lz77

local function e_char(str1, str2)
  local l
  if #str1 < #str2 then
    l = #str1
  else
    l = #str2
  end
  local i = 1
  while i <= l and str1:sub(i, i) == str2:sub(i, i) do
    i = i + 1
  end
  if i <= l then
    return i - 1
  else
    return l
  end
end

local function lz77(text, sw_l)
  sw_l = sw_l or 6
  local o = 1
  local eof = false
  while not eof do
    local sw_o = o - sw_l
    if sw_o < 1 then sw_o = 1 end
    local sw = text:sub(sw_o, o - 1)
    local o_text = text:sub(o)
    local lg = 0
    local lg_pos = 0
    for i = 1, #sw do
      local n = e_char(sw:sub(i), o_text)
      if n > lg then
        lg = n
        lg_pos = i
      end
    end
    local f_pos = o + lg
    local f
    if f_pos <= #text then
      f = text:sub(f_pos, f_pos)
    else
      f = "]"
      eof = true
    end
    io.write(string.char(lg_pos)..string.char(lg)..f)
    --print(string.format("(%d, %d, %s)", lg_pos, lg, f))
    o = f_pos + 1
  end
end

lz77("blablablabla", 30)