schemapack

The fastest and smallest JavaScript object serialization library. Efficiently encode your objects in to compact byte buffers and then decode them back in to objects on the receiver. Integrates very well with WebSockets.

Example

// On both the client and server:
var playerSchema = schemapack.build({
    health: "varuint",
    jumping: "boolean",
    position: [ "int16" ],
    attributes: { str: 'uint8', agi: 'uint8', int: 'uint8' }
});

// On the client:
var player = {
    health: 4000,
    jumping: false,
    position: [ -540, 343, 1201 ],
    attributes: { str: 87, agi: 42, int: 22 }
};

var buffer = playerSchema.encode(player);
socket.emit('player-message', buffer); // Use some JavaScript WebSocket library to get this socket variable.

// On the server:
socket.on('player-message', function(buffer) { 
    var player = playerSchema.decode(buffer);
}

In this example, the size of payload is only 13 bytes. Using JSON.stringify instead causes the payload to be 100 bytes.

If you can't emit message strings and can only send array buffers by themselves, add something like __message: "uint8" to the start of all your schemas/objects. On the receiver you can just read the first byte of the buffer to determine what message it is.

Motivation

I was working on an app that used WebSockets to talk between client and server. Usually when doing this the client and server just send JSON back and forth. However, when receiving a message the receiver already knows what the format of the message is going to be. Example:

// Client:
var message = { 'sender': 'John', 'contents': 'hi' };
socket.emit('chat', message);

// Server
socket.on('chat', function(message) {
    // We know message is going to be an object with 'sender' and 'contents' keys
});

The problems I had with sending JSON back and forth between client and server:

It's a complete waste of bandwidth to send all those keys and delimiters when the object format is known.
Even though JSON.stringify and JSON.parse are optimized native functions, they're slower than buffers.
There's no implicit central message repository where I can look at the format of all my different packets.
There's no validation so there's potential to have silent errors when accidentally sending the wrong message.

Why I didn't just use an existing schema packing library:

Too complicated: I didn't want to have to learn a schema language and format a schema for every object.
Too slow: I benchmarked a couple of other popular libraries and they were often 10x slower than using the native JSON.stringify and JSON.parse. This library is faster than even those native methods.
Too large: I didn't want to use a behemoth library with tens of thousands of lines of code and many dependencies for something so simple. This library is 300 lines of code with no dependencies.
Too much overhead: Some of the other libraries that allow you to specify a schema still waste a lot of bytes on padding/keys/etc. I desgined this library to not waste a single byte on anything that isn't your data.

Benchmarks

These were performed via encoding/decoding the player object at the start of this page on my computer. Feel free to run the benchmarks yourself by executing node index.js.

In addition, SchemaPack really shines when used with large objects with a lot of nesting and long arrays compared to the competition. I encourage you to run the benchmarks with your own objects to see what works best for you.

Library Size

2.07 KB after minify/gzip without buffer shim.

8.27 KB after minify/gzip with buffer shim.

Installation

On the server, you can just copy schemapack.js in to your project folder and require it. (Remove the ./ if installed through npm)

var schemapack = require('./schemapack');

On the client, use webpack/browserify to automatically include the prerequisite buffer shim if you're not using it already.

For example, if you had a file index.js with the following:

var schemapack = require('./schemapack');
// More code here using schemapack

You can add the Buffer shim by typing browserify index.js > bundle.js and then including that file in your HTML.

<script type="text/javascript" src="bundle.js"></script>

API

Build your schema:

var personSchema = schemapack.build({
    name: 'string',
    age: 'uint8',
    weight: 'float32'
}); // This parses, sorts, validates, flattens, and then saves the resulting schema.

Encode your objects:

var john = {
    name: 'John Smith',
    age: 32,
    weight: 188.5
};
var buffer = personSchema.encode(john);
console.log(buffer); // <Buffer 20 0a 4a 6f 68 6e 20 53 6d 69 74 68 43 3c 80 00>

Decode your buffers back to objects:

var object = personSchema.decode(buffer);
console.log(object.name); // John Smith
console.log(object.age); // 32
console.log(object.weight); // 188.5

Set the encoding used for strings:

'utf8' is the default. If you only need to support English, changing the string encoding to 'ascii' can increase speed. Choose between 'ascii', 'utf8', 'utf16le', 'ucs2', 'base64', 'binary', and 'hex'.

schemapack.setStringEncoding('ascii');

Add type aliases:

schemapack.addTypeAlias('int', 'varuint');
var builtSchema = schemapack.build([ 'string', 'int' ]);
var buffer = builtSchema.encode([ 'dave', 1, 2, 3 ]);
var object = builtSchema.decode(buffer);
console.log(object); // [ 'dave', 1, 2, 3 ]

Make single item schemas:

var builtSchema = schemapack.build("varint");
var buffer = builtSchema.encode(-350);
var item = builtSchema.decode(buffer);
console.log(item); // -350

Here is a table of the available data types for use in your schemas:

Type Name	Aliases	Bytes	Range of Values
bool	boolean	1	True or false
int8		1	-128 to 127
uint8		1	0 to 255
int16		2	-32,768 to 32,767
uint16		2	0 to 65,535
int32		4	-2,147,483,648 to 2,147,483,647
uint32		4	0 to 4,294,967,295
float32		4	3.4E +/- 38 (7 digits)
float64		8	1.7E +/- 308 (15 digits)
string		varuint length prefix followed by bytes of each character	Any string
varuint		1 byte when 0 to 127 2 bytes when 128 to 16,383 3 bytes when 16,384 to 2,097,151 4 bytes when 2,097,152 to 268,435,455 etc.	0 to 2,147,483,647
varint		1 byte when -64 to 63 2 bytes when -8,192 to 8,191 3 bytes when -1,048,576 to 1,048,575 4 bytes when -134,217,728 to 134,217,727 etc.	-1,073,741,824 to 1,073,741,823

Tests

Just clone the repository and go to the directory and run node index.js to run the test suite and benchmarks.

To add MsgPack to the benchmarks, npm install msgpack-lite and uncomment line 6 in tests.js
To add Protocol Buffers to the benchmarks, npm install protobufjs and uncomment line 7 in tests.js

Compatibility

This library uses Buffer when in the node.js environment (always included) and the buffer shim when in the browser (included with browserify/webpack).

License

MIT

Malkiz / schemapack