106 lines
2.8 KiB
C++
106 lines
2.8 KiB
C++
#include <mbgl/actor/mailbox.hpp>
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#include <mbgl/actor/message.hpp>
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#include <mbgl/actor/scheduler.hpp>
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#include <cassert>
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namespace mbgl {
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Mailbox::Mailbox() = default;
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Mailbox::Mailbox(Scheduler& scheduler_) : weakScheduler(scheduler_.makeWeakPtr()) {}
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void Mailbox::open(Scheduler& scheduler_) {
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assert(!weakScheduler);
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// As with close(), block until neither receive() nor push() are in progress, and acquire the two
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// mutexes in the same order.
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std::lock_guard<std::recursive_mutex> receivingLock(receivingMutex);
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std::lock_guard<std::mutex> pushingLock(pushingMutex);
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weakScheduler = scheduler_.makeWeakPtr();
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if (closed) {
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return;
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}
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if (!queue.empty()) {
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auto guard = weakScheduler.lock();
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if (weakScheduler) weakScheduler->schedule(makeClosure(shared_from_this()));
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}
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}
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void Mailbox::close() {
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// Block until neither receive() nor push() are in progress. Two mutexes are used because receive()
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// must not block send(). Of the two, the receiving mutex must be acquired first, because that is
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// the order that an actor will obtain them when it self-sends a message, and consistent lock
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// acquisition order prevents deadlocks.
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// The receiving mutex is recursive to allow a mailbox (and thus the actor) to close itself.
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std::lock_guard<std::recursive_mutex> receivingLock(receivingMutex);
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std::lock_guard<std::mutex> pushingLock(pushingMutex);
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closed = true;
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}
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bool Mailbox::isOpen() const {
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return bool(weakScheduler);
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}
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void Mailbox::push(std::unique_ptr<Message> message) {
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std::lock_guard<std::mutex> pushingLock(pushingMutex);
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if (closed) {
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return;
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}
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std::lock_guard<std::mutex> queueLock(queueMutex);
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bool wasEmpty = queue.empty();
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queue.push(std::move(message));
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auto guard = weakScheduler.lock();
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if (wasEmpty && weakScheduler) {
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weakScheduler->schedule(makeClosure(shared_from_this()));
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}
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}
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void Mailbox::receive() {
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std::lock_guard<std::recursive_mutex> receivingLock(receivingMutex);
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auto guard = weakScheduler.lock();
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assert(weakScheduler);
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if (closed) {
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return;
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}
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std::unique_ptr<Message> message;
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bool wasEmpty;
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{
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std::lock_guard<std::mutex> queueLock(queueMutex);
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assert(!queue.empty());
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message = std::move(queue.front());
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queue.pop();
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wasEmpty = queue.empty();
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}
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(*message)();
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if (!wasEmpty) {
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weakScheduler->schedule(makeClosure(shared_from_this()));
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}
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}
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// static
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void Mailbox::maybeReceive(std::weak_ptr<Mailbox> mailbox) {
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if (auto locked = mailbox.lock()) {
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locked->receive();
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}
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}
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// static
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std::function<void()> Mailbox::makeClosure(std::weak_ptr<Mailbox> mailbox) {
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return [mailbox]() { maybeReceive(mailbox); };
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}
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} // namespace mbgl
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