001    /*
002     * Licensed to the Apache Software Foundation (ASF) under one
003     * or more contributor license agreements.  See the NOTICE file
004     * distributed with this work for additional information
005     * regarding copyright ownership.  The ASF licenses this file
006     * to you under the Apache License, Version 2.0 (the
007     * "License"); you may not use this file except in compliance
008     * with the License.  You may obtain a copy of the License at
009     *
010     * http://www.apache.org/licenses/LICENSE-2.0
011     *
012     * Unless required by applicable law or agreed to in writing,
013     * software distributed under the License is distributed on an
014     * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
015     * KIND, either express or implied.  See the License for the
016     * specific language governing permissions and limitations
017     * under the License.
018     */
019    package org.apache.commons.compress.archivers.ar;
020    
021    import java.io.IOException;
022    import java.io.InputStream;
023    
024    import org.apache.commons.compress.archivers.ArchiveEntry;
025    import org.apache.commons.compress.archivers.ArchiveInputStream;
026    import org.apache.commons.compress.utils.ArchiveUtils;
027    
028    /**
029     * Implements the "ar" archive format as an input stream.
030     * 
031     * @NotThreadSafe
032     * 
033     */
034    public class ArArchiveInputStream extends ArchiveInputStream {
035    
036        private final InputStream input;
037        private long offset = 0;
038        private boolean closed;
039        
040        /*
041         * If getNextEnxtry has been called, the entry metadata is stored in
042         * currentEntry.
043         */
044        private ArArchiveEntry currentEntry = null;
045        
046        /*
047         * The offset where the current entry started. -1 if no entry has been
048         * called
049         */
050        private long entryOffset = -1;
051    
052        /**
053         * Constructs an Ar input stream with the referenced stream
054         * 
055         * @param pInput
056         *            the ar input stream
057         */
058        public ArArchiveInputStream(final InputStream pInput) {
059            input = pInput;
060            closed = false;
061        }
062    
063        /**
064         * Returns the next AR entry in this stream.
065         * 
066         * @return the next AR entry.
067         * @throws IOException
068         *             if the entry could not be read
069         */
070        public ArArchiveEntry getNextArEntry() throws IOException {
071            if (currentEntry != null) {
072                final long entryEnd = entryOffset + currentEntry.getLength();
073                while (offset < entryEnd) {
074                    int x = read();
075                    if (x == -1) {
076                        // hit EOF before previous entry was complete
077                        // TODO: throw an exception instead?
078                        return null;
079                    }
080                }
081                currentEntry = null;
082            }
083    
084            if (offset == 0) {
085                final byte[] expected = ArchiveUtils.toAsciiBytes(ArArchiveEntry.HEADER);
086                final byte[] realized = new byte[expected.length];
087                final int read = read(realized);
088                if (read != expected.length) {
089                    throw new IOException("failed to read header. Occured at byte: " + getCount());
090                }
091                for (int i = 0; i < expected.length; i++) {
092                    if (expected[i] != realized[i]) {
093                        throw new IOException("invalid header " + ArchiveUtils.toAsciiString(realized));
094                    }
095                }
096            }
097    
098            if (offset % 2 != 0) {
099                if (read() < 0) {
100                    // hit eof
101                    return null;
102                }
103            }
104    
105            if (input.available() == 0) {
106                return null;
107            }
108    
109            final byte[] name = new byte[16];
110            final byte[] lastmodified = new byte[12];
111            final byte[] userid = new byte[6];
112            final byte[] groupid = new byte[6];
113            final byte[] filemode = new byte[8];
114            final byte[] length = new byte[10];
115    
116            read(name);
117            read(lastmodified);
118            read(userid);
119            read(groupid);
120            read(filemode);
121            read(length);
122    
123            {
124                final byte[] expected = ArchiveUtils.toAsciiBytes(ArArchiveEntry.TRAILER);
125                final byte[] realized = new byte[expected.length];
126                final int read = read(realized);
127                if (read != expected.length) {
128                    throw new IOException("failed to read entry header. Occured at byte: " + getCount());
129                }
130                for (int i = 0; i < expected.length; i++) {
131                    if (expected[i] != realized[i]) {
132                        throw new IOException("invalid entry header. not read the content? Occured at byte: " + getCount());
133                    }
134                }
135            }
136    
137            entryOffset = offset;
138    
139            // SVR4/GNU adds a trailing "/" to names
140            // entry name is stored as ASCII string
141            String temp = ArchiveUtils.toAsciiString(name).trim();
142            if (temp.endsWith("/")) {
143                temp = temp.substring(0, temp.length() - 1);
144            }
145            currentEntry = new ArArchiveEntry(temp, Long.parseLong(new String(length).trim()));
146            return currentEntry;
147        }
148    
149        /*
150         * (non-Javadoc)
151         * 
152         * @see
153         * org.apache.commons.compress.archivers.ArchiveInputStream#getNextEntry()
154         */
155        public ArchiveEntry getNextEntry() throws IOException {
156            return getNextArEntry();
157        }
158    
159        /*
160         * (non-Javadoc)
161         * 
162         * @see java.io.InputStream#close()
163         */
164        public void close() throws IOException {
165            if (!closed) {
166                closed = true;
167                input.close();
168            }
169            currentEntry = null;
170        }
171    
172        /*
173         * (non-Javadoc)
174         * 
175         * @see java.io.InputStream#read(byte[], int, int)
176         */
177        public int read(byte[] b, final int off, final int len) throws IOException {
178            int toRead = len;
179            if (currentEntry != null) {
180                final long entryEnd = entryOffset + currentEntry.getLength();
181                if (len > 0 && entryEnd > offset) {
182                    toRead = (int) Math.min(len, entryEnd - offset);
183                } else {
184                    return -1;
185                }
186            }
187            final int ret = this.input.read(b, off, toRead);
188            count(ret);
189            offset += (ret > 0 ? ret : 0);
190            return ret;
191        }
192    
193        /**
194         * Checks if the signature matches ASCII "!<arch>" followed by a single LF
195         * control character
196         * 
197         * @param signature
198         *            the bytes to check
199         * @param length
200         *            the number of bytes to check
201         * @return true, if this stream is an Ar archive stream, false otherwise
202         */
203        public static boolean matches(byte[] signature, int length) {
204            // 3c21 7261 6863 0a3e
205    
206            if (length < 8) {
207                return false;
208            }
209            if (signature[0] != 0x21) {
210                return false;
211            }
212            if (signature[1] != 0x3c) {
213                return false;
214            }
215            if (signature[2] != 0x61) {
216                return false;
217            }
218            if (signature[3] != 0x72) {
219                return false;
220            }
221            if (signature[4] != 0x63) {
222                return false;
223            }
224            if (signature[5] != 0x68) {
225                return false;
226            }
227            if (signature[6] != 0x3e) {
228                return false;
229            }
230            if (signature[7] != 0x0a) {
231                return false;
232            }
233    
234            return true;
235        }
236    
237    }