40 lines
978 B
Lua
40 lines
978 B
Lua
local s, t = string, table
|
|
local ss = s.sub
|
|
|
|
--------------------------------------------------------------------------------
|
|
local POS_BITS = 12
|
|
local LEN_BITS = 16 - POS_BITS
|
|
local POS_SIZE = 1 << POS_BITS
|
|
local LEN_SIZE = 1 << LEN_BITS
|
|
local LEN_MIN = 3
|
|
|
|
local function lzss_decompress(input)
|
|
local offset, output = 1, {}
|
|
local window = ''
|
|
|
|
while offset <= #input do
|
|
local flags = s.byte(input, offset)
|
|
offset = offset + 1
|
|
|
|
for i = 1, 8 do
|
|
local str = nil
|
|
if (flags & 1) ~= 0 and offset <= #input then
|
|
str = ss(input, offset, offset)
|
|
offset = offset + 1
|
|
elseif offset + 1 <= #input then
|
|
local tmp = s.unpack('>I2', input, offset)
|
|
offset = offset + 2
|
|
local pos = (tmp >> LEN_BITS) + 1
|
|
local len = (tmp & (LEN_SIZE - 1)) + LEN_MIN
|
|
str = ss(window, pos, pos + len - 1)
|
|
end
|
|
flags = flags >> 1
|
|
if str then
|
|
output[#output + 1] = str
|
|
window = ss(window .. str, -POS_SIZE)
|
|
end
|
|
end
|
|
end
|
|
|
|
return t.concat(output)
|
|
end |