TarTool example source code file (TarBuffer.java)

This example TarTool source code file (TarBuffer.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - TarTool tags/keywords

default_rcdsize, incomplete, inputstream, inputstream, io, ioexception, ioexception, outputstream, outputstream, read, readblock, skiprecord, tarbuffer, tarbuffer, writerecord

The TarTool TarBuffer.java source code

/*
** Authored by Timothy Gerard Endres
** <mailto:time@gjt.org>  
** 
** This work has been placed into the public domain.
** You may use this work in any way and for any purpose you wish.
**
** THIS SOFTWARE IS PROVIDED AS-IS WITHOUT WARRANTY OF ANY KIND,
** NOT EVEN THE IMPLIED WARRANTY OF MERCHANTABILITY. THE AUTHOR
** OF THIS SOFTWARE, ASSUMES _NO_ RESPONSIBILITY FOR ANY
** CONSEQUENCE RESULTING FROM THE USE, MODIFICATION, OR
** REDISTRIBUTION OF THIS SOFTWARE. 
** 
*/

package com.ice.tar;

import java.io.*;


/**
 * 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.
 * <p>
 * You should never have a need to access this class directly.
 * TarBuffers are created by Tar IO Streams.
 *
 * @version $Revision: 1.9 $
 * @author Timothy Gerard Endres,
 *  <a href="mailto:time@gjt.org">time@trustice.com.
 * @see TarArchive
 */

public class
TarBuffer extends Object
	{
	public static final int		DEFAULT_RCDSIZE = ( 512 );
	public static final int		DEFAULT_BLKSIZE = ( DEFAULT_RCDSIZE * 20 );

	private InputStream		inStream;
	private OutputStream	outStream;

	private byte[]	blockBuffer;
	private int		currBlkIdx;
	private int		currRecIdx;
	private int		blockSize;
	private int		recordSize;
	private int		recsPerBlock;

	private boolean	debug;


	public
	TarBuffer( InputStream inStream )
		{
		this( inStream, TarBuffer.DEFAULT_BLKSIZE );
		}

	public
	TarBuffer( InputStream inStream, int blockSize )
		{
		this( inStream, blockSize, TarBuffer.DEFAULT_RCDSIZE );
		}

	public
	TarBuffer( InputStream inStream, int blockSize, int recordSize )
		{
		this.inStream = inStream;
		this.outStream = null;
		this.initialize( blockSize, recordSize );
		}

	public
	TarBuffer( OutputStream outStream )
		{
		this( outStream, TarBuffer.DEFAULT_BLKSIZE );
		}

	public
	TarBuffer( OutputStream outStream, int blockSize )
		{
		this( outStream, blockSize, TarBuffer.DEFAULT_RCDSIZE );
		}

	public
	TarBuffer( OutputStream outStream, int blockSize, int recordSize )
		{
		this.inStream = null;
		this.outStream = outStream;
		this.initialize( blockSize, recordSize );
		}

	/**
	 * Initialization common to all constructors.
	 */
	private void
	initialize( int blockSize, int recordSize )
		{
		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.
	 */
	public int
	getBlockSize()
		{
		return this.blockSize;
		}

	/**
	 * Get the TAR Buffer's 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.
	 */
	public boolean
	isEOFRecord( byte[] record )
		{
		for ( int i = 0, sz = this.getRecordSize() ; i < sz ; ++i )
			if ( record[i] != 0 )
				return false;

		return true;
		}

	/**
	 * Skip over a record on the input stream.
	 */

	public void
	skipRecord()
		throws IOException
		{
		if ( this.debug )
			{
			System.err.println
				( "SkipRecord: recIdx = " + this.currRecIdx
					+ " blkIdx = " + this.currBlkIdx );
			}

		if ( this.inStream == null )
			throw new IOException
				( "reading (via skip) from an output buffer" );

		if ( this.currRecIdx >= this.recsPerBlock )
			{
			if ( ! this.readBlock() )
				return; // UNDONE
			}

		this.currRecIdx++;
		}

	/**
	 * Read a record from the input stream and return the data.
	 *
	 * @return The record data.
	 */

	public byte[]
	readRecord()
		throws IOException
		{
		if ( this.debug )
			{
			System.err.println
				( "ReadRecord: recIdx = " + this.currRecIdx
					+ " blkIdx = " + this.currBlkIdx );
			}

		if ( this.inStream == null )
			throw new IOException
				( "reading from an output buffer" );

		if ( this.currRecIdx >= this.recsPerBlock )
			{
			if ( ! this.readBlock() )
				return null;
			}

		byte[] result = new byte[ this.recordSize ];

		System.arraycopy(
			this.blockBuffer, (this.currRecIdx * this.recordSize),
			result, 0, this.recordSize );

		this.currRecIdx++;

		return result;
		}

	/**
	 * @return false if End-Of-File, else true
	 */

	private boolean
	readBlock()
		throws IOException
		{
		if ( this.debug )
			{
			System.err.println
				( "ReadBlock: blkIdx = " + this.currBlkIdx );
			}

		if ( this.inStream == null )
			throw new IOException
				( "reading from an output buffer" );

		this.currRecIdx = 0;

		int offset = 0;
		int bytesNeeded = this.blockSize;
		for ( ; bytesNeeded > 0 ; )
			{
			long numBytes =
				this.inStream.read
					( this.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 'Yohann.Roussel@alcatel.fr' for this fix.
			//

			if ( numBytes == -1 )
				break;

			offset += numBytes;
			bytesNeeded -= numBytes;
			if ( numBytes != this.blockSize )
				{
				if ( this.debug )
					{
					System.err.println
						( "ReadBlock: INCOMPLETE READ " + numBytes
							+ " of " + this.blockSize + " bytes read." );
					}
				}
			}

		this.currBlkIdx++;

		return true;
		}

	/**
	 * Get the current block number, zero based.
	 *
	 * @return The current zero based block number.
	 */
	public int
	getCurrentBlockNum()
		{
		return this.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 this.currRecIdx - 1;
		}

	/**
	 * Write an archive record to the archive.
	 *
	 * @param record The record data to write to the archive.
	 */

	public void
	writeRecord( byte[] record )
		throws IOException
		{
		if ( this.debug )
			{
			System.err.println
				( "WriteRecord: recIdx = " + this.currRecIdx
					+ " blkIdx = " + this.currBlkIdx );
			}

		if ( this.outStream == null )
			throw new IOException
				( "writing to an input buffer" );

		if ( record.length != this.recordSize )
			throw new IOException
				( "record to write has length '" + record.length
					+ "' which is not the record size of '"
					+ this.recordSize + "'" );

		if ( this.currRecIdx >= this.recsPerBlock )
			{
			this.writeBlock();
			}

		System.arraycopy(
			record, 0,
			this.blockBuffer, (this.currRecIdx * this.recordSize),
			this.recordSize );

		this.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.
	 */

	public void
	writeRecord( byte[] buf, int offset )
		throws IOException
		{
		if ( this.debug )
			{
			System.err.println
				( "WriteRecord: recIdx = " + this.currRecIdx
					+ " blkIdx = " + this.currBlkIdx );
			}

		if ( this.outStream == null )
			throw new IOException
				( "writing to an input buffer" );

		if ( (offset + this.recordSize) > buf.length )
			throw new IOException
				( "record has length '" + buf.length
					+ "' with offset '" + offset
					+ "' which is less than the record size of '"
					+ this.recordSize + "'" );

		if ( this.currRecIdx >= this.recsPerBlock )
			{
			this.writeBlock();
			}

		System.arraycopy(
			buf, offset,
			this.blockBuffer, (this.currRecIdx * this.recordSize),
			this.recordSize );

		this.currRecIdx++;
		}

	/**
	 * Write a TarBuffer block to the archive.
	 */
	private void
	writeBlock()
		throws IOException
		{
		if ( this.debug )
			{
			System.err.println
				( "WriteBlock: blkIdx = " + this.currBlkIdx );
			}

		if ( this.outStream == null )
			throw new IOException
				( "writing to an input buffer" );

		this.outStream.write( this.blockBuffer, 0, this.blockSize );
		this.outStream.flush();

		this.currRecIdx = 0;
		this.currBlkIdx++;
		}

	/**
	 * Flush the current data block if it has any data in it.
	 */

	private void
	flushBlock()
		throws IOException
		{
		if ( this.debug )
			{
			System.err.println( "TarBuffer.flushBlock() called." );
			}

		if ( this.outStream == null )
			throw new IOException
				( "writing to an input buffer" );

		if ( this.currRecIdx > 0 )
			{
			this.writeBlock();
			}
		}

	/**
	 * Close the TarBuffer. If this is an output buffer, also flush the
	 * current block before closing.
	 */
	public void
	close()
		throws IOException
		{
		if ( this.debug )
			{
			System.err.println( "TarBuffer.closeBuffer()." );
			}

		if ( this.outStream != null )
			{
			this.flushBlock();

			if ( this.outStream != System.out
					&& this.outStream != System.err )
				{
				this.outStream.close();
				this.outStream = null;
				}
			}
		else if ( this.inStream != null )
			{
			if ( this.inStream != System.in )
				{
				this.inStream.close();
				this.inStream = null;
				}
			}
		}

	}