106 lines
3.9 KiB
C++
106 lines
3.9 KiB
C++
#pragma once
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#include <mbgl/util/pass_types.hpp>
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#include <mapbox/std/weak.hpp>
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#include <functional>
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#include <memory>
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namespace mbgl {
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class Mailbox;
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/*
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A `Scheduler` is responsible for coordinating the processing of messages by
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one or more actors via their mailboxes. It's an abstract interface. Currently,
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the following concrete implementations exist:
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* `ThreadPool` can coordinate an unlimited number of actors over any number of
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threads via a pool, preserving the following behaviors:
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- Messages from each individual mailbox are processed in order
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- Only a single message from a mailbox is processed at a time; there is no
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concurrency within a mailbox
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Subject to these constraints, processing can happen on whatever thread in the
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pool is available.
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* `Scheduler::GetCurrent()` is typically used to create a mailbox and `ActorRef`
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for an object that lives on the main thread and is not itself wrapped an
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`Actor`. The underlying implementation of this Scheduler should usually be
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a `RunLoop`
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auto mailbox = std::make_shared<Mailbox>(*Scheduler::Get());
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Actor<Worker> worker(threadPool, ActorRef<Foo>(*this, mailbox));
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*/
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class Scheduler {
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public:
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virtual ~Scheduler() = default;
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// Enqueues a function for execution.
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virtual void schedule(std::function<void()>) = 0;
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// Makes a weak pointer to this Scheduler.
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virtual mapbox::base::WeakPtr<Scheduler> makeWeakPtr() = 0;
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// Returns a closure wrapping the given one.
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//
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// When the returned closure is invoked for the first time, it schedules
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// the given closure to this scheduler, the consequent calls of the
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// returned closure are ignored.
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//
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// If this scheduler is already deleted by the time the returnded closure is
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// first invoked, the call is ignored.
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std::function<void()> bindOnce(std::function<void()>);
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// Enqueues the given |task| for execution into this scheduler's task queue and
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// then enqueues the |reply| with the captured task result to the current
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// task queue.
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//
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// The |TaskFn| return type must be compatible with the |ReplyFn| argument type.
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// Note: the task result is copied and passed by value.
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template <typename TaskFn, typename ReplyFn>
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void scheduleAndReplyValue(const TaskFn& task, const ReplyFn& reply) {
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assert(GetCurrent());
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scheduleAndReplyValue(task, reply, GetCurrent()->makeWeakPtr());
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}
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// Set/Get the current Scheduler for this thread
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static Scheduler* GetCurrent();
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static void SetCurrent(Scheduler*);
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// Get the scheduler for asynchronous tasks. This method
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// will lazily initialize a shared worker pool when ran
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// from the first time.
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// The scheduled tasks might run in parallel on different
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// threads.
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// TODO : Rename to GetPool()
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static PassRefPtr<Scheduler> GetBackground();
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// Get the *sequenced* scheduler for asynchronous tasks.
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// Unlike the method above, the returned scheduler
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// (once stored) represents a single thread, thus each
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// newly scheduled task is guarantied to run after the
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// previously scheduled one.
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//
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// Sequenced scheduler can be used for running tasks
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// on the same thread-unsafe object.
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static PassRefPtr<Scheduler> GetSequenced();
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protected:
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template <typename TaskFn, typename ReplyFn>
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void scheduleAndReplyValue(const TaskFn& task,
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const ReplyFn& reply,
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mapbox::base::WeakPtr<Scheduler> replyScheduler) {
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auto scheduled = [replyScheduler, task, reply] {
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auto lock = replyScheduler.lock();
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if (!replyScheduler) return;
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auto scheduledReply = [reply, result = task()] { reply(result); };
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replyScheduler->schedule(std::move(scheduledReply));
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};
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schedule(std::move(scheduled));
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}
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};
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} // namespace mbgl
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