等待 C++ 中的通知
与 C++ 并不严格相关，我正在寻找更多关于如何解决这个问题的设计模式或建议。
假设我有，
class A
{
public:
void process();
void wait();
}
我将首先调用 process()，它（duuh）会进行一些处理，然后调用 wait()。 wait() 函数应该等待通知然后退出。我已经在单独的线程上有了通知的逻辑，但我不确定最好的方法是什么。
我想到的是：
void A::wait()
{
while ( _notificationOccured == false )
{
}
}
其中 _notificationOccured 可以是 A 的 bool 成员，它将被通知更改。但是，我再次不确定这是最好的方法。有什么建议吗？
Not strictly related to C++, I am looking for more of a design patter or suggestion on how to approach this.
Say I have
class A
{
public:
void process();
void wait();
}
I will first call process(), which (duuh) does some processing and will then call wait(). The wait() function is supposed to wait for a notification and then exit. I already have the logic for the notification on a separate thread, but I'm not really sure what the best approach for this is.
What I thought of is:
void A::wait()
{
while ( _notificationOccured == false )
{
}
}
where _notificationOccured can be a bool member of A that will be changed by the notification. But, again, I'm not sure that this is the best approach. Any suggestions?
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变量池的性能很差，因为池线程几乎占用了所有的 CPU 时间。您需要使用事件或消息 - 这些东西是特定于平台的。您可以为此使用一些可移植库，例如 Boost。
Pooling for a variable gives terrible performance, because pooling thread takes almost all CPU time. You need to use events or messages - this stuff is platform-specific. You can use some portable library for this, for example, Boost.
您所做的称为<a href="http://en.wikipedia.org/wiki/Busy_waiting" rel="nofollow">忙等待。
有多种技术可以更好地做到这一点，最简单的是使用带有 ncondition 通知的普通互斥体（win32/pthreads/boost）。
What you do is called busy waiting.
The are various techniques to do this better, the simplest would be to use a plain mutex with ncondition notification (win32/pthreads/boost).
您当前的方法引入了电源环路，这会降低您正在运行的系统的性能。您应该引入较短的睡眠时间（10 毫秒就足够了）来防止这种情况发生。更好的是，使用库，例如 Boost （正如@Nim 建议的那样）。
顺便说一句，像你这样进行民意调查并不全是坏事。事实上，这就是所谓的自旋锁所做的。这个想法是，如果预期等待时间很短，那么短时间的轮询比锁定更有效。
Your current approach introduces a power-loop, which will kill the performance of the system you are running on. You should introduce a short sleep-time (10ms will suffice) to prevent that from happening. Better yet, use a library, like Boost (as @Nim suggested).
Btw, polling like you do is not all bad. In fact, that is what so-called spin-locks do. The idea is that a short time of polling is more efficient than locking if the expected wait-time is short.
两个选项：
两者都是特定于操作系统的，boost 支持后者。还有其他方法（例如原子操作，但如何公开这些方法是编译器特定的）。恕我直言，我会使用上述之一。
Two options:
Both are OS specific, boost has support for latter. There are other ways (such as atomic operations, but how these are exposed is compiler specific). IMHO, I would use one of the above.
我只在 Windows 上知道这一点，所以我不知道这是否可以轻松转换到其他平台。
在伪代码中：
在 Windows 中 GetEvent() 被称为 WaitForSingleObject(...)
I only know this from Windows, so I don't know if this translates easily to other plattforms.
In pseudo code:
In Windows GetEvent() is called WaitForSingleObject(...)