MDEV-15694 Windows : use GetSystemTimePreciseAsFileTime if available for high resolution time

Use high accuracy timer on Windows 8.1+ for system versioning,it needs
accurate high resoution start query time.

Continue to use the inaccurate (but much faster timer function)
GetSystemTimeAsFileTime() where accuracy does not matter, e.g in
set_timespec_time_nsec(),or my_time()

1 files changed, 35 insertions, 8 deletions

diff --git a/mysys/my_getsystime.c b/mysys/my_getsystime.c
index 1cedeb21d6e..cd9525e5ff7 100644
--- a/mysys/my_getsystime.c
+++ b/mysys/my_getsystime.c
@@ -18,9 +18,12 @@
 #include "mysys_priv.h"
 #include "my_static.h"
 
-#ifdef __WIN__
+#ifdef _WIN32
 #define OFFSET_TO_EPOC 116444736000000000LL
 static ulonglong query_performance_frequency;
+typedef void (WINAPI* get_system_time_as_filetime_t)(LPFILETIME);
+static get_system_time_as_filetime_t
+  my_GetSystemTimePreciseAsFileTime= GetSystemTimeAsFileTime;
 #endif
 #ifdef HAVE_LINUX_UNISTD_H
 #include <linux/unistd.h>
@@ -53,7 +56,7 @@ ulonglong my_interval_timer()
   return tp.tv_sec*1000000000ULL+tp.tv_nsec;
 #elif defined(HAVE_GETHRTIME)
   return gethrtime();
-#elif defined(__WIN__)
+#elif defined(_WIN32)
   LARGE_INTEGER t_cnt;
   if (query_performance_frequency)
   {
@@ -65,7 +68,7 @@ ulonglong my_interval_timer()
   else
   {
     ulonglong newtime;
-    GetSystemTimeAsFileTime((FILETIME*)&newtime);
+    my_GetSystemTimePreciseAsFileTime((FILETIME*)&newtime);
     return newtime*100ULL;
   }
 #else
@@ -82,11 +85,10 @@ ulonglong my_interval_timer()
 my_hrtime_t my_hrtime()
 {
   my_hrtime_t hrtime;
-#if defined(__WIN__)
+#if defined(_WIN32)
   ulonglong newtime;
-  GetSystemTimeAsFileTime((FILETIME*)&newtime);
-  newtime -= OFFSET_TO_EPOC;
-  hrtime.val= newtime/10;
+  my_GetSystemTimePreciseAsFileTime((FILETIME*)&newtime);
+  hrtime.val= (newtime - OFFSET_TO_EPOC)/10;
 #elif defined(HAVE_CLOCK_GETTIME)
   struct timespec tp;
   clock_gettime(CLOCK_REALTIME, &tp);
@@ -100,14 +102,39 @@ my_hrtime_t my_hrtime()
   return hrtime;
 }
 
+#ifdef _WIN32
+
+/*
+  Low accuracy, "coarse" timer.
+  Has lower latency than my_hrtime(). Used in situations, where microsecond
+  precision is not needed, e.g in Windows pthread_cond_timedwait, where POSIX 
+  interface needs nanoseconds, yet the underlying Windows function only
+  accepts millisecons.
+*/
+my_hrtime_t my_hrtime_coarse()
+{
+  my_hrtime_t hrtime;
+  ulonglong t;
+  GetSystemTimeAsFileTime((FILETIME*)&t);
+  hrtime.val= (t - OFFSET_TO_EPOC)/10;
+  return hrtime;
+}
+
+#endif
 
 void my_time_init()
 {
-#ifdef __WIN__
+#ifdef _WIN32
   compile_time_assert(sizeof(LARGE_INTEGER) ==
                       sizeof(query_performance_frequency));
   if (QueryPerformanceFrequency((LARGE_INTEGER *)&query_performance_frequency) == 0)
     query_performance_frequency= 0;
+
+  get_system_time_as_filetime_t f= (get_system_time_as_filetime_t)
+    GetProcAddress(GetModuleHandle("kernel32"),
+                   "GetSystemTimePreciseAsFileTime");
+  if (f)
+    my_GetSystemTimePreciseAsFileTime= f;
 #endif
 }