/*
** Authored by Timothy Gerard Endres
** <mailto:time@gjt.org>  <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 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: 1.10 $
 * @author Timothy Gerard Endres,
 *  <a href="mailto:time@gjt.org">time@trustice.com</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 '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" );

                // Thanks to 'Todd Kofford <tkofford@bigfoot.com>' for this patch.
                // Use a buffer initialized with 0s to initialize everything in the
                // blockBuffer after the last current, complete record. This prevents
                // any previous data that might have previously existed in the
                // blockBuffer from being written to the file.

                if ( this.currRecIdx > 0 )
                        {
                        int offset = this.currRecIdx * this.recordSize;
                        byte[]  zeroBuffer = new byte[ this.blockSize - offset ];

                        System.arraycopy
                                ( zeroBuffer, 0, this.blockBuffer, offset, zeroBuffer.length );

                        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;
                                }
                        }
                }

        }