Source code of Windows XP (NT5)
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/*****************************************************************/
/** Copyright (C) Microsoft Corp., 1994 **/
/*****************************************************************/
/* SCHED.C -- Miscellaneous scheduling helpers
*
* History:
* gregj 10/17/94 created
*/
#include "npcommon.h"
#include <sched.h>
/* FlushInputQueue is a private routine to collect and dispatch all
* messages in the input queue. It returns TRUE if a WM_QUIT message
* was detected in the queue, FALSE otherwise.
*/
BOOL FlushInputQueue(volatile DWORD *pidOtherThread)
{
MSG msgTemp;
while (PeekMessage(&msgTemp, NULL, 0, 0, PM_REMOVE)) {
DispatchMessage(&msgTemp);
// If we see a WM_QUIT in the queue, we need to do the same
// sort of thing that a modal dialog does: break out of our
// waiting, and repost the WM_QUIT to the queue so that the
// next message loop up in the app will also see it. We also
// post the message to the server thread's queue so that any
// dialog stack displayed there will be destroyed as well.
if (msgTemp.message == WM_QUIT) {
if (pidOtherThread != NULL && *pidOtherThread != NULL) {
PostThreadMessage(*pidOtherThread, msgTemp.message, msgTemp.wParam, msgTemp.lParam);
}
PostQuitMessage((int)msgTemp.wParam);
return TRUE;
}
}
return FALSE;
}
/* WaitAndYield() waits for the specified object using
* MsgWaitForMultipleObjects. If messages are received,
* they are dispatched and waiting continues. The return
* value is the same as from MsgWaitForMultipleObjects.
*/
DWORD WaitAndYield(HANDLE hObject, DWORD dwTimeout, volatile DWORD *pidOtherThread /* = NULL */)
{
DWORD dwTickCount, dwWakeReason, dwTemp;
do {
/* Flush any messages before we wait. This is because
* MsgWaitForMultipleObjects will only return when NEW
* messages are put in the queue.
*/
if (FlushInputQueue(pidOtherThread)) {
dwWakeReason = WAIT_TIMEOUT;
break;
}
// in case we handle messages, we want close to a true timeout
if ((dwTimeout != 0) &&
(dwTimeout != (DWORD)-1)) {
// if we can timeout, store the current tick count
// every time through
dwTickCount = GetTickCount();
}
dwWakeReason = MsgWaitForMultipleObjects(1,
&hObject,
FALSE,
dwTimeout,
QS_ALLINPUT);
// if we got a message, dispatch it, then try again
if (dwWakeReason == 1) {
// if we can timeout, see if we did before processing the message
// that way, if we haven't timed out yet, we'll get at least one
// more shot at the event
if ((dwTimeout != 0) &&
(dwTimeout != (DWORD)-1)) {
if ((dwTemp = (GetTickCount()-dwTickCount)) >= dwTimeout) {
// if we timed out, make us drop through
dwWakeReason = WAIT_TIMEOUT;
} else {
// subtract elapsed time from timeout and continue
// (we don't count time spent dispatching message)
dwTimeout -= dwTemp;
}
}
if (FlushInputQueue(pidOtherThread)) {
dwWakeReason = WAIT_TIMEOUT;
break;
}
}
} while (dwWakeReason == 1);
return dwWakeReason;
}
/* WaitAndProcessSends is similar to WaitAndYield, but it only processes
* SendMessage messages, not input messages.
*/
DWORD WaitAndProcessSends(HANDLE hObject, DWORD dwTimeout)
{
DWORD dwWakeReason;
do {
dwWakeReason = MsgWaitForMultipleObjects(1,
&hObject,
FALSE,
dwTimeout,
QS_SENDMESSAGE);
// if we got a message, yield, then try again
if (dwWakeReason == 1) {
MSG msgTemp;
PeekMessage(&msgTemp, NULL, 0, 0, PM_NOREMOVE | PM_NOYIELD);
}
} while (dwWakeReason == 1);
return dwWakeReason;
}