1 files changed, 44 insertions, 1 deletions
diff --git a/EmulatorPkg/Library/DxeCoreTimerLib/DxeCoreTimerLib.c b/EmulatorPkg/Library/DxeCoreTimerLib/DxeCoreTimerLib.c
index c331cbba9c..ab0de143c4 100644
--- a/EmulatorPkg/Library/DxeCoreTimerLib/DxeCoreTimerLib.c
+++ b/EmulatorPkg/Library/DxeCoreTimerLib/DxeCoreTimerLib.c
@@ -1,12 +1,13 @@
 /** @file
   A non-functional instance of the Timer Library.
 
-  Copyright (c) 2007 - 2010, Intel Corporation. All rights reserved.<BR>
+  Copyright (c) 2007 - 2019, Intel Corporation. All rights reserved.<BR>
   SPDX-License-Identifier: BSD-2-Clause-Patent
 
 **/
 
 #include <PiPei.h>
+#include <Library/BaseLib.h>
 #include <Library/TimerLib.h>
 #include <Library/DebugLib.h>
 #include <Library/EmuThunkLib.h>
@@ -119,4 +120,46 @@ GetPerformanceCounterProperties (
   return gEmuThunk->QueryPerformanceFrequency ();
 }
 
+/**
+  Converts elapsed ticks of performance counter to time in nanoseconds.
+
+  This function converts the elapsed ticks of running performance counter to
+  time value in unit of nanoseconds.
+
+  @param  Ticks     The number of elapsed ticks of running performance counter.
+
+  @return The elapsed time in nanoseconds.
+
+**/
+UINT64
+EFIAPI
+GetTimeInNanoSecond (
+  IN UINT64  Ticks
+  )
+{
+  UINT64  Frequency;
+  UINT64  NanoSeconds;
+  UINT64  Remainder;
+  INTN    Shift;
+
+  Frequency = GetPerformanceCounterProperties (NULL, NULL);
+
+  //
+  //          Ticks
+  // Time = --------- x 1,000,000,000
+  //        Frequency
+  //
+  NanoSeconds = MultU64x32 (DivU64x64Remainder (Ticks, Frequency, &Remainder), 1000000000u);
+
+  //
+  // Ensure (Remainder * 1,000,000,000) will not overflow 64-bit.
+  // Since 2^29 < 1,000,000,000 = 0x3B9ACA00 < 2^30, Remainder should < 2^(64-30) = 2^34,
+  // i.e. highest bit set in Remainder should <= 33.
+  //
+  Shift = MAX (0, HighBitSet64 (Remainder) - 33);
+  Remainder = RShiftU64 (Remainder, (UINTN) Shift);
+  Frequency = RShiftU64 (Frequency, (UINTN) Shift);
+  NanoSeconds += DivU64x64Remainder (MultU64x32 (Remainder, 1000000000u), Frequency, NULL);
 
+  return NanoSeconds;
+}