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Apache Commons Compress software defines an API for working with
compression and archive formats. These include: bzip2, gzip, pack200,
lzma, xz, Snappy, traditional Unix Compress, DEFLATE, DEFLATE64, LZ4,
Brotli, Zstandard and ar, cpio, jar, tar, zip, dump, 7z, arj.
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
*/
/*
* This package is based on the work done by Timothy Gerard Endres
* ([email protected]) to whom the Ant project is very grateful for his great code.
*/
package org.apache.commons.compress.archivers.tar;
import java.io.ByteArrayOutputStream;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import org.apache.commons.compress.archivers.ArchiveEntry;
import org.apache.commons.compress.archivers.ArchiveInputStream;
import org.apache.commons.compress.archivers.zip.ZipEncoding;
import org.apache.commons.compress.archivers.zip.ZipEncodingHelper;
import org.apache.commons.compress.utils.ArchiveUtils;
import org.apache.commons.compress.utils.BoundedInputStream;
import org.apache.commons.compress.utils.IOUtils;
/**
* The TarInputStream reads a UNIX tar archive as an InputStream.
* methods are provided to position at each successive entry in
* the archive, and the read each entry as a normal input stream
* using read().
* @NotThreadSafe
*/
public class TarArchiveInputStream extends ArchiveInputStream {
private static final int SMALL_BUFFER_SIZE = 256;
/**
* Checks if the signature matches what is expected for a tar file.
*
* @param signature
* the bytes to check
* @param length
* the number of bytes to check
* @return true, if this stream is a tar archive stream, false otherwise
*/
public static boolean matches(final byte[] signature, final int length) {
if (length < TarConstants.VERSION_OFFSET+TarConstants.VERSIONLEN) {
return false;
}
if (ArchiveUtils.matchAsciiBuffer(TarConstants.MAGIC_POSIX,
signature, TarConstants.MAGIC_OFFSET, TarConstants.MAGICLEN)
&&
ArchiveUtils.matchAsciiBuffer(TarConstants.VERSION_POSIX,
signature, TarConstants.VERSION_OFFSET, TarConstants.VERSIONLEN)
){
return true;
}
if (ArchiveUtils.matchAsciiBuffer(TarConstants.MAGIC_GNU,
signature, TarConstants.MAGIC_OFFSET, TarConstants.MAGICLEN)
&&
(
ArchiveUtils.matchAsciiBuffer(TarConstants.VERSION_GNU_SPACE,
signature, TarConstants.VERSION_OFFSET, TarConstants.VERSIONLEN)
||
ArchiveUtils.matchAsciiBuffer(TarConstants.VERSION_GNU_ZERO,
signature, TarConstants.VERSION_OFFSET, TarConstants.VERSIONLEN)
)
){
return true;
}
// COMPRESS-107 - recognise Ant tar files
return ArchiveUtils.matchAsciiBuffer(TarConstants.MAGIC_ANT,
signature, TarConstants.MAGIC_OFFSET, TarConstants.MAGICLEN)
&&
ArchiveUtils.matchAsciiBuffer(TarConstants.VERSION_ANT,
signature, TarConstants.VERSION_OFFSET, TarConstants.VERSIONLEN);
}
private final byte[] smallBuf = new byte[SMALL_BUFFER_SIZE];
/** The size the TAR header */
private final int recordSize;
/** The buffer to store the TAR header **/
private final byte[] recordBuffer;
/** The size of a block */
private final int blockSize;
/** True if file has hit EOF */
private boolean hasHitEOF;
/** Size of the current entry */
private long entrySize;
/** How far into the entry the stream is at */
private long entryOffset;
/** An input stream to read from */
private final InputStream inputStream;
/** Input streams for reading sparse entries **/
private List sparseInputStreams;
/** the index of current input stream being read when reading sparse entries */
private int currentSparseInputStreamIndex;
/** The meta-data about the current entry */
private TarArchiveEntry currEntry;
/** The encoding of the file */
private final ZipEncoding zipEncoding;
// the provided encoding (for unit tests)
final String encoding;
// the global PAX header
private Map globalPaxHeaders = new HashMap<>();
// the global sparse headers, this is only used in PAX Format 0.X
private final List globalSparseHeaders = new ArrayList<>();
private final boolean lenient;
/**
* Constructor for TarInputStream.
* @param is the input stream to use
*/
public TarArchiveInputStream(final InputStream is) {
this(is, TarConstants.DEFAULT_BLKSIZE, TarConstants.DEFAULT_RCDSIZE);
}
/**
* Constructor for TarInputStream.
* @param is the input stream to use
* @param lenient when set to true illegal values for group/userid, mode, device numbers and timestamp will be
* ignored and the fields set to {@link TarArchiveEntry#UNKNOWN}. When set to false such illegal fields cause an
* exception instead.
* @since 1.19
*/
public TarArchiveInputStream(final InputStream is, final boolean lenient) {
this(is, TarConstants.DEFAULT_BLKSIZE, TarConstants.DEFAULT_RCDSIZE, null, lenient);
}
/**
* Constructor for TarInputStream.
* @param is the input stream to use
* @param blockSize the block size to use
*/
public TarArchiveInputStream(final InputStream is, final int blockSize) {
this(is, blockSize, TarConstants.DEFAULT_RCDSIZE);
}
/**
* Constructor for TarInputStream.
* @param is the input stream to use
* @param blockSize the block size to use
* @param recordSize the record size to use
*/
public TarArchiveInputStream(final InputStream is, final int blockSize, final int recordSize) {
this(is, blockSize, recordSize, null);
}
/**
* Constructor for TarInputStream.
* @param is the input stream to use
* @param blockSize the block size to use
* @param recordSize the record size to use
* @param encoding name of the encoding to use for file names
* @since 1.4
*/
public TarArchiveInputStream(final InputStream is, final int blockSize, final int recordSize,
final String encoding) {
this(is, blockSize, recordSize, encoding, false);
}
/**
* Constructor for TarInputStream.
* @param is the input stream to use
* @param blockSize the block size to use
* @param recordSize the record size to use
* @param encoding name of the encoding to use for file names
* @param lenient when set to true illegal values for group/userid, mode, device numbers and timestamp will be
* ignored and the fields set to {@link TarArchiveEntry#UNKNOWN}. When set to false such illegal fields cause an
* exception instead.
* @since 1.19
*/
public TarArchiveInputStream(final InputStream is, final int blockSize, final int recordSize,
final String encoding, final boolean lenient) {
this.inputStream = is;
this.hasHitEOF = false;
this.encoding = encoding;
this.zipEncoding = ZipEncodingHelper.getZipEncoding(encoding);
this.recordSize = recordSize;
this.recordBuffer = new byte[recordSize];
this.blockSize = blockSize;
this.lenient = lenient;
}
/**
* Constructor for TarInputStream.
* @param is the input stream to use
* @param blockSize the block size to use
* @param encoding name of the encoding to use for file names
* @since 1.4
*/
public TarArchiveInputStream(final InputStream is, final int blockSize,
final String encoding) {
this(is, blockSize, TarConstants.DEFAULT_RCDSIZE, encoding);
}
/**
* Constructor for TarInputStream.
* @param is the input stream to use
* @param encoding name of the encoding to use for file names
* @since 1.4
*/
public TarArchiveInputStream(final InputStream is, final String encoding) {
this(is, TarConstants.DEFAULT_BLKSIZE, TarConstants.DEFAULT_RCDSIZE,
encoding);
}
private void applyPaxHeadersToCurrentEntry(final Map headers, final List sparseHeaders)
throws IOException {
currEntry.updateEntryFromPaxHeaders(headers);
currEntry.setSparseHeaders(sparseHeaders);
}
/**
* Get the available data that can be read from the current
* entry in the archive. This does not indicate how much data
* is left in the entire archive, only in the current entry.
* This value is determined from the entry's size header field
* and the amount of data already read from the current entry.
* Integer.MAX_VALUE is returned in case more than Integer.MAX_VALUE
* bytes are left in the current entry in the archive.
*
* @return The number of available bytes for the current entry.
* @throws IOException for signature
*/
@Override
public int available() throws IOException {
if (isDirectory()) {
return 0;
}
if (currEntry.getRealSize() - entryOffset > Integer.MAX_VALUE) {
return Integer.MAX_VALUE;
}
return (int) (currEntry.getRealSize() - entryOffset);
}
/**
* Build the input streams consisting of all-zero input streams and non-zero input streams.
* When reading from the non-zero input streams, the data is actually read from the original input stream.
* The size of each input stream is introduced by the sparse headers.
*
* NOTE : Some all-zero input streams and non-zero input streams have the size of 0. We DO NOT store the
* 0 size input streams because they are meaningless.
*/
private void buildSparseInputStreams() throws IOException {
currentSparseInputStreamIndex = -1;
sparseInputStreams = new ArrayList<>();
final List sparseHeaders = currEntry.getOrderedSparseHeaders();
// Stream doesn't need to be closed at all as it doesn't use any resources
final InputStream zeroInputStream = new TarArchiveSparseZeroInputStream(); //NOSONAR
// logical offset into the extracted entry
long offset = 0;
for (final TarArchiveStructSparse sparseHeader : sparseHeaders) {
final long zeroBlockSize = sparseHeader.getOffset() - offset;
if (zeroBlockSize < 0) {
// sparse header says to move backwards inside of the extracted entry
throw new IOException("Corrupted struct sparse detected");
}
// only store the zero block if it is not empty
if (zeroBlockSize > 0) {
sparseInputStreams.add(new BoundedInputStream(zeroInputStream, sparseHeader.getOffset() - offset));
}
// only store the input streams with non-zero size
if (sparseHeader.getNumbytes() > 0) {
sparseInputStreams.add(new BoundedInputStream(inputStream, sparseHeader.getNumbytes()));
}
offset = sparseHeader.getOffset() + sparseHeader.getNumbytes();
}
if (!sparseInputStreams.isEmpty()) {
currentSparseInputStreamIndex = 0;
}
}
/**
* Whether this class is able to read the given entry.
*
* @return The implementation will return true if the {@link ArchiveEntry} is an instance of {@link TarArchiveEntry}
*/
@Override
public boolean canReadEntryData(final ArchiveEntry ae) {
return ae instanceof TarArchiveEntry;
}
/**
* Closes this stream. Calls the TarBuffer's close() method.
* @throws IOException on error
*/
@Override
public void close() throws IOException {
// Close all the input streams in sparseInputStreams
if (sparseInputStreams != null) {
for (final InputStream inputStream : sparseInputStreams) {
inputStream.close();
}
}
inputStream.close();
}
/**
* This method is invoked once the end of the archive is hit, it
* tries to consume the remaining bytes under the assumption that
* the tool creating this archive has padded the last block.
*/
private void consumeRemainderOfLastBlock() throws IOException {
final long bytesReadOfLastBlock = getBytesRead() % blockSize;
if (bytesReadOfLastBlock > 0) {
final long skipped = IOUtils.skip(inputStream, blockSize - bytesReadOfLastBlock);
count(skipped);
}
}
/**
* For FileInputStream, the skip always return the number you input, so we
* need the available bytes to determine how many bytes are actually skipped
*
* @param available available bytes returned by inputStream.available()
* @param skipped skipped bytes returned by inputStream.skip()
* @param expected bytes expected to skip
* @return number of bytes actually skipped
* @throws IOException if a truncated tar archive is detected
*/
private long getActuallySkipped(final long available, final long skipped, final long expected) throws IOException {
long actuallySkipped = skipped;
if (inputStream instanceof FileInputStream) {
actuallySkipped = Math.min(skipped, available);
}
if (actuallySkipped != expected) {
throw new IOException("Truncated TAR archive");
}
return actuallySkipped;
}
/**
* Get the current TAR Archive Entry that this input stream is processing
*
* @return The current Archive Entry
*/
public TarArchiveEntry getCurrentEntry() {
return currEntry;
}
/**
* Get the next entry in this tar archive as longname data.
*
* @return The next entry in the archive as longname data, or null.
* @throws IOException on error
*/
protected byte[] getLongNameData() throws IOException {
// read in the name
final ByteArrayOutputStream longName = new ByteArrayOutputStream();
int length = 0;
while ((length = read(smallBuf)) >= 0) {
longName.write(smallBuf, 0, length);
}
getNextEntry();
if (currEntry == null) {
// Bugzilla: 40334
// Malformed tar file - long entry name not followed by entry
return null;
}
byte[] longNameData = longName.toByteArray();
// remove trailing null terminator(s)
length = longNameData.length;
while (length > 0 && longNameData[length - 1] == 0) {
--length;
}
if (length != longNameData.length) {
longNameData = Arrays.copyOf(longNameData, length);
}
return longNameData;
}
/**
* Returns the next Archive Entry in this Stream.
*
* @return the next entry,
* or {@code null} if there are no more entries
* @throws IOException if the next entry could not be read
*/
@Override
public ArchiveEntry getNextEntry() throws IOException {
return getNextTarEntry();
}
/**
* Get the next entry in this tar archive. This will skip
* over any remaining data in the current entry, if there
* is one, and place the input stream at the header of the
* next entry, and read the header and instantiate a new
* TarEntry from the header bytes and return that entry.
* If there are no more entries in the archive, null will
* be returned to indicate that the end of the archive has
* been reached.
*
* @return The next TarEntry in the archive, or null.
* @throws IOException on error
*/
public TarArchiveEntry getNextTarEntry() throws IOException {
if (isAtEOF()) {
return null;
}
if (currEntry != null) {
/* Skip will only go to the end of the current entry */
IOUtils.skip(this, Long.MAX_VALUE);
/* skip to the end of the last record */
skipRecordPadding();
}
final byte[] headerBuf = getRecord();
if (headerBuf == null) {
/* hit EOF */
currEntry = null;
return null;
}
try {
currEntry = new TarArchiveEntry(globalPaxHeaders, headerBuf, zipEncoding, lenient);
} catch (final IllegalArgumentException e) {
throw new IOException("Error detected parsing the header", e);
}
entryOffset = 0;
entrySize = currEntry.getSize();
if (currEntry.isGNULongLinkEntry()) {
final byte[] longLinkData = getLongNameData();
if (longLinkData == null) {
// Bugzilla: 40334
// Malformed tar file - long link entry name not followed by
// entry
return null;
}
currEntry.setLinkName(zipEncoding.decode(longLinkData));
}
if (currEntry.isGNULongNameEntry()) {
final byte[] longNameData = getLongNameData();
if (longNameData == null) {
// Bugzilla: 40334
// Malformed tar file - long entry name not followed by
// entry
return null;
}
// COMPRESS-509 : the name of directories should end with '/'
final String name = zipEncoding.decode(longNameData);
currEntry.setName(name);
if (currEntry.isDirectory() && !name.endsWith("/")) {
currEntry.setName(name + "/");
}
}
if (currEntry.isGlobalPaxHeader()){ // Process Global Pax headers
readGlobalPaxHeaders();
}
try {
if (currEntry.isPaxHeader()){ // Process Pax headers
paxHeaders();
} else if (!globalPaxHeaders.isEmpty()) {
applyPaxHeadersToCurrentEntry(globalPaxHeaders, globalSparseHeaders);
}
} catch (final NumberFormatException e) {
throw new IOException("Error detected parsing the pax header", e);
}
if (currEntry.isOldGNUSparse()){ // Process sparse files
readOldGNUSparse();
}
// If the size of the next element in the archive has changed
// due to a new size being reported in the posix header
// information, we update entrySize here so that it contains
// the correct value.
entrySize = currEntry.getSize();
return currEntry;
}
/**
* Get the next record in this tar archive. This will skip
* over any remaining data in the current entry, if there
* is one, and place the input stream at the header of the
* next entry.
*
* If there are no more entries in the archive, null will be
* returned to indicate that the end of the archive has been
* reached. At the same time the {@code hasHitEOF} marker will be
* set to true.
*
* @return The next header in the archive, or null.
* @throws IOException on error
*/
private byte[] getRecord() throws IOException {
byte[] headerBuf = readRecord();
setAtEOF(isEOFRecord(headerBuf));
if (isAtEOF() && headerBuf != null) {
tryToConsumeSecondEOFRecord();
consumeRemainderOfLastBlock();
headerBuf = null;
}
return headerBuf;
}
/**
* Get the record size being used by this stream's buffer.
*
* @return The TarBuffer record size.
*/
public int getRecordSize() {
return recordSize;
}
protected final boolean isAtEOF() {
return hasHitEOF;
}
private boolean isDirectory() {
return currEntry != null && currEntry.isDirectory();
}
/**
* Determine if an archive record indicate End of Archive. End of
* archive is indicated by a record that consists entirely of null bytes.
*
* @param record The record data to check.
* @return true if the record data is an End of Archive
*/
protected boolean isEOFRecord(final byte[] record) {
return record == null || ArchiveUtils.isArrayZero(record, recordSize);
}
/**
* Since we do not support marking just yet, we do nothing.
*
* @param markLimit The limit to mark.
*/
@Override
public synchronized void mark(final int markLimit) {
}
/**
* Since we do not support marking just yet, we return false.
*
* @return False.
*/
@Override
public boolean markSupported() {
return false;
}
/**
* For PAX Format 0.0, the sparse headers(GNU.sparse.offset and GNU.sparse.numbytes)
* may appear multi times, and they look like:
*
* GNU.sparse.size=size
* GNU.sparse.numblocks=numblocks
* repeat numblocks times
* GNU.sparse.offset=offset
* GNU.sparse.numbytes=numbytes
* end repeat
*
*
* For PAX Format 0.1, the sparse headers are stored in a single variable : GNU.sparse.map
*
* GNU.sparse.map
* Map of non-null data chunks. It is a string consisting of comma-separated values "offset,size[,offset-1,size-1...]"
*
*
* For PAX Format 1.X:
* The sparse map itself is stored in the file data block, preceding the actual file data.
* It consists of a series of decimal numbers delimited by newlines. The map is padded with nulls to the nearest block boundary.
* The first number gives the number of entries in the map. Following are map entries, each one consisting of two numbers
* giving the offset and size of the data block it describes.
* @throws IOException
*/
private void paxHeaders() throws IOException {
List sparseHeaders = new ArrayList<>();
final Map headers = TarUtils.parsePaxHeaders(this, sparseHeaders, globalPaxHeaders, entrySize);
// for 0.1 PAX Headers
if (headers.containsKey(TarGnuSparseKeys.MAP)) {
sparseHeaders = new ArrayList<>(TarUtils.parseFromPAX01SparseHeaders(headers.get(TarGnuSparseKeys.MAP)));
}
getNextEntry(); // Get the actual file entry
if (currEntry == null) {
throw new IOException("premature end of tar archive. Didn't find any entry after PAX header.");
}
applyPaxHeadersToCurrentEntry(headers, sparseHeaders);
// for 1.0 PAX Format, the sparse map is stored in the file data block
if (currEntry.isPaxGNU1XSparse()) {
sparseHeaders = TarUtils.parsePAX1XSparseHeaders(inputStream, recordSize);
currEntry.setSparseHeaders(sparseHeaders);
}
// sparse headers are all done reading, we need to build
// sparse input streams using these sparse headers
buildSparseInputStreams();
}
/**
* Reads bytes from the current tar archive entry.
*
* This method is aware of the boundaries of the current
* entry in the archive and will deal with them as if they
* were this stream's start and EOF.
*
* @param buf The buffer into which to place bytes read.
* @param offset The offset at which to place bytes read.
* @param numToRead The number of bytes to read.
* @return The number of bytes read, or -1 at EOF.
* @throws IOException on error
*/
@Override
public int read(final byte[] buf, final int offset, int numToRead) throws IOException {
if (numToRead == 0) {
return 0;
}
int totalRead = 0;
if (isAtEOF() || isDirectory()) {
return -1;
}
if (currEntry == null) {
throw new IllegalStateException("No current tar entry");
}
if (entryOffset >= currEntry.getRealSize()) {
return -1;
}
numToRead = Math.min(numToRead, available());
if (currEntry.isSparse()) {
// for sparse entries, we need to read them in another way
totalRead = readSparse(buf, offset, numToRead);
} else {
totalRead = inputStream.read(buf, offset, numToRead);
}
if (totalRead == -1) {
if (numToRead > 0) {
throw new IOException("Truncated TAR archive");
}
setAtEOF(true);
} else {
count(totalRead);
entryOffset += totalRead;
}
return totalRead;
}
private void readGlobalPaxHeaders() throws IOException {
globalPaxHeaders = TarUtils.parsePaxHeaders(this, globalSparseHeaders, globalPaxHeaders, entrySize);
getNextEntry(); // Get the actual file entry
if (currEntry == null) {
throw new IOException("Error detected parsing the pax header");
}
}
/**
* Adds the sparse chunks from the current entry to the sparse chunks,
* including any additional sparse entries following the current entry.
*
* @throws IOException on error
*/
private void readOldGNUSparse() throws IOException {
if (currEntry.isExtended()) {
TarArchiveSparseEntry entry;
do {
final byte[] headerBuf = getRecord();
if (headerBuf == null) {
throw new IOException("premature end of tar archive. Didn't find extended_header after header with extended flag.");
}
entry = new TarArchiveSparseEntry(headerBuf);
currEntry.getSparseHeaders().addAll(entry.getSparseHeaders());
} while (entry.isExtended());
}
// sparse headers are all done reading, we need to build
// sparse input streams using these sparse headers
buildSparseInputStreams();
}
/**
* Read a record from the input stream and return the data.
*
* @return The record data or null if EOF has been hit.
* @throws IOException on error
*/
protected byte[] readRecord() throws IOException {
final int readNow = IOUtils.readFully(inputStream, recordBuffer);
count(readNow);
if (readNow != recordSize) {
return null;
}
return recordBuffer;
}
/**
* For sparse tar entries, there are many "holes"(consisting of all 0) in the file. Only the non-zero data is
* stored in tar files, and they are stored separately. The structure of non-zero data is introduced by the
* sparse headers using the offset, where a block of non-zero data starts, and numbytes, the length of the
* non-zero data block.
* When reading sparse entries, the actual data is read out with "holes" and non-zero data combined together
* according to the sparse headers.
*
* @param buf The buffer into which to place bytes read.
* @param offset The offset at which to place bytes read.
* @param numToRead The number of bytes to read.
* @return The number of bytes read, or -1 at EOF.
* @throws IOException on error
*/
private int readSparse(final byte[] buf, final int offset, final int numToRead) throws IOException {
// if there are no actual input streams, just read from the original input stream
if (sparseInputStreams == null || sparseInputStreams.isEmpty()) {
return inputStream.read(buf, offset, numToRead);
}
if (currentSparseInputStreamIndex >= sparseInputStreams.size()) {
return -1;
}
final InputStream currentInputStream = sparseInputStreams.get(currentSparseInputStreamIndex);
final int readLen = currentInputStream.read(buf, offset, numToRead);
// if the current input stream is the last input stream,
// just return the number of bytes read from current input stream
if (currentSparseInputStreamIndex == sparseInputStreams.size() - 1) {
return readLen;
}
// if EOF of current input stream is meet, open a new input stream and recursively call read
if (readLen == -1) {
currentSparseInputStreamIndex++;
return readSparse(buf, offset, numToRead);
}
// if the rest data of current input stream is not long enough, open a new input stream
// and recursively call read
if (readLen < numToRead) {
currentSparseInputStreamIndex++;
final int readLenOfNext = readSparse(buf, offset + readLen, numToRead - readLen);
if (readLenOfNext == -1) {
return readLen;
}
return readLen + readLenOfNext;
}
// if the rest data of current input stream is enough(which means readLen == len), just return readLen
return readLen;
}
/**
* Since we do not support marking just yet, we do nothing.
*/
@Override
public synchronized void reset() {
}
protected final void setAtEOF(final boolean b) {
hasHitEOF = b;
}
protected final void setCurrentEntry(final TarArchiveEntry e) {
currEntry = e;
}
/**
* Skips over and discards {@code n} bytes of data from this input
* stream. The {@code skip} method may, for a variety of reasons, end
* up skipping over some smaller number of bytes, possibly {@code 0}.
* This may result from any of a number of conditions; reaching end of file
* or end of entry before {@code n} bytes have been skipped; are only
* two possibilities. The actual number of bytes skipped is returned. If
* {@code n} is negative, no bytes are skipped.
*
*
* @param n
* the number of bytes to be skipped.
* @return the actual number of bytes skipped.
* @throws IOException if a truncated tar archive is detected
* or some other I/O error occurs
*/
@Override
public long skip(final long n) throws IOException {
if (n <= 0 || isDirectory()) {
return 0;
}
final long availableOfInputStream = inputStream.available();
final long available = currEntry.getRealSize() - entryOffset;
final long numToSkip = Math.min(n, available);
long skipped;
if (!currEntry.isSparse()) {
skipped = IOUtils.skip(inputStream, numToSkip);
// for non-sparse entry, we should get the bytes actually skipped bytes along with
// inputStream.available() if inputStream is instance of FileInputStream
skipped = getActuallySkipped(availableOfInputStream, skipped, numToSkip);
} else {
skipped = skipSparse(numToSkip);
}
count(skipped);
entryOffset += skipped;
return skipped;
}
/**
* The last record block should be written at the full size, so skip any
* additional space used to fill a record after an entry.
*
* @throws IOException if a truncated tar archive is detected
*/
private void skipRecordPadding() throws IOException {
if (!isDirectory() && this.entrySize > 0 && this.entrySize % this.recordSize != 0) {
final long available = inputStream.available();
final long numRecords = (this.entrySize / this.recordSize) + 1;
final long padding = (numRecords * this.recordSize) - this.entrySize;
long skipped = IOUtils.skip(inputStream, padding);
skipped = getActuallySkipped(available, skipped, padding);
count(skipped);
}
}
/**
* Skip n bytes from current input stream, if the current input stream doesn't have enough data to skip,
* jump to the next input stream and skip the rest bytes, keep doing this until total n bytes are skipped
* or the input streams are all skipped
*
* @param n bytes of data to skip
* @return actual bytes of data skipped
* @throws IOException
*/
private long skipSparse(final long n) throws IOException {
if (sparseInputStreams == null || sparseInputStreams.isEmpty()) {
return inputStream.skip(n);
}
long bytesSkipped = 0;
while (bytesSkipped < n && currentSparseInputStreamIndex < sparseInputStreams.size()) {
final InputStream currentInputStream = sparseInputStreams.get(currentSparseInputStreamIndex);
bytesSkipped += currentInputStream.skip(n - bytesSkipped);
if (bytesSkipped < n) {
currentSparseInputStreamIndex++;
}
}
return bytesSkipped;
}
/**
* Tries to read the next record rewinding the stream if it is not a EOF record.
*
* This is meant to protect against cases where a tar
* implementation has written only one EOF record when two are
* expected. Actually this won't help since a non-conforming
* implementation likely won't fill full blocks consisting of - by
* default - ten records either so we probably have already read
* beyond the archive anyway.
*/
private void tryToConsumeSecondEOFRecord() throws IOException {
boolean shouldReset = true;
final boolean marked = inputStream.markSupported();
if (marked) {
inputStream.mark(recordSize);
}
try {
shouldReset = !isEOFRecord(readRecord());
} finally {
if (shouldReset && marked) {
pushedBackBytes(recordSize);
inputStream.reset();
}
}
}
}