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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-19 00:47:55 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-19 00:47:55 +0000
commit26a029d407be480d791972afb5975cf62c9360a6 (patch)
treef435a8308119effd964b339f76abb83a57c29483 /xpcom/threads/MozPromise.h
parentInitial commit. (diff)
downloadfirefox-26a029d407be480d791972afb5975cf62c9360a6.tar.xz
firefox-26a029d407be480d791972afb5975cf62c9360a6.zip
Adding upstream version 124.0.1.upstream/124.0.1
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'xpcom/threads/MozPromise.h')
-rw-r--r--xpcom/threads/MozPromise.h1757
1 files changed, 1757 insertions, 0 deletions
diff --git a/xpcom/threads/MozPromise.h b/xpcom/threads/MozPromise.h
new file mode 100644
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+++ b/xpcom/threads/MozPromise.h
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+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* 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
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#if !defined(MozPromise_h_)
+# define MozPromise_h_
+
+# include <type_traits>
+# include <utility>
+
+# include "mozilla/ErrorNames.h"
+# include "mozilla/Logging.h"
+# include "mozilla/Maybe.h"
+# include "mozilla/Monitor.h"
+# include "mozilla/Mutex.h"
+# include "mozilla/RefPtr.h"
+# include "mozilla/UniquePtr.h"
+# include "mozilla/Variant.h"
+# include "nsIDirectTaskDispatcher.h"
+# include "nsISerialEventTarget.h"
+# include "nsTArray.h"
+# include "nsThreadUtils.h"
+
+# ifdef MOZ_WIDGET_ANDROID
+# include "mozilla/jni/GeckoResultUtils.h"
+# endif
+
+# if MOZ_DIAGNOSTIC_ASSERT_ENABLED
+# define PROMISE_DEBUG
+# endif
+
+# ifdef PROMISE_DEBUG
+# define PROMISE_ASSERT MOZ_RELEASE_ASSERT
+# else
+# define PROMISE_ASSERT(...) \
+ do { \
+ } while (0)
+# endif
+
+# if DEBUG
+# include "nsPrintfCString.h"
+# endif
+
+namespace mozilla {
+
+namespace dom {
+class Promise;
+}
+
+extern LazyLogModule gMozPromiseLog;
+
+# define PROMISE_LOG(x, ...) \
+ MOZ_LOG(gMozPromiseLog, mozilla::LogLevel::Debug, (x, ##__VA_ARGS__))
+
+namespace detail {
+template <typename F>
+struct MethodTraitsHelper : MethodTraitsHelper<decltype(&F::operator())> {};
+template <typename ThisType, typename Ret, typename... ArgTypes>
+struct MethodTraitsHelper<Ret (ThisType::*)(ArgTypes...)> {
+ using ReturnType = Ret;
+ static const size_t ArgSize = sizeof...(ArgTypes);
+};
+template <typename ThisType, typename Ret, typename... ArgTypes>
+struct MethodTraitsHelper<Ret (ThisType::*)(ArgTypes...) const> {
+ using ReturnType = Ret;
+ static const size_t ArgSize = sizeof...(ArgTypes);
+};
+template <typename ThisType, typename Ret, typename... ArgTypes>
+struct MethodTraitsHelper<Ret (ThisType::*)(ArgTypes...) volatile> {
+ using ReturnType = Ret;
+ static const size_t ArgSize = sizeof...(ArgTypes);
+};
+template <typename ThisType, typename Ret, typename... ArgTypes>
+struct MethodTraitsHelper<Ret (ThisType::*)(ArgTypes...) const volatile> {
+ using ReturnType = Ret;
+ static const size_t ArgSize = sizeof...(ArgTypes);
+};
+template <typename T>
+struct MethodTrait : MethodTraitsHelper<std::remove_reference_t<T>> {};
+
+} // namespace detail
+
+template <typename MethodType>
+using TakesArgument =
+ std::integral_constant<bool, detail::MethodTrait<MethodType>::ArgSize != 0>;
+
+template <typename MethodType, typename TargetType>
+using ReturnTypeIs =
+ std::is_convertible<typename detail::MethodTrait<MethodType>::ReturnType,
+ TargetType>;
+
+template <typename ResolveValueT, typename RejectValueT, bool IsExclusive>
+class MozPromise;
+
+template <typename Return>
+struct IsMozPromise : std::false_type {};
+
+template <typename ResolveValueT, typename RejectValueT, bool IsExclusive>
+struct IsMozPromise<MozPromise<ResolveValueT, RejectValueT, IsExclusive>>
+ : std::true_type {};
+
+/*
+ * A promise manages an asynchronous request that may or may not be able to be
+ * fulfilled immediately. When an API returns a promise, the consumer may attach
+ * callbacks to be invoked (asynchronously, on a specified thread) when the
+ * request is either completed (resolved) or cannot be completed (rejected).
+ * Whereas JS promise callbacks are dispatched from Microtask checkpoints,
+ * MozPromises resolution/rejection make a normal round-trip through the event
+ * loop, which simplifies their ordering semantics relative to other native
+ * code.
+ *
+ * MozPromises attempt to mirror the spirit of JS Promises to the extent that
+ * is possible (and desirable) in C++. While the intent is that MozPromises
+ * feel familiar to programmers who are accustomed to their JS-implemented
+ * cousin, we don't shy away from imposing restrictions and adding features that
+ * make sense for the use cases we encounter.
+ *
+ * A MozPromise is ThreadSafe, and may be ->Then()ed on any thread. The Then()
+ * call accepts resolve and reject callbacks, and returns a magic object which
+ * will be implicitly converted to a MozPromise::Request or a MozPromise object
+ * depending on how the return value is used. The magic object serves several
+ * purposes for the consumer.
+ *
+ * (1) When converting to a MozPromise::Request, it allows the caller to
+ * cancel the delivery of the resolve/reject value if it has not already
+ * occurred, via Disconnect() (this must be done on the target thread to
+ * avoid racing).
+ *
+ * (2) When converting to a MozPromise (which is called a completion promise),
+ * it allows promise chaining so ->Then() can be called again to attach
+ * more resolve and reject callbacks. If the resolve/reject callback
+ * returns a new MozPromise, that promise is chained to the completion
+ * promise, such that its resolve/reject value will be forwarded along
+ * when it arrives. If the resolve/reject callback returns void, the
+ * completion promise is resolved/rejected with the same value that was
+ * passed to the callback.
+ *
+ * The MozPromise APIs skirt traditional XPCOM convention by returning nsRefPtrs
+ * (rather than already_AddRefed) from various methods. This is done to allow
+ * elegant chaining of calls without cluttering up the code with intermediate
+ * variables, and without introducing separate API variants for callers that
+ * want a return value (from, say, ->Then()) from those that don't.
+ *
+ * When IsExclusive is true, the MozPromise does a release-mode assertion that
+ * there is at most one call to either Then(...) or ChainTo(...).
+ */
+
+class MozPromiseRefcountable {
+ public:
+ NS_INLINE_DECL_THREADSAFE_REFCOUNTING(MozPromiseRefcountable)
+ protected:
+ virtual ~MozPromiseRefcountable() = default;
+};
+
+class MozPromiseBase : public MozPromiseRefcountable {
+ public:
+ virtual void AssertIsDead() = 0;
+};
+
+template <typename T>
+class MozPromiseHolder;
+template <typename T>
+class MozPromiseRequestHolder;
+template <typename ResolveValueT, typename RejectValueT, bool IsExclusive>
+class MozPromise : public MozPromiseBase {
+ static const uint32_t sMagic = 0xcecace11;
+
+ // Return a |T&&| to enable move when IsExclusive is true or
+ // a |const T&| to enforce copy otherwise.
+ template <typename T,
+ typename R = std::conditional_t<IsExclusive, T&&, const T&>>
+ static R MaybeMove(T& aX) {
+ return static_cast<R>(aX);
+ }
+
+ public:
+ typedef ResolveValueT ResolveValueType;
+ typedef RejectValueT RejectValueType;
+ class ResolveOrRejectValue {
+ public:
+ template <typename ResolveValueType_>
+ void SetResolve(ResolveValueType_&& aResolveValue) {
+ MOZ_ASSERT(IsNothing());
+ mValue = Storage(VariantIndex<ResolveIndex>{},
+ std::forward<ResolveValueType_>(aResolveValue));
+ }
+
+ template <typename RejectValueType_>
+ void SetReject(RejectValueType_&& aRejectValue) {
+ MOZ_ASSERT(IsNothing());
+ mValue = Storage(VariantIndex<RejectIndex>{},
+ std::forward<RejectValueType_>(aRejectValue));
+ }
+
+ template <typename ResolveValueType_>
+ static ResolveOrRejectValue MakeResolve(ResolveValueType_&& aResolveValue) {
+ ResolveOrRejectValue val;
+ val.SetResolve(std::forward<ResolveValueType_>(aResolveValue));
+ return val;
+ }
+
+ template <typename RejectValueType_>
+ static ResolveOrRejectValue MakeReject(RejectValueType_&& aRejectValue) {
+ ResolveOrRejectValue val;
+ val.SetReject(std::forward<RejectValueType_>(aRejectValue));
+ return val;
+ }
+
+ bool IsResolve() const { return mValue.template is<ResolveIndex>(); }
+ bool IsReject() const { return mValue.template is<RejectIndex>(); }
+ bool IsNothing() const { return mValue.template is<NothingIndex>(); }
+
+ const ResolveValueType& ResolveValue() const {
+ return mValue.template as<ResolveIndex>();
+ }
+ ResolveValueType& ResolveValue() {
+ return mValue.template as<ResolveIndex>();
+ }
+ const RejectValueType& RejectValue() const {
+ return mValue.template as<RejectIndex>();
+ }
+ RejectValueType& RejectValue() { return mValue.template as<RejectIndex>(); }
+
+ private:
+ enum { NothingIndex, ResolveIndex, RejectIndex };
+ using Storage = Variant<Nothing, ResolveValueType, RejectValueType>;
+ Storage mValue = Storage(VariantIndex<NothingIndex>{});
+ };
+
+ protected:
+ // MozPromise is the public type, and never constructed directly. Construct
+ // a MozPromise::Private, defined below.
+ MozPromise(const char* aCreationSite, bool aIsCompletionPromise)
+ : mCreationSite(aCreationSite),
+ mMutex("MozPromise Mutex"),
+ mHaveRequest(false),
+ mIsCompletionPromise(aIsCompletionPromise)
+# ifdef PROMISE_DEBUG
+ ,
+ mMagic4(&mMutex)
+# endif
+ {
+ PROMISE_LOG("%s creating MozPromise (%p)", mCreationSite, this);
+ }
+
+ public:
+ // MozPromise::Private allows us to separate the public interface (upon which
+ // consumers of the promise may invoke methods like Then()) from the private
+ // interface (upon which the creator of the promise may invoke Resolve() or
+ // Reject()). APIs should create and store a MozPromise::Private (usually
+ // via a MozPromiseHolder), and return a MozPromise to consumers.
+ //
+ // NB: We can include the definition of this class inline once B2G ICS is
+ // gone.
+ class Private;
+
+ template <typename ResolveValueType_>
+ [[nodiscard]] static RefPtr<MozPromise> CreateAndResolve(
+ ResolveValueType_&& aResolveValue, const char* aResolveSite) {
+ static_assert(std::is_convertible_v<ResolveValueType_, ResolveValueT>,
+ "Resolve() argument must be implicitly convertible to "
+ "MozPromise's ResolveValueT");
+ RefPtr<typename MozPromise::Private> p =
+ new MozPromise::Private(aResolveSite);
+ p->Resolve(std::forward<ResolveValueType_>(aResolveValue), aResolveSite);
+ return p;
+ }
+
+ template <typename RejectValueType_>
+ [[nodiscard]] static RefPtr<MozPromise> CreateAndReject(
+ RejectValueType_&& aRejectValue, const char* aRejectSite) {
+ static_assert(std::is_convertible_v<RejectValueType_, RejectValueT>,
+ "Reject() argument must be implicitly convertible to "
+ "MozPromise's RejectValueT");
+ RefPtr<typename MozPromise::Private> p =
+ new MozPromise::Private(aRejectSite);
+ p->Reject(std::forward<RejectValueType_>(aRejectValue), aRejectSite);
+ return p;
+ }
+
+ template <typename ResolveOrRejectValueType_>
+ [[nodiscard]] static RefPtr<MozPromise> CreateAndResolveOrReject(
+ ResolveOrRejectValueType_&& aValue, const char* aSite) {
+ RefPtr<typename MozPromise::Private> p = new MozPromise::Private(aSite);
+ p->ResolveOrReject(std::forward<ResolveOrRejectValueType_>(aValue), aSite);
+ return p;
+ }
+
+ typedef MozPromise<CopyableTArray<ResolveValueType>, RejectValueType,
+ IsExclusive>
+ AllPromiseType;
+
+ typedef MozPromise<CopyableTArray<ResolveOrRejectValue>, bool, IsExclusive>
+ AllSettledPromiseType;
+
+ private:
+ class AllPromiseHolder : public MozPromiseRefcountable {
+ public:
+ explicit AllPromiseHolder(size_t aDependentPromises)
+ : mPromise(new typename AllPromiseType::Private(__func__)),
+ mOutstandingPromises(aDependentPromises) {
+ MOZ_ASSERT(aDependentPromises > 0);
+ mResolveValues.SetLength(aDependentPromises);
+ }
+
+ template <typename ResolveValueType_>
+ void Resolve(size_t aIndex, ResolveValueType_&& aResolveValue) {
+ if (!mPromise) {
+ // Already rejected.
+ return;
+ }
+
+ mResolveValues[aIndex].emplace(
+ std::forward<ResolveValueType_>(aResolveValue));
+ if (--mOutstandingPromises == 0) {
+ nsTArray<ResolveValueType> resolveValues;
+ resolveValues.SetCapacity(mResolveValues.Length());
+ for (auto&& resolveValue : mResolveValues) {
+ resolveValues.AppendElement(std::move(resolveValue.ref()));
+ }
+
+ mPromise->Resolve(std::move(resolveValues), __func__);
+ mPromise = nullptr;
+ mResolveValues.Clear();
+ }
+ }
+
+ template <typename RejectValueType_>
+ void Reject(RejectValueType_&& aRejectValue) {
+ if (!mPromise) {
+ // Already rejected.
+ return;
+ }
+
+ mPromise->Reject(std::forward<RejectValueType_>(aRejectValue), __func__);
+ mPromise = nullptr;
+ mResolveValues.Clear();
+ }
+
+ AllPromiseType* Promise() { return mPromise; }
+
+ private:
+ nsTArray<Maybe<ResolveValueType>> mResolveValues;
+ RefPtr<typename AllPromiseType::Private> mPromise;
+ size_t mOutstandingPromises;
+ };
+
+ // Trying to pass ResolveOrRejectValue by value fails static analysis checks,
+ // so we need to use either a const& or an rvalue reference, depending on
+ // whether IsExclusive is true or not.
+ typedef std::conditional_t<IsExclusive, ResolveOrRejectValue&&,
+ const ResolveOrRejectValue&>
+ ResolveOrRejectValueParam;
+
+ typedef std::conditional_t<IsExclusive, ResolveValueType&&,
+ const ResolveValueType&>
+ ResolveValueTypeParam;
+
+ typedef std::conditional_t<IsExclusive, RejectValueType&&,
+ const RejectValueType&>
+ RejectValueTypeParam;
+
+ class AllSettledPromiseHolder : public MozPromiseRefcountable {
+ public:
+ explicit AllSettledPromiseHolder(size_t aDependentPromises)
+ : mPromise(new typename AllSettledPromiseType::Private(__func__)),
+ mOutstandingPromises(aDependentPromises) {
+ MOZ_ASSERT(aDependentPromises > 0);
+ mValues.SetLength(aDependentPromises);
+ }
+
+ void Settle(size_t aIndex, ResolveOrRejectValueParam aValue) {
+ if (!mPromise) {
+ // Already rejected.
+ return;
+ }
+
+ mValues[aIndex].emplace(MaybeMove(aValue));
+ if (--mOutstandingPromises == 0) {
+ nsTArray<ResolveOrRejectValue> values;
+ values.SetCapacity(mValues.Length());
+ for (auto&& value : mValues) {
+ values.AppendElement(std::move(value.ref()));
+ }
+
+ mPromise->Resolve(std::move(values), __func__);
+ mPromise = nullptr;
+ mValues.Clear();
+ }
+ }
+
+ AllSettledPromiseType* Promise() { return mPromise; }
+
+ private:
+ nsTArray<Maybe<ResolveOrRejectValue>> mValues;
+ RefPtr<typename AllSettledPromiseType::Private> mPromise;
+ size_t mOutstandingPromises;
+ };
+
+ public:
+ [[nodiscard]] static RefPtr<AllPromiseType> All(
+ nsISerialEventTarget* aProcessingTarget,
+ nsTArray<RefPtr<MozPromise>>& aPromises) {
+ if (aPromises.Length() == 0) {
+ return AllPromiseType::CreateAndResolve(
+ CopyableTArray<ResolveValueType>(), __func__);
+ }
+
+ RefPtr<AllPromiseHolder> holder = new AllPromiseHolder(aPromises.Length());
+ RefPtr<AllPromiseType> promise = holder->Promise();
+ for (size_t i = 0; i < aPromises.Length(); ++i) {
+ aPromises[i]->Then(
+ aProcessingTarget, __func__,
+ [holder, i](ResolveValueTypeParam aResolveValue) -> void {
+ holder->Resolve(i, MaybeMove(aResolveValue));
+ },
+ [holder](RejectValueTypeParam aRejectValue) -> void {
+ holder->Reject(MaybeMove(aRejectValue));
+ });
+ }
+ return promise;
+ }
+
+ [[nodiscard]] static RefPtr<AllSettledPromiseType> AllSettled(
+ nsISerialEventTarget* aProcessingTarget,
+ nsTArray<RefPtr<MozPromise>>& aPromises) {
+ if (aPromises.Length() == 0) {
+ return AllSettledPromiseType::CreateAndResolve(
+ CopyableTArray<ResolveOrRejectValue>(), __func__);
+ }
+
+ RefPtr<AllSettledPromiseHolder> holder =
+ new AllSettledPromiseHolder(aPromises.Length());
+ RefPtr<AllSettledPromiseType> promise = holder->Promise();
+ for (size_t i = 0; i < aPromises.Length(); ++i) {
+ aPromises[i]->Then(aProcessingTarget, __func__,
+ [holder, i](ResolveOrRejectValueParam aValue) -> void {
+ holder->Settle(i, MaybeMove(aValue));
+ });
+ }
+ return promise;
+ }
+
+ class Request : public MozPromiseRefcountable {
+ public:
+ virtual void Disconnect() = 0;
+
+ protected:
+ Request() : mComplete(false), mDisconnected(false) {}
+ virtual ~Request() = default;
+
+ bool mComplete;
+ bool mDisconnected;
+ };
+
+ protected:
+ /*
+ * A ThenValue tracks a single consumer waiting on the promise. When a
+ * consumer invokes promise->Then(...), a ThenValue is created. Once the
+ * Promise is resolved or rejected, a {Resolve,Reject}Runnable is dispatched,
+ * which invokes the resolve/reject method and then deletes the ThenValue.
+ */
+ class ThenValueBase : public Request {
+ friend class MozPromise;
+ static const uint32_t sMagic = 0xfadece11;
+
+ public:
+ class ResolveOrRejectRunnable final
+ : public PrioritizableCancelableRunnable {
+ public:
+ ResolveOrRejectRunnable(ThenValueBase* aThenValue, MozPromise* aPromise)
+ : PrioritizableCancelableRunnable(
+ aPromise->mPriority,
+ "MozPromise::ThenValueBase::ResolveOrRejectRunnable"),
+ mThenValue(aThenValue),
+ mPromise(aPromise) {
+ MOZ_DIAGNOSTIC_ASSERT(!mPromise->IsPending());
+ }
+
+ ~ResolveOrRejectRunnable() {
+ if (mThenValue) {
+ mThenValue->AssertIsDead();
+ }
+ }
+
+ NS_IMETHOD Run() override {
+ PROMISE_LOG("ResolveOrRejectRunnable::Run() [this=%p]", this);
+ mThenValue->DoResolveOrReject(mPromise->Value());
+ mThenValue = nullptr;
+ mPromise = nullptr;
+ return NS_OK;
+ }
+
+ nsresult Cancel() override { return Run(); }
+
+ private:
+ RefPtr<ThenValueBase> mThenValue;
+ RefPtr<MozPromise> mPromise;
+ };
+
+ ThenValueBase(nsISerialEventTarget* aResponseTarget, const char* aCallSite)
+ : mResponseTarget(aResponseTarget), mCallSite(aCallSite) {
+ MOZ_ASSERT(aResponseTarget);
+ }
+
+# ifdef PROMISE_DEBUG
+ ~ThenValueBase() {
+ mMagic1 = 0;
+ mMagic2 = 0;
+ }
+# endif
+
+ void AssertIsDead() {
+ PROMISE_ASSERT(mMagic1 == sMagic && mMagic2 == sMagic);
+ // We want to assert that this ThenValues is dead - that is to say, that
+ // there are no consumers waiting for the result. In the case of a normal
+ // ThenValue, we check that it has been disconnected, which is the way
+ // that the consumer signals that it no longer wishes to hear about the
+ // result. If this ThenValue has a completion promise (which is mutually
+ // exclusive with being disconnectable), we recursively assert that every
+ // ThenValue associated with the completion promise is dead.
+ if (MozPromiseBase* p = CompletionPromise()) {
+ p->AssertIsDead();
+ } else {
+# ifdef MOZ_DIAGNOSTIC_ASSERT_ENABLED
+ if (MOZ_UNLIKELY(!Request::mDisconnected)) {
+ MOZ_CRASH_UNSAFE_PRINTF(
+ "MozPromise::ThenValue created from '%s' destroyed without being "
+ "either disconnected, resolved, or rejected (dispatchRv: %s)",
+ mCallSite,
+ mDispatchRv ? GetStaticErrorName(*mDispatchRv)
+ : "not dispatched");
+ }
+# endif
+ }
+ }
+
+ void Dispatch(MozPromise* aPromise) {
+ PROMISE_ASSERT(mMagic1 == sMagic && mMagic2 == sMagic);
+ aPromise->mMutex.AssertCurrentThreadOwns();
+ MOZ_ASSERT(!aPromise->IsPending());
+
+ nsCOMPtr<nsIRunnable> r = new ResolveOrRejectRunnable(this, aPromise);
+ PROMISE_LOG(
+ "%s Then() call made from %s [Runnable=%p, Promise=%p, ThenValue=%p] "
+ "%s dispatch",
+ aPromise->mValue.IsResolve() ? "Resolving" : "Rejecting", mCallSite,
+ r.get(), aPromise, this,
+ aPromise->mUseSynchronousTaskDispatch ? "synchronous"
+ : aPromise->mUseDirectTaskDispatch ? "directtask"
+ : "normal");
+
+ if (aPromise->mUseSynchronousTaskDispatch &&
+ mResponseTarget->IsOnCurrentThread()) {
+ PROMISE_LOG("ThenValue::Dispatch running task synchronously [this=%p]",
+ this);
+ r->Run();
+ return;
+ }
+
+ if (aPromise->mUseDirectTaskDispatch &&
+ mResponseTarget->IsOnCurrentThread()) {
+ PROMISE_LOG(
+ "ThenValue::Dispatch dispatch task via direct task queue [this=%p]",
+ this);
+ nsCOMPtr<nsIDirectTaskDispatcher> dispatcher =
+ do_QueryInterface(mResponseTarget);
+ if (dispatcher) {
+ SetDispatchRv(dispatcher->DispatchDirectTask(r.forget()));
+ return;
+ }
+ NS_WARNING(
+ nsPrintfCString(
+ "Direct Task dispatching not available for thread \"%s\"",
+ PR_GetThreadName(PR_GetCurrentThread()))
+ .get());
+ MOZ_DIAGNOSTIC_ASSERT(
+ false,
+ "mResponseTarget must implement nsIDirectTaskDispatcher for direct "
+ "task dispatching");
+ }
+
+ // Promise consumers are allowed to disconnect the Request object and
+ // then shut down the thread or task queue that the promise result would
+ // be dispatched on. So we unfortunately can't assert that promise
+ // dispatch succeeds. :-(
+ // We do record whether or not it succeeds so that if the ThenValueBase is
+ // then destroyed and it was not disconnected, we can include that
+ // information in the assertion message.
+ SetDispatchRv(mResponseTarget->Dispatch(r.forget()));
+ }
+
+ void Disconnect() override {
+ MOZ_DIAGNOSTIC_ASSERT(mResponseTarget->IsOnCurrentThread());
+ MOZ_DIAGNOSTIC_ASSERT(!Request::mComplete);
+ Request::mDisconnected = true;
+
+ // We could support rejecting the completion promise on disconnection, but
+ // then we'd need to have some sort of default reject value. The use cases
+ // of disconnection and completion promise chaining seem pretty
+ // orthogonal, so let's use assert against it.
+ MOZ_DIAGNOSTIC_ASSERT(!CompletionPromise());
+ }
+
+ protected:
+ virtual MozPromiseBase* CompletionPromise() const = 0;
+ virtual void DoResolveOrRejectInternal(ResolveOrRejectValue& aValue) = 0;
+
+ void DoResolveOrReject(ResolveOrRejectValue& aValue) {
+ PROMISE_ASSERT(mMagic1 == sMagic && mMagic2 == sMagic);
+ MOZ_DIAGNOSTIC_ASSERT(mResponseTarget->IsOnCurrentThread());
+ Request::mComplete = true;
+ if (Request::mDisconnected) {
+ PROMISE_LOG(
+ "ThenValue::DoResolveOrReject disconnected - bailing out [this=%p]",
+ this);
+ return;
+ }
+
+ // Invoke the resolve or reject method.
+ DoResolveOrRejectInternal(aValue);
+ }
+
+ void SetDispatchRv(nsresult aRv) {
+# ifdef MOZ_DIAGNOSTIC_ASSERT_ENABLED
+ mDispatchRv = Some(aRv);
+# endif
+ }
+
+ nsCOMPtr<nsISerialEventTarget>
+ mResponseTarget; // May be released on any thread.
+# ifdef PROMISE_DEBUG
+ uint32_t mMagic1 = sMagic;
+# endif
+ const char* mCallSite;
+# ifdef PROMISE_DEBUG
+ uint32_t mMagic2 = sMagic;
+# endif
+# ifdef MOZ_DIAGNOSTIC_ASSERT_ENABLED
+ Maybe<nsresult> mDispatchRv;
+# endif
+ };
+
+ /*
+ * We create two overloads for invoking Resolve/Reject Methods so as to
+ * make the resolve/reject value argument "optional".
+ */
+ template <typename ThisType, typename MethodType, typename ValueType>
+ static std::enable_if_t<TakesArgument<MethodType>::value,
+ typename detail::MethodTrait<MethodType>::ReturnType>
+ InvokeMethod(ThisType* aThisVal, MethodType aMethod, ValueType&& aValue) {
+ return (aThisVal->*aMethod)(std::forward<ValueType>(aValue));
+ }
+
+ template <typename ThisType, typename MethodType, typename ValueType>
+ static std::enable_if_t<!TakesArgument<MethodType>::value,
+ typename detail::MethodTrait<MethodType>::ReturnType>
+ InvokeMethod(ThisType* aThisVal, MethodType aMethod, ValueType&& aValue) {
+ return (aThisVal->*aMethod)();
+ }
+
+ // Called when promise chaining is supported.
+ template <bool SupportChaining, typename ThisType, typename MethodType,
+ typename ValueType, typename CompletionPromiseType>
+ static std::enable_if_t<SupportChaining, void> InvokeCallbackMethod(
+ ThisType* aThisVal, MethodType aMethod, ValueType&& aValue,
+ CompletionPromiseType&& aCompletionPromise) {
+ auto p = InvokeMethod(aThisVal, aMethod, std::forward<ValueType>(aValue));
+ if (aCompletionPromise) {
+ p->ChainTo(aCompletionPromise.forget(), "<chained completion promise>");
+ }
+ }
+
+ // Called when promise chaining is not supported.
+ template <bool SupportChaining, typename ThisType, typename MethodType,
+ typename ValueType, typename CompletionPromiseType>
+ static std::enable_if_t<!SupportChaining, void> InvokeCallbackMethod(
+ ThisType* aThisVal, MethodType aMethod, ValueType&& aValue,
+ CompletionPromiseType&& aCompletionPromise) {
+ MOZ_DIAGNOSTIC_ASSERT(
+ !aCompletionPromise,
+ "Can't do promise chaining for a non-promise-returning method.");
+ InvokeMethod(aThisVal, aMethod, std::forward<ValueType>(aValue));
+ }
+
+ template <typename>
+ class ThenCommand;
+
+ template <typename...>
+ class ThenValue;
+
+ template <typename ThisType, typename ResolveMethodType,
+ typename RejectMethodType>
+ class ThenValue<ThisType*, ResolveMethodType, RejectMethodType>
+ : public ThenValueBase {
+ friend class ThenCommand<ThenValue>;
+
+ using R1 = typename RemoveSmartPointer<
+ typename detail::MethodTrait<ResolveMethodType>::ReturnType>::Type;
+ using R2 = typename RemoveSmartPointer<
+ typename detail::MethodTrait<RejectMethodType>::ReturnType>::Type;
+ using SupportChaining =
+ std::integral_constant<bool, IsMozPromise<R1>::value &&
+ std::is_same_v<R1, R2>>;
+
+ // Fall back to MozPromise when promise chaining is not supported to make
+ // code compile.
+ using PromiseType =
+ std::conditional_t<SupportChaining::value, R1, MozPromise>;
+
+ public:
+ ThenValue(nsISerialEventTarget* aResponseTarget, ThisType* aThisVal,
+ ResolveMethodType aResolveMethod, RejectMethodType aRejectMethod,
+ const char* aCallSite)
+ : ThenValueBase(aResponseTarget, aCallSite),
+ mThisVal(aThisVal),
+ mResolveMethod(aResolveMethod),
+ mRejectMethod(aRejectMethod) {}
+
+ void Disconnect() override {
+ ThenValueBase::Disconnect();
+
+ // If a Request has been disconnected, we don't guarantee that the
+ // resolve/reject runnable will be dispatched. Null out our refcounted
+ // this-value now so that it's released predictably on the dispatch
+ // thread.
+ mThisVal = nullptr;
+ }
+
+ protected:
+ MozPromiseBase* CompletionPromise() const override {
+ return mCompletionPromise;
+ }
+
+ void DoResolveOrRejectInternal(ResolveOrRejectValue& aValue) override {
+ if (aValue.IsResolve()) {
+ InvokeCallbackMethod<SupportChaining::value>(
+ mThisVal.get(), mResolveMethod, MaybeMove(aValue.ResolveValue()),
+ std::move(mCompletionPromise));
+ } else {
+ InvokeCallbackMethod<SupportChaining::value>(
+ mThisVal.get(), mRejectMethod, MaybeMove(aValue.RejectValue()),
+ std::move(mCompletionPromise));
+ }
+
+ // Null out mThisVal after invoking the callback so that any references
+ // are released predictably on the dispatch thread. Otherwise, it would be
+ // released on whatever thread last drops its reference to the ThenValue,
+ // which may or may not be ok.
+ mThisVal = nullptr;
+ }
+
+ private:
+ RefPtr<ThisType>
+ mThisVal; // Only accessed and refcounted on dispatch thread.
+ ResolveMethodType mResolveMethod;
+ RejectMethodType mRejectMethod;
+ RefPtr<typename PromiseType::Private> mCompletionPromise;
+ };
+
+ template <typename ThisType, typename ResolveRejectMethodType>
+ class ThenValue<ThisType*, ResolveRejectMethodType> : public ThenValueBase {
+ friend class ThenCommand<ThenValue>;
+
+ using R1 = typename RemoveSmartPointer<typename detail::MethodTrait<
+ ResolveRejectMethodType>::ReturnType>::Type;
+ using SupportChaining =
+ std::integral_constant<bool, IsMozPromise<R1>::value>;
+
+ // Fall back to MozPromise when promise chaining is not supported to make
+ // code compile.
+ using PromiseType =
+ std::conditional_t<SupportChaining::value, R1, MozPromise>;
+
+ public:
+ ThenValue(nsISerialEventTarget* aResponseTarget, ThisType* aThisVal,
+ ResolveRejectMethodType aResolveRejectMethod,
+ const char* aCallSite)
+ : ThenValueBase(aResponseTarget, aCallSite),
+ mThisVal(aThisVal),
+ mResolveRejectMethod(aResolveRejectMethod) {}
+
+ void Disconnect() override {
+ ThenValueBase::Disconnect();
+
+ // If a Request has been disconnected, we don't guarantee that the
+ // resolve/reject runnable will be dispatched. Null out our refcounted
+ // this-value now so that it's released predictably on the dispatch
+ // thread.
+ mThisVal = nullptr;
+ }
+
+ protected:
+ MozPromiseBase* CompletionPromise() const override {
+ return mCompletionPromise;
+ }
+
+ void DoResolveOrRejectInternal(ResolveOrRejectValue& aValue) override {
+ InvokeCallbackMethod<SupportChaining::value>(
+ mThisVal.get(), mResolveRejectMethod, MaybeMove(aValue),
+ std::move(mCompletionPromise));
+
+ // Null out mThisVal after invoking the callback so that any references
+ // are released predictably on the dispatch thread. Otherwise, it would be
+ // released on whatever thread last drops its reference to the ThenValue,
+ // which may or may not be ok.
+ mThisVal = nullptr;
+ }
+
+ private:
+ RefPtr<ThisType>
+ mThisVal; // Only accessed and refcounted on dispatch thread.
+ ResolveRejectMethodType mResolveRejectMethod;
+ RefPtr<typename PromiseType::Private> mCompletionPromise;
+ };
+
+ // NB: We could use std::function here instead of a template if it were
+ // supported. :-(
+ template <typename ResolveFunction, typename RejectFunction>
+ class ThenValue<ResolveFunction, RejectFunction> : public ThenValueBase {
+ friend class ThenCommand<ThenValue>;
+
+ using R1 = typename RemoveSmartPointer<
+ typename detail::MethodTrait<ResolveFunction>::ReturnType>::Type;
+ using R2 = typename RemoveSmartPointer<
+ typename detail::MethodTrait<RejectFunction>::ReturnType>::Type;
+ using SupportChaining =
+ std::integral_constant<bool, IsMozPromise<R1>::value &&
+ std::is_same_v<R1, R2>>;
+
+ // Fall back to MozPromise when promise chaining is not supported to make
+ // code compile.
+ using PromiseType =
+ std::conditional_t<SupportChaining::value, R1, MozPromise>;
+
+ public:
+ ThenValue(nsISerialEventTarget* aResponseTarget,
+ ResolveFunction&& aResolveFunction,
+ RejectFunction&& aRejectFunction, const char* aCallSite)
+ : ThenValueBase(aResponseTarget, aCallSite) {
+ mResolveFunction.emplace(std::move(aResolveFunction));
+ mRejectFunction.emplace(std::move(aRejectFunction));
+ }
+
+ void Disconnect() override {
+ ThenValueBase::Disconnect();
+
+ // If a Request has been disconnected, we don't guarantee that the
+ // resolve/reject runnable will be dispatched. Destroy our callbacks
+ // now so that any references in closures are released predictable on
+ // the dispatch thread.
+ mResolveFunction.reset();
+ mRejectFunction.reset();
+ }
+
+ protected:
+ MozPromiseBase* CompletionPromise() const override {
+ return mCompletionPromise;
+ }
+
+ void DoResolveOrRejectInternal(ResolveOrRejectValue& aValue) override {
+ // Note: The usage of InvokeCallbackMethod here requires that
+ // ResolveFunction/RejectFunction are capture-lambdas (i.e. anonymous
+ // classes with ::operator()), since it allows us to share code more
+ // easily. We could fix this if need be, though it's quite easy to work
+ // around by just capturing something.
+ if (aValue.IsResolve()) {
+ InvokeCallbackMethod<SupportChaining::value>(
+ mResolveFunction.ptr(), &ResolveFunction::operator(),
+ MaybeMove(aValue.ResolveValue()), std::move(mCompletionPromise));
+ } else {
+ InvokeCallbackMethod<SupportChaining::value>(
+ mRejectFunction.ptr(), &RejectFunction::operator(),
+ MaybeMove(aValue.RejectValue()), std::move(mCompletionPromise));
+ }
+
+ // Destroy callbacks after invocation so that any references in closures
+ // are released predictably on the dispatch thread. Otherwise, they would
+ // be released on whatever thread last drops its reference to the
+ // ThenValue, which may or may not be ok.
+ mResolveFunction.reset();
+ mRejectFunction.reset();
+ }
+
+ private:
+ Maybe<ResolveFunction>
+ mResolveFunction; // Only accessed and deleted on dispatch thread.
+ Maybe<RejectFunction>
+ mRejectFunction; // Only accessed and deleted on dispatch thread.
+ RefPtr<typename PromiseType::Private> mCompletionPromise;
+ };
+
+ template <typename ResolveRejectFunction>
+ class ThenValue<ResolveRejectFunction> : public ThenValueBase {
+ friend class ThenCommand<ThenValue>;
+
+ using R1 = typename RemoveSmartPointer<
+ typename detail::MethodTrait<ResolveRejectFunction>::ReturnType>::Type;
+ using SupportChaining =
+ std::integral_constant<bool, IsMozPromise<R1>::value>;
+
+ // Fall back to MozPromise when promise chaining is not supported to make
+ // code compile.
+ using PromiseType =
+ std::conditional_t<SupportChaining::value, R1, MozPromise>;
+
+ public:
+ ThenValue(nsISerialEventTarget* aResponseTarget,
+ ResolveRejectFunction&& aResolveRejectFunction,
+ const char* aCallSite)
+ : ThenValueBase(aResponseTarget, aCallSite) {
+ mResolveRejectFunction.emplace(std::move(aResolveRejectFunction));
+ }
+
+ void Disconnect() override {
+ ThenValueBase::Disconnect();
+
+ // If a Request has been disconnected, we don't guarantee that the
+ // resolve/reject runnable will be dispatched. Destroy our callbacks
+ // now so that any references in closures are released predictable on
+ // the dispatch thread.
+ mResolveRejectFunction.reset();
+ }
+
+ protected:
+ MozPromiseBase* CompletionPromise() const override {
+ return mCompletionPromise;
+ }
+
+ void DoResolveOrRejectInternal(ResolveOrRejectValue& aValue) override {
+ // Note: The usage of InvokeCallbackMethod here requires that
+ // ResolveRejectFunction is capture-lambdas (i.e. anonymous
+ // classes with ::operator()), since it allows us to share code more
+ // easily. We could fix this if need be, though it's quite easy to work
+ // around by just capturing something.
+ InvokeCallbackMethod<SupportChaining::value>(
+ mResolveRejectFunction.ptr(), &ResolveRejectFunction::operator(),
+ MaybeMove(aValue), std::move(mCompletionPromise));
+
+ // Destroy callbacks after invocation so that any references in closures
+ // are released predictably on the dispatch thread. Otherwise, they would
+ // be released on whatever thread last drops its reference to the
+ // ThenValue, which may or may not be ok.
+ mResolveRejectFunction.reset();
+ }
+
+ private:
+ Maybe<ResolveRejectFunction>
+ mResolveRejectFunction; // Only accessed and deleted on dispatch
+ // thread.
+ RefPtr<typename PromiseType::Private> mCompletionPromise;
+ };
+
+ public:
+ void ThenInternal(already_AddRefed<ThenValueBase> aThenValue,
+ const char* aCallSite) {
+ PROMISE_ASSERT(mMagic1 == sMagic && mMagic2 == sMagic &&
+ mMagic3 == sMagic && mMagic4 == &mMutex);
+ RefPtr<ThenValueBase> thenValue = aThenValue;
+ MutexAutoLock lock(mMutex);
+ MOZ_DIAGNOSTIC_ASSERT(
+ !IsExclusive || !mHaveRequest,
+ "Using an exclusive promise in a non-exclusive fashion");
+ mHaveRequest = true;
+ PROMISE_LOG("%s invoking Then() [this=%p, aThenValue=%p, isPending=%d]",
+ aCallSite, this, thenValue.get(), (int)IsPending());
+ if (!IsPending()) {
+ thenValue->Dispatch(this);
+ } else {
+ mThenValues.AppendElement(thenValue.forget());
+ }
+ }
+
+ protected:
+ /*
+ * A command object to store all information needed to make a request to
+ * the promise. This allows us to delay the request until further use is
+ * known (whether it is ->Then() again for more promise chaining or ->Track()
+ * to terminate chaining and issue the request).
+ *
+ * This allows a unified syntax for promise chaining and disconnection
+ * and feels more like its JS counterpart.
+ */
+ template <typename ThenValueType>
+ class ThenCommand {
+ // Allow Promise1::ThenCommand to access the private constructor,
+ // Promise2::ThenCommand(ThenCommand&&).
+ template <typename, typename, bool>
+ friend class MozPromise;
+
+ using PromiseType = typename ThenValueType::PromiseType;
+ using Private = typename PromiseType::Private;
+
+ ThenCommand(const char* aCallSite,
+ already_AddRefed<ThenValueType> aThenValue,
+ MozPromise* aReceiver)
+ : mCallSite(aCallSite), mThenValue(aThenValue), mReceiver(aReceiver) {}
+
+ ThenCommand(ThenCommand&& aOther) = default;
+
+ public:
+ ~ThenCommand() {
+ // Issue the request now if the return value of Then() is not used.
+ if (mThenValue) {
+ mReceiver->ThenInternal(mThenValue.forget(), mCallSite);
+ }
+ }
+
+ // Allow RefPtr<MozPromise> p = somePromise->Then();
+ // p->Then(thread1, ...);
+ // p->Then(thread2, ...);
+ operator RefPtr<PromiseType>() {
+ static_assert(
+ ThenValueType::SupportChaining::value,
+ "The resolve/reject callback needs to return a RefPtr<MozPromise> "
+ "in order to do promise chaining.");
+
+ // mCompletionPromise must be created before ThenInternal() to avoid race.
+ RefPtr<Private> p =
+ new Private("<completion promise>", true /* aIsCompletionPromise */);
+ mThenValue->mCompletionPromise = p;
+ // Note ThenInternal() might nullify mCompletionPromise before return.
+ // So we need to return p instead of mCompletionPromise.
+ mReceiver->ThenInternal(mThenValue.forget(), mCallSite);
+ return p;
+ }
+
+ template <typename... Ts>
+ auto Then(Ts&&... aArgs) -> decltype(std::declval<PromiseType>().Then(
+ std::forward<Ts>(aArgs)...)) {
+ return static_cast<RefPtr<PromiseType>>(*this)->Then(
+ std::forward<Ts>(aArgs)...);
+ }
+
+ void Track(MozPromiseRequestHolder<MozPromise>& aRequestHolder) {
+ aRequestHolder.Track(do_AddRef(mThenValue));
+ mReceiver->ThenInternal(mThenValue.forget(), mCallSite);
+ }
+
+ // Allow calling ->Then() again for more promise chaining or ->Track() to
+ // end chaining and track the request for future disconnection.
+ ThenCommand* operator->() { return this; }
+
+ private:
+ const char* mCallSite;
+ RefPtr<ThenValueType> mThenValue;
+ RefPtr<MozPromise> mReceiver;
+ };
+
+ public:
+ template <typename ThisType, typename... Methods,
+ typename ThenValueType = ThenValue<ThisType*, Methods...>,
+ typename ReturnType = ThenCommand<ThenValueType>>
+ ReturnType Then(nsISerialEventTarget* aResponseTarget, const char* aCallSite,
+ ThisType* aThisVal, Methods... aMethods) {
+ RefPtr<ThenValueType> thenValue =
+ new ThenValueType(aResponseTarget, aThisVal, aMethods..., aCallSite);
+ return ReturnType(aCallSite, thenValue.forget(), this);
+ }
+
+ template <typename... Functions,
+ typename ThenValueType = ThenValue<Functions...>,
+ typename ReturnType = ThenCommand<ThenValueType>>
+ ReturnType Then(nsISerialEventTarget* aResponseTarget, const char* aCallSite,
+ Functions&&... aFunctions) {
+ RefPtr<ThenValueType> thenValue =
+ new ThenValueType(aResponseTarget, std::move(aFunctions)..., aCallSite);
+ return ReturnType(aCallSite, thenValue.forget(), this);
+ }
+
+ void ChainTo(already_AddRefed<Private> aChainedPromise,
+ const char* aCallSite) {
+ MutexAutoLock lock(mMutex);
+ MOZ_DIAGNOSTIC_ASSERT(
+ !IsExclusive || !mHaveRequest,
+ "Using an exclusive promise in a non-exclusive fashion");
+ mHaveRequest = true;
+ RefPtr<Private> chainedPromise = aChainedPromise;
+ PROMISE_LOG(
+ "%s invoking Chain() [this=%p, chainedPromise=%p, isPending=%d]",
+ aCallSite, this, chainedPromise.get(), (int)IsPending());
+
+ // We want to use the same type of dispatching method with the chained
+ // promises.
+
+ // We need to ensure that the UseSynchronousTaskDispatch branch isn't taken
+ // at compilation time to ensure we're not triggering the static_assert in
+ // UseSynchronousTaskDispatch method. if constexpr (IsExclusive) ensures
+ // that.
+ if (mUseDirectTaskDispatch) {
+ chainedPromise->UseDirectTaskDispatch(aCallSite);
+ } else if constexpr (IsExclusive) {
+ if (mUseSynchronousTaskDispatch) {
+ chainedPromise->UseSynchronousTaskDispatch(aCallSite);
+ }
+ } else {
+ chainedPromise->SetTaskPriority(mPriority, aCallSite);
+ }
+
+ if (!IsPending()) {
+ ForwardTo(chainedPromise);
+ } else {
+ mChainedPromises.AppendElement(chainedPromise);
+ }
+ }
+
+# ifdef MOZ_WIDGET_ANDROID
+ // Creates a C++ MozPromise from its Java counterpart, GeckoResult.
+ [[nodiscard]] static RefPtr<MozPromise> FromGeckoResult(
+ java::GeckoResult::Param aGeckoResult) {
+ using jni::GeckoResultCallback;
+ RefPtr<Private> p = new Private("GeckoResult Glue", false);
+ auto resolve = GeckoResultCallback::CreateAndAttach<ResolveValueType>(
+ [p](ResolveValueType&& aArg) {
+ p->Resolve(MaybeMove(aArg), __func__);
+ });
+ auto reject = GeckoResultCallback::CreateAndAttach<RejectValueType>(
+ [p](RejectValueType&& aArg) { p->Reject(MaybeMove(aArg), __func__); });
+ aGeckoResult->NativeThen(resolve, reject);
+ return p;
+ }
+# endif
+
+ // Note we expose the function AssertIsDead() instead of IsDead() since
+ // checking IsDead() is a data race in the situation where the request is not
+ // dead. Therefore we enforce the form |Assert(IsDead())| by exposing
+ // AssertIsDead() only.
+ void AssertIsDead() override {
+ PROMISE_ASSERT(mMagic1 == sMagic && mMagic2 == sMagic &&
+ mMagic3 == sMagic && mMagic4 == &mMutex);
+ MutexAutoLock lock(mMutex);
+ for (auto&& then : mThenValues) {
+ then->AssertIsDead();
+ }
+ for (auto&& chained : mChainedPromises) {
+ chained->AssertIsDead();
+ }
+ }
+
+ bool IsResolved() const { return mValue.IsResolve(); }
+
+ protected:
+ bool IsPending() const { return mValue.IsNothing(); }
+
+ ResolveOrRejectValue& Value() {
+ // This method should only be called once the value has stabilized. As
+ // such, we don't need to acquire the lock here.
+ MOZ_DIAGNOSTIC_ASSERT(!IsPending());
+ return mValue;
+ }
+
+ void DispatchAll() {
+ mMutex.AssertCurrentThreadOwns();
+ for (auto&& thenValue : mThenValues) {
+ thenValue->Dispatch(this);
+ }
+ mThenValues.Clear();
+
+ for (auto&& chainedPromise : mChainedPromises) {
+ ForwardTo(chainedPromise);
+ }
+ mChainedPromises.Clear();
+ }
+
+ void ForwardTo(Private* aOther) {
+ MOZ_ASSERT(!IsPending());
+ if (mValue.IsResolve()) {
+ aOther->Resolve(MaybeMove(mValue.ResolveValue()), "<chained promise>");
+ } else {
+ aOther->Reject(MaybeMove(mValue.RejectValue()), "<chained promise>");
+ }
+ }
+
+ virtual ~MozPromise() {
+ PROMISE_LOG("MozPromise::~MozPromise [this=%p]", this);
+ AssertIsDead();
+ // We can't guarantee a completion promise will always be revolved or
+ // rejected since ResolveOrRejectRunnable might not run when dispatch fails.
+ if (!mIsCompletionPromise) {
+ MOZ_ASSERT(!IsPending());
+ MOZ_ASSERT(mThenValues.IsEmpty());
+ MOZ_ASSERT(mChainedPromises.IsEmpty());
+ }
+# ifdef PROMISE_DEBUG
+ mMagic1 = 0;
+ mMagic2 = 0;
+ mMagic3 = 0;
+ mMagic4 = nullptr;
+# endif
+ };
+
+ const char* mCreationSite; // For logging
+ Mutex mMutex MOZ_UNANNOTATED;
+ ResolveOrRejectValue mValue;
+ bool mUseSynchronousTaskDispatch = false;
+ bool mUseDirectTaskDispatch = false;
+ uint32_t mPriority = nsIRunnablePriority::PRIORITY_NORMAL;
+# ifdef PROMISE_DEBUG
+ uint32_t mMagic1 = sMagic;
+# endif
+ // Try shows we never have more than 3 elements when IsExclusive is false.
+ // So '3' is a good value to avoid heap allocation in most cases.
+ AutoTArray<RefPtr<ThenValueBase>, IsExclusive ? 1 : 3> mThenValues;
+# ifdef PROMISE_DEBUG
+ uint32_t mMagic2 = sMagic;
+# endif
+ nsTArray<RefPtr<Private>> mChainedPromises;
+# ifdef PROMISE_DEBUG
+ uint32_t mMagic3 = sMagic;
+# endif
+ bool mHaveRequest;
+ const bool mIsCompletionPromise;
+# ifdef PROMISE_DEBUG
+ void* mMagic4;
+# endif
+};
+
+template <typename ResolveValueT, typename RejectValueT, bool IsExclusive>
+class MozPromise<ResolveValueT, RejectValueT, IsExclusive>::Private
+ : public MozPromise<ResolveValueT, RejectValueT, IsExclusive> {
+ public:
+ explicit Private(const char* aCreationSite, bool aIsCompletionPromise = false)
+ : MozPromise(aCreationSite, aIsCompletionPromise) {}
+
+ template <typename ResolveValueT_>
+ void Resolve(ResolveValueT_&& aResolveValue, const char* aResolveSite) {
+ PROMISE_ASSERT(mMagic1 == sMagic && mMagic2 == sMagic &&
+ mMagic3 == sMagic && mMagic4 == &mMutex);
+ MutexAutoLock lock(mMutex);
+ PROMISE_LOG("%s resolving MozPromise (%p created at %s)", aResolveSite,
+ this, mCreationSite);
+ if (!IsPending()) {
+ PROMISE_LOG(
+ "%s ignored already resolved or rejected MozPromise (%p created at "
+ "%s)",
+ aResolveSite, this, mCreationSite);
+ return;
+ }
+ mValue.SetResolve(std::forward<ResolveValueT_>(aResolveValue));
+ DispatchAll();
+ }
+
+ template <typename RejectValueT_>
+ void Reject(RejectValueT_&& aRejectValue, const char* aRejectSite) {
+ PROMISE_ASSERT(mMagic1 == sMagic && mMagic2 == sMagic &&
+ mMagic3 == sMagic && mMagic4 == &mMutex);
+ MutexAutoLock lock(mMutex);
+ PROMISE_LOG("%s rejecting MozPromise (%p created at %s)", aRejectSite, this,
+ mCreationSite);
+ if (!IsPending()) {
+ PROMISE_LOG(
+ "%s ignored already resolved or rejected MozPromise (%p created at "
+ "%s)",
+ aRejectSite, this, mCreationSite);
+ return;
+ }
+ mValue.SetReject(std::forward<RejectValueT_>(aRejectValue));
+ DispatchAll();
+ }
+
+ template <typename ResolveOrRejectValue_>
+ void ResolveOrReject(ResolveOrRejectValue_&& aValue, const char* aSite) {
+ PROMISE_ASSERT(mMagic1 == sMagic && mMagic2 == sMagic &&
+ mMagic3 == sMagic && mMagic4 == &mMutex);
+ MutexAutoLock lock(mMutex);
+ PROMISE_LOG("%s resolveOrRejecting MozPromise (%p created at %s)", aSite,
+ this, mCreationSite);
+ if (!IsPending()) {
+ PROMISE_LOG(
+ "%s ignored already resolved or rejected MozPromise (%p created at "
+ "%s)",
+ aSite, this, mCreationSite);
+ return;
+ }
+ mValue = std::forward<ResolveOrRejectValue_>(aValue);
+ DispatchAll();
+ }
+
+ // If the caller and target are both on the same thread, run the the resolve
+ // or reject callback synchronously. Otherwise, the task will be dispatched
+ // via the target Dispatch method.
+ void UseSynchronousTaskDispatch(const char* aSite) {
+ static_assert(
+ IsExclusive,
+ "Synchronous dispatch can only be used with exclusive promises");
+ PROMISE_ASSERT(mMagic1 == sMagic && mMagic2 == sMagic &&
+ mMagic3 == sMagic && mMagic4 == &mMutex);
+ MutexAutoLock lock(mMutex);
+ PROMISE_LOG("%s UseSynchronousTaskDispatch MozPromise (%p created at %s)",
+ aSite, this, mCreationSite);
+ MOZ_ASSERT(IsPending(),
+ "A Promise must not have been already resolved or rejected to "
+ "set dispatch state");
+ mUseSynchronousTaskDispatch = true;
+ }
+
+ // If the caller and target are both on the same thread, run the
+ // resolve/reject callback off the direct task queue instead. This avoids a
+ // full trip to the back of the event queue for each additional asynchronous
+ // step when using MozPromise, and is similar (but not identical to) the
+ // microtask semantics of JS promises.
+ void UseDirectTaskDispatch(const char* aSite) {
+ PROMISE_ASSERT(mMagic1 == sMagic && mMagic2 == sMagic &&
+ mMagic3 == sMagic && mMagic4 == &mMutex);
+ MutexAutoLock lock(mMutex);
+ PROMISE_LOG("%s UseDirectTaskDispatch MozPromise (%p created at %s)", aSite,
+ this, mCreationSite);
+ MOZ_ASSERT(IsPending(),
+ "A Promise must not have been already resolved or rejected to "
+ "set dispatch state");
+ MOZ_ASSERT(!mUseSynchronousTaskDispatch,
+ "Promise already set for synchronous dispatch");
+ mUseDirectTaskDispatch = true;
+ }
+
+ // If the resolve/reject will be handled on a thread supporting priorities,
+ // one may want to tweak the priority of the task by passing a
+ // nsIRunnablePriority::PRIORITY_* to SetTaskPriority.
+ void SetTaskPriority(uint32_t aPriority, const char* aSite) {
+ PROMISE_ASSERT(mMagic1 == sMagic && mMagic2 == sMagic &&
+ mMagic3 == sMagic && mMagic4 == &mMutex);
+ MutexAutoLock lock(mMutex);
+ PROMISE_LOG("%s TaskPriority MozPromise (%p created at %s)", aSite, this,
+ mCreationSite);
+ MOZ_ASSERT(IsPending(),
+ "A Promise must not have been already resolved or rejected to "
+ "set dispatch state");
+ MOZ_ASSERT(!mUseSynchronousTaskDispatch,
+ "Promise already set for synchronous dispatch");
+ MOZ_ASSERT(!mUseDirectTaskDispatch,
+ "Promise already set for direct dispatch");
+ mPriority = aPriority;
+ }
+};
+
+// A generic promise type that does the trick for simple use cases.
+typedef MozPromise<bool, nsresult, /* IsExclusive = */ true> GenericPromise;
+
+// A generic, non-exclusive promise type that does the trick for simple use
+// cases.
+typedef MozPromise<bool, nsresult, /* IsExclusive = */ false>
+ GenericNonExclusivePromise;
+
+/*
+ * Class to encapsulate a promise for a particular role. Use this as the member
+ * variable for a class whose method returns a promise.
+ */
+template <typename PromiseType, typename ImplType>
+class MozPromiseHolderBase {
+ public:
+ MozPromiseHolderBase() = default;
+
+ MozPromiseHolderBase(MozPromiseHolderBase&& aOther) = default;
+ MozPromiseHolderBase& operator=(MozPromiseHolderBase&& aOther) = default;
+
+ ~MozPromiseHolderBase() { MOZ_ASSERT(!mPromise); }
+
+ already_AddRefed<PromiseType> Ensure(const char* aMethodName) {
+ static_cast<ImplType*>(this)->Check();
+ if (!mPromise) {
+ mPromise = new (typename PromiseType::Private)(aMethodName);
+ }
+ RefPtr<PromiseType> p = mPromise.get();
+ return p.forget();
+ }
+
+ bool IsEmpty() const {
+ static_cast<const ImplType*>(this)->Check();
+ return !mPromise;
+ }
+
+ already_AddRefed<typename PromiseType::Private> Steal() {
+ static_cast<ImplType*>(this)->Check();
+ return mPromise.forget();
+ }
+
+ template <typename ResolveValueType_>
+ void Resolve(ResolveValueType_&& aResolveValue, const char* aMethodName) {
+ static_assert(std::is_convertible_v<ResolveValueType_,
+ typename PromiseType::ResolveValueType>,
+ "Resolve() argument must be implicitly convertible to "
+ "MozPromise's ResolveValueT");
+
+ static_cast<ImplType*>(this)->Check();
+ MOZ_ASSERT(mPromise);
+ mPromise->Resolve(std::forward<ResolveValueType_>(aResolveValue),
+ aMethodName);
+ mPromise = nullptr;
+ }
+
+ template <typename ResolveValueType_>
+ void ResolveIfExists(ResolveValueType_&& aResolveValue,
+ const char* aMethodName) {
+ if (!IsEmpty()) {
+ Resolve(std::forward<ResolveValueType_>(aResolveValue), aMethodName);
+ }
+ }
+
+ template <typename RejectValueType_>
+ void Reject(RejectValueType_&& aRejectValue, const char* aMethodName) {
+ static_assert(std::is_convertible_v<RejectValueType_,
+ typename PromiseType::RejectValueType>,
+ "Reject() argument must be implicitly convertible to "
+ "MozPromise's RejectValueT");
+
+ static_cast<ImplType*>(this)->Check();
+ MOZ_ASSERT(mPromise);
+ mPromise->Reject(std::forward<RejectValueType_>(aRejectValue), aMethodName);
+ mPromise = nullptr;
+ }
+
+ template <typename RejectValueType_>
+ void RejectIfExists(RejectValueType_&& aRejectValue,
+ const char* aMethodName) {
+ if (!IsEmpty()) {
+ Reject(std::forward<RejectValueType_>(aRejectValue), aMethodName);
+ }
+ }
+
+ template <typename ResolveOrRejectValueType_>
+ void ResolveOrReject(ResolveOrRejectValueType_&& aValue,
+ const char* aMethodName) {
+ static_cast<ImplType*>(this)->Check();
+ MOZ_ASSERT(mPromise);
+ mPromise->ResolveOrReject(std::forward<ResolveOrRejectValueType_>(aValue),
+ aMethodName);
+ mPromise = nullptr;
+ }
+
+ template <typename ResolveOrRejectValueType_>
+ void ResolveOrRejectIfExists(ResolveOrRejectValueType_&& aValue,
+ const char* aMethodName) {
+ if (!IsEmpty()) {
+ ResolveOrReject(std::forward<ResolveOrRejectValueType_>(aValue),
+ aMethodName);
+ }
+ }
+
+ void UseSynchronousTaskDispatch(const char* aSite) {
+ MOZ_ASSERT(mPromise);
+ mPromise->UseSynchronousTaskDispatch(aSite);
+ }
+
+ void UseDirectTaskDispatch(const char* aSite) {
+ MOZ_ASSERT(mPromise);
+ mPromise->UseDirectTaskDispatch(aSite);
+ }
+
+ void SetTaskPriority(uint32_t aPriority, const char* aSite) {
+ MOZ_ASSERT(mPromise);
+ mPromise->SetTaskPriority(aPriority, aSite);
+ }
+
+ private:
+ RefPtr<typename PromiseType::Private> mPromise;
+};
+
+template <typename PromiseType>
+class MozPromiseHolder
+ : public MozPromiseHolderBase<PromiseType, MozPromiseHolder<PromiseType>> {
+ public:
+ using MozPromiseHolderBase<
+ PromiseType, MozPromiseHolder<PromiseType>>::MozPromiseHolderBase;
+ static constexpr void Check(){};
+};
+
+template <typename PromiseType>
+class MozMonitoredPromiseHolder
+ : public MozPromiseHolderBase<PromiseType,
+ MozMonitoredPromiseHolder<PromiseType>> {
+ public:
+ // Provide a Monitor that should always be held when accessing this instance.
+ explicit MozMonitoredPromiseHolder(Monitor* const aMonitor)
+ : mMonitor(aMonitor) {
+ MOZ_ASSERT(aMonitor);
+ }
+
+ MozMonitoredPromiseHolder(MozMonitoredPromiseHolder&& aOther) = delete;
+ MozMonitoredPromiseHolder& operator=(MozMonitoredPromiseHolder&& aOther) =
+ delete;
+
+ void Check() const { mMonitor->AssertCurrentThreadOwns(); }
+
+ private:
+ Monitor* const mMonitor;
+};
+
+/*
+ * Class to encapsulate a MozPromise::Request reference. Use this as the member
+ * variable for a class waiting on a MozPromise.
+ */
+template <typename PromiseType>
+class MozPromiseRequestHolder {
+ public:
+ MozPromiseRequestHolder() = default;
+ ~MozPromiseRequestHolder() { MOZ_ASSERT(!mRequest); }
+
+ void Track(already_AddRefed<typename PromiseType::Request> aRequest) {
+ MOZ_DIAGNOSTIC_ASSERT(!Exists());
+ mRequest = aRequest;
+ }
+
+ void Complete() {
+ MOZ_DIAGNOSTIC_ASSERT(Exists());
+ mRequest = nullptr;
+ }
+
+ // Disconnects and forgets an outstanding promise. The resolve/reject methods
+ // will never be called.
+ void Disconnect() {
+ MOZ_ASSERT(Exists());
+ mRequest->Disconnect();
+ mRequest = nullptr;
+ }
+
+ void DisconnectIfExists() {
+ if (Exists()) {
+ Disconnect();
+ }
+ }
+
+ bool Exists() const { return !!mRequest; }
+
+ private:
+ RefPtr<typename PromiseType::Request> mRequest;
+};
+
+// Asynchronous Potentially-Cross-Thread Method Calls.
+//
+// This machinery allows callers to schedule a promise-returning function
+// (a method and object, or a function object like a lambda) to be invoked
+// asynchronously on a given thread, while at the same time receiving a
+// promise upon which to invoke Then() immediately. InvokeAsync dispatches a
+// task to invoke the function on the proper thread and also chain the
+// resulting promise to the one that the caller received, so that resolve/
+// reject values are forwarded through.
+
+namespace detail {
+
+// Non-templated base class to allow us to use MOZ_COUNT_{C,D}TOR, which cause
+// assertions when used on templated types.
+class MethodCallBase {
+ public:
+ MOZ_COUNTED_DEFAULT_CTOR(MethodCallBase)
+ MOZ_COUNTED_DTOR_VIRTUAL(MethodCallBase)
+};
+
+template <typename PromiseType, typename MethodType, typename ThisType,
+ typename... Storages>
+class MethodCall : public MethodCallBase {
+ public:
+ template <typename... Args>
+ MethodCall(MethodType aMethod, ThisType* aThisVal, Args&&... aArgs)
+ : mMethod(aMethod),
+ mThisVal(aThisVal),
+ mArgs(std::forward<Args>(aArgs)...) {
+ static_assert(sizeof...(Storages) == sizeof...(Args),
+ "Storages and Args should have equal sizes");
+ }
+
+ RefPtr<PromiseType> Invoke() { return mArgs.apply(mThisVal.get(), mMethod); }
+
+ private:
+ MethodType mMethod;
+ RefPtr<ThisType> mThisVal;
+ RunnableMethodArguments<Storages...> mArgs;
+};
+
+template <typename PromiseType, typename MethodType, typename ThisType,
+ typename... Storages>
+class ProxyRunnable : public CancelableRunnable {
+ public:
+ ProxyRunnable(
+ typename PromiseType::Private* aProxyPromise,
+ MethodCall<PromiseType, MethodType, ThisType, Storages...>* aMethodCall)
+ : CancelableRunnable("detail::ProxyRunnable"),
+ mProxyPromise(aProxyPromise),
+ mMethodCall(aMethodCall) {}
+
+ NS_IMETHOD Run() override {
+ RefPtr<PromiseType> p = mMethodCall->Invoke();
+ mMethodCall = nullptr;
+ p->ChainTo(mProxyPromise.forget(), "<Proxy Promise>");
+ return NS_OK;
+ }
+
+ nsresult Cancel() override { return Run(); }
+
+ private:
+ RefPtr<typename PromiseType::Private> mProxyPromise;
+ UniquePtr<MethodCall<PromiseType, MethodType, ThisType, Storages...>>
+ mMethodCall;
+};
+
+template <typename... Storages, typename PromiseType, typename ThisType,
+ typename... ArgTypes, typename... ActualArgTypes>
+static RefPtr<PromiseType> InvokeAsyncImpl(
+ nsISerialEventTarget* aTarget, ThisType* aThisVal, const char* aCallerName,
+ RefPtr<PromiseType> (ThisType::*aMethod)(ArgTypes...),
+ ActualArgTypes&&... aArgs) {
+ MOZ_ASSERT(aTarget);
+
+ typedef RefPtr<PromiseType> (ThisType::*MethodType)(ArgTypes...);
+ typedef detail::MethodCall<PromiseType, MethodType, ThisType, Storages...>
+ MethodCallType;
+ typedef detail::ProxyRunnable<PromiseType, MethodType, ThisType, Storages...>
+ ProxyRunnableType;
+
+ MethodCallType* methodCall = new MethodCallType(
+ aMethod, aThisVal, std::forward<ActualArgTypes>(aArgs)...);
+ RefPtr<typename PromiseType::Private> p =
+ new (typename PromiseType::Private)(aCallerName);
+ RefPtr<ProxyRunnableType> r = new ProxyRunnableType(p, methodCall);
+ aTarget->Dispatch(r.forget());
+ return p;
+}
+
+constexpr bool Any() { return false; }
+
+template <typename T1>
+constexpr bool Any(T1 a) {
+ return static_cast<bool>(a);
+}
+
+template <typename T1, typename... Ts>
+constexpr bool Any(T1 a, Ts... aOthers) {
+ return a || Any(aOthers...);
+}
+
+} // namespace detail
+
+// InvokeAsync with explicitly-specified storages.
+// See ParameterStorage in nsThreadUtils.h for help.
+template <typename... Storages, typename PromiseType, typename ThisType,
+ typename... ArgTypes, typename... ActualArgTypes,
+ std::enable_if_t<sizeof...(Storages) != 0, int> = 0>
+static RefPtr<PromiseType> InvokeAsync(
+ nsISerialEventTarget* aTarget, ThisType* aThisVal, const char* aCallerName,
+ RefPtr<PromiseType> (ThisType::*aMethod)(ArgTypes...),
+ ActualArgTypes&&... aArgs) {
+ static_assert(
+ sizeof...(Storages) == sizeof...(ArgTypes),
+ "Provided Storages and method's ArgTypes should have equal sizes");
+ static_assert(sizeof...(Storages) == sizeof...(ActualArgTypes),
+ "Provided Storages and ActualArgTypes should have equal sizes");
+ return detail::InvokeAsyncImpl<Storages...>(
+ aTarget, aThisVal, aCallerName, aMethod,
+ std::forward<ActualArgTypes>(aArgs)...);
+}
+
+// InvokeAsync with no explicitly-specified storages, will copy arguments and
+// then move them out of the runnable into the target method parameters.
+template <typename... Storages, typename PromiseType, typename ThisType,
+ typename... ArgTypes, typename... ActualArgTypes,
+ std::enable_if_t<sizeof...(Storages) == 0, int> = 0>
+static RefPtr<PromiseType> InvokeAsync(
+ nsISerialEventTarget* aTarget, ThisType* aThisVal, const char* aCallerName,
+ RefPtr<PromiseType> (ThisType::*aMethod)(ArgTypes...),
+ ActualArgTypes&&... aArgs) {
+ static_assert(
+ !detail::Any(
+ std::is_pointer_v<std::remove_reference_t<ActualArgTypes>>...),
+ "Cannot pass pointer types through InvokeAsync, Storages must be "
+ "provided");
+ static_assert(sizeof...(ArgTypes) == sizeof...(ActualArgTypes),
+ "Method's ArgTypes and ActualArgTypes should have equal sizes");
+ return detail::InvokeAsyncImpl<
+ StoreCopyPassByRRef<std::decay_t<ActualArgTypes>>...>(
+ aTarget, aThisVal, aCallerName, aMethod,
+ std::forward<ActualArgTypes>(aArgs)...);
+}
+
+namespace detail {
+
+template <typename Function, typename PromiseType>
+class ProxyFunctionRunnable : public CancelableRunnable {
+ using FunctionStorage = std::decay_t<Function>;
+
+ public:
+ template <typename F>
+ ProxyFunctionRunnable(typename PromiseType::Private* aProxyPromise,
+ F&& aFunction)
+ : CancelableRunnable("detail::ProxyFunctionRunnable"),
+ mProxyPromise(aProxyPromise),
+ mFunction(new FunctionStorage(std::forward<F>(aFunction))) {}
+
+ NS_IMETHOD Run() override {
+ RefPtr<PromiseType> p = (*mFunction)();
+ mFunction = nullptr;
+ p->ChainTo(mProxyPromise.forget(), "<Proxy Promise>");
+ return NS_OK;
+ }
+
+ nsresult Cancel() override { return Run(); }
+
+ private:
+ RefPtr<typename PromiseType::Private> mProxyPromise;
+ UniquePtr<FunctionStorage> mFunction;
+};
+
+// Note: The following struct and function are not for public consumption (yet?)
+// as we would prefer all calls to pass on-the-spot lambdas (or at least moved
+// function objects). They could be moved outside of detail if really needed.
+
+// We prefer getting function objects by non-lvalue-ref (to avoid copying them
+// and their captures). This struct is a tag that allows the use of objects
+// through lvalue-refs where necessary.
+struct AllowInvokeAsyncFunctionLVRef {};
+
+// Invoke a function object (e.g., lambda or std/mozilla::function)
+// asynchronously; note that the object will be copied if provided by
+// lvalue-ref. Return a promise that the function should eventually resolve or
+// reject.
+template <typename Function>
+static auto InvokeAsync(nsISerialEventTarget* aTarget, const char* aCallerName,
+ AllowInvokeAsyncFunctionLVRef, Function&& aFunction)
+ -> decltype(aFunction()) {
+ static_assert(
+ IsRefcountedSmartPointer<decltype(aFunction())>::value &&
+ IsMozPromise<
+ typename RemoveSmartPointer<decltype(aFunction())>::Type>::value,
+ "Function object must return RefPtr<MozPromise>");
+ MOZ_ASSERT(aTarget);
+ typedef typename RemoveSmartPointer<decltype(aFunction())>::Type PromiseType;
+ typedef detail::ProxyFunctionRunnable<Function, PromiseType>
+ ProxyRunnableType;
+
+ auto p = MakeRefPtr<typename PromiseType::Private>(aCallerName);
+ auto r = MakeRefPtr<ProxyRunnableType>(p, std::forward<Function>(aFunction));
+ aTarget->Dispatch(r.forget());
+ return p;
+}
+
+} // namespace detail
+
+// Invoke a function object (e.g., lambda) asynchronously.
+// Return a promise that the function should eventually resolve or reject.
+template <typename Function>
+static auto InvokeAsync(nsISerialEventTarget* aTarget, const char* aCallerName,
+ Function&& aFunction) -> decltype(aFunction()) {
+ static_assert(!std::is_lvalue_reference_v<Function>,
+ "Function object must not be passed by lvalue-ref (to avoid "
+ "unplanned copies); Consider move()ing the object.");
+ return detail::InvokeAsync(aTarget, aCallerName,
+ detail::AllowInvokeAsyncFunctionLVRef(),
+ std::forward<Function>(aFunction));
+}
+
+# undef PROMISE_LOG
+# undef PROMISE_ASSERT
+# undef PROMISE_DEBUG
+
+} // namespace mozilla
+
+#endif