zlib.lua

#!/usr/bin/env luajit
-- Copyright (C) 2012 by Yichun Zhang (agentzh)


local ffi = require "ffi"
local assert = assert

module(...)

_VERSION = '0.01'

ffi.cdef[[
unsigned long compressBound(unsigned long sourceLen);
int compress2(uint8_t *dest, unsigned long *destLen,
          const uint8_t *source, unsigned long sourceLen, int level);
int uncompress(uint8_t *dest, unsigned long *destLen,
           const uint8_t *source, unsigned long sourceLen);
]]
local zlib = ffi.load(ffi.os == "Windows" and "zlib1" or "z")

function compress(txt)
  local n = zlib.compressBound(#txt)
  local buf = ffi.new("uint8_t[?]", n)
  local buflen = ffi.new("unsigned long[1]", n)
  local res = zlib.compress2(buf, buflen, txt, #txt, 9)
  assert(res == 0)
  return ffi.string(buf, buflen[0])
end

function uncompress(comp, n)
  local buf = ffi.new("uint8_t[?]", n)
  local buflen = ffi.new("unsigned long[1]", n)
  local res = zlib.uncompress(buf, buflen, comp, #comp)
--  if res == 0 then
--      return ffi.string(buf, buflen[0])
--  end
  assert(res == 0)
  return ffi.string(buf, buflen[0])
end

---- Simple test code.
--local txt = string.rep("abcd", 1000)
--print("Uncompressed size: ", #txt)
--local c = compress(txt)
--print("Compressed size: ", #c)
--local txt2 = uncompress(c, #txt)
--assert(txt2 == txt)