package IO::Compress::Gzip::Constants;

use strict ;
use warnings;
use bytes;

require Exporter;

our ($VERSION, @ISA, @EXPORT, %GZIP_OS_Names);
our ($GZIP_FNAME_INVALID_CHAR_RE, $GZIP_FCOMMENT_INVALID_CHAR_RE);

$VERSION = '2.060';

@ISA = qw(Exporter);

@EXPORT= qw(

GZIP_ID_SIZE
GZIP_ID1
GZIP_ID2

GZIP_FLG_DEFAULT
GZIP_FLG_FTEXT
GZIP_FLG_FHCRC
GZIP_FLG_FEXTRA
GZIP_FLG_FNAME
GZIP_FLG_FCOMMENT
GZIP_FLG_RESERVED

GZIP_CM_DEFLATED

GZIP_MIN_HEADER_SIZE
GZIP_TRAILER_SIZE

GZIP_MTIME_DEFAULT
GZIP_XFL_DEFAULT
GZIP_FEXTRA_HEADER_SIZE
GZIP_FEXTRA_MAX_SIZE
GZIP_FEXTRA_SUBFIELD_HEADER_SIZE
GZIP_FEXTRA_SUBFIELD_ID_SIZE
GZIP_FEXTRA_SUBFIELD_LEN_SIZE
GZIP_FEXTRA_SUBFIELD_MAX_SIZE

$GZIP_FNAME_INVALID_CHAR_RE
$GZIP_FCOMMENT_INVALID_CHAR_RE

GZIP_FHCRC_SIZE

GZIP_ISIZE_MAX
GZIP_ISIZE_MOD_VALUE


GZIP_NULL_BYTE

GZIP_OS_DEFAULT

%GZIP_OS_Names

GZIP_MINIMUM_HEADER

);

# Constant names derived from RFC 1952

use constant GZIP_ID_SIZE => 2 ;
use constant GZIP_ID1 => 0x1F;
use constant GZIP_ID2 => 0x8B;

use constant GZIP_MIN_HEADER_SIZE => 10 ;# minimum gzip header size
use constant GZIP_TRAILER_SIZE => 8 ;


use constant GZIP_FLG_DEFAULT => 0x00 ;
use constant GZIP_FLG_FTEXT => 0x01 ;
use constant GZIP_FLG_FHCRC => 0x02 ; # called CONTINUATION in gzip
use constant GZIP_FLG_FEXTRA => 0x04 ;
use constant GZIP_FLG_FNAME => 0x08 ;
use constant GZIP_FLG_FCOMMENT => 0x10 ;
#use constant GZIP_FLG_ENCRYPTED => 0x20 ; # documented in gzip sources
use constant GZIP_FLG_RESERVED => (0x20 | 0x40 | 0x80) ;

use constant GZIP_XFL_DEFAULT => 0x00 ;

use constant GZIP_MTIME_DEFAULT => 0x00 ;

use constant GZIP_FEXTRA_HEADER_SIZE => 2 ;
use constant GZIP_FEXTRA_MAX_SIZE => 0xFFFF ;
use constant GZIP_FEXTRA_SUBFIELD_ID_SIZE => 2 ;
use constant GZIP_FEXTRA_SUBFIELD_LEN_SIZE => 2 ;
use constant GZIP_FEXTRA_SUBFIELD_HEADER_SIZE => GZIP_FEXTRA_SUBFIELD_ID_SIZE +
GZIP_FEXTRA_SUBFIELD_LEN_SIZE;
use constant GZIP_FEXTRA_SUBFIELD_MAX_SIZE => GZIP_FEXTRA_MAX_SIZE -
GZIP_FEXTRA_SUBFIELD_HEADER_SIZE ;


if (ord('A') == 193)
{
# EBCDIC
$GZIP_FNAME_INVALID_CHAR_RE = '[\x00-\x3f\xff]';
$GZIP_FCOMMENT_INVALID_CHAR_RE = '[\x00-\x0a\x11-\x14\x16-\x3f\xff]';

}
else
{
$GZIP_FNAME_INVALID_CHAR_RE = '[\x00-\x1F\x7F-\x9F]';
$GZIP_FCOMMENT_INVALID_CHAR_RE = '[\x00-\x09\x11-\x1F\x7F-\x9F]';
}

use constant GZIP_FHCRC_SIZE => 2 ; # aka CONTINUATION in gzip

use constant GZIP_CM_DEFLATED => 8 ;

use constant GZIP_NULL_BYTE => "\x00";
use constant GZIP_ISIZE_MAX => 0xFFFFFFFF ;
use constant GZIP_ISIZE_MOD_VALUE => GZIP_ISIZE_MAX + 1 ;

# OS Names sourced from http://www.gzip.org/format.txt

use constant GZIP_OS_DEFAULT=> 0xFF ;
%GZIP_OS_Names = (
0 => 'MS-DOS',
1 => 'Amiga',
2 => 'VMS',
3 => 'Unix',
4 => 'VM/CMS',
5 => 'Atari TOS',
6 => 'HPFS (OS/2, NT)',
7 => 'Macintosh',
8 => 'Z-System',
9 => 'CP/M',
10 => 'TOPS-20',
11 => 'NTFS (NT)',
12 => 'SMS QDOS',
13 => 'Acorn RISCOS',
14 => 'VFAT file system (Win95, NT)',
15 => 'MVS',
16 => 'BeOS',
17 => 'Tandem/NSK',
18 => 'THEOS',
GZIP_OS_DEFAULT() => 'Unknown',
) ;

use constant GZIP_MINIMUM_HEADER => pack("C4 V C C",
GZIP_ID1, GZIP_ID2, GZIP_CM_DEFLATED, GZIP_FLG_DEFAULT,
GZIP_MTIME_DEFAULT, GZIP_XFL_DEFAULT, GZIP_OS_DEFAULT) ;


1;