dom/streams/StreamUtils.h

   1 /* This Source Code Form is subject to the terms of the Mozilla Public
   2  * License, v. 2.0. If a copy of the MPL was not distributed with this
   3  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   4
   5 #ifndef mozilla_dom_StreamUtils_h
   6 #define mozilla_dom_StreamUtils_h
   7
   8 #include "mozilla/ErrorResult.h"
   9 #include "mozilla/dom/Promise.h"
  10
  11 class nsIGlobalObject;
  12
  13 namespace mozilla::dom {
  14
  15 struct QueuingStrategy;
  16
  17 double ExtractHighWaterMark(const QueuingStrategy& aStrategy,
  18                             double aDefaultHWM, ErrorResult& aRv);
  19
  20 // Promisification algorithm, shared among:
  21 // Step 2 and 3 of https://streams.spec.whatwg.org/#readablestream-set-up
  22 // Step 2 and 3 of
  23 // https://streams.spec.whatwg.org/#readablestream-set-up-with-byte-reading-support
  24 // Step 2 and 3 of https://streams.spec.whatwg.org/#writablestream-set-up
  25 // Step 5 and 6 of https://streams.spec.whatwg.org/#transformstream-set-up
  26 template <typename T>
  27 MOZ_CAN_RUN_SCRIPT static already_AddRefed<Promise> PromisifyAlgorithm(
  28     nsIGlobalObject* aGlobal, T aFunc, mozilla::ErrorResult& aRv) {
  29   // Step 1. Let result be the result of running (algorithm). If this throws an
  30   // exception e, return a promise rejected with e.
  31   RefPtr<Promise> result;
  32   if constexpr (!std::is_same<decltype(aFunc(aRv)), void>::value) {
  33     result = aFunc(aRv);
  34   } else {
  35     aFunc(aRv);
  36   }
  37
  38   if (aRv.IsUncatchableException()) {
  39     return nullptr;
  40   }
  41
  42   if (aRv.Failed()) {
  43     return Promise::CreateRejectedWithErrorResult(aGlobal, aRv);
  44   }
  45
  46   // Step 2. If result is a Promise, then return result.
  47   if (result) {
  48     return result.forget();
  49   }
  50
  51   // Step 3. Return a promise resolved with undefined.
  52   return Promise::CreateResolvedWithUndefined(aGlobal, aRv);
  53 }
  54
  55 }  // namespace mozilla::dom
  56
  57 #endif  // mozilla_dom_StreamUtils_h