msgpack

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.

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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 seconds
* JSON.parse(JSON.stringify()) 22.18 seconds
* msgpack.pack() 5.80 seconds
* msgpack.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.

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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().

``javascript
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.

`javascript
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));
});
`

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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 and null values map to MSGPACK_OBJECT_NIL
* boolean values map to MSGPACK_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
* string values map to MSGPACK_OBJECT_RAW; all strings are serialized
with UTF-8 encoding
* Array values (as defined by Array.isArray()) map to
MSGPACK_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 the null value
* MSGPACK_OBJECT_BOOLEAN values map to boolean values
* MSGPACK_OBJECT_POSITIVE_INTEGER, MSGPACK_OBJECT_NEGATIVE_INTEGER and
MSGPACK_OBJECT_DOUBLE values map to number values
* MSGPACK_OBJECT_ARRAY values map to arrays; each object in the array is
packed individually using the rules in this list
* MSGPACK_OBJECT_RAW values are mapped to string values; these values are
unpacked using either UTF-8 or ASCII encoding, depending on the contents
of the raw buffer
* MSGPACK_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.

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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]

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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