MetaView

MetaView is a tiny convenience library that provides a stream-like view into your JavaScript DataView objects. It automatically handles resizing the ArrayBufferas needed.

In addition to the following examples, the source code is clean and documented with Docco. It can be found here.

Properties

MetaView.cursor

This is the cursor, tracking the current position in the ArrayBuffer. All IO occurs from this point, it is automatically updated by read and write methods. It is not read-only, you can move it as needed.

MetaView.endianness

Specifies the desired endianness of the IO methods.

Methods

MetaView.readUint8 (length) MetaView.readUint16 (length) MetaView.readUint32 (length) MetaView.readInt8 (length) MetaView.readInt16 (length) MetaView.readInt32 (length) MetaView.readFloat32 (length) MetaView.readFloat64 (length)

Reads length elements of a certain size (8 bits, 16 bits, 32 bits, 64 bits) and type (Uint, Int, Float), moving the cursor accordingly. If no length is specified it will simply read 1 element.

Returns data read an Array.

MetaView.peekUint8 (length) MetaView.peekUint16 (length) MetaView.peekUint32 (length) MetaView.peekInt8 (length) MetaView.peekInt16 (length) MetaView.peekInt32 (length) MetaView.peekFloat32 (length) MetaView.peekFloat64 (length)

Reads length elements of a certain size and type, but retains the current cursor position. If no length is specified it will simply read 1 unit.

Returns data read as an Array.

MetaView.writeUint8 (data) MetaView.writeUint16 (data) MetaView.writeUint32 (data) MetaView.writeInt8 (data) MetaView.writeInt16 (data) MetaView.writeInt32 (data) MetaView.writeFloat32 (data) MetaView.writeFloat64 (data)

Writes data - an Array of Number objects - to the buffer.

MetaView.finalize ()

Trims any space allocated but not used from the internal ArrayBuffer.

It then returns the ArrayBuffer.

MetaView.toDataURI (type)

Generates a string containing a data URI, useful for presenting the user with a download link.

Examples

Open file with MetaView

var fileInput; /// <input type="file" />
var fileReader = new FileReader();

function readFile () {
	var data = new MetaView(reader.result);
	// do stuff
}

fileReader.addEventListener("load", readFile)
fileReader.readAsArrayBuffer(fileInput.files[0]);

Save file with MetaView

var output; // populated MetaView instance
var type = "image/png"; // internet media type
output.finalize();
location.href = output.toDataURI("image/png");

Serialization

Serialization is often useful in games to provide save states in an efficient manner. Assuming the output and input arguments are MetaView instances, an implementation might look a bit like this:

GameObject.prototype.write = function (output) {
	output.writeUTF8String(this.name);
	output.writeUint16(this.health);
	output.writeFloat64(this.position.x);
	output.writeFloat64(this.position.y);
}

GameObject.prototype.read = function (input) {
	this.name = input.readUTF8String();
	this.health = input.readUint16(this.health);
	this.position.x = input.readFloat64();
	this.position.y = input.readFloat64();
}

need12648430 / metaview