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Snzip, a compression/decompression tool based on snappy
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README.md

Snzip, a compression/decompression tool based on snappy.

What is snzip.

Snzip is one of command line tools using snappy. This supports four type of file formats; snzip format, snappy-framed format snappy-java format and snappy-in-java format. The default format is snzip.

Note that the default format is changed to snappy-framed when the program name includes "snappy." If you want to use snzip as a snappy-framed compressor/decompressor, rename snzip to snappy, unsnappy or so.

Installation

Download snzip-0.9.0.tar.gz from https://github.com/kubo/snzip, uncompress and untar it, and run configure.

tar xvfz snzip-0.9.0.tar.gz
cd snzip-0.9.0
./configure

If you didn't install snappy under /usr or /usr/local, you need to specify the location by '--with-snappy' as follows.

# insall snappy
tar xvfz snappy-1.0.4.tar.gz
cd snappy-1.0.4
./configure --prefix=/usr/local/snappy
make
make install
cd ..

# install snzip
tar xvfz snzip-0.9.0.tar.gz
cd snzip-0.9.0
./configure --with-snappy=/usr/local/snappy

To use source code in the github repository.

git clone git://github.com/kubo/snzip.git
cd snzip
./autogen.sh
./configure

Usage

To compress file.tar:

snzip file.tar

Compressed file name is 'file.tar.snz' and the original file is deleted. Timestamp, mode and permissions are not changed as possible as it can.

The file format is SNZ. You need to add an option '-t snappy-java' or '-t snappy-in-java' to use other formats.

snzip -t snappy-java file.tar

or

snzip -t snappy-in-java file.tar

To compress file.tar and output to standard out.

snzip -c file.tar > file.tar.snz

or

cat file.tar | snzip > file.tar.snz

You need to add an option '-t [format-name]' to use formats except SNZ.

To uncompress file.tar.snz:

snzip -d file.tar.snz

or

snunzip file.tar.snz

Uncompressed file name is 'file.tar' and the original file is deleted. Timestamp, mode and permissions are not changed as possible as it can.

If the program name includes 'un' such as snunzip, it acts as '-d' is set.

The file format is automatically determined from the first byte of the file.

To uncompress file.tar.snz and output to standard out.

snzip -dc file.tar.snz > file.tar
snunzip -c file.tar.snz > file.tar
snzcat file.tar.snz > file.tar
cat file.tar.snz | snzcat > file.tar

If the program name includes 'cat' such as snzcat, it acts as '-dc' is set.

SNZ File format

The first three bytes are magic characters 'SNZ'.

The fourth byte is the file format version. It is 0x01.

The fifth byte is the order of the block size. The input data is divided into fixed-length blocks and each block is compressed by snappy. When it is 16 (default value), the block size is 16th power of 2; 64 kilobytes.

The rest is pairs of a compressed data length and a compressed data block The compressed data length is encoded as snappy::Varint::Encode32() does. If the length is zero, it is the end of data.

Though the rest after the end of data is ignored for now, they may be continuously read as a next compressed file as gzip does.

Note that the uncompressed length of each compressed data block must be less than or equal to the block size specified by the fifth byte.

License

2-clause BSD-style license.

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