MS-DOS extended headers

• MS-DOS attribute header : 0x40
  
  
  • Introduction
    MS-DOS attribute header contains a file attribute of MS-DOS. MS-DOS attribute header is used if needed. For example, in original LHA, MS-DOS attribute header is not added, when attribute is 0x20 which means normal file.
    
    
    
  • Structure

    offset	MS-DOS attribute header level 1 or 2
    00	Extended header identifier
    01	file attribute of MS-DOS(L)
    02	file attribute of MS-DOS(H)
    03	Size of next extended header(L)
    04	Size of next extended header(H)

    
    
  • 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	33	00	2D	6C	68	30	2D	00	00	00	00	00	00	00	00	9C		3	.	-	l	h	0	-	.	.	.	.	.	.	.	.	œ
    0x0010	6C	28	3D	20	02	00	00	4D	07	00	01	54	45	53	54	08		l	(	=			.	.	M		.		T	E	S	T	
    0x0020	00	02	54	45	53	54	FF	05	00	40	21	00	05	00	00	3D		.		T	E	S	T	ÿ		.	@	!	.		.	.	=
    0x0030	D2	00	00	--	--	--	--	--	--	--	--	--	--	--	--	--		Ò	.	.	-	-	-	-	-	-	-	-	-	-	-	-	-

    
    
  • Description

    Extended header identifier	This is the identifier for specifying an extended header. You must set 0x40 in MS-DOS attribute header.
    file attribute of MS-DOS	This is file attribute of MS-DOS. File attribute of MS-DOS is 0x21 which means read only file, in foregoing sample.
    Size of next extended header	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 foregoing sample.

  
  
  
  

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• Windows time stamp header : 0x41
  
  
  • Introduction
    Windows time stamp header contains a time stamp of Windows. Windows time stamp header is used, if needed. All times are contained by FILETIME format.
    
    
    
  • Structure

    offset	Windows time stamp header level 2	Windows time stamp header level 3
    00	Extended header identifier	Extended header identifier
    01	Creation time(LLL)	Creation time(LLL)
    02	Creation time(LLH)	Creation time(LLH)
    03	Creation time(LHL)	Creation time(LHL)
    04	Creation time(LHH)	Creation time(LHH)
    05	Creation time(HLL)	Creation time(HLL)
    06	Creation time(HLH)	Creation time(HLH)
    07	Creation time(HHL)	Creation time(HHL)
    08	Creation time(HHH)	Creation time(HHH)
    09	Last write time(LLL)	Last write time(LLL)
    10	Last write time(LLH)	Last write time(LLH)
    11	Last write time(LHL)	Last write time(LHL)
    12	Last write time(LHH)	Last write time(LHH)
    13	Last write time(HLL)	Last write time(HLL)
    14	Last write time(HLH)	Last write time(HLH)
    15	Last write time(HHL)	Last write time(HHL)
    16	Last write time(HHH)	Last write time(HHH)
    17	Last access time(LLL)	Last access time(LLL)
    18	Last access time(LLH)	Last access time(LLH)
    19	Last access time(LHL)	Last access time(LHL)
    20	Last access time(LHH)	Last access time(LHH)
    21	Last access time(HLL)	Last access time(HLL)
    22	Last access time(HLH)	Last access time(HLH)
    23	Last access time(HHL)	Last access time(HHL)
    24	Last access time(HHH)	Last access time(HHH)
    25	Size of next extended header(L)	Size of next extended header(LL)
    26	Size of next extended header(H)	Size of next extended header(LH)
    27		Size of next extended header(HL)
    28		Size of next extended header(HH)

    
    
  • 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	46	00	2D	6C	68	30	2D	00	00	00	00	00	00	00	00	0C		F	.	-	l	h	0	-	.	.	.	.	.	.	.	.
    0x0010	EE	27	3D	20	02	00	00	4D	07	00	01	74	65	73	74	05		î	'	=			.	.	M		.		t	e	s	t	
    0x0020	00	40	21	00	1B	00	41	40	36	11	34	12	27	C2	01	00		.	@	!	.		.	A	@	6		4		'	Â		.
    0x0030	8E	D0	25	88	25	C2	01	40	36	11	34	12	27	C2	01	05		Ž	Ð	%	ˆ	%	Â		@	6		4		'	Â		
    0x0040	00	00	CD	45	00	00	--	--	--	--	--	--	--	--	--	--		.	.	Í	E	.	.	-	-	-	-	-	-	-	-	-	-

    
    
  • Description

    Extended header identifier	This is the identifier for specifying an extended header. You must set 0x41 in Windows time stamp header.
    Creation time	This is date and time the file was created. Creation time is 15:31:05 on Jul 9, 2002 ( 01C22712 : 34113640 ) in foregoing sample.
    Last write time	This is date and time the file was last written to. Last write time is 16:30:20 on Jul 7, 2002 ( 01C22588 : 25D08E00 ) in foregoing sample.
    Last access time	This is date and time the file was last accessed. Last access time is 15:31:05 on Jul 9, 2002 ( 01C22712 : 34113640 ) in foregoing sample.
    Size of next extended header	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.

  
  
  

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  • File size header : 0x42
    
    
    • Introduction
      File size header contains the file size over 4,294,967,296bytes. File size header is used, if store the file which is bigger than 4,294,967,296bytes. Original size and Compressed size in base header uses low 4 bytes.
      
      
    • Structure

      offset	File size header level 2
      00	Extended header identifier
      01	Compressed size(LLL)
      02	Compressed size(LLH)
      03	Compressed size(LHL)
      04	Compressed size(LHH)
      05	Compressed size(HLL)
      06	Compressed size(HLH)
      07	Compressed size(HHL)
      08	Compressed size(HHH)
      09	Original size(LLL)
      10	Original size(LLH)
      11	Original size(LHL)
      12	Original size(LHH)
      13	Original size(HLL)
      14	Original size(HLH)
      15	Original size(HHL)
      16	Original size(HHH)
      17	Size of next extended header(L)
      18	Size of next extended header(H)

      
      
    • 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	39	00	2D	6C	68	35	2D	D1	55	00	00	00	00	00	00	34		9	.	-	l	h	5	-	Ñ	U	.	.	.	.	.	.	4
      0x0010	C0	32	3D	20	02	00	00	4D	07	00	01	74	65	73	74	13		À	2	=			.	.	M		.		t	e	s	t	
      0x0020	00	42	D1	55	00	00	00	00	00	00	00	00	00	00	01	00		.	B	Ñ	U	.	.	.	.	.	.	.	.	.	.		.
      0x0030	00	00	05	00	00	7C	9C	00	00	--	--	--	--	--	--	--		.	.		.	.	|	œ	.	.	-	-	-	-	-	-	-

      
      
      In this sample, CRC16 which is written in base header equals CRC16 which is calculated that the data extracted to the size written in the base header. In this case, in the implementation which does not correspond to the file size header, it causes the problem which stops the operation that extracts the file, without errors. (In this sample, it does not so much as extract 1 byte) Such a problem will occur with probability 1/65536. (If you do not check CRC16 of file, Such a problem will occur with probability 1/1) Micco(Author of UNLHA32.DLL) said that he had no choice but to use the file size header, because five companies which want to use a file that is over 4GB to an LHA archive, hurried him. (He said that there were only two or three-day development periods.)
      
      
    • Description

      Extended header identifier	This is the identifier for specifying an extended header. You must store 0x42 which means common header.
      Compressed size	This is the size of compressed data following this header.
      Original size	This is the original size of compressed file following this header.
      Size of next extended header	This is byte count of following extend header. Set this field as 0, when there is not following extended header.

    
    
    

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• 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
    
    
  • Micco's header.txt which is attached to UNLHA32.DLL(Japanese)
    http://www2.nsknet.or.jp/~micco/unlha32.htm