我有一个要包装的 C dll,以便我可以从 C# 调用它。一个函数使用事件在状态发生变化时通知您,并且想出处理它需要一些挖掘。它似乎工作正常,但我很好奇是否有人比我有更多的经验并且可以提供任何建议。
该函数在 dll 的 .h 文件中定义为:
int NotifyStateChange(OVERLAPPED *overlapped);
typedef int (*NOTIFY_STATE_CHANGE_PROC)(OVERLAPPED *);
调用它的示例 C 代码:
OVERLAPPED overlapped;
overlapped.hEvent = CreateEvent(NULL, FALSE, FALSE, NULL);
fns.NotifyStateChange(&overlapped);
WaitForSingleObject(overlapped.hEvent, INFINITE);
// ...query for the new state or whatever...
这就是我在 C# 中处理它的方式:
[DllImport("myfuncs.dll")]
unsafe public static extern int NotifyStateChange(NativeOverlapped* lpOverlapped);
static private ManualResetEvent m_stateChangeEvent = new ManualResetEvent(false);
public static DeviceState WaitForStateChange()
{
unsafe
{
Overlapped overlapped = new Overlapped(0, 0,
m_stateChangeEvent.SafeWaitHandle.DangerousGetHandle(), null);
IOCompletionCallback callback = StateChangeCallback;
byte[] userData = new byte[100];
NativeOverlapped* nativeOverlapped = overlapped.Pack(callback, userData);
NotifyStateChange(nativeOverlapped);
m_stateChangeEvent.WaitOne();
Overlapped.Unpack(nativeOverlapped);
Overlapped.Free(nativeOverlapped);
}
return GetCurrentState();
}
[ComVisibleAttribute(true)]
unsafe static public void StateChangeCallback (
uint errorCode,
uint bytesTransferred,
NativeOverlapped* overlapped)
{
m_stateChangeEvent.Set();
}
我不清楚的一件事是需要 userData。NotifyStateChange 只是触发一个事件,它不返回任何数据。将 null userData 传递给 Pack() 似乎工作正常,但我担心 userData 可能会在我不知道的情况下发生一些事情。
如果有更合适的方法可以做到这一点,我很感激任何建议。
埃里克