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README.md
ozip.cpp

README.md

OZIP

Ozip is a simple compression utility utilizing the Oodle high performance compression library. Ozip's functionality mimics gzip; most invocations function identically. Like gzip, Ozip supports streaming compression/decompression from stdin to stdout. Builds on Windows, Linux and Mac.

Ozip requires the Oodle SDK.

Usage

ozip [file] [opts]           (compresses)
ozip [file] [-d opts]      (decompress)

  • without file args ozip defaults to stdin/stdout compression.
  • uses .ooz extension for compressed files.
  • (!)Deletes input files unless -k --keep option is used (like gzip).
  • Ozip iterates on multiple file targets. To combine files, compose with tar (e.g. tar | ozip > "archivedfiles.tar.ooz")

Default compression settings are Oodle Kraken at Compression Level Normal (4).

Settings

Compressor selection:

    --kraken -mk  
    --leviathan -ml  
    --selkie -ms  
    --mermaid -mm  
    --hydra -mh  
 *Kraken provides a balance of ratio and speed.   
 Leviathan provides maximum compression.    
 Selkie and Mermaid are even faster.                    
 Hydra can hit performance targets between those choices.  
 For more info see http://www.radgametools.com/oodlecompressors.htm*  

compression effort level:
-1 -2 ... -9 negative levels (-4 to -1) are HyperFasts and can be set with "-ol" option (eg. -ol-2) Higher effort levels get a better compression ratio at the expense of encode time

More Options

-H
           prints Oodle compressor options help
-c --stdout
           outputs to stdout (decompress only).
-d --decompress
           decompress
-z --compress
           compress
-k --keep
           keep original file (otherwise deleted)
-f --force
           overwrite output file if exists
-F --fast
           low latency streaming compression
-b --best
           best compression. Long compress times.
-t --test
           tests existing compressed file validity
-K --verify
           verify file during compression
-q --quiet
           no prints
-v --verbose
           prints lots
-s --small
           low memory use ~2.5MB (compression only)
--bufferlimit=[1-256]
           (MB) max buffer size for compression.
--blocklimit=[8+]
           (KB) minimum block size in KB for streaming
--contextlimit=[8+]
           (KB) context limit KB. trades memory use for ratio

Unix only:
--timeout=[1000]
           time in ms to wait on inactve stdin during compression

Additional Oodle Compression options displayed with -H. See the Oodle Data Compression SDK documentation for details.

Streaming

Ozip supports nonblocking stream on linux, otherwise reading for EOF until bufferlimit. Setting a smaller blocklimit represents less tolerance for timeouts on linux, triggering a block to encode with less received data. Lower latency can also be achieved on all platforms by setting smaller max buffer size at the cost of compression ratio (this also lowers memory use)

File Format

Ozip adds a file header and block header to the compressed data stream. Values are little endian.

File Header Version 1: 16 bytes.
4 byte "OZIP" magic word.
4 byte Header Version.
8 byte filesize (=0 if unknown when streaming.)

Block Header Version 1: 16 bytes.
4 byte "OZIP" magic word.
4 bytes raw block size.
4 bytes context size.
4 bytes compressed size.

Each ozip file consists of :

File Header
repeated :
  Block Header
  Block compressed data

About

OZIP ver. 0.1.1

Ozip originally developed by:
https://github.com/jamesbloom/ozip
jamesbloom@gmail.com

About the Oodle SDK:
http://www.radgametools.com/oodle.htm

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