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'use strict';
const {
ArrayPrototypeIndexOf,
ArrayPrototypePush,
ArrayPrototypeSplice,
ObjectCreate,
ObjectGetPrototypeOf,
ObjectSetPrototypeOf,
SymbolHasInstance,
} = primordials;
const {
codes: {
ERR_INVALID_ARG_TYPE,
}
} = require('internal/errors');
const {
validateFunction,
} = require('internal/validators');
const { triggerUncaughtException } = internalBinding('errors');
const { WeakReference } = internalBinding('util');
// TODO(qard): should there be a C++ channel interface?
class ActiveChannel {
subscribe(subscription) {
validateFunction(subscription, 'subscription');
ArrayPrototypePush(this._subscribers, subscription);
}
unsubscribe(subscription) {
const index = ArrayPrototypeIndexOf(this._subscribers, subscription);
if (index === -1) return false;
ArrayPrototypeSplice(this._subscribers, index, 1);
// When there are no more active subscribers, restore to fast prototype.
if (!this._subscribers.length) {
// eslint-disable-next-line no-use-before-define
ObjectSetPrototypeOf(this, Channel.prototype);
}
return true;
}
get hasSubscribers() {
return true;
}
publish(data) {
for (let i = 0; i < this._subscribers.length; i++) {
try {
const onMessage = this._subscribers[i];
onMessage(data, this.name);
} catch (err) {
process.nextTick(() => {
triggerUncaughtException(err, false);
});
}
}
}
}
class Channel {
constructor(name) {
this._subscribers = undefined;
this.name = name;
}
static [SymbolHasInstance](instance) {
const prototype = ObjectGetPrototypeOf(instance);
return prototype === Channel.prototype ||
prototype === ActiveChannel.prototype;
}
subscribe(subscription) {
ObjectSetPrototypeOf(this, ActiveChannel.prototype);
this._subscribers = [];
this.subscribe(subscription);
}
unsubscribe() {
return false;
}
get hasSubscribers() {
return false;
}
publish() {}
}
const channels = ObjectCreate(null);
function channel(name) {
let channel;
const ref = channels[name];
if (ref) channel = ref.get();
if (channel) return channel;
if (typeof name !== 'string' && typeof name !== 'symbol') {
throw new ERR_INVALID_ARG_TYPE('channel', ['string', 'symbol'], name);
}
channel = new Channel(name);
channels[name] = new WeakReference(channel);
return channel;
}
function hasSubscribers(name) {
let channel;
const ref = channels[name];
if (ref) channel = ref.get();
if (!channel) {
return false;
}
return channel.hasSubscribers;
}
module.exports = {
channel,
hasSubscribers,
Channel
};
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