zlib-compressed file depacking library in Lua
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COPYING
README.md
zzlib.lua

README.md

zzlib

This is a pure Lua implementation of a depacker for the zlib DEFLATE(RFC1951)/GZIP(RFC1952) file format. zzlib also allows the decoding of zlib-compressed data (RFC1950). Also featured is basic support for extracting files from DEFLATE-compressed ZIP archives (no support for encryption).

The implementation is pretty fast. It makes use of the built-in bit32 (PUC-Rio Lua) or bit (LuaJIT) libraries for bitwise operations. Typical run times to depack lua-5.3.3.tar.gz on my 2013 i5 laptop are 0.87s with Lua 5.3, and 0.28s with LuaJIT 2.0.4.

zzlib is distributed under the WTFPL licence. See the COPYING file or http://www.wtfpl.net/ for more details.

Usage

There are various ways of using the library.

Stream from a GZIP file

-- import the zzlib library
zzlib = require("zzlib")

-- get the unpacked contents of the file in the 'output' string
local output,err = zzlib.gunzipf("input.gz")
if not output then error(err) end

Read GZIP/zlib data from a string

Read a file into a string, call the depacker, and get a string with the unpacked file contents, as follows:

-- import the zzlib library
zzlib = require("zzlib")
...

if use_gzip then
  -- unpack the gzip input data to the 'output' string
  output = zzlib.gunzip(input)
else
  -- unpack the zlib input data to the 'output' string
  output = zzlib.inflate(input)
end

Extract file from a ZIP archive stored in a string

Read a file into a string, call the depacker, and get a string with the unpacked contents of the chosen file, as follows:

-- import the zzlib library
zzlib = require("zzlib")
...

-- extract a specific file from the input zip file
output = zzlib.unzip(input,"lua-5.3.4/README")