本文所提方法，仅适用32位整数的大小端转换，实际上就上把数字的字节序简单粗暴的颠倒了一下。

local a = 0x12345678

local b = ENDIAN_TRANS(a)

输出的变量 b 应该是 0x78563412

alien = require "alien"

ENDIAN_TRANS = function(x) 
    s = alien.pack('>I', x)
    t = alien.unpack('I', s)
    return t
end

ENDIAN_TRANS = function(x) 
    s = string.pack('>I4', x)
    t = string.unpack('I4', s)
    return t
end

ENDIAN_TRANS = function(x)
    y = 0
    for i=1,4 do
        a, b = math.modf(x/256)
        y = y + b * math.pow(256, 5-i)
        x = a
    end

    return y
end