Source code
Revision control
Copy as Markdown
Other Tools
7z Format description (4.59)↩
----------------------------↩
↩
This file contains description of 7z archive format. ↩
7z archive can contain files compressed with any method.↩
See "Methods.txt" for description for defined compressing methods.↩
↩
↩
Format structure Overview↩
-------------------------↩
↩
Some fields can be optional.↩
↩
Archive structure↩
~~~~~~~~~~~~~~~~~ ↩
SignatureHeader↩
[PackedStreams]↩
[PackedStreamsForHeaders]↩
[↩
Header ↩
or ↩
{↩
Packed Header↩
HeaderInfo↩
}↩
]↩
↩
↩
↩
Header structure↩
~~~~~~~~~~~~~~~~ ↩
{↩
ArchiveProperties↩
AdditionalStreams↩
{↩
PackInfo↩
{↩
PackPos↩
NumPackStreams↩
Sizes[NumPackStreams]↩
CRCs[NumPackStreams]↩
}↩
CodersInfo↩
{↩
NumFolders↩
Folders[NumFolders]↩
{↩
NumCoders↩
CodersInfo[NumCoders]↩
{↩
ID↩
NumInStreams;↩
NumOutStreams;↩
PropertiesSize↩
Properties[PropertiesSize]↩
}↩
NumBindPairs↩
BindPairsInfo[NumBindPairs]↩
{↩
InIndex;↩
OutIndex;↩
}↩
PackedIndices↩
}↩
UnPackSize[Folders][Folders.NumOutstreams]↩
CRCs[NumFolders]↩
}↩
SubStreamsInfo↩
{↩
NumUnPackStreamsInFolders[NumFolders];↩
UnPackSizes[]↩
CRCs[]↩
}↩
}↩
MainStreamsInfo↩
{↩
(Same as in AdditionalStreams)↩
}↩
FilesInfo↩
{↩
NumFiles↩
Properties[]↩
{↩
ID↩
Size↩
Data↩
}↩
}↩
}↩
↩
HeaderInfo structure↩
~~~~~~~~~~~~~~~~~~~~↩
{↩
(Same as in AdditionalStreams)↩
}↩
↩
↩
↩
Notes about Notation and encoding↩
---------------------------------↩
↩
7z uses little endian encoding.↩
↩
7z archive format has optional headers that are marked as↩
[]↩
Header↩
[]↩
↩
REAL_UINT64 means real UINT64.↩
↩
UINT64 means real UINT64 encoded with the following scheme:↩
↩
Size of encoding sequence depends from first byte:↩
First_Byte Extra_Bytes Value↩
(binary) ↩
0xxxxxxx : ( xxxxxxx )↩
10xxxxxx BYTE y[1] : ( xxxxxx << (8 * 1)) + y↩
110xxxxx BYTE y[2] : ( xxxxx << (8 * 2)) + y↩
...↩
1111110x BYTE y[6] : ( x << (8 * 6)) + y↩
11111110 BYTE y[7] : y↩
11111111 BYTE y[8] : y↩
↩
↩
↩
Property IDs↩
------------↩
↩
0x00 = kEnd↩
↩
0x01 = kHeader↩
↩
0x02 = kArchiveProperties↩
↩
0x03 = kAdditionalStreamsInfo↩
0x04 = kMainStreamsInfo↩
0x05 = kFilesInfo↩
↩
0x06 = kPackInfo↩
0x07 = kUnPackInfo↩
0x08 = kSubStreamsInfo↩
↩
0x09 = kSize↩
0x0A = kCRC↩
↩
0x0B = kFolder↩
↩
0x0C = kCodersUnPackSize↩
0x0D = kNumUnPackStream↩
↩
0x0E = kEmptyStream↩
0x0F = kEmptyFile↩
0x10 = kAnti↩
↩
0x11 = kName↩
0x12 = kCTime↩
0x13 = kATime↩
0x14 = kMTime↩
0x15 = kWinAttributes↩
0x16 = kComment↩
↩
0x17 = kEncodedHeader↩
↩
0x18 = kStartPos↩
0x19 = kDummy↩
↩
↩
7z format headers↩
-----------------↩
↩
SignatureHeader↩
~~~~~~~~~~~~~~~↩
BYTE kSignature[6] = {'7', 'z', 0xBC, 0xAF, 0x27, 0x1C};↩
↩
ArchiveVersion↩
{↩
BYTE Major; // now = 0↩
BYTE Minor; // now = 2↩
};↩
↩
UINT32 StartHeaderCRC;↩
↩
StartHeader↩
{↩
REAL_UINT64 NextHeaderOffset↩
REAL_UINT64 NextHeaderSize↩
UINT32 NextHeaderCRC↩
}↩
↩
↩
...........................↩
↩
↩
ArchiveProperties↩
~~~~~~~~~~~~~~~~~↩
BYTE NID::kArchiveProperties (0x02)↩
for (;;)↩
{↩
BYTE PropertyType;↩
if (aType == 0)↩
break;↩
UINT64 PropertySize;↩
BYTE PropertyData[PropertySize];↩
}↩
↩
↩
Digests (NumStreams)↩
~~~~~~~~~~~~~~~~~~~~~↩
BYTE AllAreDefined↩
if (AllAreDefined == 0)↩
{↩
for(NumStreams)↩
BIT Defined↩
}↩
UINT32 CRCs[NumDefined]↩
↩
↩
PackInfo↩
~~~~~~~~~~~~↩
BYTE NID::kPackInfo (0x06)↩
UINT64 PackPos↩
UINT64 NumPackStreams↩
↩
[]↩
BYTE NID::kSize (0x09)↩
UINT64 PackSizes[NumPackStreams]↩
[]↩
↩
[]↩
BYTE NID::kCRC (0x0A)↩
PackStreamDigests[NumPackStreams]↩
[]↩
↩
BYTE NID::kEnd↩
↩
↩
Folder↩
~~~~~~↩
UINT64 NumCoders;↩
for (NumCoders)↩
{↩
BYTE ↩
{↩
0:3 CodecIdSize↩
4: Is Complex Coder↩
5: There Are Attributes↩
6: Reserved↩
7: There are more alternative methods. (Not used anymore, must be 0).↩
} ↩
BYTE CodecId[CodecIdSize]↩
if (Is Complex Coder)↩
{↩
UINT64 NumInStreams;↩
UINT64 NumOutStreams;↩
}↩
if (There Are Attributes)↩
{↩
UINT64 PropertiesSize↩
BYTE Properties[PropertiesSize]↩
}↩
}↩
↩
NumBindPairs = NumOutStreamsTotal - 1;↩
↩
for (NumBindPairs)↩
{↩
UINT64 InIndex;↩
UINT64 OutIndex;↩
}↩
↩
NumPackedStreams = NumInStreamsTotal - NumBindPairs;↩
if (NumPackedStreams > 1)↩
for(NumPackedStreams)↩
{↩
UINT64 Index;↩
};↩
↩
↩
↩
↩
Coders Info↩
~~~~~~~~~~~↩
↩
BYTE NID::kUnPackInfo (0x07)↩
↩
↩
BYTE NID::kFolder (0x0B)↩
UINT64 NumFolders↩
BYTE External↩
switch(External)↩
{↩
case 0:↩
Folders[NumFolders]↩
case 1:↩
UINT64 DataStreamIndex↩
}↩
↩
↩
BYTE ID::kCodersUnPackSize (0x0C)↩
for(Folders)↩
for(Folder.NumOutStreams)↩
UINT64 UnPackSize;↩
↩
↩
[]↩
BYTE NID::kCRC (0x0A)↩
UnPackDigests[NumFolders]↩
[]↩
↩
↩
↩
BYTE NID::kEnd↩
↩
↩
↩
SubStreams Info↩
~~~~~~~~~~~~~~↩
BYTE NID::kSubStreamsInfo; (0x08)↩
↩
[]↩
BYTE NID::kNumUnPackStream; (0x0D)↩
UINT64 NumUnPackStreamsInFolders[NumFolders];↩
[]↩
↩
↩
[]↩
BYTE NID::kSize (0x09)↩
UINT64 UnPackSizes[]↩
[]↩
↩
↩
[]↩
BYTE NID::kCRC (0x0A)↩
Digests[Number of streams with unknown CRC]↩
[]↩
↩
↩
BYTE NID::kEnd↩
↩
↩
Streams Info↩
~~~~~~~~~~~~↩
↩
[]↩
PackInfo↩
[]↩
↩
↩
[]↩
CodersInfo↩
[]↩
↩
↩
[]↩
SubStreamsInfo↩
[]↩
↩
BYTE NID::kEnd↩
↩
↩
FilesInfo↩
~~~~~~~~~↩
BYTE NID::kFilesInfo; (0x05)↩
UINT64 NumFiles↩
↩
for (;;)↩
{↩
BYTE PropertyType;↩
if (aType == 0)↩
break;↩
↩
UINT64 Size;↩
↩
switch(PropertyType)↩
{↩
kEmptyStream: (0x0E)↩
for(NumFiles)↩
BIT IsEmptyStream↩
↩
kEmptyFile: (0x0F)↩
for(EmptyStreams)↩
BIT IsEmptyFile↩
↩
kAnti: (0x10)↩
for(EmptyStreams)↩
BIT IsAntiFile↩
↩
case kCTime: (0x12)↩
case kATime: (0x13)↩
case kMTime: (0x14)↩
BYTE AllAreDefined↩
if (AllAreDefined == 0)↩
{↩
for(NumFiles)↩
BIT TimeDefined↩
}↩
BYTE External;↩
if(External != 0)↩
UINT64 DataIndex↩
[]↩
for(Definded Items)↩
UINT64 Time↩
[]↩
↩
kNames: (0x11)↩
BYTE External;↩
if(External != 0)↩
UINT64 DataIndex↩
[]↩
for(Files)↩
{↩
wchar_t Names[NameSize];↩
wchar_t 0;↩
}↩
[]↩
↩
kAttributes: (0x15)↩
BYTE AllAreDefined↩
if (AllAreDefined == 0)↩
{↩
for(NumFiles)↩
BIT AttributesAreDefined↩
}↩
BYTE External;↩
if(External != 0)↩
UINT64 DataIndex↩
[]↩
for(Definded Attributes)↩
UINT32 Attributes↩
[]↩
}↩
}↩
↩
↩
Header↩
~~~~~~↩
BYTE NID::kHeader (0x01)↩
↩
[]↩
ArchiveProperties↩
[]↩
↩
[]↩
BYTE NID::kAdditionalStreamsInfo; (0x03)↩
StreamsInfo↩
[]↩
↩
[]↩
BYTE NID::kMainStreamsInfo; (0x04)↩
StreamsInfo↩
[]↩
↩
[]↩
FilesInfo↩
[]↩
↩
BYTE NID::kEnd↩
↩
↩
HeaderInfo↩
~~~~~~~~~~↩
[]↩
BYTE NID::kEncodedHeader; (0x17)↩
StreamsInfo for Encoded Header↩
[]↩
↩
↩
---↩
End of document↩