wkoszek / mini_gzip

mini_gzip - embeddable, minimal, in-memory GZIP API

mini_gzip - embeddable, minimal, in-memory GZIP API

Embeddable, minimal GZIP functionality, with API designed to work from memory. Only supports decompression for now.

I wrote it when I needed a small piece of code to give me decompression in an embedded system I was working with, and I found out that most of the GZIP-related programs use POSIX FILE API, which made the examples not work for my case.

The mini_gzip is based on miniz library (https://code.google.com/p/miniz/), which provides an API for operating on data compressed according to deflate algorithm. Added is a layer which provides a container for the GZIP files and let me do some verification.

To build

Everything should be fairly self-contained, and built with:

make

How to use

The API operates on struct mini_gzip structures, which are containers for the memory with GZIPed data. You must call mini_gz_init() on the structure 1st for the rest of the API to work correctly. Next, you must call mini_gz_start(&gz, mem_in, size), where gz is the initialized container and with GZIPed data pointed by mem_in of the size of size. To unpack, you call mini_gz_unpack(&gz, mem_out, memsize), where the first argument is the initialized container, the second mem_out is a pointer to the output memory, and memsize is its lenght. It's important to have enough bytes in the output buffer for decompressed data.

To test

Simple test is provided:

make test

To test by yourself, you can do:

	wk:/w/repos/mini_gzip> ls -la miniz.o
	-rw-r--r--  1 wk  staff  114348 20 paź 09:46 miniz.o
	wk:/w/repos/mini_gzip> md5 miniz.o
	MD5 (miniz.o) = e6199aade2020b6040fa160baee47d68
	wk:/w/repos/mini_gzip> gzip miniz.o
	wk:/w/repos/mini_gzip> ls -la miniz.o.gz
	-rw-r--r--  1 wk  staff  44965 20 paź 09:46 miniz.o.gz
	wk:/w/repos/mini_gzip> ./mini_gzip miniz.o.gz miniz.o
	flag_c: 0 is_gzipped: 1
	in_fn: miniz.o.gz out_fn: miniz.o level 6
	--- testing decompression --
	out_len = 114348
	ret = 114348
	wk:/w/repos/mini_gzip> md5 miniz.o
	MD5 (miniz.o) = e6199aade2020b6040fa160baee47d68

References

After publishing mini_gzip on HackerNews, byuu (http://byuu.org/) mentioned he has much leaner implementation of GZIP:

• https://gitlab.com/higan/higan/blob/master/nall/decode/gzip.hpp
• https://gitlab.com/higan/higan/blob/master/nall/decode/inflate.hpp

Author

• Wojciech Adam Koszek, [e-mail]
• http://www.koszek.com