1 #pragma once
2 
3 #include <memory>
4 
5 namespace mbgl {
6 
7 class Mailbox;
8 
9 /*
10     A `Scheduler` is responsible for coordinating the processing of messages by
11     one or more actors via their mailboxes. It's an abstract interface. Currently,
12     the following concrete implementations exist:
13 
14     * `ThreadPool` can coordinate an unlimited number of actors over any number of
15       threads via a pool, preserving the following behaviors:
16 
17       - Messages from each individual mailbox are processed in order
18       - Only a single message from a mailbox is processed at a time; there is no
19         concurrency within a mailbox
20 
21       Subject to these constraints, processing can happen on whatever thread in the
22       pool is available.
23 
24     * `Scheduler::GetCurrent()` is typically used to create a mailbox and `ActorRef`
25       for an object that lives on the main thread and is not itself wrapped an
26       `Actor`. The underlying implementation of this Scheduler should usually be
27       a `RunLoop`
28         auto mailbox = std::make_shared<Mailbox>(*Scheduler::Get());
29         Actor<Worker> worker(threadPool, ActorRef<Foo>(*this, mailbox));
30 */
31 class Scheduler {
32 public:
33     virtual ~Scheduler() = default;
34 
35     // Used by a Mailbox when it has a message in its queue to request that it
36     // be scheduled. Specifically, the scheduler is expected to asynchronously
37     // call `receive() on the given mailbox, provided it still exists at that
38     // time.
39     virtual void schedule(std::weak_ptr<Mailbox>) = 0;
40 
41     // Set/Get the current Scheduler for this thread
42     static Scheduler* GetCurrent();
43     static void SetCurrent(Scheduler*);
44 };
45 
46 } // namespace mbgl
47