/*
    * Copyright (C) 2012 The Guava Authors
    *
    * 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.google.common.hash;
  
  import static com.google.common.base.Preconditions.checkNotNull;
  import static com.google.common.base.Preconditions.checkPositionIndexes;
  
  import com.google.common.primitives.Chars;
  import com.google.common.primitives.Ints;
  import com.google.common.primitives.Longs;
  import com.google.common.primitives.Shorts;
  
  import java.nio.ByteBuffer;
  import java.nio.ByteOrder;
  
  /**
   * Abstract {@link Hasher} that handles converting primitives to bytes using a scratch {@code
   * ByteBuffer} and streams all bytes to a sink to compute the hash.
   *
   * @author Colin Decker
   */
  abstract class AbstractByteHasher extends AbstractHasher {
  
    private final ByteBuffer scratch = ByteBuffer.allocate(8).order(ByteOrder.LITTLE_ENDIAN);
  
    /**
     * Updates this hasher with the given byte.
     */
    protected abstract void update(byte b);
  
    /**
     * Updates this hasher with the given bytes.
     */
    protected void update(byte[] b) {
      update(b, 0, b.length);
    }
  
    /**
     * Updates this hasher with {@code len} bytes starting at {@code off} in the given buffer.
     */
    protected void update(byte[] b, int off, int len) {
      for (int i = off; i < off + len; i++) {
        update(b[i]);
      }
    }
  
    @Override
    public Hasher putByte(byte b) {
      update(b);
      return this;
    }
  
    @Override
    public Hasher putBytes(byte[] bytes) {
      checkNotNull(bytes);
      update(bytes);
      return this;
    }
  
    @Override
    public Hasher putBytes(byte[] bytes, int off, int len) {
      checkPositionIndexes(off, off + len, bytes.length);
      update(bytes, off, len);
      return this;
    }
  
    /**
     * Updates the sink with the given number of bytes from the buffer.
     */
    private Hasher update(int bytes) {
      try {
        update(scratch.array(), 0, bytes);
      } finally {
        scratch.clear();
      }
      return this;
    }
  
    @Override
    public Hasher putShort(short s) {
      scratch.putShort(s);
      return update(Shorts.BYTES);
    }
  
    @Override
   public Hasher putInt(int i) {
     scratch.putInt(i);
     return update(Ints.BYTES);
   }
 
   @Override
   public Hasher putLong(long l) {
     scratch.putLong(l);
     return update(Longs.BYTES);
   }
 
   @Override
   public Hasher putChar(char c) {
     scratch.putChar(c);
     return update(Chars.BYTES);
   }
 
   @Override
   public <T> Hasher putObject(T instance, Funnel<? super T> funnel) {
     funnel.funnel(instance, this);
     return this;
   }
 }