lua MessagePack使用

example：
from：

local mp = require 'MessagePack'

mp.set_number'float'
mp.set_integer'unsigned'
mp.set_array'with_hole'
mp.set_string'string'

mpac = mp.pack(data)
data = mp.unpack(mpac)

local ltn12 = require 'ltn12'
src = ltn12.source.file(io.open('file', 'r'))
for _, v in mp.unpacker(src) do
    print(v)
end

使用：

local mp = require 'MessagePack'

mp.set_number'float'
mp.set_integer'unsigned'
mp.set_array'with_hole'
mp.set_string'string'

local tab = { a = 1.89, b = 'b' }
local s = mp.pack(tab)
print(s)
local data = mp.unpack(tabString)
print(data.a, data.b)

unpack后的浮点数精度问题，最好在server和client两端做四舍五入处理：

local math = require 'math'
local mp = require 'MessagePack'

mp.set_number'float'
mp.set_integer'unsigned'
mp.set_array'with_hole'
mp.set_string'string'

function roundOff(num, n)
    if n > 0 then
        local scale = math.pow(10, n-1)
        return math.floor(num / scale + 0.5) * scale
    elseif n < 0 then
        local scale = math.pow(10, n)
        return math.floor(num / scale + 0.5) * scale
    elseif n == 0 then
        return num
    end
end

local tab = { a = 1.89, b = 'b' }
local s = mp.pack(tab)
print(s)
local data = mp.unpack(tabString)
print(data.a, data.b)
data.a = roundOff(data.a, -2)
print(data.a, data.b)