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//
// detail/impl/strand_service.ipp
// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
//
// 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_IMPL_STRAND_SERVICE_IPP
#define ASIO_DETAIL_IMPL_STRAND_SERVICE_IPP
#if defined(_MSC_VER) && (_MSC_VER >= 1200)
# pragma once
#endif // defined(_MSC_VER) && (_MSC_VER >= 1200)
#include "asio/detail/config.hpp"
#include "asio/detail/call_stack.hpp"
#include "asio/detail/strand_service.hpp"
#include "asio/detail/push_options.hpp"
namespace asio {
namespace detail {
struct strand_service::on_do_complete_exit
{
io_context_impl* owner_;
strand_impl* impl_;
~on_do_complete_exit()
{
impl_->mutex_.lock();
impl_->ready_queue_.push(impl_->waiting_queue_);
bool more_handlers = impl_->locked_ = !impl_->ready_queue_.empty();
impl_->mutex_.unlock();
if (more_handlers)
owner_->post_immediate_completion(impl_, true);
}
};
strand_service::strand_service(asio::io_context& io_context)
: asio::detail::service_base<strand_service>(io_context),
io_context_(asio::use_service<io_context_impl>(io_context)),
mutex_(),
salt_(0)
{
}
void strand_service::shutdown()
{
op_queue<operation> ops;
asio::detail::mutex::scoped_lock lock(mutex_);
for (std::size_t i = 0; i < num_implementations; ++i)
{
if (strand_impl* impl = implementations_[i].get())
{
ops.push(impl->waiting_queue_);
ops.push(impl->ready_queue_);
}
}
}
void strand_service::construct(strand_service::implementation_type& impl)
{
asio::detail::mutex::scoped_lock lock(mutex_);
std::size_t salt = salt_++;
#if defined(ASIO_ENABLE_SEQUENTIAL_STRAND_ALLOCATION)
std::size_t index = salt;
#else // defined(ASIO_ENABLE_SEQUENTIAL_STRAND_ALLOCATION)
std::size_t index = reinterpret_cast<std::size_t>(&impl);
index += (reinterpret_cast<std::size_t>(&impl) >> 3);
index ^= salt + 0x9e3779b9 + (index << 6) + (index >> 2);
#endif // defined(ASIO_ENABLE_SEQUENTIAL_STRAND_ALLOCATION)
index = index % num_implementations;
if (!implementations_[index].get())
implementations_[index].reset(new strand_impl);
impl = implementations_[index].get();
}
bool strand_service::running_in_this_thread(
const implementation_type& impl) const
{
return call_stack<strand_impl>::contains(impl) != 0;
}
bool strand_service::do_dispatch(implementation_type& impl, operation* op)
{
// If we are running inside the io_context, and no other handler already
// holds the strand lock, then the handler can run immediately.
bool can_dispatch = io_context_.can_dispatch();
impl->mutex_.lock();
if (can_dispatch && !impl->locked_)
{
// Immediate invocation is allowed.
impl->locked_ = true;
impl->mutex_.unlock();
return true;
}
if (impl->locked_)
{
// Some other handler already holds the strand lock. Enqueue for later.
impl->waiting_queue_.push(op);
impl->mutex_.unlock();
}
else
{
// The handler is acquiring the strand lock and so is responsible for
// scheduling the strand.
impl->locked_ = true;
impl->mutex_.unlock();
impl->ready_queue_.push(op);
io_context_.post_immediate_completion(impl, false);
}
return false;
}
void strand_service::do_post(implementation_type& impl,
operation* op, bool is_continuation)
{
impl->mutex_.lock();
if (impl->locked_)
{
// Some other handler already holds the strand lock. Enqueue for later.
impl->waiting_queue_.push(op);
impl->mutex_.unlock();
}
else
{
// The handler is acquiring the strand lock and so is responsible for
// scheduling the strand.
impl->locked_ = true;
impl->mutex_.unlock();
impl->ready_queue_.push(op);
io_context_.post_immediate_completion(impl, is_continuation);
}
}
void strand_service::do_complete(void* owner, operation* base,
const asio::error_code& ec, std::size_t /*bytes_transferred*/)
{
if (owner)
{
strand_impl* impl = static_cast<strand_impl*>(base);
// Indicate that this strand is executing on the current thread.
call_stack<strand_impl>::context ctx(impl);
// Ensure the next handler, if any, is scheduled on block exit.
on_do_complete_exit on_exit;
on_exit.owner_ = static_cast<io_context_impl*>(owner);
on_exit.impl_ = impl;
// Run all ready handlers. No lock is required since the ready queue is
// accessed only within the strand.
while (operation* o = impl->ready_queue_.front())
{
impl->ready_queue_.pop();
o->complete(owner, ec, 0);
}
}
}
} // namespace detail
} // namespace asio
#include "asio/detail/pop_options.hpp"
#endif // ASIO_DETAIL_IMPL_STRAND_SERVICE_IPP
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