Level 0 Header

• Introduction
  Level 0 header was old standard header of LHA, when the LHA was still named "LHarc". Level 0 header is not unique to LHarc, it is same format as LArc (LArc is the older archiver which uses only LZSS). In other case, PMarc uses same format as Level 0 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	1F	C3	2D	6C	68	30	2D	00	00	00	00	00	00	00	00	CA		.	¢	-	l	h	0	-	.	.	.	.	.	.	.	.	Ê
  0x0010	83	E7	2C	20	00	09	74	65	73	74	5C	74	65	73	74	00		ƒ	ç	,		.	.	t	e	s	t	\	t	e	s	t	.
  0x0020	00	--	--	--	--	--	--	--	--	--	--	--	--	--	--	--		.	-	-	-	-	-	-	-	-	-	-	-	-	-	-	-

  
  
• Construction

  offset	caption	description
  00	Size of header	This is the byte count of whole header without 2 bytes of the head. Size of header is 0x1F(31) in the foregoing sample. (whole header:33 - 2 bytes of a head:2)
  01	Header checksum	This is low 1 byte of the total of each bytes of whole header without 2 bytes of the head. Header checksum is 0xC3 in the foregoing sample. (Total of each bytes of whole header without 2 bytes of the head is 0x07C3.)
  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 time(L)	This is the last modified time of file with MS-DOS format. Note that this is a local time. Last modified time is 16:30:20 in the foregoing sample.
  16	Last modified time(H)
  17	Last modified date(L)	This is the last modified date of file with MS-DOS format. Note that this is a local time. Last modified time is Jul 7, 2002 in the foregoing sample.
  18	Last modified date(H)
  19	File attribute of MS-DOS(L)	This is the file attribute with MS-DOS format. File attribute of MS-DOS is 0x0020 in the foregoing sample. (only archive flag is on.)
  20	File attribute of MS-DOS(H)	This is resurved byte of MS-DOS file attribute. This byte was used as the header level since MS-DOS always set 0 with this byte.
  21	Length of Pathname	This is the byte count of the following Pathname. Length of Pathname is 9 in the foregoing sample.
  22	Pathname(1)	This is the string which contains the filename (and directory name when you need). You must use '\' as path delimiter when you need. '\' is path delimiter of MS-DOS, which is platform of original LHarc. '\' may apper in the 2nd byte of Shift_JIS, processing of Shift_JIS is indispensable when you need full implementation of reading Pathname. Pathname is "test\test" in the foregoing sample.
  ??	...
  21 + len	Pathname(end)
  22 + len	CRC16(L)	This is CRC16 of the file before the compression. Note that some old implementation (for example, old version of LArc) makes a header without CRC16. CRC16 is 0x0000 in the foregoing sample.
  23 + len	CRC16(H)
  24 + len	Extended area(1)	This is the area for storing another infomation when you need. No Extended area is in the foregoing sample.
  ??	...
  size - 1	Extended area(end)

  
  
• About restriction of Length of Pathname
  • According to old log in Nifty
    
    Size of header structure(in C language) is 101 bytes in LHarc, So Length of Pathname is restricted by the following values according to Extended area which is defined for each OS.
    
    
    MS-DOS or no extended area::77 bytes
    (Size of header structure : 101 - Header size without Pathname : 24)
    
    With extended area for UNIX::65 bytes
    (Size of header structure : 101 - Header size without Pathname : 24 - Size of extended area for UNIX : 12)
    
    With extended area for MacOS::52 bytes
    (Size of header structure : 101 - Header size without Pathname : 24 - Size of extended area for MacOS : 25)
    
    
  • According to document in LHA for OS/2
    233 bytes(Maximum size of header : 257 - Header size without Pathname(and extended area) : 24)
    
    
  • According to document in UNLHA32.DLL
    64 bytes(Maximum length of path in MS-DOS)
    
    
  
  
• Reference
  • Joe Jared's document
    http://www.osirusoft.com/joejared/lzhformat.html
    
    
  • Eriko Tachibana's document of LHA header(Japanese)
    http://kuwa.xps.jp/x68k/KGARC/ARC/LHAHED21.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)
    (@nifty will require ID and password, to access this file.)
    https://enter.nifty.com/iw/nifty/flabo/lib/6/7.html