Metaview - A tiny, fast, simplified abstraction of JS DataViews (similar to AS3's ByteArray)

example.js

// writing
var o = new MetaView();
o.writeInt16(-128);
o.writeUint16(128);
o.writeFloat32(3.141592);
o.writeFloat32([1.5, 1.5]);
o.writeUTF8String("räksmörgås");

// saving
var s = o.finalize();

// reading
var i = new MetaView(s);
console.log(i.readInt16());
console.log(i.readUint16());
console.log(i.readFloat32());
console.log(i.readFloat32(2));
console.log(i.readUTF8String());

metaview-polyfills.js

// polyfill for Array.transfer
if (!ArrayBuffer.transfer)
	ArrayBuffer.transfer = function (oldBuffer, newLength) {
		newLength = newLength || oldBuffer.byteLength;
		var newBuffer = new ArrayBuffer(newLength);
		new Uint8Array(newBuffer).set(new Uint8Array(oldBuffer));
		return newBuffer;
	}

// very tiny TextEncoder/TextDecoder polyfills that only supports utf-8 encoding
if (!TextEncoder) {
	function TextEncoder (encoding) {}
	TextEncoder.prototype.encode = function (buffer) {
		buffer = unescape(encodeURIComponent(buffer));
		var ab = new ArrayBuffer(buffer.length),
			u8 = new Uint8Array(ab);
		for (var i = 0; i < buffer.length; i ++)
			u8[i] = buffer.charCodeAt(i);
		return u8;
	}
	function TextDecoder () {}
	TextDecoder.prototype.decode = function (buffer) {
		return decodeURIComponent(escape(String.fromCharCode.apply(null, Array.from(buffer))));
	}
}

metaview.js

var MetaView = (function () {
	function MetaView (from) {
		this.cursor = 0;
		this.contents = new ArrayBuffer(1);
		this.endianness = MetaView.LE;

		if (from)
			this.contents = ArrayBuffer.transfer(from);

		// wraps some DataView methods
		var types = {"Int": [8,16,32], "Uint": [8,16,32], "Float": [32,64]};
		for (var type in types) {
			for (var i = 0, size; i < types[type].length; i ++) {
				size = types[type][i];
				MetaView.prototype["write" + type + size] = MetaView.prototype.writeData.bind(this, type, size);
				MetaView.prototype["read" + type + size] = MetaView.prototype.readData.bind(this, type, size);
			}
		}
	}

	MetaView.LE = true;
	MetaView.BE = false;

	MetaView.prototype = {
		expandToContain: function (dataSize) {
			var newLength = this.contents.byteLength;

			while (this.cursor + dataSize > newLength)
				newLength *= 2;

			this.contents = ArrayBuffer.transfer(this.contents, newLength);
		},

		finalize: function () {
			return this.contents = this.contents.slice(0, this.cursor);
		},

		writeData: function (type, bits, data) {
			var bytes = bits / 8, dataLength = data.length || 1;

			this.expandToContain(dataLength * bytes);

			var dv = new DataView(this.contents);
			for (var i = 0; i < dataLength; i ++) {
				dv["set" + type + bits](this.cursor, data[i] || data, this.endianness);
				this.cursor += bytes;
			}
		},

		readData: function (type, bits, length) {
			length = length || 1;

			var dv = new DataView(this.contents);
			var result = [];
			while (length --) {
				result.push(dv["get" + type + bits](this.cursor, this.endianness));
				this.cursor += bits / 8;
			}

			return result.length == 1 ? result[0] : result;
		},

		writeUTF8String: function (string) {
			var encoded = new TextEncoder("utf-8").encode(string);
			this.writeUint32(encoded.byteLength);
			this.writeUint8(encoded);
		},

		readUTF8String: function () {
			var length = this.readUint32();
			var encoded = this.readUint8(length);
			return new TextDecoder("utf-8").decode(new Uint8Array(encoded));
		}
	};

	return MetaView;
})();