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337be58ee6
Implement `MessagePort` and `MessageChannel` along the lines of the DOM classes of the same names. `MessagePort`s initially support transferring only `ArrayBuffer`s. Thanks to Stephen Belanger for reviewing this change in its original form, to Benjamin Gruenbaum for reviewing the added tests in their original form, and to Olivia Hugger for reviewing the documentation in its original form. Refs: https://github.com/ayojs/ayo/pull/98 PR-URL: https://github.com/nodejs/node/pull/20876 Reviewed-By: Gireesh Punathil <gpunathi@in.ibm.com> Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com> Reviewed-By: Shingo Inoue <leko.noor@gmail.com> Reviewed-By: Matteo Collina <matteo.collina@gmail.com> Reviewed-By: Tiancheng "Timothy" Gu <timothygu99@gmail.com> Reviewed-By: John-David Dalton <john.david.dalton@gmail.com> Reviewed-By: Gus Caplan <me@gus.host>
106 lines
3.0 KiB
JavaScript
106 lines
3.0 KiB
JavaScript
'use strict';
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const EventEmitter = require('events');
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const util = require('util');
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const { internalBinding } = require('internal/bootstrap/loaders');
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const { MessagePort, MessageChannel } = internalBinding('messaging');
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const { handle_onclose } = internalBinding('symbols');
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util.inherits(MessagePort, EventEmitter);
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const kOnMessageListener = Symbol('kOnMessageListener');
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const debug = util.debuglog('worker');
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// A MessagePort consists of a handle (that wraps around an
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// uv_async_t) which can receive information from other threads and emits
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// .onmessage events, and a function used for sending data to a MessagePort
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// in some other thread.
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MessagePort.prototype[kOnMessageListener] = function onmessage(payload) {
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debug('received message', payload);
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// Emit the deserialized object to userland.
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this.emit('message', payload);
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};
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// This is for compatibility with the Web's MessagePort API. It makes sense to
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// provide it as an `EventEmitter` in Node.js, but if somebody overrides
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// `onmessage`, we'll switch over to the Web API model.
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Object.defineProperty(MessagePort.prototype, 'onmessage', {
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enumerable: true,
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configurable: true,
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get() {
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return this[kOnMessageListener];
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},
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set(value) {
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this[kOnMessageListener] = value;
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if (typeof value === 'function') {
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this.ref();
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this.start();
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} else {
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this.unref();
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this.stop();
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}
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}
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});
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// This is called from inside the `MessagePort` constructor.
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function oninit() {
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setupPortReferencing(this, this, 'message');
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}
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Object.defineProperty(MessagePort.prototype, 'oninit', {
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enumerable: true,
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writable: false,
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value: oninit
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});
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// This is called after the underlying `uv_async_t` has been closed.
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function onclose() {
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if (typeof this.onclose === 'function') {
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// Not part of the Web standard yet, but there aren't many reasonable
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// alternatives in a non-EventEmitter usage setting.
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// Refs: https://github.com/whatwg/html/issues/1766
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this.onclose();
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}
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this.emit('close');
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}
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Object.defineProperty(MessagePort.prototype, handle_onclose, {
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enumerable: false,
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writable: false,
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value: onclose
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});
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const originalClose = MessagePort.prototype.close;
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MessagePort.prototype.close = function(cb) {
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if (typeof cb === 'function')
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this.once('close', cb);
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originalClose.call(this);
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};
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function setupPortReferencing(port, eventEmitter, eventName) {
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// Keep track of whether there are any workerMessage listeners:
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// If there are some, ref() the channel so it keeps the event loop alive.
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// If there are none or all are removed, unref() the channel so the worker
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// can shutdown gracefully.
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port.unref();
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eventEmitter.on('newListener', (name) => {
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if (name === eventName && eventEmitter.listenerCount(eventName) === 0) {
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port.ref();
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port.start();
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}
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});
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eventEmitter.on('removeListener', (name) => {
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if (name === eventName && eventEmitter.listenerCount(eventName) === 0) {
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port.stop();
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port.unref();
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}
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});
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}
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module.exports = {
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MessagePort,
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MessageChannel
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};
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