extensions/renderer/resources/messaging_utils.js

   1 // Copyright 2014 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 // Routines used to normalize arguments to messaging functions.
   6
   7 function alignSendMessageArguments(args, hasOptionsArgument) {
   8   // Align missing (optional) function arguments with the arguments that
   9   // schema validation is expecting, e.g.
  10   //   extension.sendRequest(req)     -> extension.sendRequest(null, req)
  11   //   extension.sendRequest(req, cb) -> extension.sendRequest(null, req, cb)
  12   if (!args || !args.length)
  13     return null;
  14   var lastArg = args.length - 1;
  15
  16   // responseCallback (last argument) is optional.
  17   var responseCallback = null;
  18   if (typeof args[lastArg] == 'function')
  19     responseCallback = args[lastArg--];
  20
  21   var options = null;
  22   if (hasOptionsArgument && lastArg >= 1) {
  23     // options (third argument) is optional. It can also be ambiguous which
  24     // argument it should match. If there are more than two arguments remaining,
  25     // options is definitely present:
  26     if (lastArg > 1) {
  27       options = args[lastArg--];
  28     } else {
  29       // Exactly two arguments remaining. If the first argument is a string,
  30       // it should bind to targetId, and the second argument should bind to
  31       // request, which is required. In other words, when two arguments remain,
  32       // only bind options when the first argument cannot bind to targetId.
  33       if (!(args[0] === null || typeof args[0] == 'string'))
  34         options = args[lastArg--];
  35     }
  36   }
  37
  38   // request (second argument) is required.
  39   var request = args[lastArg--];
  40
  41   // targetId (first argument, extensionId in the manifest) is optional.
  42   var targetId = null;
  43   if (lastArg >= 0)
  44     targetId = args[lastArg--];
  45
  46   if (lastArg != -1)
  47     return null;
  48   if (hasOptionsArgument)
  49     return [targetId, request, options, responseCallback];
  50   return [targetId, request, responseCallback];
  51 }
  52
  53 exports.alignSendMessageArguments = alignSendMessageArguments;