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//
// detail/strand_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_SERVICE_HPP
#define ASIO_DETAIL_STRAND_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/io_context.hpp"
#include "asio/detail/mutex.hpp"
#include "asio/detail/op_queue.hpp"
#include "asio/detail/operation.hpp"
#include "asio/detail/scoped_ptr.hpp"
#include "asio/detail/push_options.hpp"
namespace asio {
namespace detail {
// Default service implementation for a strand.
class strand_service
: public asio::detail::service_base<strand_service>
{
private:
// Helper class to re-post the strand on exit.
struct on_do_complete_exit;
// Helper class to re-post the strand on exit.
struct on_dispatch_exit;
public:
// The underlying implementation of a strand.
class strand_impl
: public operation
{
public:
strand_impl();
private:
// Only this service will have access to the internal values.
friend class strand_service;
friend struct on_do_complete_exit;
friend struct on_dispatch_exit;
// Mutex to protect access to internal data.
asio::detail::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_;
// 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<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<operation> ready_queue_;
};
typedef strand_impl* implementation_type;
// Construct a new strand service for the specified io_context.
ASIO_DECL explicit strand_service(asio::io_context& io_context);
// Destroy all user-defined handler objects owned by the service.
ASIO_DECL void shutdown();
// Construct a new strand implementation.
ASIO_DECL void construct(implementation_type& impl);
// Request the io_context to invoke the given handler.
template <typename Handler>
void dispatch(implementation_type& impl, Handler& handler);
// Request the io_context to invoke the given handler and return immediately.
template <typename Handler>
void post(implementation_type& impl, Handler& handler);
// Determine whether the strand is running in the current thread.
ASIO_DECL bool running_in_this_thread(
const implementation_type& impl) const;
private:
// Helper function to dispatch a handler. Returns true if the handler should
// be dispatched immediately.
ASIO_DECL bool do_dispatch(implementation_type& impl, operation* op);
// Helper fiunction to post a handler.
ASIO_DECL void do_post(implementation_type& impl,
operation* op, bool is_continuation);
ASIO_DECL static void do_complete(void* owner,
operation* base, const asio::error_code& ec,
std::size_t bytes_transferred);
// The io_context implementation used to post completions.
io_context_impl& io_context_;
// Mutex to protect access to the array of implementations.
asio::detail::mutex mutex_;
// Number of implementations shared between all strand objects.
#if defined(ASIO_STRAND_IMPLEMENTATIONS)
enum { num_implementations = ASIO_STRAND_IMPLEMENTATIONS };
#else // defined(ASIO_STRAND_IMPLEMENTATIONS)
enum { num_implementations = 193 };
#endif // defined(ASIO_STRAND_IMPLEMENTATIONS)
// Pool of implementations.
scoped_ptr<strand_impl> implementations_[num_implementations];
// Extra value used when hashing to prevent recycled memory locations from
// getting the same strand implementation.
std::size_t salt_;
};
} // namespace detail
} // namespace asio
#include "asio/detail/pop_options.hpp"
#include "asio/detail/impl/strand_service.hpp"
#if defined(ASIO_HEADER_ONLY)
# include "asio/detail/impl/strand_service.ipp"
#endif // defined(ASIO_HEADER_ONLY)
#endif // ASIO_DETAIL_STRAND_SERVICE_HPP
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