node-msgpack
is an addon for NodeJS that provides an
API for serializing and de-serializing JavaScript objects using the
MessagePack library. The performance of this
addon compared to the native JSON
object isn't too bad, and the space
required for serialized data is far less than JSON.
Performance
node-msgpack
is currently slower than the built-in JSON.stringify()
and
JSON.parse()
methods. In recent versions of node.js, the JSON functions
have been heavily optimized. node-msgpack is still more compact, and we are
currently working performance improvements. Testing shows that, over 500k
iterations, msgpack.pack()
is about 5x slower than JSON.stringify()
, and
msgpack.unpack()
is about 3.5x slower than JSON.parse()
.
Old performance numbers are below.
The following tests were performed with 500,000 instances of
the JavaScript object {'abcdef' : 1, 'qqq' : 13, '19' : [1, 2, 3, 4]}
:
JSON.stringify()
7.17 secondsJSON.parse(JSON.stringify())
22.18 secondsmsgpack.pack()
5.80 secondsmsgpack.unpack(msgpack.pack())
8.62 seconds
Note that node-msgpack
produces and consumes Buffer objects, and a such does
not incur encoding/decoding overhead when performing I/O with native strings.
Usage
This module provides two methods: pack()
, which consumes a JavaScript object
and produces a node Buffer object; and unpack()
, which consumes a node Buffer
object and produces a JavaScript object. Packing of all native JavaScript types
(undefined, boolean, numbers, strings, arrays and objects) is supported, as
is the node Buffer type.
The below code snippet packs and then unpacks a JavaScript object, verifying
the resulting object at the end using assert.deepEqual()
.
var assert = require('assert');
var msgpack = require('msgpack');
var o = {"a" : 1, "b" : 2, "c" : [1, 2, 3]};
var b = msgpack.pack(o);
var oo = msgpack.unpack(b);
assert.deepEqual(oo, o);
As a convenience, a higher level streaming API is provided in the
msgpack.Stream
class, which can be constructed around a net.Stream
instance. This object emits msg
events when an object has been received.
var msgpack = require('msgpack');
// ... get a net.Stream instance, s, from somewhere
var ms = new msgpack.Stream(s);
ms.addListener('msg', function(m) {
sys.debug('received message: ' + sys.inspect(m));
});
Type Mapping
The JavaScript type system does not map cleanly on to the MsgPack type system, though it's pretty close.
When packing, JavaScript values are mapped to MsgPack types as follows
undefined
andnull
values map toMSGPACK_OBJECT_NIL
boolean
values map toMSGPACK_OBJECT_BOOLEAN
number
values map differently depending on their value- Floating point values map to
MSGPACK_OBJECT_DOUBLE
- Positive values map to
MSGPACK_OBJECT_POSITIVE_INTEGER
- Negative values map to
MSGPACK_OBJECT_NEGATIVE_INTEGER
- Floating point values map to
string
values map toMSGPACK_OBJECT_RAW
; all strings are serialized with UTF-8 encoding- Array values (as defined by
Array.isArray()
) map toMSGPACK_OBJECT_ARRAY
; each element in the array is packed individually the rules in this list - NodeJS Buffer values map to
MSGPACK_OBJECT_RAW
- Everything else maps to
MSGPACK_OBJECT_MAP
, where we iterate over the object's properties and pack them and their values as per the mappings in this list
When unpacking, MsgPack types are mapped to JavaScript values as follows
MSGPACK_OBJECT_NIL
values map to thenull
valueMSGPACK_OBJECT_BOOLEAN
values map toboolean
valuesMSGPACK_OBJECT_POSITIVE_INTEGER
,MSGPACK_OBJECT_NEGATIVE_INTEGER
andMSGPACK_OBJECT_DOUBLE
values map tonumber
valuesMSGPACK_OBJECT_ARRAY
values map to arrays; each object in the array is packed individually using the rules in this listMSGPACK_OBJECT_RAW
values are mapped tostring
values; these values are unpacked using either UTF-8 or ASCII encoding, depending on the contents of the raw bufferMSGPACK_OBJECT_MAP
values are mapped to JavaScript objects; keys and values are unpacked individually using the rules in this list
Strings are particularly problematic here, as it's difficult to get hints down
into the packing and unpacking codepaths about how to interpret a particular
string or MSGPACK_OBJECT_RAW
. If you have strict requirements about the
encoding of your strings, it's recommended that you populate a Buffer object
yourself (e.g. using Buffer.write()
) and pack that buffer rather than the
string. This will ensure that you can control what gets packed.
When unpacking, things are trickier as there is no way to know the encoding used when a string was packed. There is an an open ticket for the MsgPack format to address this.
Command Line Utilities
As a convenience and for debugging, bin/json2msgpack
and bin/msgpack2json
are provided to convert JSON data to and from MessagePack data, reading from
stdin and writing to stdout.
% echo '[1, 2, 3]' | ./bin/json2msgpack | xxd -
0000000: 9301 0203 ....
% echo '[1, 2, 3]' | ./bin/json2msgpack | ./bin/msgpack2json
[1,2,3]
Building, Installation, Testing
There are two ways to install msgpack.
NPM
npm install msgpack
This should build and install msgpack for you. Then just require('msgpack')
.
Manually
You will need node-gyp:
npm install -g node-gyp
Then from the root of the msgpack repo, you can run:
node-gyp rebuild
- NOTE:
- node-gyp attempts to contact the Internet and download the target version of node.js source and store it locally. This will only happen once for each time it sees a new node.js version. If you're on a host with no direct Internet access, you may need to shuffle this source over from another box or sneaker net. Good luck!
Testing
To run all tests use:
./run_tests
To run a specific test:
./run_tests test/lib/msgpack.js
- NOTE:
- Tests are based on a modified version of nodeunit (https://github.com/godsflaw/nodeunit). Follow ./run_tests instructions if you run into problems.
Benchmarks
To run benchmarks:
./run_tests test/benchmark/benchmark.js