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authorRemko Tronçon <git@el-tramo.be>2009-06-01 08:48:42 (GMT)
committerRemko Tronçon <git@el-tramo.be>2009-06-01 09:24:28 (GMT)
commit2812bddd81f8a1b804c7460f4e14cd0aa393d129 (patch)
treed46294f35150c4f0f43deaf2d31fceaf945ae715 /3rdParty/Boost/boost/asio/detail/task_io_service_2lock.hpp
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+//
+// task_io_service_2lock.hpp
+// ~~~~~~~~~~~~~~~~~~~~~~~~~
+//
+// Copyright (c) 2003-2008 Christopher M. Kohlhoff (chris at kohlhoff dot com)
+//
+// Distributed under the Boost Software License, Version 1.0. (See accompanying
+// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+//
+
+#ifndef BOOST_ASIO_DETAIL_TASK_IO_SERVICE_2LOCK_HPP
+#define BOOST_ASIO_DETAIL_TASK_IO_SERVICE_2LOCK_HPP
+
+#if defined(_MSC_VER) && (_MSC_VER >= 1200)
+# pragma once
+#endif // defined(_MSC_VER) && (_MSC_VER >= 1200)
+
+#include <boost/asio/detail/push_options.hpp>
+
+#include <boost/asio/io_service.hpp>
+#include <boost/asio/detail/call_stack.hpp>
+#include <boost/asio/detail/event.hpp>
+#include <boost/asio/detail/handler_alloc_helpers.hpp>
+#include <boost/asio/detail/handler_invoke_helpers.hpp>
+#include <boost/asio/detail/indirect_handler_queue.hpp>
+#include <boost/asio/detail/mutex.hpp>
+#include <boost/asio/detail/service_base.hpp>
+#include <boost/asio/detail/task_io_service_fwd.hpp>
+
+#include <boost/asio/detail/push_options.hpp>
+#include <boost/detail/atomic_count.hpp>
+#include <boost/system/error_code.hpp>
+#include <boost/asio/detail/pop_options.hpp>
+
+namespace boost {
+namespace asio {
+namespace detail {
+
+// An alternative task_io_service implementation based on a two-lock queue.
+
+template <typename Task>
+class task_io_service
+ : public boost::asio::detail::service_base<task_io_service<Task> >
+{
+public:
+ typedef indirect_handler_queue handler_queue;
+
+ // Constructor.
+ task_io_service(boost::asio::io_service& io_service)
+ : boost::asio::detail::service_base<task_io_service<Task> >(io_service),
+ front_mutex_(),
+ back_mutex_(),
+ task_(&use_service<Task>(io_service)),
+ outstanding_work_(0),
+ front_stopped_(false),
+ back_stopped_(false),
+ back_shutdown_(false),
+ back_first_idle_thread_(0),
+ back_task_thread_(0)
+ {
+ }
+
+ void init(size_t /*concurrency_hint*/)
+ {
+ }
+
+ // Destroy all user-defined handler objects owned by the service.
+ void shutdown_service()
+ {
+ boost::asio::detail::mutex::scoped_lock back_lock(back_mutex_);
+ back_shutdown_ = true;
+ back_lock.unlock();
+
+ // Destroy handler objects.
+ while (handler_queue::handler* h = handler_queue_.pop())
+ if (h != &task_handler_)
+ h->destroy();
+
+ // Reset to initial state.
+ task_ = 0;
+ }
+
+ // Initialise the task, if required.
+ void init_task()
+ {
+ boost::asio::detail::mutex::scoped_lock back_lock(back_mutex_);
+ if (!back_shutdown_ && !task_)
+ {
+ task_ = &use_service<Task>(this->get_io_service());
+ handler_queue_.push(&task_handler_);
+ interrupt_one_idle_thread(back_lock);
+ }
+ }
+
+ // Run the event loop until interrupted or no more work.
+ size_t run(boost::system::error_code& ec)
+ {
+ if (outstanding_work_ == 0)
+ {
+ stop();
+ ec = boost::system::error_code();
+ return 0;
+ }
+
+ typename call_stack<task_io_service>::context ctx(this);
+
+ idle_thread_info this_idle_thread;
+ this_idle_thread.next = 0;
+
+ size_t n = 0;
+ while (do_one(&this_idle_thread, ec))
+ if (n != (std::numeric_limits<size_t>::max)())
+ ++n;
+ return n;
+ }
+
+ // Run until interrupted or one operation is performed.
+ size_t run_one(boost::system::error_code& ec)
+ {
+ if (outstanding_work_ == 0)
+ {
+ stop();
+ ec = boost::system::error_code();
+ return 0;
+ }
+
+ typename call_stack<task_io_service>::context ctx(this);
+
+ idle_thread_info this_idle_thread;
+ this_idle_thread.next = 0;
+
+ return do_one(&this_idle_thread, ec);
+ }
+
+ // Poll for operations without blocking.
+ size_t poll(boost::system::error_code& ec)
+ {
+ if (outstanding_work_ == 0)
+ {
+ stop();
+ ec = boost::system::error_code();
+ return 0;
+ }
+
+ typename call_stack<task_io_service>::context ctx(this);
+
+ size_t n = 0;
+ while (do_one(0, ec))
+ if (n != (std::numeric_limits<size_t>::max)())
+ ++n;
+ return n;
+ }
+
+ // Poll for one operation without blocking.
+ size_t poll_one(boost::system::error_code& ec)
+ {
+ if (outstanding_work_ == 0)
+ {
+ stop();
+ ec = boost::system::error_code();
+ return 0;
+ }
+
+ typename call_stack<task_io_service>::context ctx(this);
+
+ return do_one(0, ec);
+ }
+
+ // Interrupt the event processing loop.
+ void stop()
+ {
+ boost::asio::detail::mutex::scoped_lock front_lock(front_mutex_);
+ front_stopped_ = true;
+ front_lock.unlock();
+
+ boost::asio::detail::mutex::scoped_lock back_lock(back_mutex_);
+ back_stopped_ = true;
+ interrupt_all_idle_threads(back_lock);
+ }
+
+ // Reset in preparation for a subsequent run invocation.
+ void reset()
+ {
+ boost::asio::detail::mutex::scoped_lock front_lock(front_mutex_);
+ front_stopped_ = false;
+ front_lock.unlock();
+
+ boost::asio::detail::mutex::scoped_lock back_lock(back_mutex_);
+ back_stopped_ = false;
+ }
+
+ // Notify that some work has started.
+ void work_started()
+ {
+ ++outstanding_work_;
+ }
+
+ // Notify that some work has finished.
+ void work_finished()
+ {
+ if (--outstanding_work_ == 0)
+ stop();
+ }
+
+ // Request invocation of the given handler.
+ template <typename Handler>
+ void dispatch(Handler handler)
+ {
+ if (call_stack<task_io_service>::contains(this))
+ boost_asio_handler_invoke_helpers::invoke(handler, &handler);
+ else
+ post(handler);
+ }
+
+ // Request invocation of the given handler and return immediately.
+ template <typename Handler>
+ void post(Handler handler)
+ {
+ // Allocate and construct an operation to wrap the handler.
+ handler_queue::scoped_ptr ptr(handler_queue::wrap(handler));
+
+ boost::asio::detail::mutex::scoped_lock back_lock(back_mutex_);
+
+ // If the service has been shut down we silently discard the handler.
+ if (back_shutdown_)
+ return;
+
+ // Add the handler to the end of the queue.
+ handler_queue_.push(ptr.get());
+ ptr.release();
+
+ // An undelivered handler is treated as unfinished work.
+ ++outstanding_work_;
+
+ // Wake up a thread to execute the handler.
+ interrupt_one_idle_thread(back_lock);
+ }
+
+private:
+ struct idle_thread_info;
+
+ size_t do_one(idle_thread_info* this_idle_thread,
+ boost::system::error_code& ec)
+ {
+ bool task_has_run = false;
+ for (;;)
+ {
+ // The front lock must be held before we can pop items from the queue.
+ boost::asio::detail::mutex::scoped_lock front_lock(front_mutex_);
+ if (front_stopped_)
+ {
+ ec = boost::system::error_code();
+ return 0;
+ }
+
+ if (handler_queue::handler* h = handler_queue_.pop())
+ {
+ if (h == &task_handler_)
+ {
+ bool more_handlers = handler_queue_.poppable();
+ unsigned long front_version = handler_queue_.front_version();
+ front_lock.unlock();
+
+ // The task is always added to the back of the queue when we exit
+ // this block.
+ task_cleanup c(*this);
+
+ // If we're polling and the task has already run then we're done.
+ bool polling = !this_idle_thread;
+ if (task_has_run && polling)
+ {
+ ec = boost::system::error_code();
+ return 0;
+ }
+
+ // If we're considering going idle we need to check whether the queue
+ // is still empty. If it is, add the thread to the list of idle
+ // threads.
+ if (!more_handlers && !polling)
+ {
+ boost::asio::detail::mutex::scoped_lock back_lock(back_mutex_);
+ if (back_stopped_)
+ {
+ ec = boost::system::error_code();
+ return 0;
+ }
+ else if (front_version == handler_queue_.back_version())
+ {
+ back_task_thread_ = this_idle_thread;
+ }
+ else
+ {
+ more_handlers = true;
+ }
+ }
+
+ // Run the task. May throw an exception. Only block if the handler
+ // queue is empty and we're not polling, otherwise we want to return
+ // as soon as possible.
+ task_has_run = true;
+ task_->run(!more_handlers && !polling);
+ }
+ else
+ {
+ front_lock.unlock();
+ handler_cleanup c(*this);
+
+ // Invoke the handler. May throw an exception.
+ h->invoke(); // invoke() deletes the handler object
+
+ ec = boost::system::error_code();
+ return 1;
+ }
+ }
+ else if (this_idle_thread)
+ {
+ unsigned long front_version = handler_queue_.front_version();
+ front_lock.unlock();
+
+ // If we're considering going idle we need to check whether the queue
+ // is still empty. If it is, add the thread to the list of idle
+ // threads.
+ boost::asio::detail::mutex::scoped_lock back_lock(back_mutex_);
+ if (back_stopped_)
+ {
+ ec = boost::system::error_code();
+ return 0;
+ }
+ else if (front_version == handler_queue_.back_version())
+ {
+ this_idle_thread->next = back_first_idle_thread_;
+ back_first_idle_thread_ = this_idle_thread;
+ this_idle_thread->wakeup_event.clear(back_lock);
+ this_idle_thread->wakeup_event.wait(back_lock);
+ }
+ }
+ else
+ {
+ ec = boost::system::error_code();
+ return 0;
+ }
+ }
+ }
+
+ // Interrupt a single idle thread.
+ void interrupt_one_idle_thread(
+ boost::asio::detail::mutex::scoped_lock& back_lock)
+ {
+ if (back_first_idle_thread_)
+ {
+ idle_thread_info* idle_thread = back_first_idle_thread_;
+ back_first_idle_thread_ = idle_thread->next;
+ idle_thread->next = 0;
+ idle_thread->wakeup_event.signal(back_lock);
+ }
+ else if (back_task_thread_ && task_)
+ {
+ back_task_thread_ = 0;
+ task_->interrupt();
+ }
+ }
+
+ // Interrupt all idle threads.
+ void interrupt_all_idle_threads(
+ boost::asio::detail::mutex::scoped_lock& back_lock)
+ {
+ while (back_first_idle_thread_)
+ {
+ idle_thread_info* idle_thread = back_first_idle_thread_;
+ back_first_idle_thread_ = idle_thread->next;
+ idle_thread->next = 0;
+ idle_thread->wakeup_event.signal(back_lock);
+ }
+
+ if (back_task_thread_ && task_)
+ {
+ back_task_thread_ = 0;
+ task_->interrupt();
+ }
+ }
+
+ // Helper class to perform task-related operations on block exit.
+ class task_cleanup;
+ friend class task_cleanup;
+ class task_cleanup
+ {
+ public:
+ task_cleanup(task_io_service& task_io_svc)
+ : task_io_service_(task_io_svc)
+ {
+ }
+
+ ~task_cleanup()
+ {
+ // Reinsert the task at the end of the handler queue.
+ boost::asio::detail::mutex::scoped_lock back_lock(
+ task_io_service_.back_mutex_);
+ task_io_service_.back_task_thread_ = 0;
+ task_io_service_.handler_queue_.push(&task_io_service_.task_handler_);
+ }
+
+ private:
+ task_io_service& task_io_service_;
+ };
+
+ // Helper class to perform handler-related operations on block exit.
+ class handler_cleanup
+ {
+ public:
+ handler_cleanup(task_io_service& task_io_svc)
+ : task_io_service_(task_io_svc)
+ {
+ }
+
+ ~handler_cleanup()
+ {
+ task_io_service_.work_finished();
+ }
+
+ private:
+ task_io_service& task_io_service_;
+ };
+
+ // Mutexes to protect access to internal data.
+ boost::asio::detail::mutex front_mutex_;
+ boost::asio::detail::mutex back_mutex_;
+
+ // The task to be run by this service.
+ Task* task_;
+
+ // Handler object to represent the position of the task in the queue.
+ class task_handler
+ : public handler_queue::handler
+ {
+ public:
+ task_handler()
+ : handler_queue::handler(0, 0)
+ {
+ }
+ } task_handler_;
+
+ // The count of unfinished work.
+ boost::detail::atomic_count outstanding_work_;
+
+ // The queue of handlers that are ready to be delivered.
+ handler_queue handler_queue_;
+
+ // Flag to indicate that the dispatcher has been stopped.
+ bool front_stopped_;
+ bool back_stopped_;
+
+ // Flag to indicate that the dispatcher has been shut down.
+ bool back_shutdown_;
+
+ // Structure containing information about an idle thread.
+ struct idle_thread_info
+ {
+ event wakeup_event;
+ idle_thread_info* next;
+ };
+
+ // The number of threads that are currently idle.
+ idle_thread_info* back_first_idle_thread_;
+
+ // The thread that is currently blocked on the task.
+ idle_thread_info* back_task_thread_;
+};
+
+} // namespace detail
+} // namespace asio
+} // namespace boost
+
+#include <boost/asio/detail/pop_options.hpp>
+
+#endif // BOOST_ASIO_DETAIL_TASK_IO_SERVICE_2LOCK_HPP