minecraft.js/lib/tag.js

Minecraft data serialization/deserialization and networking

/** @constructor */
var Tag = module.exports = function(type, name, payload) {
	if(typeof type == 'undefined') {
		throw new Error('Invalid arguments: a type is required');
	}
	
	if(typeof payload == 'undefined') {
		if(name) payload = name;
		name = '';
	}
	
	this.type = Tag.prototype.types[type.toUpperCase()];
	this.name = name || '';
	this.payload = payload;
	
	if(typeof this.payload != 'number' &&
	this.type.payload == 'number')
		this.payload = Number(this.payload);
	
	if(!this.type.payload == 'array' && typeof this.payload != this.type.payload) {
		console.log(this.payload);
		throw new Error('Invalid payload type: expected ' + this.type.payload +
			', got ' + typeof this.payload);
	}
	
	if(this.type.name == 'list') {
		var tagId;
		for(var i = 0; i < this.payload.length; i++) {
			if(!tagId) {
				tagId = this.payload[i].type.value;
			} else if(tagId != this.payload[i].type.value) {
				throw new Error('Payload array members must all be the same type');
			}
		}
	}
};

Tag.prototype.toBlob = function() {
	throw new Error('Not implemented');
};

Tag.prototype.toText = function() {
	var text = '';
	
	if(this.type.named) {
		text += this.type.value;
		if(this.name) {
    		text += this.name;
    	}
	}
	
	switch(this.type.name) {
		case 'End':
			text += '\0';
			break;
		case 'Byte_Array':
			text += new Tag("int", 'length', this.payload.length).toText();
			for(var i = 0; i < this.payload.length; i++) {
				text += this.payload[i];
			}
			break;
		case 'String':
			text += new Tag("short", 'length', this.payload.length).toText();
			text += this.payload;
			break;
		case 'List':
			var tagId = 0;
			if(this.payload.length > 0) tagId = this.payload[0].type.value;
			text += new Tag("byte", 'tagId', tagId).toText();
			text += new Tag("int", 'length', this.payload.length).toText();
			for(var i = 0; i < this.payload.value; i++) {
				text += this.payload[i].toText();
			}
			break;
		case 'Compound':
			for(var i = 0; i < this.payload.length; i++) {
				text += this.payload[i].toText();
			}
			text += new Tag('end').toText();
			break;
		default:
			text += this.payload;
			break;
	}
	
	return text;
};

Tag.prototype.append = function(data) {
	if(this.type.name == 'Byte_Array' ||
		this.type.name == 'List' ||
		this.type.name == 'Compound') {
		if(typeof data == 'array') {
			for(var i = 0; i < data.length; i++) {
				this.payload.push(data[i]);
			}
		} else if(data.constructor == Tag) {
			this.payload.push(data);
		} else {
			throw Error('appension must be an array or Tag');
		}
	} else if(this.type.name == 'String') {
		if(typeof data == 'string') {
			this.payload += data;
		} else {
			throw new Error('appension must be a string');
		}
	}
	
	return this;
};

Tag.prototype.types = {
	END: {value: 0, name: 'End', size: 0, payload: 'undefined', named: false},
	BYTE: {value: 1, name: 'Byte', size: 1, payload: 'number', named: true},
	SHORT: {value: 2, name: 'Short', size: 2, payload: 'number', named: true},
	INT: {value: 3, name: 'Int', size: 4, payload: 'number', named: true},
	LONG: {value: 4, name: 'Long', size: 8, payload: 'number', named: true},
	FLOAT: {value: 5, name: 'Float', size: 4, payload: 'number', named: true},
	DOUBLE: {value: 6, name: 'Double', size: 8, payload: 'number', named: true},
	BYTE_ARRAY: {value: 7, name: 'Byte_Array', size: 0, payload: 'array', named: true},
	STRING: {value: 8, name: 'String', size: 0, payload: 'string', named: true},
	LIST: {value: 9, name: 'List', size: 0, payload: 'array', named: true},
	COMPOUND: {value: 10, name: 'Compound', size: 0, payload: 'array', named: true}
};