MdePkg: Add missing implementation of GetTimeInNanoSecond() to TimerLib library instance DxeTimerLibEsal.

Signed-off-by: xdu2
Reviewed-by: mdkinney

git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@12297 6f19259b-4bc3-4df7-8a09-765794883524

MdePkg/Library/DxeTimerLibEsal/DxeTimerLibEsal.c

@@ -177,3 +177,47 @@ GetPerformanceCounterProperties (
 
   return BaseFrequence * (PalRet.r11 >> 32) / (UINT32)PalRet.r11;
 }
+
+/**
+  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;
+}