--[[

LUA MODULE

  compress.deflatelua - deflate (and gunzip/zlib) implemented in Lua.

SYNOPSIS

  local DEFLATE = require 'compress.deflatelua'
  -- uncompress gzip file
  local fh = assert(io.open'foo.txt.gz', 'rb')
  local ofh = assert(io.open'foo.txt', 'wb')
  DEFLATE.gunzip {input=fh, output=ofh}
  fh:close(); ofh:close()
  -- can also uncompress from string including zlib and raw DEFLATE formats.

DESCRIPTION

  This is a pure Lua implementation of decompressing the DEFLATE format,
  including the related zlib and gzip formats.

  Note: This library only supports decompression.
  Compression is not currently implemented.

API

  Note: in the following functions, input stream `fh` may be
  a file handle, string, or an iterator function that returns strings.
  Output stream `ofh` may be a file handle or a function that
  consumes one byte (number 0..255) per call.

  DEFLATE.inflate {input=fh, output=ofh}

    Decompresses input stream `fh` in the DEFLATE format
    while writing to output stream `ofh`.
    DEFLATE is detailed in http://tools.ietf.org/html/rfc1951 .

  DEFLATE.gunzip {input=fh, output=ofh, disable_crc=disable_crc}

    Decompresses input stream `fh` with the gzip format
    while writing to output stream `ofh`.
    `disable_crc` (defaults to `false`) will disable CRC-32 checking
    to increase speed.
    gzip is detailed in http://tools.ietf.org/html/rfc1952 .

  DEFLATE.inflate_zlib {input=fh, output=ofh, disable_crc=disable_crc}

    Decompresses input stream `fh` with the zlib format
    while writing to output stream `ofh`.
    `disable_crc` (defaults to `false`) will disable CRC-32 checking
    to increase speed.
    zlib is detailed in http://tools.ietf.org/html/rfc1950 .

  DEFLATE.adler32(byte, crc) --> rcrc

    Returns adler32 checksum of byte `byte` (number 0..255) appended
    to string with adler32 checksum `crc`.  This is internally used by
    `inflate_zlib`.
    ADLER32 in detailed in http://tools.ietf.org/html/rfc1950 .

COMMAND LINE UTILITY

  A `gunziplua` command line utility (in folder `bin`) is also provided.
  This mimicks the *nix `gunzip` utility but is a pure Lua implementation
  that invokes this library.  For help do

    gunziplua -h

DEPENDENCIES

  Requires 'digest.crc32lua' (used for optional CRC-32 checksum checks).
    https://github.com/davidm/lua-digest-crc32lua

  Will use a bit library ('bit', 'bit32', 'bit.numberlua') if available.  This
  is not that critical for this library but is required by digest.crc32lua.

  'pythonic.optparse' is only required by the optional `gunziplua`
  command-line utilty for command line parsing.
    https://github.com/davidm/lua-pythonic-optparse

INSTALLATION

  Copy the `compress` directory into your LUA_PATH.

REFERENCES

  [1] DEFLATE Compressed Data Format Specification version 1.3
      http://tools.ietf.org/html/rfc1951
  [2] GZIP file format specification version 4.3
      http://tools.ietf.org/html/rfc1952
  [3] http://en.wikipedia.org/wiki/DEFLATE
  [4] pyflate, by Paul Sladen
      http://www.paul.sladen.org/projects/pyflate/
  [5] Compress::Zlib::Perl - partial pure Perl implementation of
      Compress::Zlib
      http://search.cpan.org/~nwclark/Compress-Zlib-Perl/Perl.pm

LICENSE

  (c) 2008-2011 David Manura.  Licensed under the same terms as Lua (MIT).

  Permission is hereby granted, free of charge, to any person obtaining a copy
  of this software and associated documentation files (the "Software"), to deal
  in the Software without restriction, including without limitation the rights
  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  copies of the Software, and to permit persons to whom the Software is
  furnished to do so, subject to the following conditions:

  The above copyright notice and this permission notice shall be included in
  all copies or substantial portions of the Software.

  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL THE
  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  THE SOFTWARE.
  (end license)
--]] local M = {_TYPE = "module", _NAME = "compress.deflatelua", _VERSION = "0.3.20111128"}
local assert = assert
local error = error
local ipairs = ipairs
local pairs = pairs
local print = print
local require = require
local tostring = tostring
local type = type
local setmetatable = setmetatable
local io = io
local math = math
local table_sort = table.sort
local math_max = math.max
local string_char = string.char

--[[
 Requires the first module listed that exists, else raises like `require`.
 If a non-string is encountered, it is returned.
 Second return value is module name loaded (or '').
 --]] local function requireany(...)
	local errs = {}

	for i = 1, select("#", ...) do
		local name = select(i, ...)

		if type(name) ~= "string" then return name, "" end

		local ok, mod = pcall(require, name)

		if ok then return mod, name end

		errs[#errs + 1] = mod
	end

	error(table.concat(errs, "\n"), 2)
end

local crc32 = crypto.CRC32 or require("digest.crc32lua").crc32_byte
local bit, name_ = requireany("bit", "bit32", "bit.numberlua", nil)
local DEBUG = false
-- Whether to use `bit` library functions in current module.
-- Unlike the crc32 library, it doesn't make much difference in this module.
local NATIVE_BITOPS = (bit ~= nil)
local band, lshift, rshift

if NATIVE_BITOPS then
	band = bit.band
	lshift = bit.lshift
	rshift = bit.rshift
end

local function warn(s)
	io.stderr:write(s, "\n")
end

local function debug(...)
	print("DEBUG", ...)
end

local function runtime_error(s, level)
	level = level or 1
	error(s, level + 1)
end

local function make_outstate(outbs)
	local outstate = {}
	outstate.outbs = outbs
	outstate.window = {}
	outstate.window_pos = 1
	return outstate
end

local function output(outstate, byte)
	-- debug('OUTPUT:', s)
	local window_pos = outstate.window_pos
	outstate.outbs(byte)
	outstate.window[window_pos] = byte
	outstate.window_pos = window_pos % 32768 + 1 -- 32K
end

local function noeof(val)
	return assert(val, "unexpected end of file")
end

local function hasbit(bits, bit)
	return bits % (bit + bit) >= bit
end

local function memoize(f)
	local mt = {}
	local t = setmetatable({}, mt)

	function mt:__index(k)
		local v = f(k)
		t[k] = v
		return v
	end

	return t
end

-- small optimization (lookup table for powers of 2)
local pow2 = memoize(function(n)
	return 2 ^ n
end)
--local tbits = memoize(
--  function(bits)
--    return memoize( function(bit) return getbit(bits, bit) end )
--  end )
-- weak metatable marking objects as bitstream type
local is_bitstream = setmetatable({}, {__mode = "k"})

-- DEBUG
-- prints LSB first
--[[
local function bits_tostring(bits, nbits)
  local s = ''
  local tmp = bits
  local function f()
    local b = tmp % 2 == 1 and 1 or 0
    s = s .. b
    tmp = (tmp - b) / 2
  end
  if nbits then
    for i=1,nbits do f() end
  else
    while tmp ~= 0 do f() end
  end

  return s
end
--]] local function bytestream_from_file(fh)
	local o = {}

	function o:read()
		local sb = fh:read(1)

		if sb then return sb:byte() end
	end

	return o
end

local function bytestream_from_string(s)
	local i = 1
	local o = {}

	function o:read()
		local by

		if i <= #s then
			by = s:byte(i)
			i = i + 1
		end

		return by
	end

	return o
end

local function bytestream_from_function(f)
	local i = 0
	local buffer = ""
	local o = {}

	function o:read()
		i = i + 1

		if i > #buffer then
			buffer = f()

			if not buffer then return end

			i = 1
		end

		return buffer:byte(i, i)
	end

	return o
end

local function bitstream_from_bytestream(bys)
	local buf_byte = 0
	local buf_nbit = 0
	local o = {}

	function o:nbits_left_in_byte()
		return buf_nbit
	end

	if NATIVE_BITOPS then
		function o:read(nbits)
			nbits = nbits or 1

			while buf_nbit < nbits do
				local byte = bys:read()

				if not byte then return end -- note: more calls also return nil
				buf_byte = buf_byte + lshift(byte, buf_nbit)
				buf_nbit = buf_nbit + 8
			end

			local bits

			if nbits == 0 then
				bits = 0
			elseif nbits == 32 then
				bits = buf_byte
				buf_byte = 0
			else
				bits = band(buf_byte, rshift(0xffffffff, 32 - nbits))
				buf_byte = rshift(buf_byte, nbits)
			end

			buf_nbit = buf_nbit - nbits
			return bits
		end
	else
		function o:read(nbits)
			nbits = nbits or 1

			while buf_nbit < nbits do
				local byte = bys:read()

				if not byte then return end -- note: more calls also return nil
				buf_byte = buf_byte + pow2[buf_nbit] * byte
				buf_nbit = buf_nbit + 8
			end

			local m = pow2[nbits]
			local bits = buf_byte % m
			buf_byte = (buf_byte - bits) / m
			buf_nbit = buf_nbit - nbits
			return bits
		end
	end

	is_bitstream[o] = true
	return o
end

local function get_bitstream(o)
	local bs

	if is_bitstream[o] then
		return o
	elseif io.type(o) == "file" then
		bs = bitstream_from_bytestream(bytestream_from_file(o))
	elseif type(o) == "string" then
		bs = bitstream_from_bytestream(bytestream_from_string(o))
	elseif type(o) == "function" then
		bs = bitstream_from_bytestream(bytestream_from_function(o))
	else
		runtime_error("unrecognized type")
	end

	return bs
end

local function get_obytestream(o)
	local bs

	if io.type(o) == "file" then
		bs = function(sbyte)
			o:write(string_char(sbyte))
		end
	elseif type(o) == "function" then
		bs = o
	else
		runtime_error("unrecognized type: " .. tostring(o))
	end

	return bs
end

local function HuffmanTable(init, is_full)
	local t = {}

	if is_full then
		for val, nbits in pairs(init) do
			if nbits ~= 0 then
				t[#t + 1] = {val = val, nbits = nbits}
			--debug('*',val,nbits)
			end
		end
	else
		for i = 1, #init - 2, 2 do
			local firstval, nbits, nextval = init[i], init[i + 1], init[i + 2]

			--debug(val, nextval, nbits)
			if nbits ~= 0 then
				for val = firstval, nextval - 1 do
					t[#t + 1] = {val = val, nbits = nbits}
				end
			end
		end
	end

	table_sort(t, function(a, b)
		return a.nbits == b.nbits and a.val < b.val or a.nbits < b.nbits
	end)

	-- assign codes
	local code = 1 -- leading 1 marker
	local nbits = 0

	for i, s in ipairs(t) do
		if s.nbits ~= nbits then
			code = code * pow2[s.nbits - nbits]
			nbits = s.nbits
		end

		s.code = code
		--debug('huffman code:', i, s.nbits, s.val, code, bits_tostring(code))
		code = code + 1
	end

	local minbits = math.huge
	local look = {}

	for i, s in ipairs(t) do
		minbits = math.min(minbits, s.nbits)
		look[s.code] = s.val
	end

	--for _,o in ipairs(t) do
	--  debug(':', o.nbits, o.val)
	--end
	-- function t:lookup(bits) return look[bits] end
	local msb = NATIVE_BITOPS and
		function(bits, nbits)
			local res = 0

			for i = 1, nbits do
				res = lshift(res, 1) + band(bits, 1)
				bits = rshift(bits, 1)
			end

			return res
		end or
		function(bits, nbits)
			local res = 0

			for i = 1, nbits do
				local b = bits % 2
				bits = (bits - b) / 2
				res = res * 2 + b
			end

			return res
		end
	local tfirstcode = memoize(function(bits)
		return pow2[minbits] + msb(bits, minbits)
	end)

	function t:read(bs)
		local code = 1 -- leading 1 marker
		local nbits = 0

		while 1 do
			if nbits == 0 then -- small optimization (optional)
				code = tfirstcode[noeof(bs:read(minbits))]
				nbits = nbits + minbits
			else
				local b = noeof(bs:read())
				nbits = nbits + 1
				code = code * 2 + b -- MSB first
			--[[NATIVE_BITOPS
        code = lshift(code, 1) + b   -- MSB first
        --]] end

			--debug('code?', code, bits_tostring(code))
			local val = look[code]

			if val then --debug('FOUND', val)
			return val end
		end
	end

	return t
end

local function parse_gzip_header(bs)
	-- local FLG_FTEXT = 2^0
	local FLG_FHCRC = 2 ^ 1
	local FLG_FEXTRA = 2 ^ 2
	local FLG_FNAME = 2 ^ 3
	local FLG_FCOMMENT = 2 ^ 4
	local id1 = bs:read(8)
	local id2 = bs:read(8)

	if id1 ~= 31 or id2 ~= 139 then runtime_error("not in gzip format") end

	local cm = bs:read(8) -- compression method
	local flg = bs:read(8) -- FLaGs
	local mtime = bs:read(32) -- Modification TIME
	local xfl = bs:read(8) -- eXtra FLags
	local os = bs:read(8) -- Operating System
	if DEBUG then
		debug("CM=", cm)
		debug("FLG=", flg)
		debug("MTIME=", mtime)
		-- debug("MTIME_str=",os.date("%Y-%m-%d %H:%M:%S",mtime)) -- non-portable
		debug("XFL=", xfl)
		debug("OS=", os)
	end

	if not os then runtime_error("invalid header") end

	if hasbit(flg, FLG_FEXTRA) then
		local xlen = bs:read(16)
		local extra = 0

		for i = 1, xlen do
			extra = bs:read(8)
		end

		if not extra then runtime_error("invalid header") end
	end

	local function parse_zstring(bs)
		repeat
			local by = bs:read(8)

			if not by then runtime_error("invalid header") end		
		until by == 0
	end

	if hasbit(flg, FLG_FNAME) then parse_zstring(bs) end

	if hasbit(flg, FLG_FCOMMENT) then parse_zstring(bs) end

	if hasbit(flg, FLG_FHCRC) then
		local crc16 = bs:read(16)

		if not crc16 then runtime_error("invalid header") end

		-- IMPROVE: check CRC.  where is an example .gz file that
		-- has this set?
		if DEBUG then debug("CRC16=", crc16) end
	end
end

local function parse_zlib_header(bs)
	local cm = bs:read(4) -- Compression Method
	local cinfo = bs:read(4) -- Compression info
	local fcheck = bs:read(5) -- FLaGs: FCHECK (check bits for CMF and FLG)
	local fdict = bs:read(1) -- FLaGs: FDICT (present dictionary)
	local flevel = bs:read(2) -- FLaGs: FLEVEL (compression level)
	local cmf = cinfo * 16 + cm -- CMF (Compresion Method and flags)
	local flg = fcheck + fdict * 32 + flevel * 64 -- FLaGs
	if cm ~= 8 then -- not "deflate"
		runtime_error("unrecognized zlib compression method: " + cm)
	end

	if cinfo > 7 then
		runtime_error("invalid zlib window size: cinfo=" + cinfo)
	end

	local window_size = 2 ^ (cinfo + 8)

	if (cmf * 256 + flg) % 31 ~= 0 then
		runtime_error("invalid zlib header (bad fcheck sum)")
	end

	if fdict == 1 then
		runtime_error("FIX:TODO - FDICT not currently implemented")
		local dictid_ = bs:read(32)
	end

	return window_size
end

local function parse_huffmantables(bs)
	local hlit = bs:read(5) -- # of literal/length codes - 257
	local hdist = bs:read(5) -- # of distance codes - 1
	local hclen = noeof(bs:read(4)) -- # of code length codes - 4
	local ncodelen_codes = hclen + 4
	local codelen_init = {}
	local codelen_vals = {16, 17, 18, 0, 8, 7, 9, 6, 10, 5, 11, 4, 12, 3, 13, 2, 14, 1, 15}

	for i = 1, ncodelen_codes do
		local nbits = bs:read(3)
		local val = codelen_vals[i]
		codelen_init[val] = nbits
	end

	local codelentable = HuffmanTable(codelen_init, true)

	local function decode(ncodes)
		local init = {}
		local nbits
		local val = 0

		while val < ncodes do
			local codelen = codelentable:read(bs)
			--FIX:check nil?
			local nrepeat

			if codelen <= 15 then
				nrepeat = 1
				nbits = codelen
			--debug('w', nbits)
			elseif codelen == 16 then
				nrepeat = 3 + noeof(bs:read(2))
			-- nbits unchanged
			elseif codelen == 17 then
				nrepeat = 3 + noeof(bs:read(3))
				nbits = 0
			elseif codelen == 18 then
				nrepeat = 11 + noeof(bs:read(7))
				nbits = 0
			else
				error("ASSERT")
			end

			for i = 1, nrepeat do
				init[val] = nbits
				val = val + 1
			end
		end

		local huffmantable = HuffmanTable(init, true)
		return huffmantable
	end

	local nlit_codes = hlit + 257
	local ndist_codes = hdist + 1
	local littable = decode(nlit_codes)
	local disttable = decode(ndist_codes)
	return littable, disttable
end

local tdecode_len_base
local tdecode_len_nextrabits
local tdecode_dist_base
local tdecode_dist_nextrabits

local function parse_compressed_item(bs, outstate, littable, disttable)
	local val = littable:read(bs)

	--debug(val, val < 256 and string_char(val))
	if val < 256 then -- literal
		output(outstate, val)
	elseif val == 256 then -- end of block
		return true
	else
		if not tdecode_len_base then
			local t = {[257] = 3}
			local skip = 1

			for i = 258, 285, 4 do
				for j = i, i + 3 do
					t[j] = t[j - 1] + skip
				end

				if i ~= 258 then skip = skip * 2 end
			end

			t[285] = 258
			tdecode_len_base = t
		--for i=257,285 do debug('T1',i,t[i]) end
		end

		if not tdecode_len_nextrabits then
			local t = {}

			if NATIVE_BITOPS then
				for i = 257, 285 do
					local j = math_max(i - 261, 0)
					t[i] = rshift(j, 2)
				end
			else
				for i = 257, 285 do
					local j = math_max(i - 261, 0)
					t[i] = (j - (j % 4)) / 4
				end
			end

			t[285] = 0
			tdecode_len_nextrabits = t
		--for i=257,285 do debug('T2',i,t[i]) end
		end

		local len_base = tdecode_len_base[val]
		local nextrabits = tdecode_len_nextrabits[val]
		local extrabits = bs:read(nextrabits)
		local len = len_base + extrabits

		if not tdecode_dist_base then
			local t = {[0] = 1}
			local skip = 1

			for i = 1, 29, 2 do
				for j = i, i + 1 do
					t[j] = t[j - 1] + skip
				end

				if i ~= 1 then skip = skip * 2 end
			end

			tdecode_dist_base = t
		--for i=0,29 do debug('T3',i,t[i]) end
		end

		if not tdecode_dist_nextrabits then
			local t = {}

			if NATIVE_BITOPS then
				for i = 0, 29 do
					local j = math_max(i - 2, 0)
					t[i] = rshift(j, 1)
				end
			else
				for i = 0, 29 do
					local j = math_max(i - 2, 0)
					t[i] = (j - (j % 2)) / 2
				end
			end

			tdecode_dist_nextrabits = t
		--for i=0,29 do debug('T4',i,t[i]) end
		end

		local dist_val = disttable:read(bs)
		local dist_base = tdecode_dist_base[dist_val]
		local dist_nextrabits = tdecode_dist_nextrabits[dist_val]
		local dist_extrabits = bs:read(dist_nextrabits)
		local dist = dist_base + dist_extrabits

		--debug('BACK', len, dist)
		for i = 1, len do
			local pos = (outstate.window_pos - 1 - dist) % 32768 + 1 -- 32K
			output(outstate, assert(outstate.window[pos], "invalid distance at pos " .. pos))
		end
	end

	return false
end

local function parse_block(bs, outstate)
	local bfinal = bs:read(1)
	local btype = bs:read(2)
	local BTYPE_NO_COMPRESSION = 0
	local BTYPE_FIXED_HUFFMAN = 1
	local BTYPE_DYNAMIC_HUFFMAN = 2
	local BTYPE_RESERVED_ = 3

	if DEBUG then
		debug("bfinal=", bfinal)
		debug("btype=", btype)
	end

	if btype == BTYPE_NO_COMPRESSION then
		bs:read(bs:nbits_left_in_byte())
		local len = bs:read(16)
		local nlen_ = noeof(bs:read(16))

		for i = 1, len do
			local by = noeof(bs:read(8))
			output(outstate, by)
		end
	elseif btype == BTYPE_FIXED_HUFFMAN or btype == BTYPE_DYNAMIC_HUFFMAN then
		local littable, disttable

		if btype == BTYPE_DYNAMIC_HUFFMAN then
			littable, disttable = parse_huffmantables(bs)
		else
			littable = HuffmanTable({0, 8, 144, 9, 256, 7, 280, 8, 288, nil})
			disttable = HuffmanTable({0, 5, 32, nil})
		end

		repeat
			local is_done = parse_compressed_item(bs, outstate, littable, disttable)		
		until is_done
	else
		runtime_error("unrecognized compression type")
	end

	return bfinal ~= 0
end

function M.inflate(t)
	local bs = get_bitstream(t.input)
	local outbs = get_obytestream(t.output)
	local outstate = make_outstate(outbs)

	repeat
		local is_final = parse_block(bs, outstate)	
	until is_final
end

local inflate = M.inflate

function M.gunzip(t)
	local bs = get_bitstream(t.input)
	local outbs = get_obytestream(t.output)
	local disable_crc = t.disable_crc

	if disable_crc == nil then disable_crc = false end

	parse_gzip_header(bs)
	local data_crc32 = 0
	inflate(
		{
			input = bs,
			output = disable_crc and
				outbs or
				function(byte)
					data_crc32 = crc32(byte, data_crc32)
					outbs(byte)
				end,
		}
	)
	bs:read(bs:nbits_left_in_byte())
	local expected_crc32 = bs:read(32)
	local isize = bs:read(32) -- ignored
	if DEBUG then
		debug("crc32=", expected_crc32)
		debug("isize=", isize)
	end

	if not disable_crc and data_crc32 then
		if data_crc32 ~= expected_crc32 then
			runtime_error("invalid compressed data--crc error")
		end
	end

	if bs:read() then warn("trailing garbage ignored") end
end

function M.adler32(byte, crc)
	local s1 = crc % 65536
	local s2 = (crc - s1) / 65536
	s1 = (s1 + byte) % 65521
	s2 = (s2 + s1) % 65521
	return s2 * 65536 + s1
end -- 65521 is the largest prime smaller than 2^16
function M.inflate_zlib(t)
	local bs = get_bitstream(t.input)
	local outbs = get_obytestream(t.output)
	local disable_crc = t.disable_crc

	if disable_crc == nil then disable_crc = false end

	local window_size_ = parse_zlib_header(bs)
	local data_adler32 = 1
	inflate(
		{
			input = bs,
			output = disable_crc and
				outbs or
				function(byte)
					data_adler32 = M.adler32(byte, data_adler32)
					outbs(byte)
				end,
		}
	)
	bs:read(bs:nbits_left_in_byte())
	local b3 = bs:read(8)
	local b2 = bs:read(8)
	local b1 = bs:read(8)
	local b0 = bs:read(8)
	local expected_adler32 = ((b3 * 256 + b2) * 256 + b1) * 256 + b0

	if DEBUG then debug("alder32=", expected_adler32) end

	if not disable_crc then
		if data_adler32 ~= expected_adler32 then
			runtime_error("invalid compressed data--crc error")
		end
	end

	if bs:read() then warn("trailing garbage ignored") end
end

return M