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package org.hsqldb.lib.tar;

Purely static structure defining our interface to the Tar Entry Header.
The fields controlled here are fields for the individual tar file entries
in an archive.  There is no such thing as a Header Field at the top archive
level.

We use header field names as they are specified in the FreeBSD man page for
tar in section 5 (Solaris and Linux have no such page in section 5).
Where we use a constant, the constant name is just the FreeBSD field name
capitalized.
Since a single field is known as either "linkflag" or "typeflag", we are
going with the UStar name typeflag for this field.
 

We purposefully define no variable for this list of fields, since
we DO NOT WANT TO access or change these values, due to application
goals or JVM limitations:

  
gid
  
uid
  
linkname
  
magic (UStar ID),
  
magic version
  
group name
  
device major num
  
device minor num

Our application has no use for these, or Java has no ability to
work with them.
 

This class will be very elegant when refactored as an enum with enumMap(s)
and using generics with auto-boxing instead of the ugly and non-validating
casts.

Author:
Blaine Simpson (blaine dot simpson at admc dot com)/**
 * Purely static structure defining our interface to the Tar Entry Header.
 *
 * The fields controlled here are fields for the individual tar file entries
 * in an archive.  There is no such thing as a Header Field at the top archive
 * level.
 * <P>
 * We use header field names as they are specified in the FreeBSD man page for
 * tar in section 5 (Solaris and Linux have no such page in section 5).
 * Where we use a constant, the constant name is just the FreeBSD field name
 * capitalized.
 * Since a single field is known as either "linkflag" or "typeflag", we are
 * going with the UStar name typeflag for this field.
 * </P> <P>
 * We purposefully define no variable for this list of fields, since
 * we DO NOT WANT TO access or change these values, due to application
 * goals or JVM limitations:<UL>
 *   <LI>gid
 *   <LI>uid
 *   <LI>linkname
 *   <LI>magic (UStar ID),
 *   <LI>magic version
 *   <LI>group name
 *   <LI>device major num
 *   <LI>device minor num
 * </UL>
 * Our application has no use for these, or Java has no ability to
 * work with them.
 * </P> <P>
 * This class will be very elegant when refactored as an enum with enumMap(s)
 * and using generics with auto-boxing instead of the ugly and non-validating
 * casts.
 * </P>
 *
 * @author Blaine Simpson (blaine dot simpson at admc dot com)
 */
@SuppressWarnings("boxing")
public enum TarHeaderField {
    // 1 PAST last position (in normal Java substring fashion).
    /* Note that (with one exception), there is always 1 byte
     * between a numeric field stop and the next start.  This is
     * because null byte must occupy the intervening position.
     * This is not true for non-numeric fields (which includes the
     * link-indicator/type-flag field, which is used as a code,
     * and is not necessarily numeric with UStar format).
     *
     * As a consequence, there may be NO DELIMITER after
     * non-numerics, which may occupy the entire field segment.
     *
     * Arg.  man page for "pax" says that both original and ustar
     * headers must be <= 100 chars. INCLUDING the trailing \0
     * character.  ???  GNU tar certainly does not honor this.
     */
    name(0, 100),
    mode(100, 107),
    uid(108, 115),
    gid(116, 123),
    size(124, 135),
    mtime(136, 147),  // (File.lastModified()|*.getTime())/1000
    checksum(148, 156),// "Queer terminator" in original code.  ???
                      // Pax UStore does not follow spec and delimits this
                      // field like any other numeric, skipping the space byte.
    typeflag(156, 157), // 1-byte CODE
        // With current version, we are never doing anything with this
        // field.  In future, we will support x and/or g type here.
        // N.b. Gnu Tar does not honor this Stop.

    // The remaining are from UStar format:
    magic(257, 263),
    uname(265, 296),
    gname(297, 328),
    prefix(345, 399),
    ;

    TarHeaderField(int start, int stop) {
        this.start = start;
        this.stop = stop;
    }
    private int start, stop;

    // The getters below throw RuntimExceptions instead of
    // TarMalformatExceptions because these errors indicate a dev problem,
    // not some problem with a Header, or generating or reading a Header.
    public int getStart() { return start; }
    public int getStop() { return stop; }
}