org.apache.tools.tar.TarBuffer Maven / Gradle / Ivy
/*
* 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.tools.tar;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.Arrays;
/**
* The TarBuffer class implements the tar archive concept
* of a buffered input stream. This concept goes back to the
* days of blocked tape drives and special io devices. In the
* Java universe, the only real function that this class
* performs is to ensure that files have the correct "block"
* size, or other tars will complain.
*
* You should never have a need to access this class directly.
* TarBuffers are created by Tar IO Streams.
*
*/
public class TarBuffer {
/** Default record size */
public static final int DEFAULT_RCDSIZE = (512);
/** Default block size */
public static final int DEFAULT_BLKSIZE = (DEFAULT_RCDSIZE * 20);
private InputStream inStream;
private OutputStream outStream;
private final int blockSize;
private final int recordSize;
private final int recsPerBlock;
private final byte[] blockBuffer;
private int currBlkIdx;
private int currRecIdx;
private boolean debug;
/**
* Constructor for a TarBuffer on an input stream.
* @param inStream the input stream to use
*/
public TarBuffer(InputStream inStream) {
this(inStream, TarBuffer.DEFAULT_BLKSIZE);
}
/**
* Constructor for a TarBuffer on an input stream.
* @param inStream the input stream to use
* @param blockSize the block size to use
*/
public TarBuffer(InputStream inStream, int blockSize) {
this(inStream, blockSize, TarBuffer.DEFAULT_RCDSIZE);
}
/**
* Constructor for a TarBuffer on an input stream.
* @param inStream the input stream to use
* @param blockSize the block size to use
* @param recordSize the record size to use
*/
public TarBuffer(InputStream inStream, int blockSize, int recordSize) {
this(inStream, null, blockSize, recordSize);
}
/**
* Constructor for a TarBuffer on an output stream.
* @param outStream the output stream to use
*/
public TarBuffer(OutputStream outStream) {
this(outStream, TarBuffer.DEFAULT_BLKSIZE);
}
/**
* Constructor for a TarBuffer on an output stream.
* @param outStream the output stream to use
* @param blockSize the block size to use
*/
public TarBuffer(OutputStream outStream, int blockSize) {
this(outStream, blockSize, TarBuffer.DEFAULT_RCDSIZE);
}
/**
* Constructor for a TarBuffer on an output stream.
* @param outStream the output stream to use
* @param blockSize the block size to use
* @param recordSize the record size to use
*/
public TarBuffer(OutputStream outStream, int blockSize, int recordSize) {
this(null, outStream, blockSize, recordSize);
}
/**
* Private constructor to perform common setup.
*/
private TarBuffer(InputStream inStream, OutputStream outStream, int blockSize, int recordSize) {
this.inStream = inStream;
this.outStream = outStream;
this.debug = false;
this.blockSize = blockSize;
this.recordSize = recordSize;
this.recsPerBlock = (this.blockSize / this.recordSize);
this.blockBuffer = new byte[this.blockSize];
if (this.inStream != null) {
this.currBlkIdx = -1;
this.currRecIdx = this.recsPerBlock;
} else {
this.currBlkIdx = 0;
this.currRecIdx = 0;
}
}
/**
* Get the TAR Buffer's block size. Blocks consist of multiple records.
* @return the block size
*/
public int getBlockSize() {
return this.blockSize;
}
/**
* Get the TAR Buffer's record size.
* @return the record size
*/
public int getRecordSize() {
return this.recordSize;
}
/**
* Set the debugging flag for the buffer.
*
* @param debug If true, print debugging output.
*/
public void setDebug(boolean debug) {
this.debug = debug;
}
/**
* 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
*/
public boolean isEOFRecord(byte[] record) {
for (int i = 0, sz = getRecordSize(); i < sz; ++i) {
if (record[i] != 0) {
return false;
}
}
return true;
}
/**
* Skip over a record on the input stream.
* @throws IOException on error
*/
public void skipRecord() throws IOException {
if (debug) {
System.err.println("SkipRecord: recIdx = " + currRecIdx
+ " blkIdx = " + currBlkIdx);
}
if (inStream == null) {
throw new IOException("reading (via skip) from an output buffer");
}
if (currRecIdx >= recsPerBlock && !readBlock()) {
return; // UNDONE
}
currRecIdx++;
}
/**
* Read a record from the input stream and return the data.
*
* @return The record data.
* @throws IOException on error
*/
public byte[] readRecord() throws IOException {
if (debug) {
System.err.println("ReadRecord: recIdx = " + currRecIdx
+ " blkIdx = " + currBlkIdx);
}
if (inStream == null) {
if (outStream == null) {
throw new IOException("input buffer is closed");
}
throw new IOException("reading from an output buffer");
}
if (currRecIdx >= recsPerBlock && !readBlock()) {
return null;
}
byte[] result = new byte[recordSize];
System.arraycopy(blockBuffer,
(currRecIdx * recordSize), result, 0,
recordSize);
currRecIdx++;
return result;
}
/**
* @return false if End-Of-File, else true
*/
private boolean readBlock() throws IOException {
if (debug) {
System.err.println("ReadBlock: blkIdx = " + currBlkIdx);
}
if (inStream == null) {
throw new IOException("reading from an output buffer");
}
currRecIdx = 0;
int offset = 0;
int bytesNeeded = blockSize;
while (bytesNeeded > 0) {
long numBytes = inStream.read(blockBuffer, offset,
bytesNeeded);
//
// NOTE
// We have fit EOF, and the block is not full!
//
// This is a broken archive. It does not follow the standard
// blocking algorithm. However, because we are generous, and
// it requires little effort, we will simply ignore the error
// and continue as if the entire block were read. This does
// not appear to break anything upstream. We used to return
// false in this case.
//
// Thanks to '[email protected]' for this fix.
//
if (numBytes == -1) {
if (offset == 0) {
// Ensure that we do not read gigabytes of zeros
// for a corrupt tar file.
// See http://issues.apache.org/bugzilla/show_bug.cgi?id=39924
return false;
}
// However, just leaving the unread portion of the buffer dirty does
// cause problems in some cases. This problem is described in
// http://issues.apache.org/bugzilla/show_bug.cgi?id=29877
//
// The solution is to fill the unused portion of the buffer with zeros.
Arrays.fill(blockBuffer, offset, offset + bytesNeeded, (byte) 0);
break;
}
offset += numBytes;
bytesNeeded -= numBytes;
if (numBytes != blockSize) {
if (debug) {
System.err.println("ReadBlock: INCOMPLETE READ "
+ numBytes + " of " + blockSize
+ " bytes read.");
}
}
}
currBlkIdx++;
return true;
}
/**
* Get the current block number, zero based.
*
* @return The current zero based block number.
*/
public int getCurrentBlockNum() {
return currBlkIdx;
}
/**
* Get the current record number, within the current block, zero based.
* Thus, current offset = (currentBlockNum * recsPerBlk) + currentRecNum.
*
* @return The current zero based record number.
*/
public int getCurrentRecordNum() {
return currRecIdx - 1;
}
/**
* Write an archive record to the archive.
*
* @param record The record data to write to the archive.
* @throws IOException on error
*/
public void writeRecord(byte[] record) throws IOException {
if (debug) {
System.err.println("WriteRecord: recIdx = " + currRecIdx
+ " blkIdx = " + currBlkIdx);
}
if (outStream == null) {
if (inStream == null){
throw new IOException("Output buffer is closed");
}
throw new IOException("writing to an input buffer");
}
if (record.length != recordSize) {
throw new IOException("record to write has length '"
+ record.length
+ "' which is not the record size of '"
+ recordSize + "'");
}
if (currRecIdx >= recsPerBlock) {
writeBlock();
}
System.arraycopy(record, 0, blockBuffer,
(currRecIdx * recordSize),
recordSize);
currRecIdx++;
}
/**
* Write an archive record to the archive, where the record may be
* inside of a larger array buffer. The buffer must be "offset plus
* record size" long.
*
* @param buf The buffer containing the record data to write.
* @param offset The offset of the record data within buf.
* @throws IOException on error
*/
public void writeRecord(byte[] buf, int offset) throws IOException {
if (debug) {
System.err.println("WriteRecord: recIdx = " + currRecIdx
+ " blkIdx = " + currBlkIdx);
}
if (outStream == null) {
if (inStream == null){
throw new IOException("Output buffer is closed");
}
throw new IOException("writing to an input buffer");
}
if ((offset + recordSize) > buf.length) {
throw new IOException("record has length '" + buf.length
+ "' with offset '" + offset
+ "' which is less than the record size of '"
+ recordSize + "'");
}
if (currRecIdx >= recsPerBlock) {
writeBlock();
}
System.arraycopy(buf, offset, blockBuffer,
(currRecIdx * recordSize),
recordSize);
currRecIdx++;
}
/**
* Write a TarBuffer block to the archive.
*/
private void writeBlock() throws IOException {
if (debug) {
System.err.println("WriteBlock: blkIdx = " + currBlkIdx);
}
if (outStream == null) {
throw new IOException("writing to an input buffer");
}
outStream.write(blockBuffer, 0, blockSize);
outStream.flush();
currRecIdx = 0;
currBlkIdx++;
Arrays.fill(blockBuffer, (byte) 0);
}
/**
* Flush the current data block if it has any data in it.
*/
void flushBlock() throws IOException {
if (debug) {
System.err.println("TarBuffer.flushBlock() called.");
}
if (outStream == null) {
throw new IOException("writing to an input buffer");
}
if (currRecIdx > 0) {
writeBlock();
}
}
/**
* Close the TarBuffer. If this is an output buffer, also flush the
* current block before closing.
* @throws IOException on error
*/
public void close() throws IOException {
if (debug) {
System.err.println("TarBuffer.closeBuffer().");
}
if (outStream != null) {
flushBlock();
if (outStream != System.out
&& outStream != System.err) {
outStream.close();
outStream = null;
}
} else if (inStream != null) {
if (inStream != System.in) {
inStream.close();
}
inStream = null;
}
}
}