Java example source code file (AbstractByteHasher.java)

This example Java source code file (AbstractByteHasher.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

abstractbytehasher, abstracthasher, bytebuffer, canignorereturnvalue, funnel, hasher, nio, override

The AbstractByteHasher.java Java example source code

/*
 * 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 com.google.errorprone.annotations.CanIgnoreReturnValue;

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
 */
@CanIgnoreReturnValue
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 funnel) {
    funnel.funnel(instance, this);
    return this;
  }
}