Java example source code file (ZipUtils.java)

This example Java source code file (ZipUtils.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

date, filetime, suppresswarnings, threading, threads, use, util, windows_epoch_in_microseconds, ziputils

The ZipUtils.java Java example source code

/*
 * Copyright (c) 2013, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

package java.util.zip;

import java.nio.file.attribute.FileTime;
import java.util.Date;
import java.util.concurrent.TimeUnit;

import static java.util.zip.ZipConstants.*;
import static java.util.zip.ZipConstants64.*;

class ZipUtils {

    // used to adjust values between Windows and java epoch
    private static final long WINDOWS_EPOCH_IN_MICROSECONDS = -11644473600000000L;

    /**
     * Converts Windows time (in microseconds, UTC/GMT) time to FileTime.
     */
    public static final FileTime winTimeToFileTime(long wtime) {
        return FileTime.from(wtime / 10 + WINDOWS_EPOCH_IN_MICROSECONDS,
                             TimeUnit.MICROSECONDS);
    }

    /**
     * Converts FileTime to Windows time.
     */
    public static final long fileTimeToWinTime(FileTime ftime) {
        return (ftime.to(TimeUnit.MICROSECONDS) - WINDOWS_EPOCH_IN_MICROSECONDS) * 10;
    }

    /**
     * Converts "standard Unix time"(in seconds, UTC/GMT) to FileTime
     */
    public static final FileTime unixTimeToFileTime(long utime) {
        return FileTime.from(utime, TimeUnit.SECONDS);
    }

    /**
     * Converts FileTime to "standard Unix time".
     */
    public static final long fileTimeToUnixTime(FileTime ftime) {
        return ftime.to(TimeUnit.SECONDS);
    }

    /**
     * Converts DOS time to Java time (number of milliseconds since epoch).
     */
    public static long dosToJavaTime(long dtime) {
        @SuppressWarnings("deprecation") // Use of date constructor.
        Date d = new Date((int)(((dtime >> 25) & 0x7f) + 80),
                          (int)(((dtime >> 21) & 0x0f) - 1),
                          (int)((dtime >> 16) & 0x1f),
                          (int)((dtime >> 11) & 0x1f),
                          (int)((dtime >> 5) & 0x3f),
                          (int)((dtime << 1) & 0x3e));
        return d.getTime();
    }

    /**
     * Converts Java time to DOS time.
     */
    @SuppressWarnings("deprecation") // Use of date methods
    public static long javaToDosTime(long time) {
        Date d = new Date(time);
        int year = d.getYear() + 1900;
        if (year < 1980) {
            return (1 << 21) | (1 << 16);
        }
        return (year - 1980) << 25 | (d.getMonth() + 1) << 21 |
               d.getDate() << 16 | d.getHours() << 11 | d.getMinutes() << 5 |
               d.getSeconds() >> 1;
    }

    /**
     * Fetches unsigned 16-bit value from byte array at specified offset.
     * The bytes are assumed to be in Intel (little-endian) byte order.
     */
    public static final int get16(byte b[], int off) {
        return Byte.toUnsignedInt(b[off]) | (Byte.toUnsignedInt(b[off+1]) << 8);
    }

    /**
     * Fetches unsigned 32-bit value from byte array at specified offset.
     * The bytes are assumed to be in Intel (little-endian) byte order.
     */
    public static final long get32(byte b[], int off) {
        return (get16(b, off) | ((long)get16(b, off+2) << 16)) & 0xffffffffL;
    }

    /**
     * Fetches signed 64-bit value from byte array at specified offset.
     * The bytes are assumed to be in Intel (little-endian) byte order.
     */
    public static final long get64(byte b[], int off) {
        return get32(b, off) | (get32(b, off+4) << 32);
    }
}