deflatelua

--[[

LUA MODULE

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

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.

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)



    Modified by TehSomeLuigi under the above license.

--]]

local M = {_TYPE='module', _NAME='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

local DEBUG = false


local band, lshift, rshift
band = bit32.band
lshift = bit32.lshift
rshift = bit32.rshift


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, ctx)
    return assert(val, 'unexpected end of file with context ' .. tostring(ctx))
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'})

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 = {s=s}
    function o:read()
        local by
        if i <= #self.s then
            by = self.s:byte(i)
            i = i + 1
        end
        return by
    end
    return o
end

M.stringToBytestream = bytestream_from_string

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

    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

        if nbits == 16 then
            -- bugfix: swap bytes
            bits = rshift(band(bits, 0xFF00), 8) + lshift(band(bits, 0xFF), 8)
        end

        buf_nbit = buf_nbit - nbits
        return bits
    end

    is_bitstream[o] = true

    return o
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

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
    elseif type(o) == 'table' then
        -- assume __callable table
        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 = 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

    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), 1)]
                nbits = nbits + minbits
            else
                local b = noeof(bs:read(), 2)
                nbits = nbits + 1
                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) - overflow by " .. ((cmf*256 + flg) % 31))
    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), 3) -- # 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), 4)
                    -- nbits unchanged
                elseif codelen == 17 then
                    nrepeat = 3 + noeof(bs:read(3), 5)
                    nbits = 0
                elseif codelen == 18 then
                    nrepeat = 11 + noeof(bs:read(7), 6)
                    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 = {}
            for i=257,285 do
                local j = math_max(i - 261, 0)
                t[i] = rshift(j, 2)
            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 = {}
            for i=0,29 do
                local j = math_max(i - 2, 0)
                t[i] = rshift(j, 1)
            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'))
        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), 7)

        for i=1,len do
            local by = noeof(bs:read(8), 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)

    parse_gzip_header(bs)

    local data_crc32 = 0

    inflate{input=bs, output=outbs}

    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 bs:read() then
        warn 'trailing garbage ignored'
    end
end


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

    local window_size_ = parse_zlib_header(bs)

    local data_adler32 = 1

    inflate{input=bs, output=outbs}

    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