code: /*
   * 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 org.apache.commons.io;
  
  import java.io.Serializable;
  
  /**
   * Byte Order Mark (BOM) representation -
   * see {@link org.apache.commons.io.input.BOMInputStream}.
   *
   * @see org.apache.commons.io.input.BOMInputStream
   * @see <a href="http://en.wikipedia.org/wiki/Byte_order_mark">Wikipedia - Byte Order Mark</a>
   * @version $Id: ByteOrderMark.java,v 1.1.2.1 2011/01/15 20:32:25 caniszczyk Exp $
   * @since Commons IO 2.0
   */
  public class ByteOrderMark implements Serializable {
  
      private static final long serialVersionUID = 1L;
  
      /** UTF-8 BOM */
      public static final ByteOrderMark UTF_8    = new ByteOrderMark("UTF-8",    0xEF, 0xBB, 0xBF);
      /** UTF-16BE BOM (Big Endian) */
      public static final ByteOrderMark UTF_16BE = new ByteOrderMark("UTF-16BE", 0xFE, 0xFF);
      /** UTF-16LE BOM (Little Endian) */
      public static final ByteOrderMark UTF_16LE = new ByteOrderMark("UTF-16LE", 0xFF, 0xFE);
  
      private final String charsetName;
      private final int[] bytes;
  
      /**
       * Construct a new BOM.
       *
       * @param charsetName The name of the charset the BOM represents
       * @param bytes The BOM's bytes
       * @throws IllegalArgumentException if the charsetName is null or
       * zero length
       * @throws IllegalArgumentException if the bytes are null or zero
       * length
       */
      public ByteOrderMark(String charsetName, int... bytes) {
          if (charsetName == null || charsetName.length() == 0) {
              throw new IllegalArgumentException("No charsetName specified");
          }
          if (bytes == null || bytes.length == 0) {
              throw new IllegalArgumentException("No bytes specified");
          }
          this.charsetName = charsetName;
          this.bytes = new int[bytes.length];
          System.arraycopy(bytes, 0, this.bytes, 0, bytes.length);
      }
  
      /**
       * Return the name of the {@link java.nio.charset.Charset} the BOM represents.
       *
       * @return the character set name
       */
      public String getCharsetName() {
          return charsetName;
      }
  
      /**
       * Return the length of the BOM's bytes.
       *
       * @return the length of the BOM's bytes
       */
      public int length() {
          return bytes.length;
      }
  
      /**
       * The byte at the specified position.
       *
       * @param pos The position
       * @return The specified byte
       */
      public int get(int pos) {
          return bytes[pos];
      }
  
      /**
       * Return a copy of the BOM's bytes.
       *
       * @return a copy of the BOM's bytes
       */
      public byte[] getBytes() {
          byte[] copy = new byte[bytes.length];
          for (int i = 0; i < bytes.length; i++) {
              copy[i] = (byte)bytes[i];
          }
          return copy;
      }
  
      /**
       * Indicates if this BOM's bytes equals another.
       *
       * @param obj The object to compare to
       * @return true if the bom's bytes are equal, otherwise
       * false
       */
      @Override
      public boolean equals(Object obj) {
          if (!(obj instanceof ByteOrderMark)) {
              return false;
          }
          ByteOrderMark bom = (ByteOrderMark)obj;
          if (bytes.length != bom.length()) {
              return false;
          }
          for (int i = 0; i < bytes.length; i++) {
              if (bytes[i] != bom.get(i)) {
                  return false;
              }
          }
          return true;
      }
  
      /**
       * Return the hashcode for this BOM.
       *
       * @return the hashcode for this BOM.
       * @see java.lang.Object#hashCode()
       */
      @Override
      public int hashCode() {
          int hashCode = getClass().hashCode();
          for (int b : bytes) {
              hashCode += b;
          }
          return hashCode;
      }
  
      /**
       * Provide a String representation of the BOM.
       *
       * @return the length of the BOM's bytes
       */
      @Override
      public String toString() {
          StringBuilder builder = new StringBuilder();
          builder.append(getClass().getSimpleName());
          builder.append('[');
          builder.append(charsetName);
          builder.append(": ");
          for (int i = 0; i < bytes.length; i++) {
              if (i > 0) {
                  builder.append(",");
              }
              builder.append("0x");
              builder.append(Integer.toHexString(0xFF & bytes[i]).toUpperCase());
          }
          builder.append(']');
          return builder.toString();
      }
  
  }
  