Module Compress Deflate Lua

wiki

Download:

• [compress.deflatelua] (github page) [documentation]
• Dependencies:
  • Lua 5.1, Lua 5.2, or LuaJit
  • One of the following modules for BitwiseOperators:
    • [bit.numberlua] - bitwise operations implemented in pure Lua as numbers ([documentation])
    • [LuaBitOp] 'bit' library (included in LuaJit).
    • Lua 5.2 'bit32' library [documentation]
  • [digest.crc32lua] - CRC-32 checksum implemented in pure Lua (optional; CRC calculations can be omitted) [documentation]
  • [github] - Command-line processing resembling Python optparse module - (optional; command-line tool can be omitted) [documentation]

Example:

./gunziplua lua-5.1.4.tar.gz

It's somewhat slow (as expected). To decompress lua-5.1.4.tar.gz using bit.numberlua, it takes about 9 seconds with CRC-checking enabled (4 with LuaJIT 1.x) or 3 seconds with CRC checking disabled (2 with LuaJIT 1.x). It's faster when using native bitop libraries, particularly under LuaJit.

Why? Possible reasons include these: (1) for pedagogical reasons, (2) to benchmark Lua, (3) to bootstrap applications like LuaRocks/LuaDist that might not have a precompiled copy of gunzip, and (4) because DEFLATE has been implemented in other languages too [1] (including Python, Perl, and Lisp).

The modules above follow a somewhat Perl CPAN-like naming convention. Compare to [Compress::Zlib::Perl], [Digest::CRC32], and the Bit:: modules.

The modules are being packaged to be usable in LuaRocks and LuaDist. (I'm still working on the LuaRocks and LuaDist packaging.)

More notes here are expected later. See [compress.deflatelua github page]. Comments welcome.

See Also

• PortableNetworkGraphicsParser - This Lua implementation of a PNG image reader could use this module.
• This module is used by [squish][2] - packs Lua code (compression and archiving)

--DavidManura

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