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ZIP format
Byte order: Little-endian
Overall zipfile format:
[Local file header + Compressed data [+ Extended local header]?]*
[Central directory]*
[End of central directory record]
Local file header:
Offset Length Contents
0 4 bytes Local file header signature (0x04034b50)
4 2 bytes Version needed to extract
6 2 bytes General purpose bit flag
8 2 bytes Compression method
10 2 bytes Last mod file time
12 2 bytes Last mod file date
14 4 bytes CRC-32
18 4 bytes Compressed size (n)
22 4 bytes Uncompressed size
26 2 bytes Filename length (f)
28 2 bytes Extra field length (e)
(f)bytes Filename
(e)bytes Extra field
(n)bytes Compressed data
Extended local header:
Offset Length Contents
0 4 bytes Extended Local file header signature (0x08074b50)
4 4 bytes CRC-32
8 4 bytes Compressed size
12 4 bytes Uncompressed size
Central directory:
Offset Length Contents
0 4 bytes Central file header signature (0x02014b50)
4 2 bytes Version made by
6 2 bytes Version needed to extract
8 2 bytes General purpose bit flag
10 2 bytes Compression method
12 2 bytes Last mod file time
14 2 bytes Last mod file date
16 4 bytes CRC-32
20 4 bytes Compressed size
24 4 bytes Uncompressed size
28 2 bytes Filename length (f)
30 2 bytes Extra field length (e)
32 2 bytes File comment length (c)
34 2 bytes Disk number start
36 2 bytes Internal file attributes
38 4 bytes External file attributes
42 4 bytes Relative offset of local header
46 (f)bytes Filename
(e)bytes Extra field
(c)bytes File comment
End of central directory record:
Offset Length Contents
0 4 bytes End of central dir signature (0x06054b50)
4 2 bytes Number of this disk
6 2 bytes Number of the disk with the start of the central directory
8 2 bytes Total number of entries in the central dir on this disk
10 2 bytes Total number of entries in the central dir
12 4 bytes Size of the central directory
16 4 bytes Offset of start of central directory with respect to the starting disk number
20 2 bytes zipfile comment length (c)
22 (c)bytes zipfile comment
compression method: (2 bytes)
0 - The file is stored (no compression)
1 - The file is Shrunk
2 - The file is Reduced with compression factor 1
3 - The file is Reduced with compression factor 2
4 - The file is Reduced with compression factor 3
5 - The file is Reduced with compression factor 4
6 - The file is Imploded
7 - Reserved for Tokenizing compression algorithm
8 - The file is Deflated
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