset = this.offset + index;
     short n = 0;
     n = (short) ((n ^ bytes[offset]) & 0xFF);
     n = (short) (n << 8);
     n = (short) ((n ^ bytes[offset + 1]) & 0xFF);
     return n;
   }
 
   @Override
   public int getInt(int index) {
     int offset = this.offset + index;
     int n = 0;
     for (int i = offset; i < (offset + Bytes.SIZEOF_INT); i++) {
       n <<= 8;
       n ^= bytes[i] & 0xFF;
     }
     return n;
   }
 
   @Override
   public long getLong(int index) {
     int offset = this.offset + index;
     long l = 0;
     for (int i = offset; i < offset + Bytes.SIZEOF_LONG; i++) {
       l <<= 8;
       l ^= bytes[i] & 0xFF;
     }
     return l;
   }
 
   // Copied from com.google.protobuf.CodedInputStream v2.5.0 readRawVarint64
   @Override
   public long getVLong(int index) {
     int shift = 0;
     long result = 0;
     while (shift < 64) {
       final byte b = get(index++);
       result |= (long) (b & 0x7F) << shift;
       if ((b & 0x80) == 0) {
         break;
       }
       shift += 7;
     }
     return result;
   }
   // end of copied from protobuf
 
   public static int getVLongSize(long val) {
     int rPos = 0;
     while ((val & ~0x7F) != 0) {
       val >>>= 7;
       rPos++;
     }
     return rPos + 1;
   }
 
   //
   // methods for duplicating the current instance
   //
 
   @Override
   public byte[] deepCopyToNewArray() {
     byte[] result = new byte[length];
     System.arraycopy(bytes, offset, result, 0, length);
     return result;
   }
 
   @Override
   public void deepCopyTo(byte[] destination, int destinationOffset) {
     System.arraycopy(bytes, offset, destination, destinationOffset, length);
   }
 
   @Override
   public void deepCopySubRangeTo(int innerOffset, int copyLength, byte[] destination,
       int destinationOffset) {
     System.arraycopy(bytes, offset + innerOffset, destination, destinationOffset, copyLength);
   }
 
   //
   // methods used for comparison
   //
 
   @Override
   public int hashCode() {
     if (isHashCached()) {// hash is already calculated and cached
       return hash;
     }
     if (this.isEmpty()) {// return 0 for empty ByteRange
       hash = 0;
       return hash;
     }
     int off = offset;
     hash = 0;
     for (int i = 0; i < length; i++) {
       hash = 31 * hash + bytes[off++];
     }
     return hash;
   }
 
   protected boolean isHashCached() {
     return hash != UNSET_HASH_VALUE;
   }
 
   protected void clearHashCache() {
     hash = UNSET_HASH_VALUE;
   }
 
   /**
    * Bitwise comparison of each byte in the array. Unsigned comparison, not
    * paying attention to java's signed bytes.
    */
   @Override
   public int compareTo(ByteRange other) {
     return Bytes.compareTo(bytes, offset, length, other.getBytes(), other.getOffset(),
         other.getLength());
   }
 
   @Override
   public String toString() {
     return Bytes.toStringBinary(bytes, offset, length);
   }
 }