What is an LZ file?
A file with .lz extension is a compressed archive file created with Lzip, which is a free command-line tool for compression. It supports concatenation to compress support files. LZ files have media type application/lzip and support higher compression rations than BZ2. LZ are based on the LZMA (Lempel-Ziv-Markov chain) algorithm and include a 32-bit CRC checksum and ident bytes for checking the integrity of the file.
LZMA Compressed Format
The LZMA compressed format consists of a compressed stream of bits that is encoded using adaptive binary range coder. The stream is divided into packets. Each packet describes either a single byte or an LZ77 sequence. The length and distance of each packet is implicitly or explicitly encoded.
The seven types of packets are as follow (Wikipedia)
| Packed code (bit sequence) | Packet name | Packet description |
|---|---|---|
| 0 + byteCode | LIT | A single byte encoded using an adaptive binary range coder. |
| 1+0 + len + dist | MATCH | A typical LZ77 sequence describing sequence length and distance. |
| 1+1+0+0 | SHORTREP | A one-byte LZ77 sequence. Distance is equal to the last used LZ77 distance. |
| 1+1+0+1 + len | LONGREP[0] | An LZ77 sequence. Distance is equal to the last used LZ77 distance. |
| 1+1+1+0 + len | LONGREP[1] | An LZ77 sequence. Distance is equal to the second last used LZ77 distance. |
| 1+1+1+1+0 + len | LONGREP[2] | An LZ77 sequence. Distance is equal to the third last used LZ77 distance. |
| 1+1+1+1+1 + len | LONGREP[3] | An LZ77 sequence. Distance is equal to the fourth last used LZ77 distance. |
