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
019/*
020 * This package is based on the work done by Timothy Gerard Endres
021 * (time@ice.com) to whom the Ant project is very grateful for his great code.
022 */
023
024package org.apache.activemq.console.command.store.tar;
025
026/**
027 * This class provides static utility methods to work with byte streams.
028 *
029 */
030// CheckStyle:HideUtilityClassConstructorCheck OFF (bc)
031public class TarUtils {
032
033    private static final int BYTE_MASK = 255;
034
035    /**
036     * Parse an octal string from a header buffer. This is used for the
037     * file permission mode value.
038     *
039     * @param header The header buffer from which to parse.
040     * @param offset The offset into the buffer from which to parse.
041     * @param length The number of header bytes to parse.
042     * @return The long value of the octal string.
043     */
044    public static long parseOctal(byte[] header, int offset, int length) {
045        long    result = 0;
046        boolean stillPadding = true;
047        int     end = offset + length;
048
049        for (int i = offset; i < end; ++i) {
050            if (header[i] == 0) {
051                break;
052            }
053
054            if (header[i] == (byte) ' ' || header[i] == '0') {
055                if (stillPadding) {
056                    continue;
057                }
058
059                if (header[i] == (byte) ' ') {
060                    break;
061                }
062            }
063
064            stillPadding = false;
065            // CheckStyle:MagicNumber OFF
066            result = (result << 3) + (header[i] - '0');
067            // CheckStyle:MagicNumber ON
068        }
069
070        return result;
071    }
072
073    /**
074     * Parse an entry name from a header buffer.
075     *
076     * @param header The header buffer from which to parse.
077     * @param offset The offset into the buffer from which to parse.
078     * @param length The number of header bytes to parse.
079     * @return The header's entry name.
080     */
081    public static StringBuffer parseName(byte[] header, int offset, int length) {
082        StringBuffer result = new StringBuffer(length);
083        int          end = offset + length;
084
085        for (int i = offset; i < end; ++i) {
086            if (header[i] == 0) {
087                break;
088            }
089
090            result.append((char) header[i]);
091        }
092
093        return result;
094    }
095
096    /**
097     * Determine the number of bytes in an entry name.
098     *
099     * @param name The header name from which to parse.
100     * @param buf The buffer from which to parse.
101     * @param offset The offset into the buffer from which to parse.
102     * @param length The number of header bytes to parse.
103     * @return The number of bytes in a header's entry name.
104     */
105    public static int getNameBytes(StringBuffer name, byte[] buf, int offset, int length) {
106        int i;
107
108        for (i = 0; i < length && i < name.length(); ++i) {
109            buf[offset + i] = (byte) name.charAt(i);
110        }
111
112        for (; i < length; ++i) {
113            buf[offset + i] = 0;
114        }
115
116        return offset + length;
117    }
118
119    /**
120     * Parse an octal integer from a header buffer.
121     *
122     * @param value The header value
123     * @param buf The buffer from which to parse.
124     * @param offset The offset into the buffer from which to parse.
125     * @param length The number of header bytes to parse.
126     * @return The integer value of the octal bytes.
127     */
128    public static int getOctalBytes(long value, byte[] buf, int offset, int length) {
129        int    idx = length - 1;
130
131        buf[offset + idx] = 0;
132        --idx;
133        buf[offset + idx] = (byte) ' ';
134        --idx;
135
136        if (value == 0) {
137            buf[offset + idx] = (byte) '0';
138            --idx;
139        } else {
140            for (long val = value; idx >= 0 && val > 0; --idx) {
141                // CheckStyle:MagicNumber OFF
142                buf[offset + idx] = (byte) ((byte) '0' + (byte) (val & 7));
143                val = val >> 3;
144                // CheckStyle:MagicNumber ON
145            }
146        }
147
148        for (; idx >= 0; --idx) {
149            buf[offset + idx] = (byte) ' ';
150        }
151
152        return offset + length;
153    }
154
155    /**
156     * Parse an octal long integer from a header buffer.
157     *
158     * @param value The header value
159     * @param buf The buffer from which to parse.
160     * @param offset The offset into the buffer from which to parse.
161     * @param length The number of header bytes to parse.
162     * @return The long value of the octal bytes.
163     */
164    public static int getLongOctalBytes(long value, byte[] buf, int offset, int length) {
165        byte[] temp = new byte[length + 1];
166
167        getOctalBytes(value, temp, 0, length + 1);
168        System.arraycopy(temp, 0, buf, offset, length);
169
170        return offset + length;
171    }
172
173    /**
174     * Parse the checksum octal integer from a header buffer.
175     *
176     * @param value The header value
177     * @param buf The buffer from which to parse.
178     * @param offset The offset into the buffer from which to parse.
179     * @param length The number of header bytes to parse.
180     * @return The integer value of the entry's checksum.
181     */
182    public static int getCheckSumOctalBytes(long value, byte[] buf, int offset, int length) {
183        getOctalBytes(value, buf, offset, length);
184
185        buf[offset + length - 1] = (byte) ' ';
186        buf[offset + length - 2] = 0;
187
188        return offset + length;
189    }
190
191    /**
192     * Compute the checksum of a tar entry header.
193     *
194     * @param buf The tar entry's header buffer.
195     * @return The computed checksum.
196     */
197    public static long computeCheckSum(byte[] buf) {
198        long sum = 0;
199
200        for (int i = 0; i < buf.length; ++i) {
201            sum += BYTE_MASK & buf[i];
202        }
203
204        return sum;
205    }
206}