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A set of utilities and tools to speed up and ease programming in Java.
There is a newer version: 0.5
/*
 * (c) 2005 David B. Bracewell
 *
 * 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.
 */

package com.davidbracewell.io;

import com.google.common.base.Charsets;

import java.nio.charset.Charset;

/**
 * Enumeration of common Unicode Byte Order Marks
 *
 * @author David B. Bracewell
 */
public enum CommonBOM {
  /**
   * The UTF_8 BOM
   */
  UTF_8(new byte[]{(byte) 0xEF, (byte) 0xBB, (byte) 0xBF}, Charsets.UTF_8),
  /**
   * The UTF_16BE BOM.
   */
  UTF_16BE(new byte[]{(byte) 0xFE, (byte) 0xFF}, Charsets.UTF_16BE),
  /**
   * The UTF_16LE BOM.
   */
  UTF_16LE(new byte[]{(byte) 0xFF, (byte) 0xFE}, Charsets.UTF_16LE),
  /**
   * The UTF_32BE BOM.
   */
  UTF_32BE(new byte[]{(byte) 0x00, (byte) 0x00, (byte) 0xFE, (byte) 0xFF}, Charset.forName("UTF-32BE")),
  /**
   * The UTF_32LE BOM.
   */
  UTF_32LE(new byte[]{(byte) 0x00, (byte) 0x00, (byte) 0xFF, (byte) 0xFE}, Charset.forName("UTF-32LE"));

  /**
   * The constant MAX_BOM_SIZE.
   */
  public final static int MAX_BOM_SIZE;

  //Determine the max BOM size based on the current items in the enum
  static {
    int max = 0;
    for (CommonBOM bom : CommonBOM.values()) {
      if (bom.length() > max) {
        max = bom.length();
      }
    }
    MAX_BOM_SIZE = max;
  }

  private final byte[] bom;
  private final Charset charset;

  CommonBOM(byte[] bom, Charset charset) {
    this.bom = bom;
    this.charset = charset;
  }

  /**
   * The number of byhtes in the bom
   *
   * @return The BOM length
   */
  public int length() {
    return bom.length;
  }

  /**
   * The charset associated with the bom
   *
   * @return The associated Charset
   */
  public Charset getCharset() {
    return charset;
  }

  /**
   * Determines if the BOM is at the beginning of a given byte array.
   *
   * @param rhs The byte array to compare against
   * @return True if the BOM is present, false otherwise
   */
  public boolean matches(byte[] rhs) {
    if (rhs == null || rhs.length < bom.length) {
      return false;
    }
    for (int i = 0; i < bom.length; i++) {
      if (bom[i] != rhs[i]) {
        return false;
      }
    }
    return true;
  }

}// END OF CommonBOM