简介

task_io_service运行在多线程情况时，call_stack来管理运行io_service的多个线程

结构

其中key为task_io_service，value为task_io_service_thread_info

初始化

是在task_io_service::run中，创建task_io_service_thread_info的局部变量（循环没有退出时一直存在），同时添加到call_stack的栈顶

std::size_t task_io_service::run(boost::system::error_code& ec)
{ec = boost::system::error_code();if (outstanding_work_ == 0){stop();return 0;}thread_info this_thread;this_thread.private_outstanding_work = 0;thread_call_stack::context ctx(this, this_thread);mutex::scoped_lock lock(mutex_);std::size_t n = 0;for (; do_run_one(lock, this_thread, ec); lock.lock())if (n != (std::numeric_limits<std::size_t>::max)())++n;return n;
}

使用

在任务分发时，如果当前调用线程是io线程，则直接调用，否则放入对应的队列中

template <typename Handler>
void task_io_service::dispatch(Handler& handler)
{if (thread_call_stack::contains(this)){fenced_block b(fenced_block::full);boost_asio_handler_invoke_helpers::invoke(handler, handler);}else{// Allocate and construct an operation to wrap the handler.typedef completion_handler<Handler> op;typename op::ptr p = { boost::asio::detail::addressof(handler),boost_asio_handler_alloc_helpers::allocate(sizeof(op), handler), 0 };p.p = new (p.v) op(handler);BOOST_ASIO_HANDLER_CREATION((p.p, "io_service", this, "dispatch"));do_dispatch(p.p);p.v = p.p = 0;}
}