    001    /*
    002     *  Licensed to the Apache Software Foundation (ASF) under one or more
    003     *  contributor license agreements.  See the NOTICE file distributed with
    004     *  this work for additional information regarding copyright ownership.
    005     *  The ASF licenses this file to You under the Apache License, Version 2.0
    006     *  (the "License"); you may not use this file except in compliance with
    007     *  the License.  You may obtain a copy of the License at
    008     *
    009     *      http://www.apache.org/licenses/LICENSE-2.0
    010     *
    011     *  Unless required by applicable law or agreed to in writing, software
    012     *  distributed under the License is distributed on an "AS IS" BASIS,
    013     *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    014     *  See the License for the specific language governing permissions and
    015     *  limitations under the License.
    016     *
    017     */
    018    package org.apache.commons.compress.archivers.zip;
    019
    020    /**
    021     * Utility class that represents a four byte integer with conversion
    022     * rules for the big endian byte order of ZIP files.
    023     * @Immutable
    024     */
    025    public final class ZipLong implements Cloneable {
    026
    027        private static final int WORD = 4;
    028        //private static final int BYTE_BIT_SIZE = 8;
    029        private static final int BYTE_MASK = 0xFF;
    030
    031        private static final int BYTE_1 = 1;
    032        private static final int BYTE_1_MASK = 0xFF00;
    033        private static final int BYTE_1_SHIFT = 8;
    034
    035        private static final int BYTE_2 = 2;
    036        private static final int BYTE_2_MASK = 0xFF0000;
    037        private static final int BYTE_2_SHIFT = 16;
    038
    039        private static final int BYTE_3 = 3;
    040        private static final long BYTE_3_MASK = 0xFF000000L;
    041        private static final int BYTE_3_SHIFT = 24;
    042
    043        private final long value;
    044
    045        /** Central File Header Signature */
    046        public static final ZipLong CFH_SIG = new ZipLong(0X02014B50L);
    047
    048        /** Local File Header Signature */
    049        public static final ZipLong LFH_SIG = new ZipLong(0X04034B50L);
    050
    051        /**
    052         * Create instance from a number.
    053         * @param value the long to store as a ZipLong
    054         */
    055        public ZipLong(long value) {
    056            this.value = value;
    057        }
    058
    059        /**
    060         * Create instance from bytes.
    061         * @param bytes the bytes to store as a ZipLong
    062         */
    063        public ZipLong (byte[] bytes) {
    064            this(bytes, 0);
    065        }
    066
    067        /**
    068         * Create instance from the four bytes starting at offset.
    069         * @param bytes the bytes to store as a ZipLong
    070         * @param offset the offset to start
    071         */
    072        public ZipLong (byte[] bytes, int offset) {
    073            value = ZipLong.getValue(bytes, offset);
    074        }
    075
    076        /**
    077         * Get value as four bytes in big endian byte order.
    078         * @return value as four bytes in big endian order
    079         */
    080        public byte[] getBytes() {
    081            return ZipLong.getBytes(value);
    082        }
    083
    084        /**
    085         * Get value as Java long.
    086         * @return value as a long
    087         */
    088        public long getValue() {
    089            return value;
    090        }
    091
    092        /**
    093         * Get value as four bytes in big endian byte order.
    094         * @param value the value to convert
    095         * @return value as four bytes in big endian byte order
    096         */
    097        public static byte[] getBytes(long value) {
    098            byte[] result = new byte[WORD];
    099            result[0] = (byte) ((value & BYTE_MASK));
    100            result[BYTE_1] = (byte) ((value & BYTE_1_MASK) >> BYTE_1_SHIFT);
    101            result[BYTE_2] = (byte) ((value & BYTE_2_MASK) >> BYTE_2_SHIFT);
    102            result[BYTE_3] = (byte) ((value & BYTE_3_MASK) >> BYTE_3_SHIFT);
    103            return result;
    104        }
    105
    106        /**
    107         * Helper method to get the value as a Java long from four bytes starting at given array offset
    108         * @param bytes the array of bytes
    109         * @param offset the offset to start
    110         * @return the correspondanding Java long value
    111         */
    112        public static long getValue(byte[] bytes, int offset) {
    113            long value = (bytes[offset + BYTE_3] << BYTE_3_SHIFT) & BYTE_3_MASK;
    114            value += (bytes[offset + BYTE_2] << BYTE_2_SHIFT) & BYTE_2_MASK;
    115            value += (bytes[offset + BYTE_1] << BYTE_1_SHIFT) & BYTE_1_MASK;
    116            value += (bytes[offset] & BYTE_MASK);
    117            return value;
    118        }
    119
    120        /**
    121         * Helper method to get the value as a Java long from a four-byte array
    122         * @param bytes the array of bytes
    123         * @return the correspondanding Java long value
    124         */
    125        public static long getValue(byte[] bytes) {
    126            return getValue(bytes, 0);
    127        }
    128
    129        /**
    130         * Override to make two instances with same value equal.
    131         * @param o an object to compare
    132         * @return true if the objects are equal
    133         */
    134        public boolean equals(Object o) {
    135            if (o == null || !(o instanceof ZipLong)) {
    136                return false;
    137            }
    138            return value == ((ZipLong) o).getValue();
    139        }
    140
    141        /**
    142         * Override to make two instances with same value equal.
    143         * @return the value stored in the ZipLong
    144         */
    145        public int hashCode() {
    146            return (int) value;
    147        }
    148
    149        public Object clone() {
    150            try {
    151                return super.clone();
    152            } catch (CloneNotSupportedException cnfe) {
    153                // impossible
    154                throw new RuntimeException(cnfe);
    155            }
    156        }
    157    }