// Copyright 2016 Google Inc. 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
//
// https://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.
#if defined(_WIN32) || defined(_WIN64)
#define _CRT_SECURE_NO_WARNINGS 1
#endif
#include "time_zone_libc.h"
#include <chrono>
#include <ctime>
#include <limits>
#include <utility>
#include "absl/base/config.h"
#include "absl/time/internal/cctz/include/cctz/civil_time.h"
#include "absl/time/internal/cctz/include/cctz/time_zone.h"
#if defined(_AIX)
extern "C" {
extern long altzone;
}
#endif
namespace absl {
ABSL_NAMESPACE_BEGIN
namespace time_internal {
namespace cctz {
namespace {
#if defined(_WIN32) || defined(_WIN64)
// Uses the globals: '_timezone', '_dstbias' and '_tzname'.
auto tm_gmtoff(const std::tm& tm) -> decltype(_timezone + _dstbias) {
const bool is_dst = tm.tm_isdst > 0;
return _timezone + (is_dst ? _dstbias : 0);
}
auto tm_zone(const std::tm& tm) -> decltype(_tzname[0]) {
const bool is_dst = tm.tm_isdst > 0;
return _tzname[is_dst];
}
#elif defined(__sun) || defined(_AIX)
// Uses the globals: 'timezone', 'altzone' and 'tzname'.
auto tm_gmtoff(const std::tm& tm) -> decltype(timezone) {
const bool is_dst = tm.tm_isdst > 0;
return is_dst ? altzone : timezone;
}
auto tm_zone(const std::tm& tm) -> decltype(tzname[0]) {
const bool is_dst = tm.tm_isdst > 0;
return tzname[is_dst];
}
#elif defined(__native_client__) || defined(__myriad2__) || \
defined(__EMSCRIPTEN__)
// Uses the globals: 'timezone' and 'tzname'.
auto tm_gmtoff(const std::tm& tm) -> decltype(_timezone + 0) {
const bool is_dst = tm.tm_isdst > 0;
return _timezone + (is_dst ? 60 * 60 : 0);
}
auto tm_zone(const std::tm& tm) -> decltype(tzname[0]) {
const bool is_dst = tm.tm_isdst > 0;
return tzname[is_dst];
}
#else
// Adapt to different spellings of the struct std::tm extension fields.
#if defined(tm_gmtoff)
auto tm_gmtoff(const std::tm& tm) -> decltype(tm.tm_gmtoff) {
return tm.tm_gmtoff;
}
#elif defined(__tm_gmtoff)
auto tm_gmtoff(const std::tm& tm) -> decltype(tm.__tm_gmtoff) {
return tm.__tm_gmtoff;
}
#else
template <typename T>
auto tm_gmtoff(const T& tm) -> decltype(tm.tm_gmtoff) {
return tm.tm_gmtoff;
}
template <typename T>
auto tm_gmtoff(const T& tm) -> decltype(tm.__tm_gmtoff) {
return tm.__tm_gmtoff;
}
#endif // tm_gmtoff
#if defined(tm_zone)
auto tm_zone(const std::tm& tm) -> decltype(tm.tm_zone) { return tm.tm_zone; }
#elif defined(__tm_zone)
auto tm_zone(const std::tm& tm) -> decltype(tm.__tm_zone) {
return tm.__tm_zone;
}
#else
template <typename T>
auto tm_zone(const T& tm) -> decltype(tm.tm_zone) {
return tm.tm_zone;
}
template <typename T>
auto tm_zone(const T& tm) -> decltype(tm.__tm_zone) {
return tm.__tm_zone;
}
#endif // tm_zone
#endif
inline std::tm* gm_time(const std::time_t* timep, std::tm* result) {
#if defined(_WIN32) || defined(_WIN64)
return gmtime_s(result, timep) ? nullptr : result;
#else
return gmtime_r(timep, result);
#endif
}
inline std::tm* local_time(const std::time_t* timep, std::tm* result) {
#if defined(_WIN32) || defined(_WIN64)
return localtime_s(result, timep) ? nullptr : result;
#else
return localtime_r(timep, result);
#endif
}
// Converts a civil second and "dst" flag into a time_t and UTC offset.
// Returns false if time_t cannot represent the requested civil second.
// Caller must have already checked that cs.year() will fit into a tm_year.
bool make_time(const civil_second& cs, int is_dst, std::time_t* t, int* off) {
std::tm tm;
tm.tm_year = static_cast<int>(cs.year() - year_t{1900});
tm.tm_mon = cs.month() - 1;
tm.tm_mday = cs.day();
tm.tm_hour = cs.hour();
tm.tm_min = cs.minute();
tm.tm_sec = cs.second();
tm.tm_isdst = is_dst;
*t = std::mktime(&tm);
if (*t == std::time_t{-1}) {
std::tm tm2;
const std::tm* tmp = local_time(t, &tm2);
if (tmp == nullptr || tmp->tm_year != tm.tm_year ||
tmp->tm_mon != tm.tm_mon || tmp->tm_mday != tm.tm_mday ||
tmp->tm_hour != tm.tm_hour || tmp->tm_min != tm.tm_min ||
tmp->tm_sec != tm.tm_sec) {
// A true error (not just one second before the epoch).
return false;
}
}
*off = static_cast<int>(tm_gmtoff(tm));
return true;
}
// Find the least time_t in [lo:hi] where local time matches offset, given:
// (1) lo doesn't match, (2) hi does, and (3) there is only one transition.
std::time_t find_trans(std::time_t lo, std::time_t hi, int offset) {
std::tm tm;
while (lo + 1 != hi) {
const std::time_t mid = lo + (hi - lo) / 2;
std::tm* tmp = local_time(&mid, &tm);
if (tmp != nullptr) {
if (tm_gmtoff(*tmp) == offset) {
hi = mid;
} else {
lo = mid;
}
} else {
// If std::tm cannot hold some result we resort to a linear search,
// ignoring all failed conversions. Slow, but never really happens.
while (++lo != hi) {
tmp = local_time(&lo, &tm);
if (tmp != nullptr) {
if (tm_gmtoff(*tmp) == offset) break;
}
}
return lo;
}
}
return hi;
}
} // namespace
TimeZoneLibC::TimeZoneLibC(const std::string& name)
: local_(name == "localtime") {}
time_zone::absolute_lookup TimeZoneLibC::BreakTime(
const time_point<seconds>& tp) const {
time_zone::absolute_lookup al;
al.offset = 0;
al.is_dst = false;
al.abbr = "-00";
const std::int_fast64_t s = ToUnixSeconds(tp);
// If std::time_t cannot hold the input we saturate the output.
if (s < std::numeric_limits<std::time_t>::min()) {
al.cs = civil_second::min();
return al;
}
if (s > std::numeric_limits<std::time_t>::max()) {
al.cs = civil_second::max();
return al;
}
const std::time_t t = static_cast<std::time_t>(s);
std::tm tm;
std::tm* tmp = local_ ? local_time(&t, &tm) : gm_time(&t, &tm);
// If std::tm cannot hold the result we saturate the output.
if (tmp == nullptr) {
al.cs = (s < 0) ? civil_second::min() : civil_second::max();
return al;
}
const year_t year = tmp->tm_year + year_t{1900};
al.cs = civil_second(year, tmp->tm_mon + 1, tmp->tm_mday, tmp->tm_hour,
tmp->tm_min, tmp->tm_sec);
al.offset = static_cast<int>(tm_gmtoff(*tmp));
al.abbr = local_ ? tm_zone(*tmp) : "UTC"; // as expected by cctz
al.is_dst = tmp->tm_isdst > 0;
return al;
}
time_zone::civil_lookup TimeZoneLibC::MakeTime(const civil_second& cs) const {
if (!local_) {
// If time_point<seconds> cannot hold the result we saturate.
static const civil_second min_tp_cs =
civil_second() + ToUnixSeconds(time_point<seconds>::min());
static const civil_second max_tp_cs =
civil_second() + ToUnixSeconds(time_point<seconds>::max());
const time_point<seconds> tp = (cs < min_tp_cs) ? time_point<seconds>::min()
: (cs > max_tp_cs)
? time_point<seconds>::max()
: FromUnixSeconds(cs - civil_second());
return {time_zone::civil_lookup::UNIQUE, tp, tp, tp};
}
// If tm_year cannot hold the requested year we saturate the result.
if (cs.year() < 0) {
if (cs.year() < std::numeric_limits<int>::min() + year_t{1900}) {
const time_point<seconds> tp = time_point<seconds>::min();
return {time_zone::civil_lookup::UNIQUE, tp, tp, tp};
}
} else {
if (cs.year() - year_t{1900} > std::numeric_limits<int>::max()) {
const time_point<seconds> tp = time_point<seconds>::max();
return {time_zone::civil_lookup::UNIQUE, tp, tp, tp};
}
}
// We probe with "is_dst" values of 0 and 1 to try to distinguish unique
// civil seconds from skipped or repeated ones. This is not always possible
// however, as the "dst" flag does not change over some offset transitions.
// We are also subject to the vagaries of mktime() implementations.
std::time_t t0, t1;
int offset0, offset1;
if (make_time(cs, 0, &t0, &offset0) && make_time(cs, 1, &t1, &offset1)) {
if (t0 == t1) {
// The civil time was singular (pre == trans == post).
const time_point<seconds> tp = FromUnixSeconds(t0);
return {time_zone::civil_lookup::UNIQUE, tp, tp, tp};
}
if (t0 > t1) {
std::swap(t0, t1);
std::swap(offset0, offset1);
}
const std::time_t tt = find_trans(t0, t1, offset1);
const time_point<seconds> trans = FromUnixSeconds(tt);
if (offset0 < offset1) {
// The civil time did not exist (pre >= trans > post).
const time_point<seconds> pre = FromUnixSeconds(t1);
const time_point<seconds> post = FromUnixSeconds(t0);
return {time_zone::civil_lookup::SKIPPED, pre, trans, post};
}
// The civil time was ambiguous (pre < trans <= post).
const time_point<seconds> pre = FromUnixSeconds(t0);
const time_point<seconds> post = FromUnixSeconds(t1);
return {time_zone::civil_lookup::REPEATED, pre, trans, post};
}
// make_time() failed somehow so we saturate the result.
const time_point<seconds> tp = (cs < civil_second())
? time_point<seconds>::min()
: time_point<seconds>::max();
return {time_zone::civil_lookup::UNIQUE, tp, tp, tp};
}
bool TimeZoneLibC::NextTransition(const time_point<seconds>&,
time_zone::civil_transition*) const {
return false;
}
bool TimeZoneLibC::PrevTransition(const time_point<seconds>&,
time_zone::civil_transition*) const {
return false;
}
std::string TimeZoneLibC::Version() const {
return std::string(); // unknown
}
std::string TimeZoneLibC::Description() const {
return local_ ? "localtime" : "UTC";
}
} // namespace cctz
} // namespace time_internal
ABSL_NAMESPACE_END
} // namespace absl
