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//
// detail/strand_executor_service.hpp
// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
//
// Copyright (c) 2003-2018 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 ASIO_DETAIL_STRAND_EXECUTOR_SERVICE_HPP
#define ASIO_DETAIL_STRAND_EXECUTOR_SERVICE_HPP
#if defined(_MSC_VER) && (_MSC_VER >= 1200)
# pragma once
#endif // defined(_MSC_VER) && (_MSC_VER >= 1200)
#include "asio/detail/config.hpp"
#include "asio/detail/atomic_count.hpp"
#include "asio/detail/executor_op.hpp"
#include "asio/detail/memory.hpp"
#include "asio/detail/mutex.hpp"
#include "asio/detail/op_queue.hpp"
#include "asio/detail/scheduler_operation.hpp"
#include "asio/detail/scoped_ptr.hpp"
#include "asio/execution_context.hpp"
#include "asio/detail/push_options.hpp"
namespace asio {
namespace detail {
// Default service implementation for a strand.
class strand_executor_service
: public execution_context_service_base<strand_executor_service>
{
public:
// The underlying implementation of a strand.
class strand_impl
{
public:
ASIO_DECL ~strand_impl();
private:
friend class strand_executor_service;
// Mutex to protect access to internal data.
mutex* mutex_;
// Indicates whether the strand is currently "locked" by a handler. This
// means that there is a handler upcall in progress, or that the strand
// itself has been scheduled in order to invoke some pending handlers.
bool locked_;
// Indicates that the strand has been shut down and will accept no further
// handlers.
bool shutdown_;
// The handlers that are waiting on the strand but should not be run until
// after the next time the strand is scheduled. This queue must only be
// modified while the mutex is locked.
op_queue<scheduler_operation> waiting_queue_;
// The handlers that are ready to be run. Logically speaking, these are the
// handlers that hold the strand's lock. The ready queue is only modified
// from within the strand and so may be accessed without locking the mutex.
op_queue<scheduler_operation> ready_queue_;
// Pointers to adjacent handle implementations in linked list.
strand_impl* next_;
strand_impl* prev_;
// The strand service in where the implementation is held.
strand_executor_service* service_;
};
typedef shared_ptr<strand_impl> implementation_type;
// Construct a new strand service for the specified context.
ASIO_DECL explicit strand_executor_service(execution_context& context);
// Destroy all user-defined handler objects owned by the service.
ASIO_DECL void shutdown();
// Create a new strand_executor implementation.
ASIO_DECL implementation_type create_implementation();
// Request invocation of the given function.
template <typename Executor, typename Function, typename Allocator>
static void dispatch(const implementation_type& impl, Executor& ex,
ASIO_MOVE_ARG(Function) function, const Allocator& a);
// Request invocation of the given function and return immediately.
template <typename Executor, typename Function, typename Allocator>
static void post(const implementation_type& impl, Executor& ex,
ASIO_MOVE_ARG(Function) function, const Allocator& a);
// Request invocation of the given function and return immediately.
template <typename Executor, typename Function, typename Allocator>
static void defer(const implementation_type& impl, Executor& ex,
ASIO_MOVE_ARG(Function) function, const Allocator& a);
// Determine whether the strand is running in the current thread.
ASIO_DECL static bool running_in_this_thread(
const implementation_type& impl);
private:
friend class strand_impl;
template <typename Executor> class invoker;
// Adds a function to the strand. Returns true if it acquires the lock.
ASIO_DECL static bool enqueue(const implementation_type& impl,
scheduler_operation* op);
// Mutex to protect access to the service-wide state.
mutex mutex_;
// Number of mutexes shared between all strand objects.
enum { num_mutexes = 193 };
// Pool of mutexes.
scoped_ptr<mutex> mutexes_[num_mutexes];
// Extra value used when hashing to prevent recycled memory locations from
// getting the same mutex.
std::size_t salt_;
// The head of a linked list of all implementations.
strand_impl* impl_list_;
};
} // namespace detail
} // namespace asio
#include "asio/detail/pop_options.hpp"
#include "asio/detail/impl/strand_executor_service.hpp"
#if defined(ASIO_HEADER_ONLY)
# include "asio/detail/impl/strand_executor_service.ipp"
#endif // defined(ASIO_HEADER_ONLY)
#endif // ASIO_DETAIL_STRAND_EXECUTOR_SERVICE_HPP
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