Freeze/Melt

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|formattype=electronic
 
|formattype=electronic
 
|subcat=Compression
 
|subcat=Compression
|extensions={{ext|F}}, {{ext|f}}, {{ext|lzc}}
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|extensions={{ext|F}}, {{ext|lzc}}
 
|released=≤1991
 
|released=≤1991
 
}}
 
}}
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'''Freeze''' is a file compression utility used from the command line in Unix-style operating systems. '''Melt''' is the corresponding decompressor. The format is sometimes called "'''frozen'''". It was developed by Leonid A. Broukhis. It is considered obsolete now in favor of [[gzip]].
 
'''Freeze''' is a file compression utility used from the command line in Unix-style operating systems. '''Melt''' is the corresponding decompressor. The format is sometimes called "'''frozen'''". It was developed by Leonid A. Broukhis. It is considered obsolete now in favor of [[gzip]].
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== Discussion ==
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File attributes, ownership, etc., are preserved, and a .F extension is added.
  
 
== Format details ==
 
== Format details ==
A two-pass compression is done with a [[Lempel-Zev]] algorithm on the first pass and a dynamic [[Huffman coding|Huffman algorithm]] on the second. The characteristics of the Huffman table used are added to the file. File attributes, ownership, etc., are preserved, and a .F extension is added. A two-byte magic number is prepended to the file (\037\236 octal for versions 1.x, and \037\237 for later versions).
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Freeze/Melt uses [[LZ77 with Huffman coding]]. The compressed data format is similar in design to that of [[LHA]]'s "lh" compression methods.
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''Codes'' are compressed with [[adaptive Huffman coding]]. For the newer format, ''offsets'' are decoded with the help of a static Huffman tree stored near the beginning of the file. For the older format, a predefined Huffman-like code is used.
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The adaptive Huffman format is derived from the same source ("lzhuf.c") as that used by [[LHA]]/LHarc's "lh1" compression method.
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== Identification ==
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Files begin with a two-byte signature: {{magic|0x1f 0x9e}} for versions 1.x, and {{magic|0x1f 0x9f}} for later versions.  
  
 
== Software ==
 
== Software ==
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* [http://www.esrl.noaa.gov/gmd/dv/hats/cats/stations/qnxman/freeze.html Man page] (in NOAA site, which should know something about freezing!)
 
* [http://www.esrl.noaa.gov/gmd/dv/hats/cats/stations/qnxman/freeze.html Man page] (in NOAA site, which should know something about freezing!)
  
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[[Category:File formats with extension .f]]
 
[[Category:File formats with case sensitive extensions]]
 
[[Category:File formats with case sensitive extensions]]

Latest revision as of 14:33, 18 September 2020

File Format
Name Freeze/Melt
Ontology
Extension(s) .F, .lzc
Released ≤1991
See Freeze for other formats with that name.

Freeze is a file compression utility used from the command line in Unix-style operating systems. Melt is the corresponding decompressor. The format is sometimes called "frozen". It was developed by Leonid A. Broukhis. It is considered obsolete now in favor of gzip.

Contents

[edit] Discussion

File attributes, ownership, etc., are preserved, and a .F extension is added.

[edit] Format details

Freeze/Melt uses LZ77 with Huffman coding. The compressed data format is similar in design to that of LHA's "lh" compression methods.

Codes are compressed with adaptive Huffman coding. For the newer format, offsets are decoded with the help of a static Huffman tree stored near the beginning of the file. For the older format, a predefined Huffman-like code is used.

The adaptive Huffman format is derived from the same source ("lzhuf.c") as that used by LHA/LHarc's "lh1" compression method.

[edit] Identification

Files begin with a two-byte signature: 0x1f 0x9e for versions 1.x, and 0x1f 0x9f for later versions.

[edit] Software

[edit] References

  • Man page (in NOAA site, which should know something about freezing!)
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