\u8fd9\u4e2a\u4f8b\u5b50\u4f4d\u4e8easio\u7684examples\\cpp14\\excutors\\priority_scheduler.cpp<\/p>\n
<\/p>\n
#include <asio\/ts\/executor.hpp>\r\n#include <condition_variable>\r\n#include <iostream>\r\n#include <memory>\r\n#include <mutex>\r\n#include <queue>\r\n\r\nusing asio::dispatch;\r\nusing asio::execution_context;\r\n\r\nclass priority_scheduler : public execution_context\r\n{\r\npublic:\r\n \/\/ A class that satisfies the Executor requirements.\r\n class executor_type\r\n {\r\n public:\r\n executor_type(priority_scheduler& ctx, int pri) noexcept\r\n : context_(ctx), priority_(pri)\r\n {\r\n }\r\n\r\n priority_scheduler& context() const noexcept\r\n {\r\n return context_;\r\n }\r\n\r\n void on_work_started() const noexcept\r\n {\r\n \/\/ This executor doesn't count work. Instead, the scheduler simply runs\r\n \/\/ until explicitly stopped.\r\n }\r\n\r\n void on_work_finished() const noexcept\r\n {\r\n \/\/ This executor doesn't count work. Instead, the scheduler simply runs\r\n \/\/ until explicitly stopped.\r\n }\r\n\r\n template <class Func, class Alloc>\r\n void dispatch(Func&& f, const Alloc& a) const\r\n {\r\n post(std::forward<Func>(f), a);\r\n }\r\n\r\n template <class Func, class Alloc>\r\n void post(Func f, const Alloc& a) const\r\n {\r\n auto p(std::allocate_shared<item<Func>>(\r\n typename std::allocator_traits<\r\n Alloc>::template rebind_alloc<char>(a),\r\n priority_, std::move(f)));\r\n std::lock_guard<std::mutex> lock(context_.mutex_);\r\n context_.queue_.push(p);\r\n context_.condition_.notify_one();\r\n }\r\n\r\n template <class Func, class Alloc>\r\n void defer(Func&& f, const Alloc& a) const\r\n {\r\n post(std::forward<Func>(f), a);\r\n }\r\n\r\n friend bool operator==(const executor_type& a,\r\n const executor_type& b) noexcept\r\n {\r\n return &a.context_ == &b.context_;\r\n }\r\n\r\n friend bool operator!=(const executor_type& a,\r\n const executor_type& b) noexcept\r\n {\r\n return &a.context_ != &b.context_;\r\n }\r\n\r\n private:\r\n priority_scheduler& context_;\r\n int priority_;\r\n };\r\n\r\n executor_type get_executor(int pri = 0) noexcept\r\n {\r\n return executor_type(*const_cast<priority_scheduler*>(this), pri);\r\n }\r\n\r\n void run()\r\n {\r\n std::unique_lock<std::mutex> lock(mutex_);\r\n for (;;)\r\n {\r\n condition_.wait(lock, [&]{ return stopped_ || !queue_.empty(); });\r\n if (stopped_)\r\n return;\r\n auto p(queue_.top());\r\n queue_.pop();\r\n lock.unlock();\r\n p->execute_(p);\r\n lock.lock();\r\n }\r\n }\r\n\r\n void stop()\r\n {\r\n std::lock_guard<std::mutex> lock(mutex_);\r\n stopped_ = true;\r\n condition_.notify_all();\r\n }\r\n\r\nprivate:\r\n struct item_base\r\n {\r\n int priority_;\r\n void (*execute_)(std::shared_ptr<item_base>&);\r\n };\r\n\r\n template <class Func>\r\n struct item : item_base\r\n {\r\n item(int pri, Func f) : function_(std::move(f))\r\n {\r\n priority_ = pri;\r\n execute_ = [](std::shared_ptr<item_base>& p)\r\n {\r\n Func tmp(std::move(static_cast<item*>(p.get())->function_));\r\n p.reset();\r\n tmp();\r\n };\r\n }\r\n\r\n Func function_;\r\n };\r\n\r\n struct item_comp\r\n {\r\n bool operator()(\r\n const std::shared_ptr<item_base>& a,\r\n const std::shared_ptr<item_base>& b)\r\n {\r\n return a->priority_ < b->priority_;\r\n }\r\n };\r\n\r\n std::mutex mutex_;\r\n std::condition_variable condition_;\r\n std::priority_queue<\r\n std::shared_ptr<item_base>,\r\n std::vector<std::shared_ptr<item_base>>,\r\n item_comp> queue_;\r\n bool stopped_ = false;\r\n};\r\n\r\nint main()\r\n{\r\n priority_scheduler sched;\r\n auto low = sched.get_executor(0);\r\n auto med = sched.get_executor(1);\r\n auto high = sched.get_executor(2);\r\n dispatch(low, []{ std::cout << \"1\\n\"; });\r\n dispatch(low, []{ std::cout << \"11\\n\"; });\r\n dispatch(med, []{ std::cout << \"2\\n\"; });\r\n dispatch(med, []{ std::cout << \"22\\n\"; });\r\n dispatch(high, []{ std::cout << \"3\\n\"; });\r\n dispatch(high, []{ std::cout << \"33\\n\"; });\r\n dispatch(high, []{ std::cout << \"333\\n\"; });\r\n dispatch(sched.get_executor(-1), [&]{ sched.stop(); });\r\n sched.run();\r\n}\r\n<\/pre>\n <\/p>\n","protected":false},"excerpt":{"rendered":"
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