v8/src/base/platform/platform-posix-time.cc

// Copyright 2017 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include <cmath>

#include "src/base/platform/platform-posix-time.h"

namespace v8 {
namespace base {

const char* PosixDefaultTimezoneCache::LocalTimezone(double time) {
  if (std::isnan(time)) return "";
  time_t tv = static_cast<time_t>(std::floor(time / msPerSecond));
  struct tm tm;
  struct tm* t = localtime_r(&tv, &tm);
  if (!t || !t->tm_zone) return "";
  return t->tm_zone;
}

double PosixDefaultTimezoneCache::LocalTimeOffset(double time_ms, bool is_utc) {
  // Preserve the old behavior for non-ICU implementation by ignoring both
  // time_ms and is_utc.
  time_t tv = time(nullptr);
  struct tm tm;
  struct tm* t = localtime_r(&tv, &tm);
  // tm_gmtoff includes any daylight savings offset, so subtract it.
  return static_cast<double>(t->tm_gmtoff * msPerSecond -
                             (t->tm_isdst > 0 ? 3600 * msPerSecond : 0));
}

}  // namespace base
}  // namespace v8