100 lines
2.5 KiB
JavaScript
100 lines
2.5 KiB
JavaScript
/**
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* @file stream.js
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*/
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/**
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* A lightweight readable stream implemention that handles event dispatching.
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*
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* @class Stream
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*/
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export default class Stream {
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constructor() {
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this.listeners = {};
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}
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/**
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* Add a listener for a specified event type.
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*
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* @param {String} type the event name
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* @param {Function} listener the callback to be invoked when an event of
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* the specified type occurs
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*/
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on(type, listener) {
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if (!this.listeners[type]) {
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this.listeners[type] = [];
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}
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this.listeners[type].push(listener);
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}
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/**
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* Remove a listener for a specified event type.
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*
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* @param {String} type the event name
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* @param {Function} listener a function previously registered for this
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* type of event through `on`
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* @return {Boolean} if we could turn it off or not
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*/
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off(type, listener) {
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if (!this.listeners[type]) {
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return false;
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}
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const index = this.listeners[type].indexOf(listener);
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this.listeners[type].splice(index, 1);
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return index > -1;
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}
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/**
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* Trigger an event of the specified type on this stream. Any additional
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* arguments to this function are passed as parameters to event listeners.
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*
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* @param {String} type the event name
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*/
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trigger(type) {
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const callbacks = this.listeners[type];
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let i;
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let length;
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let args;
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if (!callbacks) {
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return;
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}
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// Slicing the arguments on every invocation of this method
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// can add a significant amount of overhead. Avoid the
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// intermediate object creation for the common case of a
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// single callback argument
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if (arguments.length === 2) {
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length = callbacks.length;
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for (i = 0; i < length; ++i) {
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callbacks[i].call(this, arguments[1]);
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}
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} else {
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args = Array.prototype.slice.call(arguments, 1);
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length = callbacks.length;
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for (i = 0; i < length; ++i) {
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callbacks[i].apply(this, args);
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}
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}
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}
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/**
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* Destroys the stream and cleans up.
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*/
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dispose() {
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this.listeners = {};
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}
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/**
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* Forwards all `data` events on this stream to the destination stream. The
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* destination stream should provide a method `push` to receive the data
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* events as they arrive.
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*
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* @param {Stream} destination the stream that will receive all `data` events
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* @see http://nodejs.org/api/stream.html#stream_readable_pipe_destination_options
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*/
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pipe(destination) {
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this.on('data', function(data) {
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destination.push(data);
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});
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}
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}
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