Two functions allowing for Lua's number serialization.

doubleSerialize.lua

--[[
The MIT License (MIT)

Copyright (c) 2015 Jakub (Kubuxu) Sztandera

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function readDouble(bytes) 
  local sign = 1
  local mantissa = bytes[2] % 2^4
  for i = 3, 8 do
    mantissa = mantissa * 256 + bytes[i]
  end
  if bytes[1] > 127 then sign = -1 end
  local exponent = (bytes[1] % 128) * 2^4 + math.floor(bytes[2] / 2^4)
  
  if exponent == 0 then
    return 0
  end
  mantissa = (math.ldexp(mantissa, -52) + 1) * sign
  return math.ldexp(mantissa, exponent - 1023)
end

function writeDouble(num)
  local bytes = {0,0,0,0, 0,0,0,0}
  if num == 0 then
    return bytes
  end
  local anum = math.abs(num)
  
  local mantissa, exponent = math.frexp(anum)
  exponent = exponent - 1
  mantissa = mantissa * 2 - 1
  local sign = num ~= anum and 128 or 0
  exponent = exponent + 1023
  
  bytes[1] = sign + math.floor(exponent / 2^4)
  mantissa = mantissa * 2^4
  local currentmantissa = math.floor(mantissa)
  mantissa = mantissa - currentmantissa
  bytes[2] = (exponent % 2^4) * 2^4 + currentmantissa
  for i= 3, 8 do
    mantissa = mantissa * 2^8
    currentmantissa = math.floor(mantissa)
    mantissa = mantissa - currentmantissa
    bytes[i] = currentmantissa
  end
  return bytes
end

Thanks! This saved me a big headache