AE info encode

codec.lua

local M
do
  -- cache
  local char = string.char
  --
  local encode_info = function(args)
    local r = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0} -- FIXME: lowlevel createtable with 8 + 2 * #args elements?
    local n = 0
    -- enlist arguments separated with NL
    for i = 1, #args do
      local s = args[i]
      r[7 + 2*i] = s -- FIXME: cache 2*i?
      r[8 + 2*i] = "\n"
      n = n + #s + 1 -- FIXME: +1 optimized to initial n = #args
    end
    -- fill header
    r[1] = "\2" -- version
    r[2] = "\1" -- "info"
    for i = 8, 3, -1 do
      r[i] = char(n % 256)
      n = n / 256
    end
    -- NB: nginx accepts a table of strings, no need to concat
    return r
  end
  local decode_header = function(header)
    local _ver = header:byte(1)
    local t = header:byte(2) -- NB: 1 "info", 3 "message"
    local n = 0
    for i = 3, 8 do
      n = n * 256 + header:byte(i)
    end
    return t, n
  -- expose
  M = {
    decode_header = decode_header,
    encode_info = encode_info,
  }
end
return M