/*

 * 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

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 */

package java.util.zip;

import java.nio.file.attribute.FileTime;

import java.time.Instant;

import java.time.LocalDateTime;

import java.time.ZoneId;

import java.util.concurrent.TimeUnit;

import static java.util.zip.ZipConstants.ENDHDR;

class ZipUtils {

    // used to adjust values between Windows and java epoch

    private static final long WINDOWS_EPOCH_IN_MICROSECONDS = -11644473600000000L;

    // used to indicate the corresponding windows time is not available

    public static final long WINDOWS_TIME_NOT_AVAILABLE = Long.MIN_VALUE;

    /**

     * 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;

    }

    /**

     * The upper bound of the 32-bit unix time, the "year 2038 problem".

     */

    public static final long UPPER_UNIXTIME_BOUND = 0x7fffffff;

    /**

     * 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) {

        LocalDateTime ldt = LocalDateTime.of(

                (int) (((dtime >> 25) & 0x7f) + 1980),

                (int) ((dtime >> 21) & 0x0f),

                (int) ((dtime >> 16) & 0x1f),

                (int) ((dtime >> 11) & 0x1f),

                (int) ((dtime >> 5) & 0x3f),

                (int) ((dtime << 1) & 0x3e));

        return TimeUnit.MILLISECONDS.convert(ldt.toEpochSecond(

                ZoneId.systemDefault().getRules().getOffset(ldt)), TimeUnit.SECONDS);

    }

    /**

     * Converts extended DOS time to Java time, where up to 1999 milliseconds

     * might be encoded into the upper half of the returned long.

     *

     * @param xdostime the extended DOS time value

     * @return milliseconds since epoch

     */

    public static long extendedDosToJavaTime(long xdostime) {

        long time = dosToJavaTime(xdostime);

        return time + (xdostime >> 32);

    }

    /**

     * Converts Java time to DOS time.

     */

    private static long javaToDosTime(long time) {

        Instant instant = Instant.ofEpochMilli(time);

        LocalDateTime ldt = LocalDateTime.ofInstant(

                instant, ZoneId.systemDefault());

        int year = ldt.getYear() - 1980;

        if (year < 0) {

            return (1 << 21) | (1 << 16);

        }

        return (year << 25 |

            ldt.getMonthValue() << 21 |

            ldt.getDayOfMonth() << 16 |

            ldt.getHour() << 11 |

            ldt.getMinute() << 5 |

            ldt.getSecond() >> 1) & 0xffffffffL;

    }

    /**

     * Converts Java time to DOS time, encoding any milliseconds lost

     * in the conversion into the upper half of the returned long.

     *

     * @param time milliseconds since epoch

     * @return DOS time with 2s remainder encoded into upper half

     */

    public static long javaToExtendedDosTime(long time) {

        if (time < 0) {

            return ZipEntry.DOSTIME_BEFORE_1980;

        }

        long dostime = javaToDosTime(time);

        return (dostime != ZipEntry.DOSTIME_BEFORE_1980)

                ? dostime + ((time % 2000) << 32)

                : ZipEntry.DOSTIME_BEFORE_1980;

    }

    /**

     * 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 (b[off] & 0xff) | ((b[off + 1] & 0xff) << 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);

    }

    /**

     * Fetches signed 32-bit value from byte array at specified offset.

     * The bytes are assumed to be in Intel (little-endian) byte order.

     *

     */

    public static final int get32S(byte b[], int off) {

        return (get16(b, off) | (get16(b, off+2) << 16));

    }

    // fields access methods

    static final int CH(byte[] b, int n) {

        return b[n] & 0xff ;

    }

    static final int SH(byte[] b, int n) {

        return (b[n] & 0xff) | ((b[n + 1] & 0xff) << 8);

    }

    static final long LG(byte[] b, int n) {

        return ((SH(b, n)) | (SH(b, n + 2) << 16)) & 0xffffffffL;

    }

    static final long LL(byte[] b, int n) {

        return (LG(b, n)) | (LG(b, n + 4) << 32);

    }

    static final long GETSIG(byte[] b) {

        return LG(b, 0);

    }

    // local file (LOC) header fields

    static final long LOCSIG(byte[] b) { return LG(b, 0); } // signature

    static final int  LOCVER(byte[] b) { return SH(b, 4); } // version needed to extract

    static final int  LOCFLG(byte[] b) { return SH(b, 6); } // general purpose bit flags

    static final int  LOCHOW(byte[] b) { return SH(b, 8); } // compression method

    static final long LOCTIM(byte[] b) { return LG(b, 10);} // modification time

    static final long LOCCRC(byte[] b) { return LG(b, 14);} // crc of uncompressed data

    static final long LOCSIZ(byte[] b) { return LG(b, 18);} // compressed data size

    static final long LOCLEN(byte[] b) { return LG(b, 22);} // uncompressed data size

    static final int  LOCNAM(byte[] b) { return SH(b, 26);} // filename length

    static final int  LOCEXT(byte[] b) { return SH(b, 28);} // extra field length

    // extra local (EXT) header fields

    static final long EXTCRC(byte[] b) { return LG(b, 4);}  // crc of uncompressed data

    static final long EXTSIZ(byte[] b) { return LG(b, 8);}  // compressed size

    static final long EXTLEN(byte[] b) { return LG(b, 12);} // uncompressed size

    // end of central directory header (END) fields

    static final int  ENDSUB(byte[] b) { return SH(b, 8); }  // number of entries on this disk

    static final int  ENDTOT(byte[] b) { return SH(b, 10);}  // total number of entries

    static final long ENDSIZ(byte[] b) { return LG(b, 12);}  // central directory size

    static final long ENDOFF(byte[] b) { return LG(b, 16);}  // central directory offset

    static final int  ENDCOM(byte[] b) { return SH(b, 20);}  // size of zip file comment

    static final int  ENDCOM(byte[] b, int off) { return SH(b, off + 20);}

    // zip64 end of central directory recoder fields

    static final long ZIP64_ENDTOD(byte[] b) { return LL(b, 24);}  // total number of entries on disk

    static final long ZIP64_ENDTOT(byte[] b) { return LL(b, 32);}  // total number of entries

    static final long ZIP64_ENDSIZ(byte[] b) { return LL(b, 40);}  // central directory size

    static final long ZIP64_ENDOFF(byte[] b) { return LL(b, 48);}  // central directory offset

    static final long ZIP64_LOCOFF(byte[] b) { return LL(b, 8);}   // zip64 end offset

    // central directory header (CEN) fields

    static final long CENSIG(byte[] b, int pos) { return LG(b, pos + 0); }

    static final int  CENVEM(byte[] b, int pos) { return SH(b, pos + 4); }

    static final int  CENVER(byte[] b, int pos) { return SH(b, pos + 6); }

    static final int  CENFLG(byte[] b, int pos) { return SH(b, pos + 8); }

    static final int  CENHOW(byte[] b, int pos) { return SH(b, pos + 10);}

    static final long CENTIM(byte[] b, int pos) { return LG(b, pos + 12);}

    static final long CENCRC(byte[] b, int pos) { return LG(b, pos + 16);}

    static final long CENSIZ(byte[] b, int pos) { return LG(b, pos + 20);}

    static final long CENLEN(byte[] b, int pos) { return LG(b, pos + 24);}

    static final int  CENNAM(byte[] b, int pos) { return SH(b, pos + 28);}

    static final int  CENEXT(byte[] b, int pos) { return SH(b, pos + 30);}

    static final int  CENCOM(byte[] b, int pos) { return SH(b, pos + 32);}

    static final int  CENDSK(byte[] b, int pos) { return SH(b, pos + 34);}

    static final int  CENATT(byte[] b, int pos) { return SH(b, pos + 36);}

    static final long CENATX(byte[] b, int pos) { return LG(b, pos + 38);}

    static final long CENOFF(byte[] b, int pos) { return LG(b, pos + 42);}

    // The END header is followed by a variable length comment of size < 64k.

    static final long END_MAXLEN = 0xFFFF + ENDHDR;

    static final int READBLOCKSZ = 128;

}