ASIO IO 完成回调顺序与实际 IO 操作的顺序
ASIO IO completion callbacks order vs the order of actual IO operations
从实现中可以明显看出，在单线程模式下 运行 时，IO 完成回调的调用顺序与实际 IO 操作相同，但我找不到相应的文档部分来确认.它是否明确地写在任何地方？
io-object 类 上所有 async_xxx 方法的文档中有这样一段话：
Regardless of whether the asynchronous operation completes immediately or not, the handler will not be invoked from within this function. Invocation of the handler will be performed in a manner equivalent to using boost::asio::io_service::post().
正在查看 boost::asio::io_service::post() 的文档...
This function is used to ask the io_service to execute the given handler, but without allowing the io_service to call the handler from inside this function.
The io_service guarantees that the handler will only be called in a thread in which the run(), run_one(), poll() or poll_one() member functions is currently being invoked.
这就是您的全部保证。
如果您的代码依赖于异步事件的时间顺序，那么它就不是异步代码。
甚至 run_one() 的文档也无法保证 它将调度哪个 处理程序：
The run_one() function blocks until one handler has been dispatched, or until the io_service has been stopped.
如果您必须对单个异步操作（例如读取）进行排序，那么您有义务：
从第一个处理程序启动第二个操作，或者
在操作的处理程序未完成时保持标志设置，并且仅在标志为 false 时才启动另一个操作。
从实现中可以明显看出，在单线程模式下 运行 时，IO 完成回调的调用顺序与实际 IO 操作相同，但我找不到相应的文档部分来确认.它是否明确地写在任何地方？
io-object 类 上所有 async_xxx 方法的文档中有这样一段话：
Regardless of whether the asynchronous operation completes immediately or not, the handler will not be invoked from within this function. Invocation of the handler will be performed in a manner equivalent to using
boost::asio::io_service::post().
正在查看 boost::asio::io_service::post() 的文档...
This function is used to ask the io_service to execute the given handler, but without allowing the io_service to call the handler from inside this function.
The io_service guarantees that the handler will only be called in a thread in which the
run(),run_one(),poll()orpoll_one()member functions is currently being invoked.
这就是您的全部保证。
如果您的代码依赖于异步事件的时间顺序，那么它就不是异步代码。
甚至 run_one() 的文档也无法保证 它将调度哪个 处理程序：
The run_one() function blocks until one handler has been dispatched, or until the io_service has been stopped.
如果您必须对单个异步操作（例如读取）进行排序，那么您有义务：
从第一个处理程序启动第二个操作，或者
在操作的处理程序未完成时保持标志设置，并且仅在标志为 false 时才启动另一个操作。