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 * This package is based on the work done by Timothy Gerard Endres
020 * (time@ice.com) to whom the Ant project is very grateful for his great code.
021 */
022
023package org.apache.commons.compress.archivers.tar;
024
025import java.io.ByteArrayOutputStream;
026import java.io.FileInputStream;
027import java.io.IOException;
028import java.io.InputStream;
029import java.util.ArrayList;
030import java.util.Arrays;
031import java.util.HashMap;
032import java.util.List;
033import java.util.Map;
034
035import org.apache.commons.compress.archivers.ArchiveEntry;
036import org.apache.commons.compress.archivers.ArchiveInputStream;
037import org.apache.commons.compress.archivers.zip.ZipEncoding;
038import org.apache.commons.compress.archivers.zip.ZipEncodingHelper;
039import org.apache.commons.compress.utils.ArchiveUtils;
040import org.apache.commons.compress.utils.BoundedInputStream;
041import org.apache.commons.compress.utils.IOUtils;
042
043/**
044 * The TarInputStream reads a UNIX tar archive as an InputStream.
045 * methods are provided to position at each successive entry in
046 * the archive, and the read each entry as a normal input stream
047 * using read().
048 * @NotThreadSafe
049 */
050public class TarArchiveInputStream extends ArchiveInputStream {
051
052    private static final int SMALL_BUFFER_SIZE = 256;
053
054    /**
055     * Checks if the signature matches what is expected for a tar file.
056     *
057     * @param signature
058     *            the bytes to check
059     * @param length
060     *            the number of bytes to check
061     * @return true, if this stream is a tar archive stream, false otherwise
062     */
063    public static boolean matches(final byte[] signature, final int length) {
064        if (length < TarConstants.VERSION_OFFSET+TarConstants.VERSIONLEN) {
065            return false;
066        }
067
068        if (ArchiveUtils.matchAsciiBuffer(TarConstants.MAGIC_POSIX,
069                signature, TarConstants.MAGIC_OFFSET, TarConstants.MAGICLEN)
070            &&
071            ArchiveUtils.matchAsciiBuffer(TarConstants.VERSION_POSIX,
072                signature, TarConstants.VERSION_OFFSET, TarConstants.VERSIONLEN)
073                ){
074            return true;
075        }
076        if (ArchiveUtils.matchAsciiBuffer(TarConstants.MAGIC_GNU,
077                signature, TarConstants.MAGIC_OFFSET, TarConstants.MAGICLEN)
078            &&
079            (
080             ArchiveUtils.matchAsciiBuffer(TarConstants.VERSION_GNU_SPACE,
081                signature, TarConstants.VERSION_OFFSET, TarConstants.VERSIONLEN)
082            ||
083            ArchiveUtils.matchAsciiBuffer(TarConstants.VERSION_GNU_ZERO,
084                signature, TarConstants.VERSION_OFFSET, TarConstants.VERSIONLEN)
085            )
086                ){
087            return true;
088        }
089        // COMPRESS-107 - recognise Ant tar files
090        return ArchiveUtils.matchAsciiBuffer(TarConstants.MAGIC_ANT,
091                signature, TarConstants.MAGIC_OFFSET, TarConstants.MAGICLEN)
092                &&
093                ArchiveUtils.matchAsciiBuffer(TarConstants.VERSION_ANT,
094                        signature, TarConstants.VERSION_OFFSET, TarConstants.VERSIONLEN);
095    }
096
097    private final byte[] smallBuf = new byte[SMALL_BUFFER_SIZE];
098
099    /** The size the TAR header */
100    private final int recordSize;
101
102    /** The buffer to store the TAR header **/
103    private final byte[] recordBuffer;
104
105    /** The size of a block */
106    private final int blockSize;
107
108    /** True if file has hit EOF */
109    private boolean hasHitEOF;
110
111    /** Size of the current entry */
112    private long entrySize;
113
114    /** How far into the entry the stream is at */
115    private long entryOffset;
116
117    /** An input stream to read from */
118    private final InputStream inputStream;
119
120    /** Input streams for reading sparse entries **/
121    private List<InputStream> sparseInputStreams;
122
123    /** the index of current input stream being read when reading sparse entries */
124    private int currentSparseInputStreamIndex;
125
126    /** The meta-data about the current entry */
127    private TarArchiveEntry currEntry;
128
129    /** The encoding of the file */
130    private final ZipEncoding zipEncoding;
131
132    // the provided encoding (for unit tests)
133    final String encoding;
134
135    // the global PAX header
136    private Map<String, String> globalPaxHeaders = new HashMap<>();
137
138    // the global sparse headers, this is only used in PAX Format 0.X
139    private final List<TarArchiveStructSparse> globalSparseHeaders = new ArrayList<>();
140
141    private final boolean lenient;
142
143    /**
144     * Constructor for TarInputStream.
145     * @param is the input stream to use
146     */
147    public TarArchiveInputStream(final InputStream is) {
148        this(is, TarConstants.DEFAULT_BLKSIZE, TarConstants.DEFAULT_RCDSIZE);
149    }
150
151    /**
152     * Constructor for TarInputStream.
153     * @param is the input stream to use
154     * @param lenient when set to true illegal values for group/userid, mode, device numbers and timestamp will be
155     * ignored and the fields set to {@link TarArchiveEntry#UNKNOWN}. When set to false such illegal fields cause an
156     * exception instead.
157     * @since 1.19
158     */
159    public TarArchiveInputStream(final InputStream is, final boolean lenient) {
160        this(is, TarConstants.DEFAULT_BLKSIZE, TarConstants.DEFAULT_RCDSIZE, null, lenient);
161    }
162
163    /**
164     * Constructor for TarInputStream.
165     * @param is the input stream to use
166     * @param blockSize the block size to use
167     */
168    public TarArchiveInputStream(final InputStream is, final int blockSize) {
169        this(is, blockSize, TarConstants.DEFAULT_RCDSIZE);
170    }
171
172    /**
173     * Constructor for TarInputStream.
174     * @param is the input stream to use
175     * @param blockSize the block size to use
176     * @param recordSize the record size to use
177     */
178    public TarArchiveInputStream(final InputStream is, final int blockSize, final int recordSize) {
179        this(is, blockSize, recordSize, null);
180    }
181
182    /**
183     * Constructor for TarInputStream.
184     * @param is the input stream to use
185     * @param blockSize the block size to use
186     * @param recordSize the record size to use
187     * @param encoding name of the encoding to use for file names
188     * @since 1.4
189     */
190    public TarArchiveInputStream(final InputStream is, final int blockSize, final int recordSize,
191                                 final String encoding) {
192        this(is, blockSize, recordSize, encoding, false);
193    }
194
195    /**
196     * Constructor for TarInputStream.
197     * @param is the input stream to use
198     * @param blockSize the block size to use
199     * @param recordSize the record size to use
200     * @param encoding name of the encoding to use for file names
201     * @param lenient when set to true illegal values for group/userid, mode, device numbers and timestamp will be
202     * ignored and the fields set to {@link TarArchiveEntry#UNKNOWN}. When set to false such illegal fields cause an
203     * exception instead.
204     * @since 1.19
205     */
206    public TarArchiveInputStream(final InputStream is, final int blockSize, final int recordSize,
207                                 final String encoding, final boolean lenient) {
208        this.inputStream = is;
209        this.hasHitEOF = false;
210        this.encoding = encoding;
211        this.zipEncoding = ZipEncodingHelper.getZipEncoding(encoding);
212        this.recordSize = recordSize;
213        this.recordBuffer = new byte[recordSize];
214        this.blockSize = blockSize;
215        this.lenient = lenient;
216    }
217
218    /**
219     * Constructor for TarInputStream.
220     * @param is the input stream to use
221     * @param blockSize the block size to use
222     * @param encoding name of the encoding to use for file names
223     * @since 1.4
224     */
225    public TarArchiveInputStream(final InputStream is, final int blockSize,
226                                 final String encoding) {
227        this(is, blockSize, TarConstants.DEFAULT_RCDSIZE, encoding);
228    }
229
230    /**
231     * Constructor for TarInputStream.
232     * @param is the input stream to use
233     * @param encoding name of the encoding to use for file names
234     * @since 1.4
235     */
236    public TarArchiveInputStream(final InputStream is, final String encoding) {
237        this(is, TarConstants.DEFAULT_BLKSIZE, TarConstants.DEFAULT_RCDSIZE,
238             encoding);
239    }
240
241    private void applyPaxHeadersToCurrentEntry(final Map<String, String> headers, final List<TarArchiveStructSparse> sparseHeaders)
242        throws IOException {
243        currEntry.updateEntryFromPaxHeaders(headers);
244        currEntry.setSparseHeaders(sparseHeaders);
245    }
246
247    /**
248     * Get the available data that can be read from the current
249     * entry in the archive. This does not indicate how much data
250     * is left in the entire archive, only in the current entry.
251     * This value is determined from the entry's size header field
252     * and the amount of data already read from the current entry.
253     * Integer.MAX_VALUE is returned in case more than Integer.MAX_VALUE
254     * bytes are left in the current entry in the archive.
255     *
256     * @return The number of available bytes for the current entry.
257     * @throws IOException for signature
258     */
259    @Override
260    public int available() throws IOException {
261        if (isDirectory()) {
262            return 0;
263        }
264
265        if (currEntry.getRealSize() - entryOffset > Integer.MAX_VALUE) {
266            return Integer.MAX_VALUE;
267        }
268        return (int) (currEntry.getRealSize() - entryOffset);
269    }
270
271
272    /**
273     * Build the input streams consisting of all-zero input streams and non-zero input streams.
274     * When reading from the non-zero input streams, the data is actually read from the original input stream.
275     * The size of each input stream is introduced by the sparse headers.
276     *
277     * NOTE : Some all-zero input streams and non-zero input streams have the size of 0. We DO NOT store the
278     *        0 size input streams because they are meaningless.
279     */
280    private void buildSparseInputStreams() throws IOException {
281        currentSparseInputStreamIndex = -1;
282        sparseInputStreams = new ArrayList<>();
283
284        final List<TarArchiveStructSparse> sparseHeaders = currEntry.getOrderedSparseHeaders();
285
286        // Stream doesn't need to be closed at all as it doesn't use any resources
287        final InputStream zeroInputStream = new TarArchiveSparseZeroInputStream(); //NOSONAR
288        // logical offset into the extracted entry
289        long offset = 0;
290        for (final TarArchiveStructSparse sparseHeader : sparseHeaders) {
291            final long zeroBlockSize = sparseHeader.getOffset() - offset;
292            if (zeroBlockSize < 0) {
293                // sparse header says to move backwards inside the extracted entry
294                throw new IOException("Corrupted struct sparse detected");
295            }
296
297            // only store the zero block if it is not empty
298            if (zeroBlockSize > 0) {
299                sparseInputStreams.add(new BoundedInputStream(zeroInputStream, sparseHeader.getOffset() - offset));
300            }
301
302            // only store the input streams with non-zero size
303            if (sparseHeader.getNumbytes() > 0) {
304                sparseInputStreams.add(new BoundedInputStream(inputStream, sparseHeader.getNumbytes()));
305            }
306
307            offset = sparseHeader.getOffset() + sparseHeader.getNumbytes();
308        }
309
310        if (!sparseInputStreams.isEmpty()) {
311            currentSparseInputStreamIndex = 0;
312        }
313    }
314
315    /**
316     * Whether this class is able to read the given entry.
317     *
318     * @return The implementation will return true if the {@link ArchiveEntry} is an instance of {@link TarArchiveEntry}
319     */
320    @Override
321    public boolean canReadEntryData(final ArchiveEntry ae) {
322        return ae instanceof TarArchiveEntry;
323    }
324
325    /**
326     * Closes this stream. Calls the TarBuffer's close() method.
327     * @throws IOException on error
328     */
329    @Override
330    public void close() throws IOException {
331        // Close all the input streams in sparseInputStreams
332        if (sparseInputStreams != null) {
333            for (final InputStream inputStream : sparseInputStreams) {
334                inputStream.close();
335            }
336        }
337
338        inputStream.close();
339    }
340
341    /**
342     * This method is invoked once the end of the archive is hit, it
343     * tries to consume the remaining bytes under the assumption that
344     * the tool creating this archive has padded the last block.
345     */
346    private void consumeRemainderOfLastBlock() throws IOException {
347        final long bytesReadOfLastBlock = getBytesRead() % blockSize;
348        if (bytesReadOfLastBlock > 0) {
349            final long skipped = IOUtils.skip(inputStream, blockSize - bytesReadOfLastBlock);
350            count(skipped);
351        }
352    }
353
354    /**
355     * For FileInputStream, the skip always return the number you input, so we
356     * need the available bytes to determine how many bytes are actually skipped
357     *
358     * @param available available bytes returned by inputStream.available()
359     * @param skipped   skipped bytes returned by inputStream.skip()
360     * @param expected  bytes expected to skip
361     * @return number of bytes actually skipped
362     * @throws IOException if a truncated tar archive is detected
363     */
364    private long getActuallySkipped(final long available, final long skipped, final long expected) throws IOException {
365        long actuallySkipped = skipped;
366        if (inputStream instanceof FileInputStream) {
367            actuallySkipped = Math.min(skipped, available);
368        }
369
370        if (actuallySkipped != expected) {
371            throw new IOException("Truncated TAR archive");
372        }
373
374        return actuallySkipped;
375    }
376
377    /**
378     * Get the current TAR Archive Entry that this input stream is processing
379     *
380     * @return The current Archive Entry
381     */
382    public TarArchiveEntry getCurrentEntry() {
383        return currEntry;
384    }
385
386    /**
387     * Get the next entry in this tar archive as longname data.
388     *
389     * @return The next entry in the archive as longname data, or null.
390     * @throws IOException on error
391     */
392    protected byte[] getLongNameData() throws IOException {
393        // read in the name
394        final ByteArrayOutputStream longName = new ByteArrayOutputStream();
395        int length = 0;
396        while ((length = read(smallBuf)) >= 0) {
397            longName.write(smallBuf, 0, length);
398        }
399        getNextEntry();
400        if (currEntry == null) {
401            // Bugzilla: 40334
402            // Malformed tar file - long entry name not followed by entry
403            return null;
404        }
405        byte[] longNameData = longName.toByteArray();
406        // remove trailing null terminator(s)
407        length = longNameData.length;
408        while (length > 0 && longNameData[length - 1] == 0) {
409            --length;
410        }
411        if (length != longNameData.length) {
412            longNameData = Arrays.copyOf(longNameData, length);
413        }
414        return longNameData;
415    }
416
417    /**
418     * Returns the next Archive Entry in this Stream.
419     *
420     * @return the next entry,
421     *         or {@code null} if there are no more entries
422     * @throws IOException if the next entry could not be read
423     */
424    @Override
425    public ArchiveEntry getNextEntry() throws IOException {
426        return getNextTarEntry();
427    }
428
429    /**
430     * Get the next entry in this tar archive. This will skip
431     * over any remaining data in the current entry, if there
432     * is one, and place the input stream at the header of the
433     * next entry, and read the header and instantiate a new
434     * TarEntry from the header bytes and return that entry.
435     * If there are no more entries in the archive, null will
436     * be returned to indicate that the end of the archive has
437     * been reached.
438     *
439     * @return The next TarEntry in the archive, or null.
440     * @throws IOException on error
441     */
442    public TarArchiveEntry getNextTarEntry() throws IOException {
443        if (isAtEOF()) {
444            return null;
445        }
446
447        if (currEntry != null) {
448            /* Skip will only go to the end of the current entry */
449            IOUtils.skip(this, Long.MAX_VALUE);
450
451            /* skip to the end of the last record */
452            skipRecordPadding();
453        }
454
455        final byte[] headerBuf = getRecord();
456
457        if (headerBuf == null) {
458            /* hit EOF */
459            currEntry = null;
460            return null;
461        }
462
463        try {
464            currEntry = new TarArchiveEntry(globalPaxHeaders, headerBuf, zipEncoding, lenient);
465        } catch (final IllegalArgumentException e) {
466            throw new IOException("Error detected parsing the header", e);
467        }
468
469        entryOffset = 0;
470        entrySize = currEntry.getSize();
471
472        if (currEntry.isGNULongLinkEntry()) {
473            final byte[] longLinkData = getLongNameData();
474            if (longLinkData == null) {
475                // Bugzilla: 40334
476                // Malformed tar file - long link entry name not followed by
477                // entry
478                return null;
479            }
480            currEntry.setLinkName(zipEncoding.decode(longLinkData));
481        }
482
483        if (currEntry.isGNULongNameEntry()) {
484            final byte[] longNameData = getLongNameData();
485            if (longNameData == null) {
486                // Bugzilla: 40334
487                // Malformed tar file - long entry name not followed by
488                // entry
489                return null;
490            }
491
492            // COMPRESS-509 : the name of directories should end with '/'
493            final String name = zipEncoding.decode(longNameData);
494            currEntry.setName(name);
495            if (currEntry.isDirectory() && !name.endsWith("/")) {
496                currEntry.setName(name + "/");
497            }
498        }
499
500        if (currEntry.isGlobalPaxHeader()){ // Process Global Pax headers
501            readGlobalPaxHeaders();
502        }
503
504        try {
505            if (currEntry.isPaxHeader()){ // Process Pax headers
506                paxHeaders();
507            } else if (!globalPaxHeaders.isEmpty()) {
508                applyPaxHeadersToCurrentEntry(globalPaxHeaders, globalSparseHeaders);
509            }
510        } catch (final NumberFormatException e) {
511            throw new IOException("Error detected parsing the pax header", e);
512        }
513
514        if (currEntry.isOldGNUSparse()){ // Process sparse files
515            readOldGNUSparse();
516        }
517
518        // If the size of the next element in the archive has changed
519        // due to a new size being reported in the posix header
520        // information, we update entrySize here so that it contains
521        // the correct value.
522        entrySize = currEntry.getSize();
523
524        return currEntry;
525    }
526
527    /**
528     * Get the next record in this tar archive. This will skip
529     * over any remaining data in the current entry, if there
530     * is one, and place the input stream at the header of the
531     * next entry.
532     *
533     * <p>If there are no more entries in the archive, null will be
534     * returned to indicate that the end of the archive has been
535     * reached.  At the same time the {@code hasHitEOF} marker will be
536     * set to true.</p>
537     *
538     * @return The next header in the archive, or null.
539     * @throws IOException on error
540     */
541    private byte[] getRecord() throws IOException {
542        byte[] headerBuf = readRecord();
543        setAtEOF(isEOFRecord(headerBuf));
544        if (isAtEOF() && headerBuf != null) {
545            tryToConsumeSecondEOFRecord();
546            consumeRemainderOfLastBlock();
547            headerBuf = null;
548        }
549        return headerBuf;
550    }
551
552    /**
553     * Get the record size being used by this stream's buffer.
554     *
555     * @return The TarBuffer record size.
556     */
557    public int getRecordSize() {
558        return recordSize;
559    }
560
561    protected final boolean isAtEOF() {
562        return hasHitEOF;
563    }
564
565    private boolean isDirectory() {
566        return currEntry != null && currEntry.isDirectory();
567    }
568
569    /**
570     * Determine if an archive record indicate End of Archive. End of
571     * archive is indicated by a record that consists entirely of null bytes.
572     *
573     * @param record The record data to check.
574     * @return true if the record data is an End of Archive
575     */
576    protected boolean isEOFRecord(final byte[] record) {
577        return record == null || ArchiveUtils.isArrayZero(record, recordSize);
578    }
579
580    /**
581     * Since we do not support marking just yet, we do nothing.
582     *
583     * @param markLimit The limit to mark.
584     */
585    @Override
586    public synchronized void mark(final int markLimit) {
587    }
588
589    /**
590     * Since we do not support marking just yet, we return false.
591     *
592     * @return False.
593     */
594    @Override
595    public boolean markSupported() {
596        return false;
597    }
598
599    /**
600     * For PAX Format 0.0, the sparse headers(GNU.sparse.offset and GNU.sparse.numbytes)
601     * may appear multi times, and they look like:
602     *
603     * GNU.sparse.size=size
604     * GNU.sparse.numblocks=numblocks
605     * repeat numblocks times
606     *   GNU.sparse.offset=offset
607     *   GNU.sparse.numbytes=numbytes
608     * end repeat
609     *
610     *
611     * For PAX Format 0.1, the sparse headers are stored in a single variable : GNU.sparse.map
612     *
613     * GNU.sparse.map
614     *    Map of non-null data chunks. It is a string consisting of comma-separated values "offset,size[,offset-1,size-1...]"
615     *
616     *
617     * For PAX Format 1.X:
618     * The sparse map itself is stored in the file data block, preceding the actual file data.
619     * It consists of a series of decimal numbers delimited by newlines. The map is padded with nulls to the nearest block boundary.
620     * The first number gives the number of entries in the map. Following are map entries, each one consisting of two numbers
621     * giving the offset and size of the data block it describes.
622     * @throws IOException
623     */
624    private void paxHeaders() throws IOException {
625        List<TarArchiveStructSparse> sparseHeaders = new ArrayList<>();
626        final Map<String, String> headers = TarUtils.parsePaxHeaders(this, sparseHeaders, globalPaxHeaders, entrySize);
627
628        // for 0.1 PAX Headers
629        if (headers.containsKey(TarGnuSparseKeys.MAP)) {
630            sparseHeaders = new ArrayList<>(TarUtils.parseFromPAX01SparseHeaders(headers.get(TarGnuSparseKeys.MAP)));
631        }
632        getNextEntry(); // Get the actual file entry
633        if (currEntry == null) {
634            throw new IOException("premature end of tar archive. Didn't find any entry after PAX header.");
635        }
636        applyPaxHeadersToCurrentEntry(headers, sparseHeaders);
637
638        // for 1.0 PAX Format, the sparse map is stored in the file data block
639        if (currEntry.isPaxGNU1XSparse()) {
640            sparseHeaders = TarUtils.parsePAX1XSparseHeaders(inputStream, recordSize);
641            currEntry.setSparseHeaders(sparseHeaders);
642        }
643
644        // sparse headers are all done reading, we need to build
645        // sparse input streams using these sparse headers
646        buildSparseInputStreams();
647    }
648
649    /**
650     * Reads bytes from the current tar archive entry.
651     *
652     * This method is aware of the boundaries of the current
653     * entry in the archive and will deal with them as if they
654     * were this stream's start and EOF.
655     *
656     * @param buf The buffer into which to place bytes read.
657     * @param offset The offset at which to place bytes read.
658     * @param numToRead The number of bytes to read.
659     * @return The number of bytes read, or -1 at EOF.
660     * @throws IOException on error
661     */
662    @Override
663    public int read(final byte[] buf, final int offset, int numToRead) throws IOException {
664        if (numToRead == 0) {
665            return 0;
666        }
667        int totalRead = 0;
668
669        if (isAtEOF() || isDirectory()) {
670            return -1;
671        }
672
673        if (currEntry == null) {
674            throw new IllegalStateException("No current tar entry");
675        }
676
677        if (entryOffset >= currEntry.getRealSize()) {
678            return -1;
679        }
680
681        numToRead = Math.min(numToRead, available());
682
683        if (currEntry.isSparse()) {
684            // for sparse entries, we need to read them in another way
685            totalRead = readSparse(buf, offset, numToRead);
686        } else {
687            totalRead = inputStream.read(buf, offset, numToRead);
688        }
689
690        if (totalRead == -1) {
691            if (numToRead > 0) {
692                throw new IOException("Truncated TAR archive");
693            }
694            setAtEOF(true);
695        } else {
696            count(totalRead);
697            entryOffset += totalRead;
698        }
699
700        return totalRead;
701    }
702
703    private void readGlobalPaxHeaders() throws IOException {
704        globalPaxHeaders = TarUtils.parsePaxHeaders(this, globalSparseHeaders, globalPaxHeaders, entrySize);
705        getNextEntry(); // Get the actual file entry
706
707        if (currEntry == null) {
708            throw new IOException("Error detected parsing the pax header");
709        }
710    }
711
712    /**
713     * Adds the sparse chunks from the current entry to the sparse chunks,
714     * including any additional sparse entries following the current entry.
715     *
716     * @throws IOException on error
717     */
718    private void readOldGNUSparse() throws IOException {
719        if (currEntry.isExtended()) {
720            TarArchiveSparseEntry entry;
721            do {
722                final byte[] headerBuf = getRecord();
723                if (headerBuf == null) {
724                    throw new IOException("premature end of tar archive. Didn't find extended_header after header with extended flag.");
725                }
726                entry = new TarArchiveSparseEntry(headerBuf);
727                currEntry.getSparseHeaders().addAll(entry.getSparseHeaders());
728            } while (entry.isExtended());
729        }
730
731        // sparse headers are all done reading, we need to build
732        // sparse input streams using these sparse headers
733        buildSparseInputStreams();
734    }
735
736    /**
737     * Read a record from the input stream and return the data.
738     *
739     * @return The record data or null if EOF has been hit.
740     * @throws IOException on error
741     */
742    protected byte[] readRecord() throws IOException {
743        final int readNow = IOUtils.readFully(inputStream, recordBuffer);
744        count(readNow);
745        if (readNow != recordSize) {
746            return null;
747        }
748
749        return recordBuffer;
750    }
751
752    /**
753     * For sparse tar entries, there are many "holes"(consisting of all 0) in the file. Only the non-zero data is
754     * stored in tar files, and they are stored separately. The structure of non-zero data is introduced by the
755     * sparse headers using the offset, where a block of non-zero data starts, and numbytes, the length of the
756     * non-zero data block.
757     * When reading sparse entries, the actual data is read out with "holes" and non-zero data combined together
758     * according to the sparse headers.
759     *
760     * @param buf The buffer into which to place bytes read.
761     * @param offset The offset at which to place bytes read.
762     * @param numToRead The number of bytes to read.
763     * @return The number of bytes read, or -1 at EOF.
764     * @throws IOException on error
765     */
766    private int readSparse(final byte[] buf, final int offset, final int numToRead) throws IOException {
767        // if there are no actual input streams, just read from the original input stream
768        if (sparseInputStreams == null || sparseInputStreams.isEmpty()) {
769            return inputStream.read(buf, offset, numToRead);
770        }
771
772        if (currentSparseInputStreamIndex >= sparseInputStreams.size()) {
773            return -1;
774        }
775
776        final InputStream currentInputStream = sparseInputStreams.get(currentSparseInputStreamIndex);
777        final int readLen = currentInputStream.read(buf, offset, numToRead);
778
779        // if the current input stream is the last input stream,
780        // just return the number of bytes read from current input stream
781        if (currentSparseInputStreamIndex == sparseInputStreams.size() - 1) {
782            return readLen;
783        }
784
785        // if EOF of current input stream is meet, open a new input stream and recursively call read
786        if (readLen == -1) {
787            currentSparseInputStreamIndex++;
788            return readSparse(buf, offset, numToRead);
789        }
790
791        // if the rest data of current input stream is not long enough, open a new input stream
792        // and recursively call read
793        if (readLen < numToRead) {
794            currentSparseInputStreamIndex++;
795            final int readLenOfNext = readSparse(buf, offset + readLen, numToRead - readLen);
796            if (readLenOfNext == -1) {
797                return readLen;
798            }
799
800            return readLen + readLenOfNext;
801        }
802
803        // if the rest data of current input stream is enough(which means readLen == len), just return readLen
804        return readLen;
805    }
806
807    /**
808     * Since we do not support marking just yet, we do nothing.
809     */
810    @Override
811    public synchronized void reset() {
812    }
813
814    protected final void setAtEOF(final boolean b) {
815        hasHitEOF = b;
816    }
817
818    protected final void setCurrentEntry(final TarArchiveEntry e) {
819        currEntry = e;
820    }
821
822    /**
823     * Skips over and discards {@code n} bytes of data from this input
824     * stream. The {@code skip} method may, for a variety of reasons, end
825     * up skipping over some smaller number of bytes, possibly {@code 0}.
826     * This may result from any of a number of conditions; reaching end of file
827     * or end of entry before {@code n} bytes have been skipped; are only
828     * two possibilities. The actual number of bytes skipped is returned. If
829     * {@code n} is negative, no bytes are skipped.
830     *
831     *
832     * @param n
833     *            the number of bytes to be skipped.
834     * @return the actual number of bytes skipped.
835     * @throws IOException if a truncated tar archive is detected
836     *                     or some other I/O error occurs
837     */
838    @Override
839    public long skip(final long n) throws IOException {
840        if (n <= 0 || isDirectory()) {
841            return 0;
842        }
843
844        final long availableOfInputStream = inputStream.available();
845        final long available = currEntry.getRealSize() - entryOffset;
846        final long numToSkip = Math.min(n, available);
847        long skipped;
848
849        if (!currEntry.isSparse()) {
850            skipped = IOUtils.skip(inputStream, numToSkip);
851            // for non-sparse entry, we should get the bytes actually skipped bytes along with
852            // inputStream.available() if inputStream is instance of FileInputStream
853            skipped = getActuallySkipped(availableOfInputStream, skipped, numToSkip);
854        } else {
855            skipped = skipSparse(numToSkip);
856        }
857
858
859        count(skipped);
860        entryOffset += skipped;
861        return skipped;
862    }
863
864    /**
865     * The last record block should be written at the full size, so skip any
866     * additional space used to fill a record after an entry.
867     *
868     * @throws IOException if a truncated tar archive is detected
869     */
870    private void skipRecordPadding() throws IOException {
871        if (!isDirectory() && this.entrySize > 0 && this.entrySize % this.recordSize != 0) {
872            final long available = inputStream.available();
873            final long numRecords = (this.entrySize / this.recordSize) + 1;
874            final long padding = (numRecords * this.recordSize) - this.entrySize;
875            long skipped = IOUtils.skip(inputStream, padding);
876
877            skipped = getActuallySkipped(available, skipped, padding);
878
879            count(skipped);
880        }
881    }
882
883    /**
884     * Skip n bytes from current input stream, if the current input stream doesn't have enough data to skip,
885     * jump to the next input stream and skip the rest bytes, keep doing this until total n bytes are skipped
886     * or the input streams are all skipped
887     *
888     * @param n bytes of data to skip
889     * @return actual bytes of data skipped
890     * @throws IOException
891     */
892    private long skipSparse(final long n) throws IOException {
893        if (sparseInputStreams == null || sparseInputStreams.isEmpty()) {
894            return inputStream.skip(n);
895        }
896
897        long bytesSkipped = 0;
898
899        while (bytesSkipped < n && currentSparseInputStreamIndex < sparseInputStreams.size()) {
900            final InputStream  currentInputStream = sparseInputStreams.get(currentSparseInputStreamIndex);
901            bytesSkipped += currentInputStream.skip(n - bytesSkipped);
902
903            if (bytesSkipped < n) {
904                currentSparseInputStreamIndex++;
905            }
906        }
907
908        return bytesSkipped;
909    }
910
911    /**
912     * Tries to read the next record rewinding the stream if it is not an EOF record.
913     *
914     * <p>This is meant to protect against cases where a tar
915     * implementation has written only one EOF record when two are
916     * expected.  Actually this won't help since a non-conforming
917     * implementation likely won't fill full blocks consisting of - by
918     * default - ten records either so we probably have already read
919     * beyond the archive anyway.</p>
920     */
921    private void tryToConsumeSecondEOFRecord() throws IOException {
922        boolean shouldReset = true;
923        final boolean marked = inputStream.markSupported();
924        if (marked) {
925            inputStream.mark(recordSize);
926        }
927        try {
928            shouldReset = !isEOFRecord(readRecord());
929        } finally {
930            if (shouldReset && marked) {
931                pushedBackBytes(recordSize);
932                inputStream.reset();
933            }
934        }
935    }
936}