Hex value to string lua using ffi

main.lua

local ffi = require("ffi")
ffi.cdef[[
typedef struct {
  union {
    uint64_t rgba;
    struct {
      uint8_t a;
      uint8_t b;
      uint8_t g;
      uint8_t r;
    };
  };
} leColor;

typedef struct {
  union {
    uint64_t rgba;
    struct {
      uint8_t r;
      uint8_t g;
      uint8_t b;
      uint8_t a;
    };
  };
} beColor;
]]

local ffiColorToString = function(foo)
  return ("0x%02x%02x%02x%02x"):format(foo.r,foo.g,foo.b,foo.a)
end

local color = 0x000000FF
local struct
if ffi.abi("le") then
  struct = ffi.new("leColor")
else
  struct = ffi.new("beColor")
end
struct.rgba = color

local print = love.graphics.print
love.draw = function()
  print(ffiColorToString(struct)) -- prints 0x000000FF
end