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TarTool example source code file (TarHeader.java)

This example TarTool source code file (TarHeader.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

invalidheaderexception, lf_fifo, lf_link, lf_symlink, modtimelen, object, object, string, string, stringbuffer, stringbuffer, tarheader, tarheader, tmagic

The TarTool TarHeader.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;

/**
 * This class encapsulates the Tar Entry Header used in Tar Archives.
 * The class also holds a number of tar constants, used mostly in headers.
 */

public class
TarHeader extends Object
	{
	/**
	 * The length of the name field in a header buffer.
	 */
	public static final int		NAMELEN = 100;
	/**
	 * The length of the mode field in a header buffer.
	 */
	public static final int		MODELEN = 8;
	/**
	 * The length of the user id field in a header buffer.
	 */
	public static final int		UIDLEN = 8;
	/**
	 * The length of the group id field in a header buffer.
	 */
	public static final int		GIDLEN = 8;
	/**
	 * The length of the checksum field in a header buffer.
	 */
	public static final int		CHKSUMLEN = 8;
	/**
	 * The length of the size field in a header buffer.
	 */
	public static final int		SIZELEN = 12;
	/**
	 * The length of the magic field in a header buffer.
	 */
	public static final int		MAGICLEN = 8;
	/**
	 * The length of the modification time field in a header buffer.
	 */
	public static final int		MODTIMELEN = 12;
	/**
	 * The length of the user name field in a header buffer.
	 */
	public static final int		UNAMELEN = 32;
	/**
	 * The length of the group name field in a header buffer.
	 */
	public static final int		GNAMELEN = 32;
	/**
	 * The length of the devices field in a header buffer.
	 */
	public static final int		DEVLEN = 8;

	/**
	 * LF_ constants represent the "link flag" of an entry, or more commonly,
	 * the "entry type". This is the "old way" of indicating a normal file.
	 */
	public static final byte	LF_OLDNORM	= 0;
	/**
	 * Normal file type.
	 */
	public static final byte	LF_NORMAL	= (byte) '0';
	/**
	 * Link file type.
	 */
	public static final byte	LF_LINK		= (byte) '1';
	/**
	 * Symbolic link file type.
	 */
	public static final byte	LF_SYMLINK	= (byte) '2';
	/**
	 * Character device file type.
	 */
	public static final byte	LF_CHR		= (byte) '3';
	/**
	 * Block device file type.
	 */
	public static final byte	LF_BLK		= (byte) '4';
	/**
	 * Directory file type.
	 */
	public static final byte	LF_DIR		= (byte) '5';
	/**
	 * FIFO (pipe) file type.
	 */
	public static final byte	LF_FIFO		= (byte) '6';
	/**
	 * Contiguous file type.
	 */
	public static final byte	LF_CONTIG	= (byte) '7';

	/**
	 * The magic tag representing a POSIX tar archive.
	 */
	public static final String	TMAGIC		= "ustar";

	/**
	 * The magic tag representing a GNU tar archive.
	 */
	public static final String	GNU_TMAGIC	= "ustar  ";

	/**
	 * The entry's name.
	 */
	public StringBuffer		name;
	/**
	 * The entry's permission mode.
	 */
	public int				mode;
	/**
	 * The entry's user id.
	 */
	public int				userId;
	/**
	 * The entry's group id.
	 */
	public int				groupId;
	/**
	 * The entry's size.
	 */
	public long				size;
	/**
	 * The entry's modification time.
	 */
	public long				modTime;
	/**
	 * The entry's checksum.
	 */
	public int				checkSum;
	/**
	 * The entry's link flag.
	 */
	public byte				linkFlag;
	/**
	 * The entry's link name.
	 */
	public StringBuffer		linkName;
	/**
	 * The entry's magic tag.
	 */
	public StringBuffer		magic;
	/**
	 * The entry's user name.
	 */
	public StringBuffer		userName;
	/**
	 * The entry's group name.
	 */
	public StringBuffer		groupName;
	/**
	 * The entry's major device number.
	 */
	public int				devMajor;
	/**
	 * The entry's minor device number.
	 */
	public int				devMinor;


	public
	TarHeader()
		{
		this.magic = new StringBuffer( TarHeader.TMAGIC );

		this.name = new StringBuffer();
		this.linkName = new StringBuffer();

		String user =
			System.getProperty( "user.name", "" );

		if ( user.length() > 31 )
			user = user.substring( 0, 31 );

		this.userId = 0;
		this.groupId = 0;
		this.userName = new StringBuffer( user );
		this.groupName = new StringBuffer( "" );
		}

	/**
	 * TarHeaders can be cloned.
	 */
	public Object
	clone()
		{
		TarHeader hdr = null;

		try {
			hdr = (TarHeader) super.clone();

			hdr.name =
				(this.name == null ) ? null
					: new StringBuffer( this.name.toString() );
			hdr.mode = this.mode;
			hdr.userId = this.userId;
			hdr.groupId = this.groupId;
			hdr.size = this.size;
			hdr.modTime = this.modTime;
			hdr.checkSum = this.checkSum;
			hdr.linkFlag = this.linkFlag;
			hdr.linkName =
				(this.linkName == null ) ? null
					: new StringBuffer( this.linkName.toString() );
			hdr.magic =
				(this.magic == null ) ? null
					: new StringBuffer( this.magic.toString() );
			hdr.userName =
				(this.userName == null ) ? null
					: new StringBuffer( this.userName.toString() );
			hdr.groupName =
				(this.groupName == null ) ? null
					: new StringBuffer( this.groupName.toString() );
			hdr.devMajor = this.devMajor;
			hdr.devMinor = this.devMinor;
			}
		catch ( CloneNotSupportedException ex )
			{
			ex.printStackTrace();
			}

		return hdr;
		}

	/**
	 * Get the name of this entry.
	 *
	 * @return Teh entry's name.
	 */
	public String
	getName()
		{
		return this.name.toString();
		}

	/**
	 * Parse an octal string from a header buffer. This is used for the
	 * file permission mode value.
	 *
	 * @param header The header buffer from which to parse.
	 * @param offset The offset into the buffer from which to parse.
	 * @param length The number of header bytes to parse.
	 * @return The long value of the octal string.
	 */
	public static long
	parseOctal( byte[] header, int offset, int length )
		throws InvalidHeaderException
		{
		long result = 0;
		boolean stillPadding = true;

		int end = offset + length;
		for ( int i = offset ; i < end ; ++i )
			{
			if ( header[i] == 0 )
				break;

			if ( header[i] == (byte) ' ' || header[i] == '0' )
				{
				if ( stillPadding )
					continue;

				if ( header[i] == (byte) ' ' )
					break;
				}
			
			stillPadding = false;

			result =
				(result << 3)
					+ (header[i] - '0');
			}

		return result;
		}

	/**
	 * Parse an entry name from a header buffer.
	 *
	 * @param header The header buffer from which to parse.
	 * @param offset The offset into the buffer from which to parse.
	 * @param length The number of header bytes to parse.
	 * @return The header's entry name.
	 */
	public static StringBuffer
	parseName( byte[] header, int offset, int length )
		throws InvalidHeaderException
		{
		StringBuffer result = new StringBuffer( length );

		int end = offset + length;
		for ( int i = offset ; i < end ; ++i )
			{
			if ( header[i] == 0 )
				break;
			result.append( (char)header[i] );
			}

		return result;
		}

	/**
	 * Determine the number of bytes in an entry name.
	 *
	 * @param header The header buffer from which to parse.
	 * @param offset The offset into the buffer from which to parse.
	 * @param length The number of header bytes to parse.
	 * @return The number of bytes in a header's entry name.
	 */
	public static int
	getNameBytes( StringBuffer name, byte[] buf, int offset, int length )
		{
		int i;

		for ( i = 0 ; i < length && i < name.length() ; ++i )
			{
			buf[ offset + i ] = (byte) name.charAt( i );
			}

		for ( ; i < length ; ++i )
			{
			buf[ offset + i ] = 0;
			}

		return offset + length;
		}

	/**
	 * Parse an octal integer from a header buffer.
	 *
	 * @param header The header buffer from which to parse.
	 * @param offset The offset into the buffer from which to parse.
	 * @param length The number of header bytes to parse.
	 * @return The integer value of the octal bytes.
	 */
	public static int
	getOctalBytes( long value, byte[] buf, int offset, int length )
		{
		byte[] result = new byte[ length ];

		int idx = length - 1;

		buf[ offset + idx ] = 0;
		--idx;
		buf[ offset + idx ] = (byte) ' ';
		--idx;

		if ( value == 0 )
			{
			buf[ offset + idx ] = (byte) '0';
			--idx;
			}
		else
			{
			for ( long val = value ; idx >= 0 && val > 0 ; --idx )
				{
				buf[ offset + idx ] = (byte)
					( (byte) '0' + (byte) (val & 7) );
				val = val >> 3;
				}
			}

		for ( ; idx >= 0 ; --idx )
			{
			buf[ offset + idx ] = (byte) ' ';
			}

		return offset + length;
		}

	/**
	 * Parse an octal long integer from a header buffer.
	 *
	 * @param header The header buffer from which to parse.
	 * @param offset The offset into the buffer from which to parse.
	 * @param length The number of header bytes to parse.
	 * @return The long value of the octal bytes.
	 */
	public static int
	getLongOctalBytes( long value, byte[] buf, int offset, int length )
		{
		byte[] temp = new byte[ length + 1 ];
		TarHeader.getOctalBytes( value, temp, 0, length + 1 );
		System.arraycopy( temp, 0, buf, offset, length );
		return offset + length;
		}

	/**
	 * Parse the checksum octal integer from a header buffer.
	 *
	 * @param header The header buffer from which to parse.
	 * @param offset The offset into the buffer from which to parse.
	 * @param length The number of header bytes to parse.
	 * @return The integer value of the entry's checksum.
	 */
	public static int
	getCheckSumOctalBytes( long value, byte[] buf, int offset, int length )
		{
		TarHeader.getOctalBytes( value, buf, offset, length );
		buf[ offset + length - 1 ] = (byte) ' ';
		buf[ offset + length - 2 ] = 0;
		return offset + length;
		}

	}
 

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