Bug 164841: use high performance timers (again) on OS/2.

nsprpub/pr/src/md/os2/os2inrval.c

@@ -39,22 +39,62 @@
 
 #include "primpl.h"
 
+static PRBool useHighResTimer = PR_FALSE;
+PRIntervalTime _os2_ticksPerSec = -1;
+PRIntn _os2_bitShift = 0;
+PRInt32 _os2_highMask = 0;
    
 void
 _PR_MD_INTERVAL_INIT()
 {
+    ULONG timerFreq = 0; /* OS/2 high-resolution timer frequency in Hz */
+    APIRET rc = DosTmrQueryFreq(&timerFreq);
+    if (NO_ERROR == rc) {
+        useHighResTimer = PR_TRUE;
+        PR_ASSERT(timerFreq != 0);
+        while (timerFreq > PR_INTERVAL_MAX) {
+            timerFreq >>= 1;
+            _os2_bitShift++;
+            _os2_highMask = (_os2_highMask << 1)+1;
+        }
+
+        _os2_ticksPerSec = timerFreq;
+        PR_ASSERT(_os2_ticksPerSec > PR_INTERVAL_MIN);
+    }
 }
 
 PRIntervalTime
 _PR_MD_GET_INTERVAL()
 {
-    ULONG msCount = PR_FAILURE;
-    DosQuerySysInfo(QSV_MS_COUNT, QSV_MS_COUNT, &msCount, sizeof(msCount));
-    return msCount;
+    if (useHighResTimer) {
+        QWORD timestamp;
+        PRInt32 top;
+        APIRET rc = DosTmrQueryTime(&timestamp);
+        if (NO_ERROR != rc) {
+            return -1;
+        }
+        /* Sadly, nspr requires the interval to range from 1000 ticks per
+         * second to only 100000 ticks per second. DosTmrQueryTime is too
+         * high resolution...
+         */
+        top = timestamp.ulHi & _os2_highMask;
+        top = top << (32 - _os2_bitShift);
+        timestamp.ulLo = timestamp.ulLo >> _os2_bitShift;   
+        timestamp.ulLo = timestamp.ulLo + top; 
+        return (PRUint32)timestamp.ulLo;
+    } else {
+        ULONG msCount = -1;
+        DosQuerySysInfo(QSV_MS_COUNT, QSV_MS_COUNT, &msCount, sizeof(msCount));
+        return msCount;
+    }
 }
 
 PRIntervalTime
 _PR_MD_INTERVAL_PER_SEC()
 {
-    return 1000;
+    if (useHighResTimer) {
+        return _os2_ticksPerSec;
+    } else {
+        return 1000;
+    }
 }