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我想在同一时间使用Boost.Asio的链和优先包装。如何结合束包装和优先包装Boost Asio
之前，我写我的代码，我已经阅读了以下信息：
Boost asio priority and strand
http://thread.gmane.org/gmane.comp.lib.boost.asio.user/3531
Why do I need strand per connection when using boost::asio?
我想使用的包装方法，因为我想使用各种异步API，如async_read，a sync_write和async_connect。 根据http://thread.gmane.org/gmane.comp.lib.boost.asio.user/3531，似乎可以合并优先包装和链包装。
所以我写了基于下面的示例代码：
这里是我的代码：
#include <iostream>
#include <functional>
#include <queue>
#include <vector>
#include <thread>
#include <mutex>
#include <boost/asio.hpp>
#include <boost/optional.hpp>
#define ENABLE_STRAND 1
#define ENABLE_PRIORITY 1
class handler_priority_queue {
public:
template <typename Handler>
void add(int priority, Handler&& handler) {
std::cout << "add(" << priority << ")" << std::endl;
std::lock_guard<std::mutex> g(mtx_);
handlers_.emplace(priority, std::forward<Handler>(handler));
}
void execute_all() {
auto top = [&]() -> boost::optional<queued_handler> {
std::lock_guard<std::mutex> g(mtx_);
if (handlers_.empty()) return boost::none;
boost::optional<queued_handler> opt = handlers_.top();
handlers_.pop();
return opt;
};
while (auto h_opt = top()) {
h_opt.get().execute();
}
}
template <typename Handler>
class wrapped_handler {
public:
wrapped_handler(handler_priority_queue& q, int p, Handler h)
: queue_(q), priority_(p), handler_(std::move(h))
{
}
template <typename... Args>
void operator()(Args&&... args) {
std::cout << "operator() " << std::endl;
handler_(std::forward<Args>(args)...);
}
//private:
handler_priority_queue& queue_;
int priority_;
Handler handler_;
};
template <typename Handler>
wrapped_handler<Handler> wrap(int priority, Handler&& handler) {
return wrapped_handler<Handler>(*this, priority, std::forward<Handler>(handler));
}
private:
class queued_handler {
public:
template <typename Handler>
queued_handler(int p, Handler&& handler)
: priority_(p), function_(std::forward<Handler>(handler))
{
std::cout << "queued_handler()" << std::endl;
}
void execute() {
std::cout << "execute(" << priority_ << ")" << std::endl;
function_();
}
friend bool operator<(
queued_handler const& lhs,
queued_handler const & rhs) {
return lhs.priority_ < rhs.priority_;
}
private:
int priority_;
std::function<void()> function_;
};
std::priority_queue<queued_handler> handlers_;
std::mutex mtx_;
};
// Custom invocation hook for wrapped handlers.
template <typename Function, typename Handler>
void asio_handler_invoke(Function&& f,
handler_priority_queue::wrapped_handler<Handler>* h) {
std::cout << "asio_handler_invoke " << std::endl;
h->queue_.add(h->priority_, std::forward<Function>(f));
}
//----------------------------------------------------------------------
int main() {
int const num_of_threads = 4;
int const num_of_tasks = 5;
boost::asio::io_service ios;
boost::asio::strand strand(ios);
handler_priority_queue pq;
for (int i = 0; i != num_of_tasks; ++i) {
ios.post(
#if ENABLE_STRAND
strand.wrap(
#endif
#if ENABLE_PRIORITY
pq.wrap(
i,
#endif
[=] {
std::cout << "[called] " << i << "," << std::this_thread::get_id() << std::endl;
}
#if ENABLE_PRIORITY
)
#endif
#if ENABLE_STRAND
)
#endif
);
}
std::vector<std::thread> pool;
for (int i = 0; i != num_of_threads; ++i) {
pool.emplace_back([&]{
std::cout << "before run_one()" << std::endl;
while (ios.run_one()) {
std::cout << "before poll_one()" << std::endl;
while (ios.poll_one())
;
std::cout << "before execute_all()" << std::endl;
pq.execute_all();
}
}
);
}
for (auto& t : pool) t.join();
}
的包装由下列宏启用：
#define ENABLE_STRAND 1
#define ENABLE_PRIORITY 1
当两个宏都启用时，我得到以下结果T：
before run_one()
asio_handler_invoke
add(0)
queued_handler()
before poll_one()
asio_handler_invoke
add(1)
queued_handler()
asio_handler_invoke
add(2)
queued_handler()
asio_handler_invoke
add(3)
queued_handler()
asio_handler_invoke
add(4)
queued_handler()
before execute_all()
execute(4)
execute(3)
execute(2)
execute(1)
execute(0)
before run_one()
before run_one()
before run_one()
我希望我得到了
[called] priority,thread_id
输出
[called] 1,140512649541376
，但我没有得到它。
看起来功能，function_()被调用，但不调用wrapped_handler::operator()。 （该功能从pq.execute_all();在我的代码调用。）
void execute() {
std::cout << "execute(" << priority_ << ")" << std::endl;
function_(); // It is called.
}
template <typename Handler>
class wrapped_handler {
public:
template <typename... Args>
void operator()(Args&&... args) { // It is NOT called
std::cout << "operator() " << std::endl;
handler_(std::forward<Args>(args)...);
}
我跟踪的序列function_()后调用。
下列函数调用：
https://github.com/boostorg/asio/blob/boost-1.63.0/include/boost/asio/detail/wrapped_handler.hpp#L191 https://github.com/boostorg/asio/blob/boost-1.63.0/include/boost/asio/detail/wrapped_handler.hpp#L76 https://github.com/boostorg/asio/blob/boost-1.63.0/include/boost/asio/strand.hpp#L158 https://github.com/boostorg/asio/blob/boost-1.63.0/include/boost/asio/detail/impl/strand_service.hpp#L55 https://github.com/boostorg/asio/blob/boost-1.63.0/include/boost/asio/detail/impl/strand_service.ipp#L94
在功能bool strand_service::do_dispatch(implementation_type& impl, operation* op)
然后，操作op不叫，但被推入队列INT以下行：
我不知道为什么function_()被调度到strand_service。我认为，链包装已经在以下点在我的代码unwraped：
template <typename Function, typename Handler>
void asio_handler_invoke(Function&& f,
handler_priority_queue::wrapped_handler<Handler>* h) {
std::cout << "asio_handler_invoke " << std::endl;
h->queue_.add(h->priority_, std::forward<Function>(f));
}
如果我只启用了优先级的包装，我得到了以下的结果。 看来，这是按我的预期工作。
before run_one()
asio_handler_invoke
add(0)
queued_handler()
before poll_one()
asio_handler_invoke
add(1)
queued_handler()
asio_handler_invoke
add(2)
queued_handler()
asio_handler_invoke
add(3)
queued_handler()
asio_handler_invoke
add(4)
queued_handler()
before execute_all()
execute(4)
operator()
[called] 4,140512649541376
execute(3)
operator()
[called] 3,140512649541376
execute(2)
operator()
[called] 2,140512649541376
execute(1)
operator()
[called] 1,140512649541376
execute(0)
operator()
[called] 0,140512649541376
before run_one()
before run_one()
before run_one()
如果我只启用了strand wrapper，我得到了以下结果。 看来，我也在按预期工作。
before run_one()
[called] 0,140127385941760
before poll_one()
[called] 1,140127385941760
[called] 2,140127385941760
[called] 3,140127385941760
[called] 4,140127385941760
before execute_all()
before run_one()
before run_one()
before run_one()
任何想法？