local lz = require "lzss"
local buffer = require "buffer"

lz16 = {}

local function cint(n,l)
 local t={}
 for i = 0, 7 do
  t[i+1] = (n >> (i * 8)) & 0xFF
 end
 return string.reverse(string.char(table.unpack(t)):sub(1,l))
end
local function toint(s)
 local n = 0
 local i = 1
 for p in s:gmatch(".") do
  n = n << 8
  n = n | string.byte(p)
  i=i+1
 end
 return n
end

local function readBuffer(fi)
 local stream = {}
 if fi:read(4) ~= "lz16" then
  return false, "not an lz16 archive"
 end
 function stream.read()
  local len = toint(fi:read(2) or "\0\0")
  if len < 1 then
   return nil
  end
  coroutine.yield()
  return lz.decompress(fi:read(len))
 end
 function stream.close()
  fi:close()
 end
 return buffer.new("rb",stream)
end

local function writeBuffer(fo)
 local stream = {}
 function stream:write(data)
  local cblock = lz.compress(data)
  fo:write(cint(cblock:len(),2)..cblock)
  return cblock:len()+2
 end
 function stream.close()
  fo:close()
 end
 fo:write("lz16") -- write header
 return buffer.new("wb",stream)
end

function lz16.buffer(stream)
 if stream.mode.w then
  return writeBuffer(stream)
 end
 return readBuffer(stream)
end

function lz16.open(fname, mode)
 local f = io.open(fname, mode)
 if not f then return false end
 f.mode.b = true
 return lz16.buffer(f)
end

return lz16