Level 2 Header

Introduction

Level 2 header is a standard header now. LHA became popular then LHA was ported to other OS than MS-DOS. Restriction of filename length in Level 0 Header became a problem. Another problem is that Level 0 Header has only the infomation which depends on MS-DOS. Level 2 Header was defined in order to solve these problems. Severe restriction of filename length like Level 0 header go away by storing filename in extended header. Moreover, Level 2 Header can contain a new information without changing the format of the base header by not including the OS dependence information in base header.

Sample

	+0	+1	+2	+3	+4	+5	+6	+7	+8	+9	+A	+B	+C	+D	+E	+F	0	1	2	3	4	5	6	7	8	9	A	B	C	D	E	F
0x0000	2E	00	2D	6C	68	30	2D	00	00	00	00	00	00	00	00	0C	.	.	-	l	h	0	-	.	.	.	.	.	.	.	.
0x0010	EE	27	3D	20	02	00	00	4A	05	00	00	CF	4F	07	00	01	î	'	=			.	.	J		.	.	Ï	O		.
0x0020	74	65	73	74	08	00	02	74	65	73	74	FF	00	00	--	--	t	e	s	t		.		t	e	s	t	ÿ	.	.	-	-

Construction

offset	caption	description
00	Size of header(L)	This is the byte count of whole header (which is sum of the byte count of base header and the total of byte count of each extended headers). Size of header is 0x002E(46) in the foregoing sample.
01	Size of header(H)
02	Compress method(1)	Compress method identifies the compression algorithm of compressed data which is following this header. The format of compress method is "-???-". (the 1st byte and the 5th byte must be '-', and the length must be 5bytes) Compress method is "-lh0-" which means no compression, in the foregoing sample.
03	Compress method(2)
04	Compress method(3)
05	Compress method(4)
06	Compress method(5)
07	Compressed size(LL)	This is the byte count of compressed file which is following this header. Compressed size is 0x00000000 in the foregoing sample.
08	Compressed size(LH)
09	Compressed size(HL)
10	Compressed size(HH)
11	Original size(LL)	This is the byte count of the file before the compression. Original size is 0x00000000 in the foregoing sample.
12	Original size(LH)
13	Original size(HL)
14	Original size(HH)
15	Last modified date and time(LL)	This is the count of the elapsed seconds from 0:0:0 on january 1 1970 UTC to the last modified time of file. When the time zone is not correctly set up, you can interconvert with an uncertainty of maximum of 24 hours local time and UTC. Last modified date and time is 16:30:20 on Jul 7, 2002 in the foregoing sample.
16	Last modified date and time(LH)
17	Last modified date and time(HL)
18	Last modified date and time(HH)
19	Resurved	You must set 0x20 which means normal file in MS-DOS attribute.
20	Header level	You must set 0x02 which means header level.
21	CRC16(L)	This is CRC16 of the file before the compression. CRC16 is 0x0000 in the foregoing sample.
22	CRC16(H)
23	OS ID	This is a identifier of Operating System which compressed the file. OS ID is 'J'(0x4A) which means Java in the foregoing sample.
24	Size of next extended header(L)	This is the byte count of following extended header. Set this field as 0, when there is not following extended header. Size of next extended header is 0x0005 in the foregoing sample.
25	Size of next extended header(H)

About Size of header

In LHA, the head of the base header must not be 0x00 (since it means the end of archive). Therefore, when low byte of Size of header is 0x00, you must add a extra byte(it seems that 0x00 is added, usually) to tail of header and set low byte of Size of header as 0x01.

**Wrong sample**
	+0	+1	+2	+3	+4	+5	+6	+7	+8	+9	+A	+B	+C	+D	+E	+F	0	1	2	3	4	5	6	7	8	9	A	B	C	D	E	F
0x0000	00	01	2D	6C	68	30	2D	00	00	00	00	00	00	00	00	75	.		-	l	h	0	-	.	.	.	.	.	.	.	.	u
0x0010	CA	34	3D	20	02	00	00	4A	05	00	00	42	A5	E1	00	01	Ê	4	=			.	.	J		.	.	B	¥	á	.
0x0020	74	68	69	73	20	69	73	20	61	20	77	72	6F	6E	67	20	t	h	i	s		i	s		a		w	r	o	n	g
0x0030	73	61	6D	70	6C	65	20	6F	66	20	73	69	7A	65	20	6F	s	a	m	p	l	e		o	f		s	i	z	e		o
0x0040	66	20	68	65	61	64	65	72	2E	20	74	68	65	20	6C	6F	f		h	e	a	d	e	r	.		t	h	e		l	o
0x0050	77	20	62	79	74	65	20	6F	66	20	73	69	7A	65	20	6F	w		b	y	t	e		o	f		s	i	z	e		o
0x0060	66	20	68	65	61	64	65	72	20	6D	75	73	74	20	6E	6F	f		h	e	a	d	e	r		m	u	s	t		n	o
0x0070	74	20	62	65	20	30	78	30	30	2E	20	20	74	68	65	20	t		b	e		0	x	0	0	.			t	h	e
0x0080	66	6F	6C	6C	6F	77	69	6E	67	20	73	61	6D	70	6C	65	f	o	l	l	o	w	i	n	g		s	a	m	p	l	e
0x0090	20	69	73	20	63	6F	72	72	65	63	74	20	73	61	6D	70		i	s		c	o	r	r	e	c	t		s	a	m	p
0x00A0	6C	65	2E	20	20	74	68	69	73	20	69	73	20	61	20	77	l	e	.			t	h	i	s		i	s		a		w
0x00B0	72	6F	6E	67	20	73	61	6D	70	6C	65	20	6F	66	20	73	r	o	n	g		s	a	m	p	l	e		o	f		s
0x00C0	69	7A	65	20	6F	66	20	68	65	61	64	65	72	2E	20	74	i	z	e		o	f		h	e	a	d	e	r	.		t
0x00D0	68	65	20	6C	6F	77	20	62	79	74	65	20	6F	66	20	73	h	e		l	o	w		b	y	t	e		o	f		s
0x00E0	69	7A	65	20	6F	66	20	68	65	61	64	65	72	20	6D	75	i	z	e		o	f		h	e	a	d	e	r		m	u
0x00F0	73	74	20	6E	6F	74	20	62	65	20	30	78	30	30	00	00	s	t		n	o	t		b	e		0	x	0	0	.	.

**Correct sample**
	+0	+1	+2	+3	+4	+5	+6	+7	+8	+9	+A	+B	+C	+D	+E	+F	0	1	2	3	4	5	6	7	8	9	A	B	C	D	E	F
0x0000	01	01	2D	6C	68	30	2D	00	00	00	00	00	00	00	00	75			-	l	h	0	-	.	.	.	.	.	.	.	.	u
0x0010	CA	34	3D	20	02	00	00	4A	05	00	00	40	49	E1	00	01	Ê	4	=			.	.	J		.	.	@	I	á	.
0x0020	74	68	69	73	20	69	73	20	61	20	63	6F	72	72	65	63	t	h	i	s		i	s		a		c	o	r	r	e	c
0x0030	74	20	73	61	6D	70	6C	65	20	6F	66	20	73	69	7A	65	t		s	a	m	p	l	e		o	f		s	i	z	e
0x0040	20	6F	66	20	68	65	61	64	65	72	2E	20	74	68	65	20		o	f		h	e	a	d	e	r	.		t	h	e
0x0050	6C	6F	77	20	62	79	74	65	20	6F	66	20	73	69	7A	65	l	o	w		b	y	t	e		o	f		s	i	z	e
0x0060	20	6F	66	20	68	65	61	64	65	72	20	6D	75	73	74	20		o	f		h	e	a	d	e	r		m	u	s	t
0x0070	6E	6F	74	20	62	65	20	30	78	30	30	2E	20	74	68	65	n	o	t		b	e		0	x	0	0	.		t	h	e
0x0080	20	66	6F	72	65	67	6F	69	6E	67	20	73	61	6D	70	6C		f	o	r	e	g	o	i	n	g		s	a	m	p	l
0x0090	65	20	69	73	20	77	72	6F	6E	67	20	73	61	6D	70	6C	e		i	s		w	r	o	n	g		s	a	m	p	l
0x00A0	65	2E	20	74	68	69	73	20	69	73	20	61	20	63	6F	72	e	.		t	h	i	s		i	s		a		c	o	r
0x00B0	72	65	63	74	20	73	61	6D	70	6C	65	20	6F	66	20	73	r	e	c	t		s	a	m	p	l	e		o	f		s
0x00C0	69	7A	65	20	6F	66	20	68	65	61	64	65	72	2E	20	74	i	z	e		o	f		h	e	a	d	e	r	.		t
0x00D0	68	65	20	6C	6F	77	20	62	79	74	65	20	6F	66	20	73	h	e		l	o	w		b	y	t	e		o	f		s
0x00E0	69	7A	65	20	6F	66	20	68	65	61	64	65	72	20	6D	75	i	z	e		o	f		h	e	a	d	e	r		m	u
0x00F0	73	74	20	6E	6F	74	20	62	65	20	30	78	30	30	00	00	s	t		n	o	t		b	e		0	x	0	0	.	.
0x0100	00	--	--	--	--	--	--	--	--	--	--	--	--	--	--	--	.	-	-	-	-	-	-	-	-	-	-	-	-	-	-	-

Reference

Joe Jared's document
http://www.osirusoft.com/joejared/lzhformat.html
Eriko Tachibana's document of LHA header(Japanese)
http://kuwa.omosiro.com/KGARC2/ARC/LHAHED15.ZIP
Satoshi Hiramatsu's header.tex which is attached to LHA for OS/2(Japanese)
http://www02.so-net.ne.jp/~hiramatu/lha/lha2-2.08.lzh
Micco's header.txt which is attached to UNLHA32.DLL(Japanese)
http://www2.nsknet.or.jp/~micco/unlha32.htm
old log in Nifty FLABO MES(6) 1(1989/05/13)-256(1989/08/17) (Japanese)
(when you access this file, Nifty is required ID and password.)
https://enter.nifty.com/iw/nifty/flabo/lib/6/DLB.7/archive1.lzh

Author does not certify about accuracy of this document.
When you found typographical errors or omissions, Please mail to cqw10305@nifty.com.
The company name and product name which are used in this document, it is the trademark or registered trademark of each company generally.

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