TarBuffer


1   /*
2    *  Licensed to the Apache Software Foundation (ASF) under one or more
3    *  contributor license agreements.  See the NOTICE file distributed with
4    *  this work for additional information regarding copyright ownership.
5    *  The ASF licenses this file to You under the Apache License, Version 2.0
6    *  (the "License"); you may not use this file except in compliance with
7    *  the License.  You may obtain a copy of the License at
8    *
9    *      http://www.apache.org/licenses/LICENSE-2.0
10   *
11   *  Unless required by applicable law or agreed to in writing, software
12   *  distributed under the License is distributed on an "AS IS" BASIS,
13   *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14   *  See the License for the specific language governing permissions and
15   *  limitations under the License.
16   *
17   */
18  
19  /*
20   * This package is based on the work done by Timothy Gerard Endres
21   * (time@ice.com) to whom the Ant project is very grateful for his great code.
22   */
23  
24  package org.apache.tools.tar;
25  
26  import java.io.InputStream  ;
27  import java.io.OutputStream  ;
28  import java.io.IOException  ;
29  import java.util.Arrays  ;
30  
31  /**
32   * The TarBuffer class implements the tar archive concept
33   * of a buffered input stream. This concept goes back to the
34   * days of blocked tape drives and special io devices. In the
35   * Java universe, the only real function that this class
36   * performs is to ensure that files have the correct "block"
37   * size, or other tars will complain.
38   * <p>
39   * You should never have a need to access this class directly.
40   * TarBuffers are created by Tar IO Streams.
41   *
42   */
43  
44  public class TarBuffer {
45  
46      /** Default record size */
47      public static final int DEFAULT_RCDSIZE = (512);
48  
49      /** Default block size */
50      public static final int DEFAULT_BLKSIZE = (DEFAULT_RCDSIZE * 20);
51  
52      private InputStream       inStream;
53      private OutputStream      outStream;
54      private byte[]          blockBuffer;
55      private int             currBlkIdx;
56      private int             currRecIdx;
57      private int             blockSize;
58      private int             recordSize;
59      private int             recsPerBlock;
60      private boolean         debug;
61  
62      /**
63       * Constructor for a TarBuffer on an input stream.
64       * @param inStream the input stream to use
65       */
66      public TarBuffer(InputStream   inStream) {
67          this(inStream, TarBuffer.DEFAULT_BLKSIZE);
68      }
69  
70      /**
71       * Constructor for a TarBuffer on an input stream.
72       * @param inStream the input stream to use
73       * @param blockSize the block size to use
74       */
75      public TarBuffer(InputStream   inStream, int blockSize) {
76          this(inStream, blockSize, TarBuffer.DEFAULT_RCDSIZE);
77      }
78  
79      /**
80       * Constructor for a TarBuffer on an input stream.
81       * @param inStream the input stream to use
82       * @param blockSize the block size to use
83       * @param recordSize the record size to use
84       */
85      public TarBuffer(InputStream   inStream, int blockSize, int recordSize) {
86          this.inStream = inStream;
87          this.outStream = null;
88  
89          this.initialize(blockSize, recordSize);
90      }
91  
92      /**
93       * Constructor for a TarBuffer on an output stream.
94       * @param outStream the output stream to use
95       */
96      public TarBuffer(OutputStream   outStream) {
97          this(outStream, TarBuffer.DEFAULT_BLKSIZE);
98      }
99  
100     /**
101      * Constructor for a TarBuffer on an output stream.
102      * @param outStream the output stream to use
103      * @param blockSize the block size to use
104      */
105     public TarBuffer(OutputStream   outStream, int blockSize) {
106         this(outStream, blockSize, TarBuffer.DEFAULT_RCDSIZE);
107     }
108 
109     /**
110      * Constructor for a TarBuffer on an output stream.
111      * @param outStream the output stream to use
112      * @param blockSize the block size to use
113      * @param recordSize the record size to use
114      */
115     public TarBuffer(OutputStream   outStream, int blockSize, int recordSize) {
116         this.inStream = null;
117         this.outStream = outStream;
118 
119         this.initialize(blockSize, recordSize);
120     }
121 
122     /**
123      * Initialization common to all constructors.
124      */
125     private void initialize(int blockSize, int recordSize) {
126         this.debug = false;
127         this.blockSize = blockSize;
128         this.recordSize = recordSize;
129         this.recsPerBlock = (this.blockSize / this.recordSize);
130         this.blockBuffer = new byte[this.blockSize];
131 
132         if (this.inStream != null) {
133             this.currBlkIdx = -1;
134             this.currRecIdx = this.recsPerBlock;
135         } else {
136             this.currBlkIdx = 0;
137             this.currRecIdx = 0;
138         }
139     }
140 
141     /**
142      * Get the TAR Buffer's block size. Blocks consist of multiple records.
143      * @return the block size
144      */
145     public int getBlockSize() {
146         return this.blockSize;
147     }
148 
149     /**
150      * Get the TAR Buffer's record size.
151      * @return the record size
152      */
153     public int getRecordSize() {
154         return this.recordSize;
155     }
156 
157     /**
158      * Set the debugging flag for the buffer.
159      *
160      * @param debug If true, print debugging output.
161      */
162     public void setDebug(boolean debug) {
163         this.debug = debug;
164     }
165 
166     /**
167      * Determine if an archive record indicate End of Archive. End of
168      * archive is indicated by a record that consists entirely of null bytes.
169      *
170      * @param record The record data to check.
171      * @return true if the record data is an End of Archive
172      */
173     public boolean isEOFRecord(byte[] record) {
174         for (int i = 0, sz = this.getRecordSize(); i < sz; ++i) {
175             if (record[i] != 0) {
176                 return false;
177             }
178         }
179 
180         return true;
181     }
182 
183     /**
184      * Skip over a record on the input stream.
185      * @throws IOException on error
186      */
187     public void skipRecord() throws IOException   {
188         if (this.debug) {
189             System.err.println("SkipRecord: recIdx = " + this.currRecIdx
190                                + " blkIdx = " + this.currBlkIdx);
191         }
192 
193         if (this.inStream == null) {
194             throw new IOException  ("reading (via skip) from an output buffer");
195         }
196 
197         if (this.currRecIdx >= this.recsPerBlock) {
198             if (!this.readBlock()) {
199                 return;    // UNDONE
200             }
201         }
202 
203         this.currRecIdx++;
204     }
205 
206     /**
207      * Read a record from the input stream and return the data.
208      *
209      * @return The record data.
210      * @throws IOException on error
211      */
212     public byte[] readRecord() throws IOException   {
213         if (this.debug) {
214             System.err.println("ReadRecord: recIdx = " + this.currRecIdx
215                                + " blkIdx = " + this.currBlkIdx);
216         }
217 
218         if (this.inStream == null) {
219             throw new IOException  ("reading from an output buffer");
220         }
221 
222         if (this.currRecIdx >= this.recsPerBlock) {
223             if (!this.readBlock()) {
224                 return null;
225             }
226         }
227 
228         byte[] result = new byte[this.recordSize];
229 
230         System.arraycopy(this.blockBuffer,
231                          (this.currRecIdx * this.recordSize), result, 0,
232                          this.recordSize);
233 
234         this.currRecIdx++;
235 
236         return result;
237     }
238 
239     /**
240      * @return false if End-Of-File, else true
241      */
242     private boolean readBlock() throws IOException   {
243         if (this.debug) {
244             System.err.println("ReadBlock: blkIdx = " + this.currBlkIdx);
245         }
246 
247         if (this.inStream == null) {
248             throw new IOException  ("reading from an output buffer");
249         }
250 
251         this.currRecIdx = 0;
252 
253         int offset = 0;
254         int bytesNeeded = this.blockSize;
255 
256         while (bytesNeeded > 0) {
257             long numBytes = this.inStream.read(this.blockBuffer, offset,
258                                                bytesNeeded);
259 
260             //
261             // NOTE
262             // We have fit EOF, and the block is not full!
263             //
264             // This is a broken archive. It does not follow the standard
265             // blocking algorithm. However, because we are generous, and
266             // it requires little effort, we will simply ignore the error
267             // and continue as if the entire block were read. This does
268             // not appear to break anything upstream. We used to return
269             // false in this case.
270             //
271             // Thanks to 'Yohann.Roussel@alcatel.fr' for this fix.
272             //
273             if (numBytes == -1) {
274                 if (offset == 0) {
275                     // Ensure that we do not read gigabytes of zeros
276                     // for a corrupt tar file.
277                     // See http://issues.apache.org/bugzilla/show_bug.cgi?id=39924
278                     return false;
279                 }
280                 // However, just leaving the unread portion of the buffer dirty does
281                 // cause problems in some cases.  This problem is described in
282                 // http://issues.apache.org/bugzilla/show_bug.cgi?id=29877
283                 //
284                 // The solution is to fill the unused portion of the buffer with zeros.
285 
286                 Arrays.fill(blockBuffer, offset, offset + bytesNeeded, (byte) 0);
287 
288                 break;
289             }
290 
291             offset += numBytes;
292             bytesNeeded -= numBytes;
293 
294             if (numBytes != this.blockSize) {
295                 if (this.debug) {
296                     System.err.println("ReadBlock: INCOMPLETE READ "
297                                        + numBytes + " of " + this.blockSize
298                                        + " bytes read.");
299                 }
300             }
301         }
302 
303         this.currBlkIdx++;
304 
305         return true;
306     }
307 
308     /**
309      * Get the current block number, zero based.
310      *
311      * @return The current zero based block number.
312      */
313     public int getCurrentBlockNum() {
314         return this.currBlkIdx;
315     }
316 
317     /**
318      * Get the current record number, within the current block, zero based.
319      * Thus, current offset = (currentBlockNum * recsPerBlk) + currentRecNum.
320      *
321      * @return The current zero based record number.
322      */
323     public int getCurrentRecordNum() {
324         return this.currRecIdx - 1;
325     }
326 
327     /**
328      * Write an archive record to the archive.
329      *
330      * @param record The record data to write to the archive.
331      * @throws IOException on error
332      */
333     public void writeRecord(byte[] record) throws IOException   {
334         if (this.debug) {
335             System.err.println("WriteRecord: recIdx = " + this.currRecIdx
336                                + " blkIdx = " + this.currBlkIdx);
337         }
338 
339         if (this.outStream == null) {
340             throw new IOException  ("writing to an input buffer");
341         }
342 
343         if (record.length != this.recordSize) {
344             throw new IOException  ("record to write has length '"
345                                   + record.length
346                                   + "' which is not the record size of '"
347                                   + this.recordSize + "'");
348         }
349 
350         if (this.currRecIdx >= this.recsPerBlock) {
351             this.writeBlock();
352         }
353 
354         System.arraycopy(record, 0, this.blockBuffer,
355                          (this.currRecIdx * this.recordSize),
356                          this.recordSize);
357 
358         this.currRecIdx++;
359     }
360 
361     /**
362      * Write an archive record to the archive, where the record may be
363      * inside of a larger array buffer. The buffer must be "offset plus
364      * record size" long.
365      *
366      * @param buf The buffer containing the record data to write.
367      * @param offset The offset of the record data within buf.
368      * @throws IOException on error
369      */
370     public void writeRecord(byte[] buf, int offset) throws IOException   {
371         if (this.debug) {
372             System.err.println("WriteRecord: recIdx = " + this.currRecIdx
373                                + " blkIdx = " + this.currBlkIdx);
374         }
375 
376         if (this.outStream == null) {
377             throw new IOException  ("writing to an input buffer");
378         }
379 
380         if ((offset + this.recordSize) > buf.length) {
381             throw new IOException  ("record has length '" + buf.length
382                                   + "' with offset '" + offset
383                                   + "' which is less than the record size of '"
384                                   + this.recordSize + "'");
385         }
386 
387         if (this.currRecIdx >= this.recsPerBlock) {
388             this.writeBlock();
389         }
390 
391         System.arraycopy(buf, offset, this.blockBuffer,
392                          (this.currRecIdx * this.recordSize),
393                          this.recordSize);
394 
395         this.currRecIdx++;
396     }
397 
398     /**
399      * Write a TarBuffer block to the archive.
400      */
401     private void writeBlock() throws IOException   {
402         if (this.debug) {
403             System.err.println("WriteBlock: blkIdx = " + this.currBlkIdx);
404         }
405 
406         if (this.outStream == null) {
407             throw new IOException  ("writing to an input buffer");
408         }
409 
410         this.outStream.write(this.blockBuffer, 0, this.blockSize);
411         this.outStream.flush();
412 
413         this.currRecIdx = 0;
414         this.currBlkIdx++;
415     }
416 
417     /**
418      * Flush the current data block if it has any data in it.
419      */
420     private void flushBlock() throws IOException   {
421         if (this.debug) {
422             System.err.println("TarBuffer.flushBlock() called.");
423         }
424 
425         if (this.outStream == null) {
426             throw new IOException  ("writing to an input buffer");
427         }
428 
429         if (this.currRecIdx > 0) {
430             this.writeBlock();
431         }
432     }
433 
434     /**
435      * Close the TarBuffer. If this is an output buffer, also flush the
436      * current block before closing.
437      * @throws IOException on error
438      */
439     public void close() throws IOException   {
440         if (this.debug) {
441             System.err.println("TarBuffer.closeBuffer().");
442         }
443 
444         if (this.outStream != null) {
445             this.flushBlock();
446 
447             if (this.outStream != System.out
448                     && this.outStream != System.err) {
449                 this.outStream.close();
450 
451                 this.outStream = null;
452             }
453         } else if (this.inStream != null) {
454             if (this.inStream != System.in) {
455                 this.inStream.close();
456 
457                 this.inStream = null;
458             }
459         }
460     }
461 }
462
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