package org.codehaus.plexus.archiver.tar;

/*
 * Copyright  2000,2002,2004 The Apache Software Foundation
 *
 *  Licensed 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
 * (time@ice.com) to whom the Ant project is very grateful for his great code.
 */

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.
 * <p/>
 * You should never have a need to access this class directly.
 * TarBuffers are created by Tar IO Streams.
 *
 * @version $Revision$ $Date$
 *          from org.apache.ant.tools.tar.TarBuffer v1.12
 */

public class TarBuffer
{

    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;

        while ( 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 )
            {
                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 != 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++;
        Arrays.fill(blockBuffer, (byte) 0);
    }

    /**
     * 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;
            }
        }
    }
}
