Add waitable_executor

beast/asio/waitable_executor.h

@@ -0,0 +1,315 @@
+//------------------------------------------------------------------------------
+/*
+    This file is part of Beast: https://github.com/vinniefalco/Beast
+    Copyright 2013, Vinnie Falco <vinnie.falco@gmail.com>
+
+    Permission to use, copy, modify, and/or distribute this software for any
+    purpose  with  or without fee is hereby granted, provided that the above
+    copyright notice and this permission notice appear in all copies.
+
+    THE  SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+    WITH  REGARD  TO  THIS  SOFTWARE  INCLUDING  ALL  IMPLIED  WARRANTIES  OF
+    MERCHANTABILITY  AND  FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+    ANY  SPECIAL ,  DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+    WHATSOEVER  RESULTING  FROM  LOSS  OF USE, DATA OR PROFITS, WHETHER IN AN
+    ACTION  OF  CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+    OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+*/
+//==============================================================================
+
+#ifndef BEAST_ASIO_WAITABLE_EXECUTOR_H_INCLUDED
+#define BEAST_ASIO_WAITABLE_EXECUTOR_H_INCLUDED
+
+#include <boost/asio/handler_alloc_hook.hpp>
+#include <boost/asio/handler_continuation_hook.hpp>
+#include <boost/asio/handler_invoke_hook.hpp>
+#include <condition_variable>
+#include <functional>
+#include <memory>
+#include <mutex>
+#include <beast/cxx14/type_traits.h> // <type_traits>
+#include <utility>
+#include <vector>
+
+namespace beast {
+namespace asio {
+
+namespace detail {
+
+template <class Owner, class Handler>
+class waitable_executor_wrapped_handler
+{
+private:
+    static_assert (std::is_same <std::decay_t <Owner>, Owner>::value,
+        "Owner cannot be a const or reference type");
+
+    Handler handler_;
+    std::reference_wrapper <Owner> owner_;
+    bool cont_;
+
+public:
+    waitable_executor_wrapped_handler (Owner& owner,
+        Handler&& handler, bool continuation = false)
+        : handler_ (std::move(handler))
+        , owner_ (owner)
+    {
+        using boost::asio::asio_handler_is_continuation;
+        cont_ = continuation ? true :
+            asio_handler_is_continuation(
+                std::addressof(handler_));
+        owner_.get().increment();
+    }
+
+    waitable_executor_wrapped_handler (Owner& owner,
+        Handler const& handler, bool continuation = false)
+        : handler_ (handler)
+        , owner_ (owner)
+    {
+        using boost::asio::asio_handler_is_continuation;
+        cont_ = continuation ? true :
+            asio_handler_is_continuation(
+                std::addressof(handler_));
+        owner_.get().increment();
+    }
+
+    ~waitable_executor_wrapped_handler()
+    {
+        owner_.get().decrement();
+    }
+
+    waitable_executor_wrapped_handler (
+            waitable_executor_wrapped_handler const& other)
+        : handler_ (other.handler_)
+        , owner_ (other.owner_)
+        , cont_ (other.cont_)
+    {
+        owner_.get().increment();
+    }
+
+    waitable_executor_wrapped_handler (
+            waitable_executor_wrapped_handler&& other)
+        : handler_ (std::move(other.handler_))
+        , owner_ (other.owner_)
+        , cont_ (other.cont_)
+    {
+        owner_.get().increment();
+    }
+
+    waitable_executor_wrapped_handler& operator=(
+        waitable_executor_wrapped_handler const&) = delete;
+
+    template <class... Args>
+    void
+    operator()(Args&&... args)
+    {
+        handler_(std::forward<Args>(args)...);
+    }
+
+    template <class... Args>
+    void
+    operator()(Args&&... args) const
+    {
+        handler_(std::forward<Args>(args)...);
+    }
+
+    template <class Function>
+    friend
+    void
+    asio_handler_invoke (Function& f,
+        waitable_executor_wrapped_handler* h)
+    {
+        using boost::asio::asio_handler_invoke;
+        asio_handler_invoke(f,
+            std::addressof(h->handler_));
+    }
+
+    template <class Function>
+    friend
+    void
+    asio_handler_invoke (Function const& f,
+        waitable_executor_wrapped_handler* h)
+    {
+        using boost::asio::asio_handler_invoke;
+        asio_handler_invoke(f,
+            std::addressof(h->handler_));
+    }
+
+    friend
+    void*
+    asio_handler_allocate (std::size_t size,
+        waitable_executor_wrapped_handler* h)
+    {
+        using boost::asio::asio_handler_allocate;
+        return asio_handler_allocate(
+            size, std::addressof(h->handler_));
+    }
+
+    friend
+    void
+    asio_handler_deallocate (void* p, std::size_t size,
+        waitable_executor_wrapped_handler* h)
+    {
+        using boost::asio::asio_handler_deallocate;
+        asio_handler_deallocate(
+            p, size, std::addressof(h->handler_));
+    }
+
+    friend
+    bool
+    asio_handler_is_continuation (
+        waitable_executor_wrapped_handler* h)
+    {
+        return h->cont_;
+    }
+};
+
+} // detail
+
+//------------------------------------------------------------------------------
+
+/** Executor which provides blocking until all handlers are called. */
+class waitable_executor
+{
+private:
+    template <class, class>
+    friend class detail::waitable_executor_wrapped_handler;
+
+    std::mutex mutex_;
+    std::condition_variable cond_;
+    std::size_t count_ = 0;
+    std::vector<std::function<void(void)>> notify_;
+
+public:
+    /** Block until all handlers are called. */
+    template <class = void>
+    void
+    wait();
+
+    /** Blocks until all handlers are called or time elapses.
+        @return `true` if all handlers are done or `false` if the time elapses.
+    */
+    template <class Rep, class Period>
+    bool
+    wait_for (std::chrono::duration<
+        Rep, Period> const& elapsed_time);
+
+    /** Blocks until all handlers are called or a time is reached.
+        @return `true` if all handlers are done or `false` on timeout.
+    */
+    template <class Clock, class Duration>
+    bool
+    wait_until (std::chrono::time_point<
+        Clock, Duration> const& timeout_time);
+
+    /** Call a function asynchronously after all handlers are called.
+        The function may be called on the callers thread.
+    */
+    template <class = void>
+    void
+    async_wait(std::function<void(void)> f);
+
+    /** Create a new handler that dispatches the wrapped handler on the Context. */
+    template <class Handler>
+    detail::waitable_executor_wrapped_handler<waitable_executor,
+        std::remove_reference_t<Handler>>
+    wrap (Handler&& handler);
+
+private:
+    template <class = void>
+    void
+    increment();
+
+    template <class = void>
+    void
+    decrement();
+};
+
+template <class>
+void
+waitable_executor::wait()
+{
+    std::unique_lock<std::mutex> lock(mutex_);
+    cond_.wait(lock,
+        [this]() { return count_ == 0; });
+}
+
+template <class Rep, class Period>
+bool
+waitable_executor::wait_for (std::chrono::duration<
+    Rep, Period> const& elapsed_time)
+{
+    std::unique_lock<std::mutex> lock(mutex_);
+    return cond_.wait_for(lock, elapsed_time,
+        [this]() { return count_ == 0; }) ==
+            std::cv_status::no_timeout;
+}
+
+template <class Clock, class Duration>
+bool
+waitable_executor::wait_until (std::chrono::time_point<
+    Clock, Duration> const& timeout_time)
+{
+    std::unique_lock<std::mutex> lock(mutex_);
+    return cond_.wait_until(lock, timeout_time,
+        [this]() { return count_ == 0; }) ==
+            std::cv_status::no_timeout;
+    return true;
+}
+
+template <class>
+void
+waitable_executor::async_wait(std::function<void(void)> f)
+{
+    bool busy;
+    {
+        std::lock_guard<std::mutex> _(mutex_);
+        busy = count_ > 0;
+        if (busy)
+            notify_.emplace_back(std::move(f));
+    }
+    if (! busy)
+        f();
+}
+
+template <class Handler>
+detail::waitable_executor_wrapped_handler<waitable_executor,
+    std::remove_reference_t<Handler>>
+waitable_executor::wrap (Handler&& handler)
+{
+    return detail::waitable_executor_wrapped_handler<
+        waitable_executor, std::remove_reference_t<Handler>>(
+            *this, std::forward<Handler>(handler));
+}
+
+template <class>
+void
+waitable_executor::increment()
+{
+    std::lock_guard<std::mutex> _(mutex_);
+    ++count_;
+}
+
+template <class>
+void
+waitable_executor::decrement()
+{
+    bool notify;
+    std::vector<std::function<void(void)>> list;
+    {
+        std::lock_guard<std::mutex> _(mutex_);
+        notify = --count_ == 0;
+        if (notify)
+            std::swap(list, notify_);
+    }
+    if (notify)
+    {
+        cond_.notify_all();
+        for(auto& _ : list)
+            _();
+    }
+}
+
+} // asio
+} // beast
+
+#endif