win: clock implementation

util/misc/clock_win.cc

+// Copyright 2014 The Crashpad Authors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "util/misc/clock.h"
+
+#include <sys/types.h>
+#include <windows.h>
+
+namespace {
+
+LARGE_INTEGER QpcFrequencyInternal() {
+  LARGE_INTEGER frequency;
+  QueryPerformanceFrequency(&frequency);
+  return frequency;
+}
+
+int64_t QpcFrequency() {
+  static LARGE_INTEGER frequency = QpcFrequencyInternal();
+  return frequency.QuadPart;
+}
+
+}  // namespace
+
+namespace crashpad {
+
+uint64_t ClockMonotonicNanoseconds() {
+  LARGE_INTEGER time;
+  QueryPerformanceCounter(&time);
+  int64_t frequency = QpcFrequency();
+  int64_t whole_seconds = time.QuadPart / frequency;
+  int64_t leftover_ticks = time.QuadPart / (whole_seconds * frequency);
+  const int64_t kNanosecondsPerSecond = static_cast<const int64_t>(1E9);
+  return (whole_seconds * kNanosecondsPerSecond) +
+         ((leftover_ticks * kNanosecondsPerSecond) / frequency);
+}
+
+void SleepNanoseconds(uint64_t nanoseconds) {
+  // This is both inaccurate (will be way too long for short sleeps) and
+  // incorrect (can sleep for less than requested). But it's what's available
+  // without implementing a busy loop.

[Mark Mentovai, 2014/12/17 01:12:23]

Probably should do the loop until ClockMonotonicNanoseconds() is at least at its
original value + nanoseconds, but it’s not important now if you don’t want to do
that. This function is unused everywhere except for some very Mac-specific code
that will may soon be declared dead.

[scottmg, 2014/12/17 01:58:11]

Done. I look forward to deleting it!

+  const uint64_t kNanosecondsPerMillisecond = static_cast<const uint64_t>(1E6);
+  Sleep(static_cast<DWORD>(nanoseconds / kNanosecondsPerMillisecond));
+}
+
+}  // namespace crashpad