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Add zstd fast levels and update 7z property sizes

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- add the "fast compression levels" of zstd via "fast" option (fast=1..64)
- change the 7-Zip property sizes of LZ4, LZ5 and Zstandard to 3
- 3 and 5 byte header are valid now (default is 3)
- update the Methods-Extern.md file, to reflect the property changes
This commit is contained in:
Tino Reichardt
2018-11-25 18:03:13 +01:00
parent 4728ce24ef
commit f98edef556
15 changed files with 129 additions and 88 deletions
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40
DOC/Methods-Extern.md
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@@ -62,22 +62,22 @@ License:
Zstandard library is provided as open source software using the BSD license.
7-Zip Container Header:
This header is mandatory and must be exact 5 bytes. The data within that header
This header is mandatory and must be exact 3 or 5 bytes. The data within that header
is for informational purposes only and not used by the decoder. If the header
is not there, or has another size, the decoder will not decompress the content.
``` C
Byte _ver_major; // currently 1
Byte _ver_minor; // currently 2
Byte _level; // currently 1..22
Byte _reserved[2];
Byte _ver_major; // currently 1
Byte _ver_minor; // currently 2
Byte _level; // currently 1..22 or 33..MaxFastLevel
Byte _reserved[2]; // not given in 3 byte header
```
- this header holds some information about the version, which was
used for creating that 7-Zip container data
- _ver_major should contain the major release of zstd
- _ver_minor should contain the major release of zstd
- _level should contain the level, the data is packed with
- the other two bytes should be set to zero currently and are
reserved for future use
- negative fast level values are stored as fastlevel+32 (33 = fastlevel 1 and so on..)
- the other two bytes, if present, should be set to zero currently and are reserved for future use
Algorithm author: Yann Collet
- Homepage: https://facebook.github.io/zstd/
@@ -164,22 +164,21 @@ License:
LZ4 library is provided as open source software using the BSD license.
7-Zip Container Header:
This header is mandatory and must be exact 5 bytes. The data within that header
This header is mandatory and must be exact 3 or 5 bytes. The data within that header
is for informational purposes only and not used by the decoder. If the header
is not there, or has another size, the decoder will not decompress the content.
``` C
Byte _ver_major; // currently 1
Byte _ver_minor; // currently 7
Byte _level; // 1..12
Byte _reserved[2];
Byte _ver_major; // currently 1
Byte _ver_minor; // currently 7
Byte _level; // 1..12
Byte _reserved[2]; // not given in 3 byte header
```
- this header holds some information about the version, which was
used for creating that 7-Zip container data
- _ver_major should contain the major release of LZ4
- _ver_minor should contain the major release of LZ4
- _level should contain the level, the data is packed with
- the other two bytes should be set to zero currently and are
reserved for future use
- the other two bytes, if present, should be set to zero currently and are reserved for future use
Algorithm author: Yann Collet
- Homepage: https://lz4.github.io/lz4/
@@ -215,22 +214,21 @@ License:
LZ5 library is provided as open source software using the BSD license.
7-Zip Container Header:
This header is mandatory and must be exact 5 bytes. The data within that header
This header is mandatory and must be exact 3 or 5 bytes. The data within that header
is for informational purposes only and not used by the decoder. If the header
is not there, or has another size, the decoder will not decompress the content.
``` C
Byte _ver_major; // currently 1
Byte _ver_minor; // currently 5
Byte _level; // 1..15
Byte _reserved[2];
Byte _ver_major; // currently 1
Byte _ver_minor; // currently 5
Byte _level; // 1..15
Byte _reserved[2]; // not given in 3 byte header
```
- this header holds some information about the version, which was used for
creating that 7-Zip container data
- _ver_major should contain the major release of LZ5
- _ver_minor should contain the major release of LZ5
- _level should contain the level, the data is packed with
- the other two bytes should be set to zero currently and are reserved for
future use
- the other two bytes, if present, should be set to zero currently and are reserved for future use
Algorithm author: Przemyslaw Skibinski
- Homepage: https://github.com/inikep/lz5