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 // Storage area for extra long names (GNU ar)
047 private byte[] namebuffer = null;
048
049 /*
050 * The offset where the current entry started. -1 if no entry has been
051 * called
052 */
053 private long entryOffset = -1;
054
055 /**
056 * Constructs an Ar input stream with the referenced stream
057 *
058 * @param pInput
059 * the ar input stream
060 */
061 public ArArchiveInputStream(final InputStream pInput) {
062 input = pInput;
063 closed = false;
064 }
065
066 /**
067 * Returns the next AR entry in this stream.
068 *
069 * @return the next AR entry.
070 * @throws IOException
071 * if the entry could not be read
072 */
073 public ArArchiveEntry getNextArEntry() throws IOException {
074 if (currentEntry != null) {
075 final long entryEnd = entryOffset + currentEntry.getLength();
076 while (offset < entryEnd) {
077 int x = read();
078 if (x == -1) {
079 // hit EOF before previous entry was complete
080 // TODO: throw an exception instead?
081 return null;
082 }
083 }
084 currentEntry = null;
085 }
086
087 if (offset == 0) {
088 final byte[] expected = ArchiveUtils.toAsciiBytes(ArArchiveEntry.HEADER);
089 final byte[] realized = new byte[expected.length];
090 final int read = read(realized);
091 if (read != expected.length) {
092 throw new IOException("failed to read header. Occured at byte: " + getBytesRead());
093 }
094 for (int i = 0; i < expected.length; i++) {
095 if (expected[i] != realized[i]) {
096 throw new IOException("invalid header " + ArchiveUtils.toAsciiString(realized));
097 }
098 }
099 }
100
101 if (offset % 2 != 0) {
102 if (read() < 0) {
103 // hit eof
104 return null;
105 }
106 }
107
108 if (input.available() == 0) {
109 return null;
110 }
111
112 final byte[] name = new byte[16];
113 final byte[] lastmodified = new byte[12];
114 final byte[] userid = new byte[6];
115 final byte[] groupid = new byte[6];
116 final byte[] filemode = new byte[8];
117 final byte[] length = new byte[10];
118
119 read(name);
120 read(lastmodified);
121 read(userid);
122 read(groupid);
123 read(filemode);
124 read(length);
125
126 {
127 final byte[] expected = ArchiveUtils.toAsciiBytes(ArArchiveEntry.TRAILER);
128 final byte[] realized = new byte[expected.length];
129 final int read = read(realized);
130 if (read != expected.length) {
131 throw new IOException("failed to read entry trailer. Occured at byte: " + getBytesRead());
132 }
133 for (int i = 0; i < expected.length; i++) {
134 if (expected[i] != realized[i]) {
135 throw new IOException("invalid entry trailer. not read the content? Occured at byte: " + getBytesRead());
136 }
137 }
138 }
139
140 entryOffset = offset;
141
142 // GNU ar stores multiple extended filenames in the data section of a file with the name "//", this record is referred to by future headers. A header references an extended filename by storing a "/" followed by a decimal offset to the start of the filename in the extended filename data section. The format of this "//" file itself is simply a list of the long filenames, each separated by one or more LF characters. Note that the decimal offsets are number of characters, not line or string number within the "//" file.
143 //
144 // GNU ar uses a '/' to mark the end of the filename; this allows for the use of spaces without the use of an extended filename.
145
146 // entry name is stored as ASCII string
147 String temp = ArchiveUtils.toAsciiString(name).trim();
148
149 if (temp.equals("//")){ // GNU extended filenames entry
150 int bufflen = asInt(length); // Assume length will fit in an int
151 namebuffer = new byte[bufflen];
152 int read = read(namebuffer, 0, bufflen);
153 if (read != bufflen){
154 throw new IOException("Failed to read complete // record: expected="+bufflen+" read="+read);
155 }
156 currentEntry = new ArArchiveEntry(temp, bufflen);
157 return getNextArEntry();
158 } else if (temp.endsWith("/")) { // GNU terminator
159 temp = temp.substring(0, temp.length() - 1);
160 } else if (temp.matches("^/\\d+")) {// GNU long filename ref.
161 int offset = Integer.parseInt(temp.substring(1));// get the offset
162 temp = getExtendedName(offset); // convert to the long name
163 }
164 currentEntry = new ArArchiveEntry(temp, asLong(length), asInt(userid),
165 asInt(groupid), asInt(filemode, 8),
166 asLong(lastmodified));
167 return currentEntry;
168 }
169
170 /**
171 * Get an extended name from the GNU extended name buffer.
172 *
173 * @param offset pointer to entry within the buffer
174 * @return the extended file name; without trailing "/" if present.
175 * @throws IOException if name not found or buffer not set up
176 */
177 private String getExtendedName(int offset) throws IOException{
178 if (namebuffer == null) {
179 throw new IOException("Cannot process GNU long filename as no // record was found");
180 }
181 for(int i=offset; i < namebuffer.length; i++){
182 if (namebuffer[i]=='\012'){
183 if (namebuffer[i-1]=='/') {
184 i--; // drop trailing /
185 }
186 return ArchiveUtils.toAsciiString(namebuffer, offset, i-offset);
187 }
188 }
189 throw new IOException("Failed to read entry: "+offset);
190 }
191 private long asLong(byte[] input) {
192 return Long.parseLong(new String(input).trim());
193 }
194
195 private int asInt(byte[] input) {
196 return asInt(input, 10);
197 }
198
199 private int asInt(byte[] input, int base) {
200 return Integer.parseInt(new String(input).trim(), base);
201 }
202
203 /*
204 * (non-Javadoc)
205 *
206 * @see
207 * org.apache.commons.compress.archivers.ArchiveInputStream#getNextEntry()
208 */
209 public ArchiveEntry getNextEntry() throws IOException {
210 return getNextArEntry();
211 }
212
213 /*
214 * (non-Javadoc)
215 *
216 * @see java.io.InputStream#close()
217 */
218 public void close() throws IOException {
219 if (!closed) {
220 closed = true;
221 input.close();
222 }
223 currentEntry = null;
224 }
225
226 /*
227 * (non-Javadoc)
228 *
229 * @see java.io.InputStream#read(byte[], int, int)
230 */
231 public int read(byte[] b, final int off, final int len) throws IOException {
232 int toRead = len;
233 if (currentEntry != null) {
234 final long entryEnd = entryOffset + currentEntry.getLength();
235 if (len > 0 && entryEnd > offset) {
236 toRead = (int) Math.min(len, entryEnd - offset);
237 } else {
238 return -1;
239 }
240 }
241 final int ret = this.input.read(b, off, toRead);
242 count(ret);
243 offset += (ret > 0 ? ret : 0);
244 return ret;
245 }
246
247 /**
248 * Checks if the signature matches ASCII "!<arch>" followed by a single LF
249 * control character
250 *
251 * @param signature
252 * the bytes to check
253 * @param length
254 * the number of bytes to check
255 * @return true, if this stream is an Ar archive stream, false otherwise
256 */
257 public static boolean matches(byte[] signature, int length) {
258 // 3c21 7261 6863 0a3e
259
260 if (length < 8) {
261 return false;
262 }
263 if (signature[0] != 0x21) {
264 return false;
265 }
266 if (signature[1] != 0x3c) {
267 return false;
268 }
269 if (signature[2] != 0x61) {
270 return false;
271 }
272 if (signature[3] != 0x72) {
273 return false;
274 }
275 if (signature[4] != 0x63) {
276 return false;
277 }
278 if (signature[5] != 0x68) {
279 return false;
280 }
281 if (signature[6] != 0x3e) {
282 return false;
283 }
284 if (signature[7] != 0x0a) {
285 return false;
286 }
287
288 return true;
289 }
290
291 }