rerouterator/numberConverter.lua

local numberConverter = {}
local bit = require("bit")


-- nic'd these from stack overflow
-- https://stackoverflow.com/a/19996852
function numberConverter.float2hex(n)
  if n == 0.0 then return 0.0 end
  local sign = 0
  if n < 0.0 then
    sign = 0x80
    n = -n
  end
  local mant, expo = math.frexp(n)
  local hext = {}
  if mant ~= mant then
    hext[#hext+1] = string.char(0xFF, 0x88, 0x00, 0x00)
  elseif mant == math.huge or expo > 0x80 then
    if sign == 0 then
      hext[#hext+1] = string.char(0x7F, 0x80, 0x00, 0x00)
    else
      hext[#hext+1] = string.char(0xFF, 0x80, 0x00, 0x00)
    end
  elseif (mant == 0.0 and expo == 0) or expo < -0x7E then
    hext[#hext+1] = string.char(sign, 0x00, 0x00, 0x00)
  else
    expo = expo + 0x7E
    mant = (mant * 2.0 - 1.0) * math.ldexp(0.5, 24)
    hext[#hext+1] = string.char(sign + math.floor(expo / 0x2),
                                (expo % 0x2) * 0x80 + math.floor(mant / 0x10000),
                                math.floor(mant / 0x100) % 0x100,
                                mant % 0x100)
  end

  return tonumber(string.gsub(table.concat(hext),"(.)",
  function (c) return string.format("%02X%s",string.byte(c),"") end), 16)
end

-- nic'd these from stack overflow
-- https://stackoverflow.com/a/19996852
function numberConverter.hex2float(c)
  if c == 0 then return 0.0 end
  local c = string.gsub(string.format("%X", c),"(..)",function (x) return string.char(tonumber(x, 16)) end)
  local b1,b2,b3,b4 = string.byte(c, 1, 4)
  local sign = b1 > 0x7F
  local expo = (b1 % 0x80) * 0x2 + math.floor(b2 / 0x80)
  local mant = ((b2 % 0x80) * 0x100 + b3) * 0x100 + b4
  if sign then
    sign = -1
  else
    sign = 1
  end
  local n
  if mant == 0 and expo == 0 then
    n = sign * 0.0
  elseif expo == 0xFF then
    if mant == 0 then
      n = sign * math.huge
    else
      n = 0.0/0.0
    end
  else
    n = sign * math.ldexp(1.0 + mant / 0x800000, expo - 0x7F)
  end
  return n
end

function numberConverter.toNetworkFloat(f)
  local n = numberConverter.float2hex(f)
  return numberConverter.toNetworkInt(n)
end

function numberConverter.toNetworkInt(originalNumber)
  local byteA = bit.band(originalNumber,0xff)
  local byteB = bit.band(originalNumber,0xff00)
  byteB = bit.rshift(byteB,8)
  local byteC = bit.band(originalNumber,0xff0000)
  byteC = bit.rshift(byteC,16)
  local byteD = bit.band(originalNumber,0xff000000)
  byteD = bit.rshift(byteD,24)

  return (string.char(byteD) ..
          string.char(byteC) ..
          string.char(byteB) ..
          string.char(byteA))
end

function numberConverter.toNetworkNumber(originalNumber)
  local n = originalNumber
  if type(originalNumber) == "string" then
    n = tonumber(originalNumber)
  end

  if n == math.floor(n) then
    return numberConverter.toNetworkInt(n)
  else
    return numberConverter.toNetworkFloat(n)
  end
end

function numberConverter.intToLuaNumber(netNumString)
  local retval = 0
  local byteD = netNumString:sub(1,1):byte()
  local byteC = netNumString:sub(2,2):byte()
  local byteB = netNumString:sub(3,3):byte()
  local byteA = netNumString:sub(4,4):byte()

  retval = retval + byteA
  retval = retval + bit.lshift(byteB,8)
  retval = retval + bit.lshift(byteC,16)
  retval = retval + bit.lshift(byteD,24)
  return retval
end

function numberConverter.floatToLuaNumber(netNumString)
  local hexes = numberConverter.intToLuaNumber(netNumString)
  return numberConverter.hex2float(hexes)
end

return numberConverter