Freeze/Melt

Revision as of 01:35, 24 August 2022

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.

Discussion

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

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 LZHUF.

Identification

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

Software

• v2.4.0 source code
• v2.5.0 source code
• Versions 2.1–2.5 were posted to the comp.sources.misc Usenet group in 1991–1993:
  • [1], [2], [3]
  • Source Code CD ROM (Walnut Creek) (March 1994)

Sample files

• https://telparia.com/fileFormatSamples/archive/freeze/

References

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