changeset:   97174:917cebba8cb9
tag:         tip
user:        Victor Stinner <victor.stinner@gmail.com>
date:        Fri Jul 31 23:46:07 2015 +0200
files:       Doc/library/time.rst Doc/whatsnew/3.6.rst Python/pytime.c
description:
Use GetSystemTimePreciseAsFileTime

On Windows, time.time() now uses GetSystemTimePreciseAsFileTime() when
available: Windows 8, Windows Server 2012 and newer.


diff -r 74fc1af57c72 -r 917cebba8cb9 Doc/library/time.rst
--- a/Doc/library/time.rst	Fri Jul 31 23:36:28 2015 +0200
+++ b/Doc/library/time.rst	Fri Jul 31 23:46:07 2015 +0200
@@ -576,6 +576,11 @@ The module defines the following functio
    lower value than a previous call if the system clock has been set back between
    the two calls.
 
+   .. versionchanged:: 3.6
+      On Windows, the ``GetSystemTimePreciseAsFileTime()`` C function is now
+      used when available: Windows 8, Windows Server 2012 and newer.
+
+
 .. data:: timezone
 
    The offset of the local (non-DST) timezone, in seconds west of UTC (negative in
diff -r 74fc1af57c72 -r 917cebba8cb9 Doc/whatsnew/3.6.rst
--- a/Doc/whatsnew/3.6.rst	Fri Jul 31 23:36:28 2015 +0200
+++ b/Doc/whatsnew/3.6.rst	Fri Jul 31 23:46:07 2015 +0200
@@ -95,7 +95,12 @@ New Modules
 Improved Modules
 ================
 
-* None yet.
+time
+----
+
+* On Windows, :func:`time.time` now uses the
+  ``GetSystemTimePreciseAsFileTime()`` C function when available: Windows 8,
+  Windows Server 2012 and newer.
 
 
 Optimizations
diff -r 74fc1af57c72 -r 917cebba8cb9 Python/pytime.c
--- a/Python/pytime.c	Fri Jul 31 23:36:28 2015 +0200
+++ b/Python/pytime.c	Fri Jul 31 23:46:07 2015 +0200
@@ -23,6 +23,10 @@
 #define NS_TO_MS (1000 * 1000)
 #define NS_TO_US (1000)
 
+#ifdef MS_WINDOWS
+static VOID (CALLBACK *Py_GetSystemTimePreciseAsFileTime)(LPFILETIME) = NULL;
+#endif
+
 static void
 error_time_t_overflow(void)
 {
@@ -429,7 +433,10 @@ pygettimeofday_new(_PyTime_t *tp, _Py_cl
 
     assert(info == NULL || raise);
 
-    GetSystemTimeAsFileTime(&system_time);
+    if (Py_GetSystemTimePreciseAsFileTime)
+        Py_GetSystemTimePreciseAsFileTime(&system_time);
+    else
+        GetSystemTimeAsFileTime(&system_time);
     large.u.LowPart = system_time.dwLowDateTime;
     large.u.HighPart = system_time.dwHighDateTime;
     /* 11,644,473,600,000,000,000: number of nanoseconds between
@@ -440,16 +447,32 @@ pygettimeofday_new(_PyTime_t *tp, _Py_cl
         DWORD timeAdjustment, timeIncrement;
         BOOL isTimeAdjustmentDisabled, ok;
 
-        info->implementation = "GetSystemTimeAsFileTime()";
-        info->monotonic = 0;
-        ok = GetSystemTimeAdjustment(&timeAdjustment, &timeIncrement,
-                                     &isTimeAdjustmentDisabled);
-        if (!ok) {
-            PyErr_SetFromWindowsErr(0);
-            return -1;
+        if (Py_GetSystemTimePreciseAsFileTime) {
+            LARGE_INTEGER freq;
+
+            info->implementation = "GetSystemTimePreciseAsFileTime()";
+            info->monotonic = 0;
+            ok = GetSystemTimeAdjustment(&timeAdjustment, &timeIncrement,
+                                         &isTimeAdjustmentDisabled);
+            if (!QueryPerformanceFrequency(&freq) || freq.QuadPart == 0) {
+                PyErr_SetFromWindowsErr(0);
+                return -1;
+            }
+            info->resolution = 1.0 / (double)freq.QuadPart;
+            info->adjustable = 1;
         }
-        info->resolution = timeIncrement * 1e-7;
-        info->adjustable = 1;
+        else {
+            info->implementation = "GetSystemTimeAsFileTime()";
+            info->monotonic = 0;
+            ok = GetSystemTimeAdjustment(&timeAdjustment, &timeIncrement,
+                                         &isTimeAdjustmentDisabled);
+            if (!ok) {
+                PyErr_SetFromWindowsErr(0);
+                return -1;
+            }
+            info->resolution = timeIncrement * 1e-7;
+            info->adjustable = 1;
+        }
     }
 
 #else   /* MS_WINDOWS */
@@ -662,6 +685,14 @@ int
 _PyTime_Init(void)
 {
     _PyTime_t t;
+#ifdef MS_WINDOWS
+    HINSTANCE hKernel32;
+
+    hKernel32 = GetModuleHandleW(L"KERNEL32");
+    /* Function available on Windows 8, Windows Server 2012 and newer */
+    *(FARPROC*)&Py_GetSystemTimePreciseAsFileTime = GetProcAddress(hKernel32,
+            "GetSystemTimePreciseAsFileTime");
+#endif
 
     /* ensure that the system clock works */
     if (_PyTime_GetSystemClockWithInfo(&t, NULL) < 0)