/*
 *  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.tools.zip;

/**
 * Utility class that represents a four byte integer with conversion rules for
 * the big endian byte order of ZIP files.
 * 
 */
public final class ZipLong implements Cloneable {

  private long value;

  /**
   * Create instance from a number.
   * 
   * @param value
   *          the long to store as a ZipLong
   * @since 1.1
   */
  public ZipLong(long value) {
    this.value = value;
  }

  /**
   * Create instance from bytes.
   * 
   * @param bytes
   *          the bytes to store as a ZipLong
   * @since 1.1
   */
  public ZipLong(byte[] bytes) {
    this(bytes, 0);
  }

  /**
   * Create instance from the four bytes starting at offset.
   * 
   * @param bytes
   *          the bytes to store as a ZipLong
   * @param offset
   *          the offset to start
   * @since 1.1
   */
  public ZipLong(byte[] bytes, int offset) {
    value = ZipLong.getValue(bytes, offset);
  }

  /**
   * Get value as four bytes in big endian byte order.
   * 
   * @since 1.1
   * @return value as four bytes in big endian order
   */
  public byte[] getBytes() {
    return ZipLong.getBytes(value);
  }

  /**
   * Get value as Java long.
   * 
   * @since 1.1
   * @return value as a long
   */
  public long getValue() {
    return value;
  }

  /**
   * Get value as four bytes in big endian byte order.
   * 
   * @param value
   *          the value to convert
   * @return value as four bytes in big endian byte order
   */
  public static byte[] getBytes(long value) {
    byte[] result = new byte[4];
    result[0] = (byte) ((value & 0xFF));
    result[1] = (byte) ((value & 0xFF00) >> 8);
    result[2] = (byte) ((value & 0xFF0000) >> 16);
    result[3] = (byte) ((value & 0xFF000000L) >> 24);
    return result;
  }

  /**
   * Helper method to get the value as a Java long from four bytes starting at
   * given array offset
   * 
   * @param bytes
   *          the array of bytes
   * @param offset
   *          the offset to start
   * @return the correspondanding Java long value
   */
  public static long getValue(byte[] bytes, int offset) {
    long value = (bytes[offset + 3] << 24) & 0xFF000000L;
    value += (bytes[offset + 2] << 16) & 0xFF0000;
    value += (bytes[offset + 1] << 8) & 0xFF00;
    value += (bytes[offset] & 0xFF);
    return value;
  }

  /**
   * Helper method to get the value as a Java long from a four-byte array
   * 
   * @param bytes
   *          the array of bytes
   * @return the correspondanding Java long value
   */
  public static long getValue(byte[] bytes) {
    return getValue(bytes, 0);
  }

  /**
   * Override to make two instances with same value equal.
   * 
   * @param o
   *          an object to compare
   * @return true if the objects are equal
   * @since 1.1
   */
  public boolean equals(Object o) {
    if (o == null || !(o instanceof ZipLong)) {
      return false;
    }
    return value == ((ZipLong) o).getValue();
  }

  /**
   * Override to make two instances with same value equal.
   * 
   * @return the value stored in the ZipLong
   * @since 1.1
   */
  public int hashCode() {
    return (int) value;
  }
}