SkTime::GetNSecs()

tools/timer/SysTimer_windows.cpp

-/*
- * Copyright 2011 Google Inc.
- *
- * Use of this source code is governed by a BSD-style license that can be
- * found in the LICENSE file.
- */
-#include "SysTimer_windows.h"
-
-#include <intrin.h>
-
-static ULONGLONG win_cpu_time() {
-    FILETIME createTime;
-    FILETIME exitTime;
-    FILETIME usrTime;
-    FILETIME sysTime;
-    if (0 == GetProcessTimes(GetCurrentProcess(), &createTime, &exitTime, &sysTime, &usrTime)) {
-        return 0;
-    }
-    ULARGE_INTEGER start_cpu_sys;
-    ULARGE_INTEGER start_cpu_usr;
-    start_cpu_sys.LowPart  = sysTime.dwLowDateTime;
-    start_cpu_sys.HighPart = sysTime.dwHighDateTime;
-    start_cpu_usr.LowPart  = usrTime.dwLowDateTime;
-    start_cpu_usr.HighPart = usrTime.dwHighDateTime;
-    return start_cpu_sys.QuadPart + start_cpu_usr.QuadPart;
-}
-
-void SysTimer::startCpu() {
-    fStartCpu = win_cpu_time();
-}
-
-double SysTimer::endCpu() {
-    ULONGLONG end_cpu = win_cpu_time();
-    return static_cast<double>(end_cpu - fStartCpu) / 10000.0L;
-}
-
-// On recent Intel chips (roughly, "has Core or Atom in its name") __rdtsc will always tick
-// at the CPU's maximum rate, even while power management clocks the CPU up and down.
-// That's great, because it makes measuring wall time super simple.
-
-void SysTimer::startWall() {
-    fStartWall = __rdtsc();
-}
-
-double SysTimer::endWall() {
-    unsigned __int64 end = __rdtsc();
-
-    // This seems to, weirdly, give the CPU frequency in kHz.  That's exactly what we want!
-    LARGE_INTEGER freq_khz;
-    QueryPerformanceFrequency(&freq_khz);
-
-    return static_cast<double>(end - fStartWall) / static_cast<double>(freq_khz.QuadPart);
-}