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Implementation

Mercurial (d38398e5144e)

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PromiseObject

PromiseSlots

PromiseTask

Macros

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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
 * vim: set ts=8 sts=4 et sw=4 tw=99:
 * 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/. */

#ifndef builtin_Promise_h
#define builtin_Promise_h

#include "builtin/SelfHostingDefines.h"
#include "vm/NativeObject.h"

namespace js {

enum PromiseSlots {
    PromiseSlot_Flags = 0,
    PromiseSlot_ReactionsOrResult,
    PromiseSlot_RejectFunction,
    PromiseSlot_AwaitGenerator = PromiseSlot_RejectFunction,
    PromiseSlot_AllocationSite,
    PromiseSlot_ResolutionSite,
    PromiseSlot_AllocationTime,
    PromiseSlot_ResolutionTime,
    PromiseSlot_Id,
    PromiseSlots,
};

#define PROMISE_FLAG_RESOLVED  0x1
#define PROMISE_FLAG_FULFILLED 0x2
#define PROMISE_FLAG_HANDLED   0x4
#define PROMISE_FLAG_REPORTED  0x8
#define PROMISE_FLAG_DEFAULT_RESOLVE_FUNCTION 0x10
#define PROMISE_FLAG_DEFAULT_REJECT_FUNCTION  0x20
#define PROMISE_FLAG_ASYNC    0x40

class AutoSetNewObjectMetadata;

class PromiseObject : public NativeObject
{
  public:
    static const unsigned RESERVED_SLOTS = PromiseSlots;
    static const Class class_;
    static const Class protoClass_;
    static PromiseObject* create(JSContext* cx, HandleObject executor,
                                 HandleObject proto = nullptr, bool needsWrapping = false);

    static PromiseObject* createSkippingExecutor(JSContext* cx);

    static JSObject* unforgeableResolve(JSContext* cx, HandleValue value);
    static JSObject* unforgeableReject(JSContext* cx, HandleValue value);

    JS::PromiseState state() {
        int32_t flags = getFixedSlot(PromiseSlot_Flags).toInt32();
        if (!(flags & PROMISE_FLAG_RESOLVED)) {
            MOZ_ASSERT(!(flags & PROMISE_FLAG_FULFILLED));
            return JS::PromiseState::Pending;
        }
        if (flags & PROMISE_FLAG_FULFILLED)
            return JS::PromiseState::Fulfilled;
        return JS::PromiseState::Rejected;
    }
    Value value()  {
        MOZ_ASSERT(state() == JS::PromiseState::Fulfilled);
        return getFixedSlot(PromiseSlot_ReactionsOrResult);
    }
    Value reason() {
        MOZ_ASSERT(state() == JS::PromiseState::Rejected);
        return getFixedSlot(PromiseSlot_ReactionsOrResult);
    }

    static MOZ_MUST_USE bool resolve(JSContext* cx, Handle<PromiseObject*> promise,
                                     HandleValue resolutionValue);
    static MOZ_MUST_USE bool reject(JSContext* cx, Handle<PromiseObject*> promise,
                                    HandleValue rejectionValue);

    static void onSettled(JSContext* cx, Handle<PromiseObject*> promise);

    double allocationTime() { return getFixedSlot(PromiseSlot_AllocationTime).toNumber(); }
    double resolutionTime() { return getFixedSlot(PromiseSlot_ResolutionTime).toNumber(); }
    JSObject* allocationSite() {
        return getFixedSlot(PromiseSlot_AllocationSite).toObjectOrNull();
    }
    JSObject* resolutionSite() {
        return getFixedSlot(PromiseSlot_ResolutionSite).toObjectOrNull();
    }
    double lifetime();
    double timeToResolution() {
        MOZ_ASSERT(state() != JS::PromiseState::Pending);
        return resolutionTime() - allocationTime();
    }
    MOZ_MUST_USE bool dependentPromises(JSContext* cx, MutableHandle<GCVector<Value>> values);
    uint64_t getID();
    bool isUnhandled() {
        MOZ_ASSERT(state() == JS::PromiseState::Rejected);
        return !(getFixedSlot(PromiseSlot_Flags).toInt32() & PROMISE_FLAG_HANDLED);
    }
    void markAsReported() {
        MOZ_ASSERT(isUnhandled());
        int32_t flags = getFixedSlot(PromiseSlot_Flags).toInt32();
        setFixedSlot(PromiseSlot_Flags, Int32Value(flags | PROMISE_FLAG_REPORTED));
    }
};

/**
 * Enqueues resolve/reject reactions in the given Promise's reactions lists
 * in a content-invisible way.
 *
 * Used internally to implement DOM functionality.
 *
 * Note: the reactions pushed using this function contain a `promise` field
 * that can contain null. That field is only ever used by devtools, which have
 * to treat these reactions specially.
 */
MOZ_MUST_USE bool
EnqueuePromiseReactions(JSContext* cx, Handle<PromiseObject*> promise,
                        HandleObject dependentPromise,
                        HandleValue onFulfilled, HandleValue onRejected);

MOZ_MUST_USE JSObject*
GetWaitForAllPromise(JSContext* cx, const JS::AutoObjectVector& promises);

MOZ_MUST_USE JSObject*
OriginalPromiseThen(JSContext* cx, Handle<PromiseObject*> promise, HandleValue onFulfilled,
                    HandleValue onRejected);

MOZ_MUST_USE PromiseObject*
CreatePromiseObjectForAsync(JSContext* cx, HandleValue generatorVal);

MOZ_MUST_USE bool
AsyncFunctionReturned(JSContext* cx, Handle<PromiseObject*> resultPromise, HandleValue value);

MOZ_MUST_USE bool
AsyncFunctionThrown(JSContext* cx, Handle<PromiseObject*> resultPromise);

MOZ_MUST_USE bool
AsyncFunctionAwait(JSContext* cx, Handle<PromiseObject*> resultPromise, HandleValue value);

/**
 * A PromiseTask represents a task that can be dispatched to a helper thread
 * (via StartPromiseTask), executed (by implementing PromiseTask::execute()),
 * and then resolved back on the original JSContext owner thread.
 * Because it contains a PersistentRooted, a PromiseTask will only be destroyed
 * on the JSContext's owner thread.
 */
class PromiseTask : public JS::AsyncTask
{
    JSRuntime* runtime_;
    PersistentRooted<PromiseObject*> promise_;

    // PromiseTask implements JS::AsyncTask and prevents derived classes from
    // overriding; derived classes should implement the new pure virtual
    // functions introduced below. Both of these methods 'delete this'.
    void finish(JSContext* cx) override final;
    void cancel(JSContext* cx) override final;

  protected:
    // Called by PromiseTask on the JSContext's owner thread after execute()
    // completes on the helper thread, assuming JS::FinishAsyncTaskCallback
    // succeeds. After this method returns, the task will be deleted.
    virtual bool finishPromise(JSContext* cx, Handle<PromiseObject*> promise) = 0;

  public:
    PromiseTask(JSContext* cx, Handle<PromiseObject*> promise);
    ~PromiseTask();
    JSRuntime* runtime() const { return runtime_; }

    // Called on a helper thread after StartAsyncTask. After execute()
    // completes, the JS::FinishAsyncTaskCallback will be called. If this fails
    // the task will be enqueued for deletion at some future point without ever
    // calling finishPromise().
    virtual void execute() = 0;

    // May be called in the absence of helper threads to synchronously execute
    // and finish a PromiseTask.
    bool executeAndFinish(JSContext* cx);
};

bool
Promise_static_resolve(JSContext* cx, unsigned argc, Value* vp);
bool
Promise_reject(JSContext* cx, unsigned argc, Value* vp);
bool
Promise_then(JSContext* cx, unsigned argc, Value* vp);

} // namespace js

#endif /* builtin_Promise_h */