[reactos] 01/01: [WINMM] Improve implementation of timeGetTime, timeBeginPeriod, timeEndPeriod (#2933)

[Thomas Brogan]

https://git.reactos.org/?p=reactos.git;a=commitdiff;h=88300ec3b3bbb2fc024f1d...

commit 88300ec3b3bbb2fc024f1d960d317dd802c4a3f6
Author:     Thomas Brogan [e-mail]
AuthorDate: Sat Jun 20 13:28:25 2020 +0300
Commit:     GitHub [e-mail]
CommitDate: Sat Jun 20 13:28:25 2020 +0300

[WINMM] Improve implementation of timeGetTime, timeBeginPeriod, timeEndPeriod (#2933)

Use QueryPerformanceCounter if a high-resolution timer is requested (<= 5ms) instead of the more inaccurate GetTickCount.
---
 dll/win32/winmm/time.c | 25 ++++++++++++++++++++++---
 1 file changed, 22 insertions(+), 3 deletions(-)

diff --git a/dll/win32/winmm/time.c b/dll/win32/winmm/time.c
index 5da3f2f0752..832a45ba4fa 100644
--- a/dll/win32/winmm/time.c
+++ b/dll/win32/winmm/time.c
@@ -47,6 +47,7 @@ static    LPWINE_TIMERENTRY 	TIME_TimersList;
 static    HANDLE                TIME_hKillEvent;
 static    HANDLE                TIME_hWakeEvent;
 static    BOOL                  TIME_TimeToDie = TRUE;
+static    LARGE_INTEGER         TIME_qpcFreq;

/*
  * Some observations on the behavior of winmm on Windows.
@@ -422,7 +423,14 @@ MMRESULT WINAPI timeGetDevCaps(LPTIMECAPS lpCaps, UINT wSize)
 MMRESULT WINAPI timeBeginPeriod(UINT wPeriod)
 {
     if (wPeriod < MMSYSTIME_MININTERVAL || wPeriod > MMSYSTIME_MAXINTERVAL)
-	return TIMERR_NOCANDO;
+        return TIMERR_NOCANDO;
+
+    /*  High resolution timer requested, use QPC */
+    if (wPeriod <= 5 && TIME_qpcFreq.QuadPart == 0)
+    {
+        if (QueryPerformanceFrequency(&TIME_qpcFreq))
+            TIME_qpcFreq.QuadPart /= 1000;
+    }

if (wPeriod > MMSYSTIME_MININTERVAL)
     {
@@ -438,7 +446,11 @@ MMRESULT WINAPI timeBeginPeriod(UINT wPeriod)
 MMRESULT WINAPI timeEndPeriod(UINT wPeriod)
 {
     if (wPeriod < MMSYSTIME_MININTERVAL || wPeriod > MMSYSTIME_MAXINTERVAL)
-	return TIMERR_NOCANDO;
+        return TIMERR_NOCANDO;
+
+    /*  High resolution timer no longer requested, stop using QPC */
+    if (wPeriod <= 5 && TIME_qpcFreq.QuadPart != 0)
+        TIME_qpcFreq.QuadPart = 0;

if (wPeriod > MMSYSTIME_MININTERVAL)
     {
@@ -453,6 +465,7 @@ MMRESULT WINAPI timeEndPeriod(UINT wPeriod)
  */
 DWORD WINAPI timeGetTime(void)
 {
+    LARGE_INTEGER perfCount;
 #if defined(COMMENTOUTPRIORTODELETING)
     DWORD       count;

@@ -462,6 +475,12 @@ DWORD WINAPI timeGetTime(void)
     if (pFnReleaseThunkLock) pFnReleaseThunkLock(&count);
     if (pFnRestoreThunkLock) pFnRestoreThunkLock(count);
 #endif
-
+    /* Use QPC if a high-resolution timer was requested (<= 5ms) */
+    if (TIME_qpcFreq.QuadPart != 0)
+    {
+        QueryPerformanceCounter(&perfCount);
+        return (DWORD)(perfCount.QuadPart / TIME_qpcFreq.QuadPart);
+    }
+    /* Otherwise continue using GetTickCount */
     return GetTickCount();
 }