alvinalexander.com | career | drupal | java | mac | mysql | perl | scala | uml | unix  

Java example source code file (AbstractNonStreamingHashFunction.java)

This example Java source code file (AbstractNonStreamingHashFunction.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

abstracthasher, abstractnonstreaminghashfunction, bottom_byte, bufferinghasher, charset, exposedbytearrayoutputstream, funnel, hashcode, hasher, ioexception, override, runtimeexception

The AbstractNonStreamingHashFunction.java Java example source code

/*
 * Copyright (C) 2011 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 com.google.common.base.Preconditions;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.nio.charset.Charset;

/**
 * Skeleton implementation of {@link HashFunction}, appropriate for non-streaming algorithms. All
 * the hash computation done using {@linkplain #newHasher()} are delegated to the
 * {@linkplain #hashBytes(byte[], int, int)} method.
 *
 * @author Dimitris Andreou
 */
abstract class AbstractNonStreamingHashFunction implements HashFunction {
  @Override
  public Hasher newHasher() {
    return new BufferingHasher(32);
  }

  @Override
  public Hasher newHasher(int expectedInputSize) {
    Preconditions.checkArgument(expectedInputSize >= 0);
    return new BufferingHasher(expectedInputSize);
  }

  @Override
  public <T> HashCode hashObject(T instance, Funnel funnel) {
    return newHasher().putObject(instance, funnel).hash();
  }

  @Override
  public HashCode hashUnencodedChars(CharSequence input) {
    int len = input.length();
    Hasher hasher = newHasher(len * 2);
    for (int i = 0; i < len; i++) {
      hasher.putChar(input.charAt(i));
    }
    return hasher.hash();
  }

  @Override
  public HashCode hashString(CharSequence input, Charset charset) {
    return hashBytes(input.toString().getBytes(charset));
  }

  @Override
  public HashCode hashInt(int input) {
    return newHasher(4).putInt(input).hash();
  }

  @Override
  public HashCode hashLong(long input) {
    return newHasher(8).putLong(input).hash();
  }

  @Override
  public HashCode hashBytes(byte[] input) {
    return hashBytes(input, 0, input.length);
  }

  /**
   * In-memory stream-based implementation of Hasher.
   */
  private final class BufferingHasher extends AbstractHasher {
    final ExposedByteArrayOutputStream stream;
    static final int BOTTOM_BYTE = 0xFF;

    BufferingHasher(int expectedInputSize) {
      this.stream = new ExposedByteArrayOutputStream(expectedInputSize);
    }

    @Override
    public Hasher putByte(byte b) {
      stream.write(b);
      return this;
    }

    @Override
    public Hasher putBytes(byte[] bytes) {
      try {
        stream.write(bytes);
      } catch (IOException e) {
        throw new RuntimeException(e);
      }
      return this;
    }

    @Override
    public Hasher putBytes(byte[] bytes, int off, int len) {
      stream.write(bytes, off, len);
      return this;
    }

    @Override
    public Hasher putShort(short s) {
      stream.write(s & BOTTOM_BYTE);
      stream.write((s >>> 8) & BOTTOM_BYTE);
      return this;
    }

    @Override
    public Hasher putInt(int i) {
      stream.write(i & BOTTOM_BYTE);
      stream.write((i >>> 8) & BOTTOM_BYTE);
      stream.write((i >>> 16) & BOTTOM_BYTE);
      stream.write((i >>> 24) & BOTTOM_BYTE);
      return this;
    }

    @Override
    public Hasher putLong(long l) {
      for (int i = 0; i < 64; i += 8) {
        stream.write((byte) ((l >>> i) & BOTTOM_BYTE));
      }
      return this;
    }

    @Override
    public Hasher putChar(char c) {
      stream.write(c & BOTTOM_BYTE);
      stream.write((c >>> 8) & BOTTOM_BYTE);
      return this;
    }

    @Override
    public <T> Hasher putObject(T instance, Funnel funnel) {
      funnel.funnel(instance, this);
      return this;
    }

    @Override
    public HashCode hash() {
      return hashBytes(stream.byteArray(), 0, stream.length());
    }
  }

  // Just to access the byte[] without introducing an unnecessary copy
  private static final class ExposedByteArrayOutputStream extends ByteArrayOutputStream {
    ExposedByteArrayOutputStream(int expectedInputSize) {
      super(expectedInputSize);
    }

    byte[] byteArray() {
      return buf;
    }

    int length() {
      return count;
    }
  }
}

Other Java examples (source code examples)

Here is a short list of links related to this Java AbstractNonStreamingHashFunction.java source code file:

... this post is sponsored by my books ...

#1 New Release!

FP Best Seller

 

new blog posts

 

Copyright 1998-2021 Alvin Alexander, alvinalexander.com
All Rights Reserved.

A percentage of advertising revenue from
pages under the /java/jwarehouse URI on this website is
paid back to open source projects.