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/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
const lazy = {};
ChromeUtils.defineESModuleGetters(lazy, {
EventEmitter: "resource://gre/modules/EventEmitter.sys.mjs",
NetworkUtils:
"resource://devtools/shared/network-observer/NetworkUtils.sys.mjs",
});
const OBSERVER_TOPIC_RESOURCE_CACHE_RESPONSE =
"http-on-resource-cache-response";
/**
* The CachedResourceListener can be used to listen for
* http-on-resource-cache-response notifications emitted for resources
* which are served by the image/CSS/JS cache.
* This notification needs to be monitored in content processes.
*
* Example:
* ```
* const listener = new CachedResourceListener();
* listener.on("cached-resource-sent", CachedResourceListener);
* listener.startListening();
*
* const onCachedResourceSent = (eventName, data = {}) => {
* const { channel } = data;
* ...
* };
* ```
*
* @fires cached-resource-sent
* The CachedResourceListener emits "cached-resource-sent" event with the
* following object as payload:
* - {nsIHttpChannel} channel
* The channel for which the observer notification was emitted.
*/
export class CachedResourceListener {
#context;
#listening;
/**
* Create a new CachedResourceListener instance.
*
* @param {BrowsingContext} context
* The browsing context to filter the events for.
*/
constructor(context) {
lazy.EventEmitter.decorate(this);
this.#listening = false;
this.#context = context;
}
destroy() {
this.stopListening();
}
observe(subject, topic) {
switch (topic) {
case OBSERVER_TOPIC_RESOURCE_CACHE_RESPONSE: {
// file channels are not supported:
if (!(subject instanceof Ci.nsIHttpChannel)) {
return;
}
const channel = subject.QueryInterface(Ci.nsIHttpChannel);
const id = lazy.NetworkUtils.getChannelBrowsingContextID(channel);
const browsingContext = BrowsingContext.get(id);
// Send the event only if the notification comes for observed context.
if (this.#context === browsingContext) {
this.emit("cached-resource-sent", {
channel,
});
}
break;
}
}
}
startListening() {
if (this.#listening) {
return;
}
Services.obs.addObserver(this, OBSERVER_TOPIC_RESOURCE_CACHE_RESPONSE);
this.#listening = true;
}
stopListening() {
if (!this.#listening) {
return;
}
Services.obs.removeObserver(this, OBSERVER_TOPIC_RESOURCE_CACHE_RESPONSE);
this.#listening = false;
}
}