Support new-style Mojo JS core API on IOS.

ios/web/webui/resources/mojo_api.js

+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+goog.provide('__crWeb.mojoApi');
+
+// Note: The API should stay in sync with the IDL definitions in
+// third_party/WebKit/Source/core/mojo
+
+var Mojo = Mojo || {};

[Eugene But (OOO till 7-30), 2017/06/24 01:09:51]

Does this global variable also exist on other platforms? I'm asking, because on
iOS we want to hide __gCRWeb and generally avoid adding variables to the global
namespace.

[yzshen1, 2017/06/26 20:10:00]

Yes. This is exposed to the webpage as the Mojo public system API, the same as
on other platforms.

+
+/**
+ * MojoResult {number}: Result codes for Mojo operations.
+ */
+Mojo.RESULT_OK = 0;
+Mojo.RESULT_CANCELLED = 1;
+Mojo.RESULT_UNKNOWN = 2;
+Mojo.RESULT_INVALID_ARGUMENT = 3;
+Mojo.RESULT_DEADLINE_EXCEEDED = 4;
+Mojo.RESULT_NOT_FOUND = 5;
+Mojo.RESULT_ALREADY_EXISTS = 6;
+Mojo.RESULT_PERMISSION_DENIED = 7;
+Mojo.RESULT_RESOURCE_EXHAUSTED = 8;
+Mojo.RESULT_FAILED_PRECONDITION = 9;
+Mojo.RESULT_ABORTED = 10;
+Mojo.RESULT_OUT_OF_RANGE = 11;
+Mojo.RESULT_UNIMPLEMENTED = 12;
+Mojo.RESULT_INTERNAL = 13;
+Mojo.RESULT_UNAVAILABLE = 14;
+Mojo.RESULT_DATA_LOSS = 15;
+Mojo.RESULT_BUSY = 16;
+Mojo.RESULT_SHOULD_WAIT = 17;
+
+/**
+ * Creates a message pipe.
+ *
+ * @return {result: !MojoResult, handle0: !MojoHandle=, handle1: !MojoHandle=}
+ *     Result code and (on success) the two message pipe handles.
+ */
+Mojo.createMessagePipe = function() {
+  var result = Mojo.internal.sendMessage({
+    name: "Mojo.createMessagePipe",
+    args: {}
+  });
+  if (result.result == Mojo.RESULT_OK) {
+    result.handle0 = new MojoHandle(result.handle0);
+    result.handle1 = new MojoHandle(result.handle1);
+  }
+  return result;
+};
+
+/**
+ * Binds to the specified Mojo interface.
+ * @param {string} interfaceName The interface name to connect.
+ * @param {!MojoHandle} requestHandle The interface request handle.
+ */
+Mojo.bindInterface = function(interfaceName, requestHandle) {
+  Mojo.internal.sendMessage({
+    name: "Mojo.bindInterface",
+    args: {
+      interfaceName: interfaceName,
+      requestHandle: requestHandle.takeNativeHandle_()
+    }
+  });
+};
+
+/**
+ * @constructor
+ * @param {?number=} nativeHandle An opaque number representing the underlying
+ *     Mojo system resource.
+ */
+var MojoHandle = function(nativeHandle) {
+  if (nativeHandle === undefined)
+    nativeHandle = null;
+
+  /**
+   * @type {number|null}
+   */
+  this.nativeHandle_ = nativeHandle;
+};
+
+/**
+ * Takes the native handle value. This is not part of the public API.
+ * @return {?number}
+ */
+MojoHandle.prototype.takeNativeHandle_ = function() {
+  var nativeHandle = this.nativeHandle_;
+  this.nativeHandle_ = null;
+  return nativeHandle;
+};
+
+/**
+ * Closes the handle.
+ */
+MojoHandle.prototype.close = function() {
+  if (this.nativeHandle_ === null)
+    return;
+
+  var nativeHandle = this.nativeHandle_;
+  this.nativeHandle_ = null;
+  Mojo.internal.sendMessage({
+    name: "MojoHandle.close",
+    args: {
+      handle: nativeHandle
+    }
+  });
+};
+
+/**
+ * Begins watching the handle for |signals| to be satisfied or unsatisfiable.
+ *
+ * @param {readable: boolean=, writable: boolean=, peerClosed: boolean=} signals
+ *     The signals to watch.
+ * @param {!function(!MojoResult)} calback Called with a result any time
+ *     the watched signals become satisfied or unsatisfiable.
+ *
+ * @return {!MojoWatcher} A MojoWatcher instance that could be used to cancel
+ *     the watch.
+ */
+MojoHandle.prototype.watch = function(signals, callback) {
+  var HANDLE_SIGNAL_NONE = 0;
+  var HANDLE_SIGNAL_READABLE = 1;
+  var HANDLE_SIGNAL_WRITABLE = 2;
+  var HANDLE_SIGNAL_PEER_CLOSED = 4;
+
+  var signalsValue = HANDLE_SIGNAL_NONE;
+  if (signals.readable) {
+    signalsValue |= HANDLE_SIGNAL_READABLE;
+  }
+  if (signals.writable) {
+    signalsValue |= HANDLE_SIGNAL_WRITABLE;
+  }
+  if (signalsValue.peerClosed) {
+    signalsValue |= HANDLE_SIGNAL_PEER_CLOSED;
+  }
+
+  var watchId = Mojo.internal.sendMessage({
+    name: "MojoHandle.watch",
+    args: {
+      handle: this.nativeHandle_,
+      signals: signalsValue,
+      callbackId: Mojo.internal.watchCallbacksHolder.getNextCallbackId()
+    }
+  });
+  Mojo.internal.watchCallbacksHolder.addWatchCallback(watchId, callback);
+
+  return new MojoWatcher(watchId);
+};
+
+/**
+ * Writes a message to the message pipe.
+ *
+ * @param {!ArrayBufferView} buffer The message data. May be empty.
+ * @param {!Array<!MojoHandle>} handles Any handles to attach. Handles are
+ *     transferred and will no longer be valid. May be empty.
+ * @return {!MojoResult} Result code.
+ */
+MojoHandle.prototype.writeMessage = function(buffer, handles) {
+  var nativeHandles = handles.map(function(handle) {
+    return handle.takeNativeHandle_();
+  });
+  return Mojo.internal.sendMessage({
+    name: "MojoHandle.writeMessage",
+    args: {
+      handle: this.nativeHandle_,
+      buffer: buffer,
+      handles: nativeHandles,
+    }
+  });
+};
+
+/**
+ * Reads a message from the message pipe.
+ *
+ * @return {result: !MojoResult,
+ *          buffer: !ArrayBufferView=,
+ *          handles: !Array<!MojoHandle>=}
+ *     Result code and (on success) the data and handles recevied.
+ */
+MojoHandle.prototype.readMessage = function() {
+  var result = Mojo.internal.sendMessage({
+    name: "MojoHandle.readMessage",
+    args: {
+      handle: this.nativeHandle_
+    }
+  });
+
+  if (result.result == Mojo.RESULT_OK) {
+    result.buffer = new Uint8Array(result.buffer).buffer;
+    result.handles = result.handles.map(function(handle) {
+      return new MojoHandle(handle);
+    });
+  }
+  return result;
+};
+
+/**
+ * MojoWatcher identifies a watch on a MojoHandle and can be used to cancel the
+ * watch.
+ *
+ * @constructor
+ * @param {number} An opaque id representing the watch.
+ */
+var MojoWatcher = function(watchId) {
+  this.watchId_ = watchId;
+};
+
+/*
+ * Cancels a handle watch.
+ */
+MojoWatcher.prototype.cancel = function() {
+  Mojo.internal.sendMessage({
+    name: "MojoWatcher.cancel",
+    args: {
+      watchId: this.watchId_
+    }
+  });
+  Mojo.internal.watchCallbacksHolder.removeWatchCallback(watchId);
+};
+
+// -----------------------------------------------------------------------------
+// Mojo API implementation details. It is not part of the public API.
+
+Mojo.internal = Mojo.internal || {};
+
+/**
+ * Synchronously sends a message to Mojo backend.
+ * @param {!Object} message The message to send.
+ * @return {Object=} Response from Mojo backend.
+ */
+Mojo.internal.sendMessage = function(message) {
+  var response = window.prompt(__gCrWeb.common.JSONStringify(message));
+  return response ? JSON.parse(response) : undefined;
+};
+
+/**
+ * Holds callbacks for all currently active watches.
+ */
+Mojo.internal.watchCallbacksHolder = (function() {
+  /**
+   * Next callback id to be used for watch.
+   * @type{number}
+   */
+  var nextCallbackId = 0;
+
+  /**
+   * Map where keys are callbacks ids and values are callbacks.
+   * @type {!Map<number, !function(!MojoResult)>}
+   */
+  var callbacks = new Map();
+
+  /**
+   * Map where keys are watch ids and values are callback ids.
+   * @type {!Map<number, number>}
+   */
+  var callbackIds = new Map();
+
+  /**
+   * Calls watch callback.
+   *
+   * @param {number} callbackId Callback id previously returned from
+         {@code getNextCallbackId}.
+   * @param {!MojoResult} mojoResult The result code to call the callback with.
+   */
+  var callCallback = function(callbackId, mojoResult) {
+    var callback = callbacks.get(callbackId);
+
+    // Signalling the watch is asynchronous operation and this function may be
+    // called for already removed watch.
+    if (callback)
+      callback(mojoResult);
+  };
+
+  /**
+   * Returns next callback id to be used for watch (idempotent).
+   *
+   * @return {number} callback id.
+   */
+  var getNextCallbackId = function() {
+    return nextCallbackId;
+  };
+
+  /**
+   * Adds callback which must be executed when the watch fires.
+   *
+   * @param {number} watchId The value returned from "MojoHandle.watch" Mojo
+   *     backend.
+   * @param {!function(!MojoResult)} callback The callback which should be
+   *     executed when the watch fires.
+   */
+  var addWatchCallback = function(watchId, callback) {
+    callbackIds.set(watchId, nextCallbackId);
+    callbacks.set(nextCallbackId, callback);
+    ++nextCallbackId;
+  };
+
+  /**
+   * Removes callback which should no longer be executed.
+   *
+   * @param {!number} watchId The id to remove callback for.
+   */
+  var removeWatchCallback = function (watchId) {
+    callbacks.delete(callbackIds.get(watchId));
+    callbackIds.delete(watchId);
+  };
+
+  return {
+    callCallback: callCallback,
+    getNextCallbackId: getNextCallbackId,
+    addWatchCallback: addWatchCallback,
+    removeWatchCallback: removeWatchCallback
+  };
+})();
+