619 lines
20 KiB
JavaScript
619 lines
20 KiB
JavaScript
/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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"use strict";
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/**
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* This module provides wrappers around standard message managers to
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* simplify bidirectional communication. It currently allows a caller to
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* send a message to a single listener, and receive a reply. If there
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* are no matching listeners, or the message manager disconnects before
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* a reply is received, the caller is returned an error.
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*
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* Since each message must have only one recipient, the listener end may
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* specify filters for the messages it wishes to receive, and the sender
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* end likewise may specify recipient tags to match the filters.
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*
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* The message handler on the listener side may return its response
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* value directly, or may return a promise, the resolution or rejection
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* of which will be returned instead. The sender end likewise receives a
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* promise which resolves or rejects to the listener's response.
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*
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*
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* A basic setup works something like this:
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*
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* A content script adds a message listener to its global
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* nsIContentFrameMessageManager, with an appropriate set of filters:
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*
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* {
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* init(messageManager, window, extensionID) {
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* this.window = window;
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*
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* MessageChannel.addListener(
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* messageManager, "ContentScript:TouchContent",
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* this);
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*
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* this.messageFilter = {
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* innerWindowID: getInnerWindowID(window),
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* extensionID: extensionID,
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* };
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* },
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*
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* receiveMessage({ target, messageName, sender, recipient, data }) {
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* if (messageName == "ContentScript:TouchContent") {
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* return new Promise(resolve => {
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* this.touchWindow(data.touchWith, result => {
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* resolve({ touchResult: result });
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* });
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* });
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* }
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* },
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* };
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*
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* A script in the parent process sends a message to the content process
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* via a tab message manager, including recipient tags to match its
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* filter, and an optional sender tag to identify itself:
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*
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* let data = { touchWith: "pencil" };
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* let sender = { extensionID, contextID };
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* let recipient = { innerWindowID: tab.linkedBrowser.innerWindowID, extensionID };
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*
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* MessageChannel.sendMessage(
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* tab.linkedBrowser.messageManager, "ContentScript:TouchContent",
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* data, recipient, sender
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* ).then(result => {
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* alert(result.touchResult);
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* });
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*
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* Since the lifetimes of message senders and receivers may not always
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* match, either side of the message channel may cancel pending
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* responses which match its sender or recipient tags.
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*
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* For the above client, this might be done from an
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* inner-window-destroyed observer, when its target scope is destroyed:
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*
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* observe(subject, topic, data) {
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* if (topic == "inner-window-destroyed") {
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* let innerWindowID = subject.QueryInterface(Ci.nsISupportsPRUint64).data;
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*
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* MessageChannel.abortResponses({ innerWindowID });
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* }
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* },
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*
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* From the parent, it may be done when its context is being destroyed:
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*
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* onDestroy() {
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* MessageChannel.abortResponses({
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* extensionID: this.extensionID,
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* contextID: this.contextID,
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* });
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* },
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*
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*/
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this.EXPORTED_SYMBOLS = ["MessageChannel"];
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/* globals MessageChannel */
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const Ci = Components.interfaces;
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const Cc = Components.classes;
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const Cu = Components.utils;
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const Cr = Components.results;
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Cu.import("resource://gre/modules/XPCOMUtils.jsm");
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Cu.import("resource://gre/modules/Services.jsm");
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XPCOMUtils.defineLazyModuleGetter(this, "PromiseUtils",
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"resource://gre/modules/PromiseUtils.jsm");
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XPCOMUtils.defineLazyModuleGetter(this, "Task",
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"resource://gre/modules/Task.jsm");
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/**
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* Handles the mapping and dispatching of messages to their registered
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* handlers. There is one broker per message manager and class of
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* messages. Each class of messages is mapped to one native message
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* name, e.g., "MessageChannel:Message", and is dispatched to handlers
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* based on an internal message name, e.g., "Extension:ExecuteScript".
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*/
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class FilteringMessageManager {
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/**
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* @param {string} messageName
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* The name of the native message this broker listens for.
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* @param {function} callback
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* A function which is called for each message after it has been
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* mapped to its handler. The function receives two arguments:
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*
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* result:
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* An object containing either a `handler` or an `error` property.
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* If no error occurs, `handler` will be a matching handler that
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* was registered by `addHandler`. Otherwise, the `error` property
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* will contain an object describing the error.
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*
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* data:
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* An object describing the message, as defined in
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* `MessageChannel.addListener`.
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*/
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constructor(messageName, callback, messageManager) {
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this.messageName = messageName;
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this.callback = callback;
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this.messageManager = messageManager;
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this.messageManager.addMessageListener(this.messageName, this);
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this.handlers = new Map();
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}
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/**
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* Receives a message from our message manager, maps it to a handler, and
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* passes the result to our message callback.
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*/
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receiveMessage({ data, target }) {
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let handlers = Array.from(this.getHandlers(data.messageName, data.recipient));
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let result = {};
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if (handlers.length == 0) {
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result.error = { result: MessageChannel.RESULT_NO_HANDLER,
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message: "No matching message handler" };
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} else if (handlers.length > 1) {
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result.error = { result: MessageChannel.RESULT_MULTIPLE_HANDLERS,
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message: `Multiple matching handlers for ${data.messageName}` };
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} else {
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result.handler = handlers[0];
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}
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data.target = target;
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this.callback(result, data);
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}
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/**
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* Iterates over all handlers for the given message name. If `recipient`
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* is provided, only iterates over handlers whose filters match it.
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*
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* @param {string|number} messageName
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* The message for which to return handlers.
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* @param {object} recipient
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* The recipient data on which to filter handlers.
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*/
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* getHandlers(messageName, recipient) {
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let handlers = this.handlers.get(messageName) || new Set();
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for (let handler of handlers) {
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if (MessageChannel.matchesFilter(handler.messageFilter, recipient)) {
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yield handler;
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}
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}
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}
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/**
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* Registers a handler for the given message.
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*
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* @param {string} messageName
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* The internal message name for which to register the handler.
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* @param {object} handler
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* An opaque handler object. The object must have a `messageFilter`
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* property on which to filter messages. Final dispatching is handled
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* by the message callback passed to the constructor.
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*/
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addHandler(messageName, handler) {
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if (!this.handlers.has(messageName)) {
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this.handlers.set(messageName, new Set());
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}
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this.handlers.get(messageName).add(handler);
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}
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/**
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* Unregisters a handler for the given message.
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*
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* @param {string} messageName
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* The internal message name for which to unregister the handler.
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* @param {object} handler
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* The handler object to unregister.
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*/
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removeHandler(messageName, handler) {
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this.handlers.get(messageName).delete(handler);
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}
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}
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/**
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* Manages mappings of message managers to their corresponding message
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* brokers. Brokers are lazily created for each message manager the
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* first time they are accessed. In the case of content frame message
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* managers, they are also automatically destroyed when the frame
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* unload event fires.
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*/
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class FilteringMessageManagerMap extends Map {
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// Unfortunately, we can't use a WeakMap for this, because message
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// managers do not support preserved wrappers.
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/**
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* @param {string} messageName
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* The native message name passed to `FilteringMessageManager` constructors.
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* @param {function} callback
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* The message callback function passed to
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* `FilteringMessageManager` constructors.
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*/
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constructor(messageName, callback) {
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super();
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this.messageName = messageName;
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this.callback = callback;
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}
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/**
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* Returns, and possibly creates, a message broker for the given
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* message manager.
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*
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* @param {nsIMessageSender} target
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* The message manager for which to return a broker.
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*
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* @returns {FilteringMessageManager}
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*/
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get(target) {
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if (this.has(target)) {
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return super.get(target);
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}
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let broker = new FilteringMessageManager(this.messageName, this.callback, target);
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this.set(target, broker);
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if (target instanceof Ci.nsIDOMEventTarget) {
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let onUnload = event => {
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target.removeEventListener("unload", onUnload);
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this.delete(target);
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};
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target.addEventListener("unload", onUnload);
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}
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return broker;
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}
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}
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const MESSAGE_MESSAGE = "MessageChannel:Message";
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const MESSAGE_RESPONSE = "MessageChannel:Response";
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let gChannelId = 0;
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this.MessageChannel = {
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init() {
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Services.obs.addObserver(this, "message-manager-close", false);
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Services.obs.addObserver(this, "message-manager-disconnect", false);
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this.messageManagers = new FilteringMessageManagerMap(
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MESSAGE_MESSAGE, this._handleMessage.bind(this));
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this.responseManagers = new FilteringMessageManagerMap(
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MESSAGE_RESPONSE, this._handleResponse.bind(this));
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/**
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* Contains a list of pending responses, either waiting to be
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* received or waiting to be sent. @see _addPendingResponse
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*/
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this.pendingResponses = new Set();
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},
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RESULT_SUCCESS: 0,
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RESULT_DISCONNECTED: 1,
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RESULT_NO_HANDLER: 2,
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RESULT_MULTIPLE_HANDLERS: 3,
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RESULT_ERROR: 4,
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REASON_DISCONNECTED: {
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result: this.RESULT_DISCONNECTED,
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message: "Message manager disconnected",
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},
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/**
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* Returns true if the given `data` object matches the given `filter`
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* object. The objects match if every property of `filter` is present
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* in `data`, and the values in both objects are strictly equal.
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*
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* @param {object} filter
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* The filter object to match against.
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* @param {object} data
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* The data object being matched.
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* @returns {bool} True if the objects match.
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*/
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matchesFilter(filter, data) {
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return Object.keys(filter).every(key => {
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return key in data && data[key] === filter[key];
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});
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},
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/**
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* Adds a message listener to the given message manager.
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*
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* @param {nsIMessageSender} target
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* The message manager on which to listen.
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* @param {string|number} messageName
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* The name of the message to listen for.
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* @param {MessageReceiver} handler
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* The handler to dispatch to. Must be an object with the following
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* properties:
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*
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* receiveMessage:
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* A method which is called for each message received by the
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* listener. The method takes one argument, an object, with the
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* following properties:
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*
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* messageName:
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* The internal message name, as passed to `sendMessage`.
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*
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* target:
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* The message manager which received this message.
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*
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* channelId:
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* The internal ID of the transaction, used to map responses to
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* the original sender.
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*
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* sender:
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* An object describing the sender, as passed to `sendMessage`.
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*
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* recipient:
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* An object describing the recipient, as passed to
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* `sendMessage`.
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*
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* data:
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* The contents of the message, as passed to `sendMessage`.
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*
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* The method may return any structured-clone-compatible
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* object, which will be returned as a response to the message
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* sender. It may also instead return a `Promise`, the
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* resolution or rejection value of which will likewise be
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* returned to the message sender.
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*
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* messageFilter:
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* An object containing arbitrary properties on which to filter
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* received messages. Messages will only be dispatched to this
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* object if the `recipient` object passed to `sendMessage`
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* matches this filter, as determined by `matchesFilter`.
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*/
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addListener(target, messageName, handler) {
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this.messageManagers.get(target).addHandler(messageName, handler);
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},
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/**
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* Removes a message listener from the given message manager.
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*
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* @param {nsIMessageSender} target
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* The message manager on which to stop listening.
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* @param {string|number} messageName
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* The name of the message to stop listening for.
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* @param {MessageReceiver} handler
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* The handler to stop dispatching to.
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*/
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removeListener(target, messageName, handler) {
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this.messageManagers.get(target).removeListener(messageName, handler);
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},
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/**
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* Sends a message via the given message manager. Returns a promise which
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* resolves or rejects with the return value of the message receiver.
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*
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* The promise also rejects if there is no matching listener, or the other
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* side of the message manager disconnects before the response is received.
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*
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* @param {nsIMessageSender} target
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* The message manager on which to send the message.
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* @param {string} messageName
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* The name of the message to send, as passed to `addListener`.
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* @param {object} data
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* A structured-clone-compatible object to send to the message
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* recipient.
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* @param {object} [recipient]
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* A structured-clone-compatible object to identify the message
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* recipient. The object must match the `messageFilter` defined by
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* recipients in order for the message to be received.
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* @param {object} [sender]
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* A structured-clone-compatible object to identify the message
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* sender. This object may also be used as a filter to prematurely
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* abort responses when the sender is being destroyed.
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* @see `abortResponses`.
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* @returns Promise
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*/
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sendMessage(target, messageName, data, recipient = {}, sender = {}) {
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let channelId = gChannelId++;
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let message = { messageName, channelId, sender, recipient, data };
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let deferred = PromiseUtils.defer();
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deferred.messageFilter = {};
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deferred.sender = recipient;
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deferred.messageManager = target;
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this._addPendingResponse(deferred);
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// The channel ID is used as the message name when routing responses.
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// Add a message listener to the response broker, and remove it once
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// we've gotten (or canceled) a response.
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let broker = this.responseManagers.get(target);
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broker.addHandler(channelId, deferred);
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let cleanup = () => {
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broker.removeHandler(channelId, deferred);
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};
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deferred.promise.then(cleanup, cleanup);
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target.sendAsyncMessage(MESSAGE_MESSAGE, message);
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return deferred.promise;
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},
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/**
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* Handles dispatching message callbacks from the message brokers to their
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* appropriate `MessageReceivers`, and routing the responses back to the
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* original senders.
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*
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* Each handler object is a `MessageReceiver` object as passed to
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* `addListener`.
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*/
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_handleMessage({ handler, error }, data) {
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// The target passed to `receiveMessage` is sometimes a message manager
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// owner instead of a message manager, so make sure to convert it to a
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// message manager first if necessary.
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let { target } = data;
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if (!(target instanceof Ci.nsIMessageSender)) {
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target = target.messageManager;
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}
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let deferred = {
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sender: data.sender,
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messageManager: target,
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};
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deferred.promise = new Promise((resolve, reject) => {
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deferred.reject = reject;
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if (handler) {
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let result = handler.receiveMessage(data);
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resolve(result);
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} else {
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reject(error);
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}
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}).then(
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value => {
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let response = {
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result: this.RESULT_SUCCESS,
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messageName: data.channelId,
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recipient: {},
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value,
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};
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target.sendAsyncMessage(MESSAGE_RESPONSE, response);
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},
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error => {
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let response = {
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result: this.RESULT_ERROR,
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messageName: data.channelId,
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recipient: {},
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error: {},
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};
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if (error && typeof(error) == "object") {
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if (error.result) {
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response.result = error.result;
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}
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// Error objects are not structured-clonable, so just copy
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// over the important properties.
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for (let key of ["fileName", "filename", "lineNumber",
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"columnNumber", "message", "stack", "result"]) {
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if (key in error) {
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response.error[key] = error[key];
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}
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}
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}
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target.sendAsyncMessage(MESSAGE_RESPONSE, response);
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});
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this._addPendingResponse(deferred);
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},
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/**
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* Handles message callbacks from the response brokers.
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*
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* Each handler object is a deferred object created by `sendMessage`, and
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* should be resolved or rejected based on the contents of the response.
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*/
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_handleResponse({ handler, error }, data) {
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if (error) {
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// If we have an error at this point, we have handler to report it to,
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// so just log it.
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Cu.reportError(error.message);
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} else if (data.result === this.RESULT_SUCCESS) {
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handler.resolve(data.value);
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} else {
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handler.reject(data.error);
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}
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},
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|
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/**
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|
* Adds a pending response to the the `pendingResponses` list.
|
|
*
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|
* The response object must be a deferred promise with the following
|
|
* properties:
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*
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* promise:
|
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* The promise object which resolves or rejects when the response
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* is no longer pending.
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*
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* reject:
|
|
* A function which, when called, causes the `promise` object to be
|
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* rejected.
|
|
*
|
|
* sender:
|
|
* A sender object, as passed to `sendMessage.
|
|
*
|
|
* messageManager:
|
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* The message manager the response will be sent or received on.
|
|
*
|
|
* When the promise resolves or rejects, it will be removed from the
|
|
* list.
|
|
*
|
|
* These values are used to clear pending responses when execution
|
|
* contexts are destroyed.
|
|
*/
|
|
_addPendingResponse(deferred) {
|
|
let cleanup = () => {
|
|
this.pendingResponses.delete(deferred);
|
|
};
|
|
this.pendingResponses.add(deferred);
|
|
deferred.promise.then(cleanup, cleanup);
|
|
},
|
|
|
|
/**
|
|
* Aborts any pending message responses to senders matching the given
|
|
* filter.
|
|
*
|
|
* @param {object} sender
|
|
* The object on which to filter senders, as determined by
|
|
* `matchesFilter`.
|
|
* @param {object} [reason]
|
|
* An optional object describing the reason the response was aborted.
|
|
* Will be passed to the promise rejection handler of all aborted
|
|
* responses.
|
|
*/
|
|
abortResponses(sender, reason = this.REASON_DISCONNECTED) {
|
|
for (let response of this.pendingResponses) {
|
|
if (this.matchesFilter(sender, response.sender)) {
|
|
response.reject(reason);
|
|
}
|
|
}
|
|
},
|
|
|
|
/**
|
|
* Aborts any pending message responses to the broker for the given
|
|
* message manager.
|
|
*
|
|
* @param {nsIMessageSender} target
|
|
* The message manager for which to abort brokers.
|
|
* @param {object} reason
|
|
* An object describing the reason the responses were aborted.
|
|
* Will be passed to the promise rejection handler of all aborted
|
|
* responses.
|
|
*/
|
|
abortMessageManager(target, reason) {
|
|
for (let response of this.pendingResponses) {
|
|
if (response.messageManager === target) {
|
|
response.reject(reason);
|
|
}
|
|
}
|
|
},
|
|
|
|
observe(subject, topic, data) {
|
|
switch (topic) {
|
|
case "message-manager-close":
|
|
case "message-manager-disconnect":
|
|
try {
|
|
if (this.responseManagers.has(subject)) {
|
|
this.abortMessageManager(subject, this.REASON_DISCONNECTED);
|
|
}
|
|
} finally {
|
|
this.responseManagers.delete(subject);
|
|
this.messageManagers.delete(subject);
|
|
}
|
|
break;
|
|
}
|
|
},
|
|
};
|
|
|
|
MessageChannel.init();
|