content: /*******************************************************************************
   * Copyright 2014 Trevor Robinson
   * 
   * 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.scurrilous.circe.impl;
  
  import java.nio.ByteBuffer;
  import com.scurrilous.circe.IncrementalLongHash;
  import com.scurrilous.circe.StatefulLongHash;
  
  /**
   * Base implementation for incremental stateless long integer hash functions.
   */
  public abstract class AbstractIncrementalLongHash implements IncrementalLongHash {
  
      @Override
      public boolean supportsUnsafe() {
          return false;
      }
  
      @Override
      public StatefulLongHash createStateful() {
          return new IncrementalLongStatefulHash(this);
      }
  
      @Override
      public long calculate(byte[] input) {
          return resume(initial(), input);
      }
  
      @Override
      public long calculate(byte[] input, int index, int length) {
          return resume(initial(), input, index, length);
      }
  
      @Override
      public long calculate(ByteBuffer input) {
          return resume(initial(), input);
      }
  
      @Override
      public long calculate(long address, long length) {
          return resume(initial(), address, length);
      }
  
      @Override
      public long resume(long current, byte[] input) {
          return resumeUnchecked(current, input, 0, input.length);
      }
  
      @Override
      public long resume(long current, byte[] input, int index, int length) {
          if (length < 0)
              throw new IllegalArgumentException();
          if (index < 0 || index + length > input.length)
              throw new IndexOutOfBoundsException();
          return resumeUnchecked(current, input, index, length);
      }
  
      @Override
      public long resume(long current, ByteBuffer input) {
          final byte[] array;
          final int index;
          final int length = input.remaining();
          if (input.hasArray()) {
              array = input.array();
              index = input.arrayOffset() + input.position();
              input.position(input.limit());
          } else {
              array = new byte[length];
              index = 0;
              input.get(array);
          }
          return resumeUnchecked(current, array, index, length);
      }
  
      @Override
      public long resume(long current, long address, long length) {
          throw new UnsupportedOperationException();
      }
  
      /**
       * The initial state of the hash function, which is the same as the output
       * value for an empty input sequence.
       * 
       * @return the initial hash state/output
       */
      protected abstract long initial();
  
      /**
       * Evaluates this hash function as if the given range of the given input
       * array were appended to the previously hashed input. The index and length
       * parameters have already been validated.
       * 
       * @param current the hash output for input hashed so far
       * @param input the input array
       * @param index the starting index of the first input byte
       * @param length the length of the input range
       * @return the output of the hash function for the concatenated input
       */
      protected abstract long resumeUnchecked(long current, byte[] input, int index, int length);
  }
  