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Datei: TarBuffer.java Sprache: JAVA

Original von: Isabelle^©

/*
** Authored by Timothy Gerard Endres
** <mailto:[email protected]>  <http://www.trustice.com>
**
** 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.
* <p>
* You should never have a need to access this class directly.
* TarBuffers are created by Tar IO Streams.
*
* @version $Revision: 12504 $
* @author Timothy Gerard Endres,
*  <a href="mailto:[email protected]">[email protected]</a>.
* @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 '[email protected]' 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;
    }
   }
  }

}

¤ Dauer der Verarbeitung: 0.5 Sekunden (vorverarbeitet) ¤

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