content: /*
   * 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.ctrip.framework.foundation.internals.io;
  
  import java.io.Serializable;
  
  /**
   * Byte Order Mark (BOM) representation - see {@link BOMInputStream}.
   *
   * @see BOMInputStream
   * @see <a href="http://en.wikipedia.org/wiki/Byte_order_mark">Wikipedia: Byte Order Mark</a>
   * @see <a href="http://www.w3.org/TR/2006/REC-xml-20060816/#sec-guessing">W3C: Autodetection of Character Encodings
   *      (Non-Normative)</a>
   * @version $Id: ByteOrderMark.java 1586504 2014-04-10 23:34:37Z ggregory $
   * @since 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);
  
    /**
     * UTF-32BE BOM (Big-Endian)
     * 
     * @since 2.2
     */
    public static final ByteOrderMark UTF_32BE = new ByteOrderMark("UTF-32BE", 0x00, 0x00, 0xFE, 0xFF);
  
    /**
     * UTF-32LE BOM (Little-Endian)
     * 
     * @since 2.2
     */
    public static final ByteOrderMark UTF_32LE = new ByteOrderMark("UTF-32LE", 0xFF, 0xFE, 0x00, 0x00);
  
    /**
     * Unicode BOM character; external form depends on the encoding.
     * 
     * @see <a href="http://unicode.org/faq/utf_bom.html#BOM">Byte Order Mark (BOM) FAQ</a>
     * @since 2.5
     */
    public static final char UTF_BOM = '\uFEFF';
  
    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(final String charsetName, final int... bytes) {
      if (charsetName == null || charsetName.isEmpty()) {
        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(final int pos) {
      return bytes[pos];
    }
  
    /**
     * Return a copy of the BOM's bytes.
     *
     * @return a copy of the BOM's bytes
     */
    public byte[] getBytes() {
      final 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(final Object obj) {
      if (!(obj instanceof ByteOrderMark)) {
        return false;
      }
      final 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 Object#hashCode()
     */
    @Override
    public int hashCode() {
      int hashCode = getClass().hashCode();
      for (final 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() {
      final 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();
    }
  
  }
  
  
  