poi/src/java/org/apache/poi/hpsf/Util.java

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/* ====================================================================
* The Apache Software License, Version 1.1
*
* Copyright (c) 2000 The Apache Software Foundation. All rights
* reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
*
* 3. The end-user documentation included with the redistribution,
* if any, must include the following acknowledgment:
* "This product includes software developed by the
* Apache Software Foundation (http://www.apache.org/)."
* Alternately, this acknowledgment may appear in the software itself,
* if and wherever such third-party acknowledgments normally appear.
*
* 4. The names "Apache" and "Apache Software Foundation" must
* not be used to endorse or promote products derived from this
* software without prior written permission. For written
* permission, please contact apache@apache.org.
*
* 5. Products derived from this software may not be called "Apache",
* nor may "Apache" appear in their name, without prior written
* permission of the Apache Software Foundation.
*
* THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
* ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
* USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
* ====================================================================
*
* This software consists of voluntary contributions made by many
* individuals on behalf of the Apache Software Foundation. For more
* information on the Apache Software Foundation, please see
* <http://www.apache.org/>.
*/
package org.apache.poi.hpsf;
import java.util.*;
/**
* <p>Provides various static utility methods.</p>
*
* @author Rainer Klute (klute@rainer-klute.de)
* @version $Id$
* @since 2002-02-09
*/
public class Util
{
/**
* <p>Checks whether two byte arrays <var>a</var> and <var>b</var>
* are equal. They are equal</p>
*
* <ul>
* <li><p>if they have the same length and</p></li>
*
* <li><p>if for each <var>i</var> with
* <var>i</var>&nbsp;&gt;=&nbsp;0 and
* <var>i</var>&nbsp;&lt;&nbsp;<var>a.length</var> holds
* <var>a</var>[<var>i</var>]&nbsp;==&nbsp;<var>b</var>[<var>i</var>].</p></li>
* </ul>
*/
public static boolean equal(final byte[] a, final byte[] b)
{
if (a.length != b.length)
return false;
for (int i = 0; i < a.length; i++)
if (a[i] != b[i])
return false;
return true;
}
/**
* <p>Copies a part of a byte array into another byte array.</p>
*/
public static void copy(final byte[] src, final int srcOffset,
final int length,
final byte[] dst, final int dstOffset)
{
for (int i = 0; i < length; i++)
dst[dstOffset + i] = src[srcOffset + i];
}
/**
* <p>Concatenates the contents of several byte arrays into a
* single one.</p>
*
* @param byteArrays The byte arrays to be concatened.
*
* @return A new byte array containing the concatenated byte
* arrays.
*/
public static byte[] cat(final byte[][] byteArrays)
{
int capacity = 0;
for (int i = 0; i < byteArrays.length; i++)
capacity += byteArrays[i].length;
final byte[] result = new byte[capacity];
int r = 0;
for (int i = 0; i < byteArrays.length; i++)
for (int j = 0; j < byteArrays[i].length; j++)
result[r++] = byteArrays[i][j];
return result;
}
/**
* <p>Copies bytes from a source byte array into a new byte
* array.</p>
*
* @param src Copy from this byte array.
*
* @param offset Start copying here.
*
* @param length Copy this many bytes.
*
* @return The new byte array. Its length is number of copied bytes.
*/
public static byte[] copy(final byte[] src, final int offset,
final int length)
{
final byte[] result = new byte[length];
copy(src, offset, length, result, 0);
return result;
}
/**
* <p>The difference between the Windows epoch (1601-01-01
* 00:00:00) and the Unix epoch (1970-01-01 00:00:00) in
* milliseconds: 11644473600000L. (Use your favorite spreadsheet
* program to verify the correctness of this value. By the way,
* did you notice that you can tell from the epochs which
* operating system is the modern one? :-))</p>
*/
public final static long EPOCH_DIFF = 11644473600000L;
/**
* <p>Converts a Windows FILETIME into a {@link Date}. The Windows
* FILETIME structure holds a date and time associated with a
* file. The structure identifies a 64-bit integer specifying the
* number of 100-nanosecond intervals which have passed since
* January 1, 1601. This 64-bit value is split into the two double
* word stored in the structure.</p>
*
* @param high The higher double word of the FILETIME structure.
*
* @param low The lower double word of the FILETIME structure.
*/
public static Date filetimeToDate(final int high, final int low)
{
final long filetime = ((long) high) << 32 | ((long) low);
final long ms_since_16010101 = filetime / (1000 * 10);
final long ms_since_19700101 = ms_since_16010101 - EPOCH_DIFF;
return new Date(ms_since_19700101);
}
}