win: add equivalent of gettimeofday

util/win/time.cc

+// Copyright 2015 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/win/time.h"
+
+#include <inttypes.h>
+#include <windows.h>
+
+#include "base/logging.h"
+
+namespace crashpad {
+
+void GetTimeOfDay(timeval* tv) {
+  FILETIME filetime;
+  GetSystemTimeAsFileTime(&filetime);
+  uint64_t t = (static_cast<uint64_t>(filetime.dwHighDateTime) << 32) |
+               filetime.dwLowDateTime;
+  t /= 10;  // 100 nanosecond intervals to microseconds.
+  // Windows epoch is 1601-01-01, and FILETIME ticks are 100 nanoseconds.
+  // 1601 to 1970 is 369 years + 89 leap days = 134774 days * 86400 seconds per
+  // day. It's not entirely clear, but it appears that these are solar seconds,
+  // not SI seconds, so there are no leap seconds to be considered.
+  const uint64_t kNumSecondsFrom1601To1970 = (369 * 365 + 89) * 86400ULL;
+  const uint64_t kMicrosecondsPerSecond = static_cast<uint64_t>(1E6);
+  DCHECK_GE(t, kNumSecondsFrom1601To1970 * kMicrosecondsPerSecond);
+  t -= kNumSecondsFrom1601To1970 * kMicrosecondsPerSecond;
+  tv->tv_sec = static_cast<long>(t / kMicrosecondsPerSecond);
+  tv->tv_usec = static_cast<long>(t % kMicrosecondsPerSecond);
+}
+
+}  // namespace crashpad