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-rw-r--r--include/mbgl/util/work_task_impl.hpp92
1 files changed, 92 insertions, 0 deletions
diff --git a/include/mbgl/util/work_task_impl.hpp b/include/mbgl/util/work_task_impl.hpp
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+++ b/include/mbgl/util/work_task_impl.hpp
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+#pragma once
+
+#include <mbgl/util/work_task.hpp>
+#include <mbgl/util/run_loop.hpp>
+
+#include <mutex>
+
+namespace mbgl {
+
+template <class F, class P>
+class WorkTaskImpl : public WorkTask {
+public:
+ WorkTaskImpl(F&& f, P&& p, std::shared_ptr<std::atomic<bool>> canceled_)
+ : canceled(std::move(canceled_)),
+ func(std::move(f)),
+ params(std::move(p)) {
+ }
+
+ void operator()() override {
+ // Lock the mutex while processing so that cancel() will block.
+ std::lock_guard<std::recursive_mutex> lock(mutex);
+ if (!*canceled) {
+ invoke(std::make_index_sequence<std::tuple_size<P>::value>{});
+ }
+ }
+
+ // If the task has not yet begun, this will cancel it.
+ // If the task is in progress, this will block until it completed. (Currently
+ // necessary because of shared state, but should be removed.) It will also
+ // cancel the after callback.
+ // If the task has completed, but the after callback has not executed, this
+ // will cancel the after callback.
+ // If the task has completed and the after callback has executed, this will
+ // do nothing.
+ void cancel() override {
+ std::lock_guard<std::recursive_mutex> lock(mutex);
+ *canceled = true;
+ }
+
+private:
+ template <std::size_t... I>
+ void invoke(std::index_sequence<I...>) {
+ func(std::move(std::get<I>(std::forward<P>(params)))...);
+ }
+
+ std::recursive_mutex mutex;
+ std::shared_ptr<std::atomic<bool>> canceled;
+
+ F func;
+ P params;
+};
+
+template <class Fn, class... Args>
+std::shared_ptr<WorkTask> WorkTask::make(Fn&& fn, Args&&... args) {
+ auto flag = std::make_shared<std::atomic<bool>>();
+ *flag = false;
+
+ auto tuple = std::make_tuple(std::move(args)...);
+ return std::make_shared<WorkTaskImpl<Fn, decltype(tuple)>>(
+ std::move(fn),
+ std::move(tuple),
+ flag);
+}
+
+template <class Fn, class Cb, class... Args>
+std::shared_ptr<WorkTask> WorkTask::makeWithCallback(Fn&& fn, Cb&& callback, Args&&... args) {
+ auto flag = std::make_shared<std::atomic<bool>>();
+ *flag = false;
+
+ // Create a lambda L1 that invokes another lambda L2 on the current RunLoop R, that calls
+ // the callback C. Both lambdas check the flag before proceeding. L1 needs to check the flag
+ // because if the request was cancelled, then R might have been destroyed. L2 needs to check
+ // the flag because the request may have been cancelled after L2 was invoked but before it
+ // began executing.
+ auto after = [flag, current = util::RunLoop::Get(), callback1 = std::move(callback)] (auto&&... results1) {
+ if (!*flag) {
+ current->invoke([flag, callback2 = std::move(callback1)] (auto&&... results2) {
+ if (!*flag) {
+ callback2(std::move(results2)...);
+ }
+ }, std::move(results1)...);
+ }
+ };
+
+ auto tuple = std::make_tuple(std::move(args)..., after);
+ return std::make_shared<WorkTaskImpl<Fn, decltype(tuple)>>(
+ std::move(fn),
+ std::move(tuple),
+ flag);
+}
+
+} // namespace mbgl