zip文件结构

总体结构

[local file header 1]
[encryption header 1]
[file data 1]
[data descriptor 1]
. 
.
.
[local file header n]
[encryption header n]
[file data n]
[data descriptor n]
[archive decryption header] 
[archive extra data record] 
[central directory header 1]
.
.
.
[central directory header n]
[zip64 end of central directory record]
[zip64 end of central directory locator] 
[end of central directory record]

local file header

offset	description
0	Local file header signature = 0x04034b50 (read as a little-endian number)
4	Version needed to extract (minimum)
6	General purpose bit flag
8	Compression method
10	File last modification time
12	File last modification date
14	CRC-32 of uncompressed data
18	Compressed size (or 0xffffffff for ZIP64)
22	Uncompressed size (or 0xffffffff for ZIP64)
26	File name length (n)
28	Extra field length (m)
30	File name
30+n	Extra field
30+n+m	the end

encryption header

TODO

data descriptor

offset	description
0	Optional data descriptor signature = 0x08074b50
0/4	CRC-32 of uncompressed data
4/8	Compressed size
8/12	Uncompressed size

central directory header

offset	description
0	Central directory file header signature = 0x02014b50
4	Version made by
6	Version needed to extract (minimum)
8	General purpose bit flag
10	Compression method
12	File last modification time
14	File last modification date
16	CRC-32 of uncompressed data
20	Compressed size (or 0xffffffff for ZIP64)
24	Uncompressed size (or 0xffffffff for ZIP64)
28	File name length (n)
30	Extra field length (m)
32	File comment length (k)
34	Disk number where file starts
36	Internal file attributes
38	External file attributes
42	Relative offset of local file header. This is the number of bytes between the start of the first disk on which the file occurs, and the start of the local file header. This allows software reading the central directory to locate the position of the file inside the ZIP file.
46	File name
46+n	Extra field
46+n+m	File comment
46+n+m+k	the end

end of central directory record

EOCD

offset	description
0	End of central directory signature = 0x06054b50
4	Number of this disk
6	Disk where central directory starts
8	Number of central directory records on this disk
10	Total number of central directory records
12	Size of central directory (bytes)
16	Offset of start of central directory, relative to start of archive
20	Comment length (n)
22	Comment
22+n	the end

EOCD64

offset	description
0	End of central directory signature = 0x06064b50
4	Size of the EOCD64 - 8
8	Version made by
10	Version needed to extract (minimum)
12	Number of this disk
16	Disk where central directory starts
20	Number of central directory records on this disk
28	Total number of central directory records
36	Size of central directory (bytes)
44	Offset of start of central directory, relative to start of archive
52	Comment (up to the size of EOCD64)
52+n	the end

Refs

• wiki: ZIP (file format)
• zip文件格式说明：表格，清晰，不包含zip64, 不包含加密
• 权威zip说明