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The source code

/*
** Authored by Timothy Gerard Endres
**   
** 
** 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 installer;

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.
 * 

* You should never have a need to access this class directly. * TarBuffers are created by Tar IO Streams. * * @version $Revision: 1.1 $ * @author Timothy Gerard Endres, * 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; } } } }

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