luajit-msgpack-pure

Warning

This library implements MessagePack spec v4 with some extensions compatible with msgpack-js. It does not implement spec v5. If you need support for spec v5 (including STR8, BIN types, etc), see alternatives.

Presentation

This is yet another implementation of MessagePack for LuaJIT. However, unlike luajit-msgpack, luajit-msgpack-pure does not depend on the MessagePack C library. Everything is re-implemented in LuaJIT code (using the FFI but only to manipulate data structures).

Alternatives

If I had to pick a single MessagePack implementation, it would be lua-MessagePack. It is pure Lua, its performance is very close to luajit-msgpack-pure and it supports the latest revision of the standard. If it had existed earlier, I would not have written this one. If you start a new project, use it.

Another interesting implementation is lua-cmsgpack, written in C specifically for use in Redis.

Other implementations:

• lua-msgpack (pure Lua)
• lua-msgpack-native (Lua-specific C implementation targeting luvit)
• MPLua (binding)

Before luajit-msgpack-pure, I had written luajit-msgpack, a FFI binding which is now deprecated.

TODO

• Missing datatype tests
• Comparison tests vs. other implementations

Usage

Basics

local mp = require "luajit-msgpack-pure"
local my_data = {this = {"is",4,"test"}}
local encoded = mp.pack(my_data)
local offset,decoded = mp.unpack(encoded)
assert(offset == #encoded)

Concatenating encoded data

local mp = require "luajit-msgpack-pure"
local my_data_1 = 42
local my_data_2 = "foo"
local encoded = mp.pack(my_data_1) .. mp.pack(my_data_2)
local offset_1,decoded_1 = mp.unpack(encoded)
assert(decoded_1 == 42)
local offset_2,decoded_2 = mp.unpack(encoded,offset_1)
assert(decoded_2 == "foo")
local offset_3,decoded_3 = mp.unpack(encoded,offset_2)
assert((not offset_3) and (decoded_3 == nil))

Setting floating point precision

local mp = require "luajit-msgpack-pure"
local my_data = math.pi
local encoded_1 = mp.pack(my_data) -- default is double
local offset_1,decoded_1 = mp.unpack(encoded_1)
assert(offset_1 == 9) -- 1 byte overhead + 8 bytes double
assert(decoded_1 == math.pi)
mp.set_fp_type("float")
local encoded_2 = mp.pack(my_data)
local offset_2,decoded_2 = mp.unpack(encoded_2)
assert(offset_2 == 5) -- 1 byte overhead + 5 bytes float
assert(decoded_2 ~= math.pi) -- loss of precision
mp.set_fp_type("double") -- back to double precision
local encoded_3 = mp.pack(my_data)
local offset_3,decoded_3 = mp.unpack(encoded_3)
assert((offset_3 == 9) and (decoded_3 == math.pi))

Copyright

Copyright (c) 2011-2019 Pierre Chapuis