/jtar/src/main/java/org/xeustechnologies/jtar/TarHeader.java

/**

 * Copyright 2012 Kamran Zafar 

 * 

 * 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. 

 * 

 */



package org.xeustechnologies.jtar;



/**

 * Header

 * 

 * <pre>

 * Offset  Size     Field

 * 0       100      File name

 * 100     8        File mode

 * 108     8        Owner's numeric user ID

 * 116     8        Group's numeric user ID

 * 124     12       File size in bytes

 * 136     12       Last modification time in numeric Unix time format

 * 148     8        Checksum for header block

 * 156     1        Link indicator (file type)

 * 157     100      Name of linked file

 * </pre>

 * 

 * 

 * File Types

 * 

 * <pre>

 * Value        Meaning

 * '0'          Normal file

 * (ASCII NUL)  Normal file (now obsolete)

 * '1'          Hard link

 * '2'          Symbolic link

 * '3'          Character special

 * '4'          Block special

 * '5'          Directory

 * '6'          FIFO

 * '7'          Contigous

 * </pre>

 * 

 * 

 * 

 * Ustar header

 * 

 * <pre>

 * Offset  Size    Field

 * 257     6       UStar indicator "ustar"

 * 263     2       UStar version "00"

 * 265     32      Owner user name

 * 297     32      Owner group name

 * 329     8       Device major number

 * 337     8       Device minor number

 * 345     155     Filename prefix

 * </pre>

 */



public class TarHeader {



    /*

     * Header

     */

    public static final int NAMELEN = 100;

    public static final int MODELEN = 8;

    public static final int UIDLEN = 8;

    public static final int GIDLEN = 8;

    public static final int SIZELEN = 12;

    public static final int MODTIMELEN = 12;

    public static final int CHKSUMLEN = 8;

    public static final byte LF_OLDNORM = 0;



    /*

     * File Types

     */

    public static final byte LF_NORMAL = (byte) '0';

    public static final byte LF_LINK = (byte) '1';

    public static final byte LF_SYMLINK = (byte) '2';

    public static final byte LF_CHR = (byte) '3';

    public static final byte LF_BLK = (byte) '4';

    public static final byte LF_DIR = (byte) '5';

    public static final byte LF_FIFO = (byte) '6';

    public static final byte LF_CONTIG = (byte) '7';



    /*

     * Ustar header

     */



    public static final int MAGICLEN = 8;

    /**

     * 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  ";



    public static final int UNAMELEN = 32;

    public static final int GNAMELEN = 32;

    public static final int DEVLEN = 8;



    // Header values

    public StringBuffer name;

    public int mode;

    public int userId;

    public int groupId;

    public long size;

    public long modTime;

    public int checkSum;

    public byte linkFlag;

    public StringBuffer linkName;

    public StringBuffer magic;

    public StringBuffer userName;

    public StringBuffer groupName;

    public int devMajor;

    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( "" );

    }



    /**

     * Parse an entry name from a header buffer.

     * 

     * @param 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 header's entry name.

     */

    public static StringBuffer parseName(byte[] header, int offset, int length) {

        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 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;

    }



}