Level 3 Header

• Introduction
  Level 3 Header is proposed in order to solve a problem of Level 2 header which restricts the maximum size of extended header to 65500 bytes. so Level 2 header can not contain extended attribute of OS/2. Although it seems author has a plan that original LHA starts to use Level 3 header at next version (version 3.0), author stopped upgrade of LHA from version 2.67(May 28, 1995). Now, Level 3 header is used by LHA version 2.67, LHA for OS/2, UNLHA32.DLL, etc on a trial basis only. Moreover, it seems Level 3 header which is proposed now has a issue that still uses 32-bit value as size of file. I am afraid this issue should be fixed.
  
  
  
• 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	04	00	2D	6C	68	30	2D	00	00	00	00	00	00	00	00	0C			.	-	l	h	0	-	.	.	.	.	.	.	.	.
  0x0010	EE	27	3D	20	03	00	00	4A	3A	00	00	00	07	00	00	00		î	'	=			.	.	J	:	.	.	.		.	.	.
  0x0020	00	90	E7	09	00	00	00	01	74	65	73	74	0A	00	00	00		.		ç		.	.	.		t	e	s	t		.	.	.
  0x0030	02	74	65	73	74	FF	00	00	00	00	--	--	--	--	--	--			t	e	s	t	ÿ	.	.	.	.	-	-	-	-	-	-

  
  
• Construction

  offset	caption	description
  00	Word size(L)	The byte count required to store file size etc. In the future, when file size will be extended, you will use Word Size as other value than 4.(probably 8) However, you must set Word size as 4 yet.
  01	Word size(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 00:00:00 on Jan 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 0x03 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 header(LL)	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 0x0000003A(58) in the foregoing sample.
  25	Size of header(LH)
  26	Size of header(HL)
  27	Size of header(HH)
  28	Size of next extended header(LL)	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 0x0007 in the foregoing sample.
  29	Size of next extended header(LH)
  30	Size of next extended header(HL)
  31	Size of next extended header(HH)

  
  
• Reference
  • 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
    
    
  • Haruyasu Yoshizaki's specification of Level 3 header Nifty FLABO MES3(590) 94/06/28(Japanese)
    (when you access this file, Nifty is required ID and password.)
    https://enter.nifty.com/iw/nifty/flabo/mes/3/590.html
    
    
  • Satoshi Hiramatsu's specification of Level 3 header Nifty FLABO MES3(669) 94/08/14(Japanese)
    (when you access this file, Nifty is required ID and password.)
    https://enter.nifty.com/iw/nifty/flabo/mes/3/669.html
    
    
  • Tshuguo Okamoto's specification of Level 3 header Nifty FLABO MES3(820) 95/06/25(Japanese)
    (when you access this file, Nifty is required ID and password.)
    https://enter.nifty.com/iw/nifty/flabo/mes/3/820.html