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#include "common.hh"
#include "tz_str.hh"
#include <math.h>
#include <stdint.h>
namespace tz {
namespace {
inline bool is_alpha(char c) {
return (c >= 'A' && c <= 'Z') || (c >= 'a' && c <= 'z');
}
inline bool is_digit(char c) {
return c >= '0' && c <= '9';
}
inline bool is_alphnumeric(char c) {
return is_alpha(c) || is_digit(c);
}
std::optional<std::string_view> read_abbr(std::string_view str,
size_t& offset) {
if (offset >= str.size())
return std::nullopt;
auto const start = offset;
std::string_view ret;
if (str[offset] == '<') {
size_t end = str.find('>', offset + 1);
if (end == std::string_view::npos)
return std::nullopt;
offset = end + 1;
ret = str.substr(start + 1, end - (start + 1));
for (auto const& c : ret) {
if (!(is_alphnumeric(c) || c == '+' || c == '-'))
return std::nullopt;
}
} else {
while (offset < str.size() && is_alpha(str[offset]))
++offset;
ret = str.substr(start, offset - start);
}
if (ret.size() < 3)
return std::nullopt;
return ret;
}
std::optional<uint32_t> read_num(std::string_view str,
size_t& offset) {
if (offset >= str.size() || !is_digit(str[offset]))
return std::nullopt;
uint32_t ret = str[offset++] - '0';
while (offset < str.size() && is_digit(str[offset])) {
auto value = ret * 10 + (str[offset++] - '0');
if (value < ret)
return std::nullopt;
ret = value;
}
return ret;
}
std::optional<time_t> read_time(std::string_view str,
size_t& offset) {
auto hh = read_num(str, offset);
if (!hh)
return std::nullopt;
if (hh.value() > 24)
return std::nullopt;
time_t ret = hh.value() * 60 * 60;
if (offset < str.size() && str[offset] == ':') {
++offset;
auto mm = read_num(str, offset);
if (!mm)
return std::nullopt;
if (mm.value() > 59)
return std::nullopt;
ret += mm.value() * 60;
if (offset < str.size() && str[offset] == ':') {
++offset;
auto ss = read_num(str, offset);
if (!ss)
return std::nullopt;
if (ss.value() > 59)
return std::nullopt;
ret += ss.value();
}
}
return ret;
}
std::optional<time_t> read_offset(std::string_view str,
size_t& offset) {
bool negative;
if (offset < str.size() && (str[offset] == '+' || str[offset] == '-'))
negative = str[offset++] == '+'; // Yes, this is correct. ('-' is east)
else
negative = true; // Yes, this is correct. (default is west)
auto ret = read_time(str, offset);
if (!ret)
return std::nullopt;
return negative ? -ret.value() : ret.value();
}
inline bool leap_year(int32_t local_year) {
return (local_year % 4) == 0 &&
((local_year % 100) || ((local_year % 400) == 0));
}
uint8_t week_day_for_day_of_month(int32_t year, uint8_t month,
uint8_t day_of_month) {
auto k = static_cast<int>(day_of_month);
auto m = month >= 3 ? month - 2 : 10 + month;
auto C = year % 100;
auto Y = year / 100;
if (m > 10)
--Y;
return abs((k + static_cast<int>((2.6 * m - 0.2))
- 2 * C + Y + (Y / 4) + (C / 4))) % 7;
}
std::optional<time_t> read_date_and_time(std::string_view str,
int32_t local_year,
size_t& offset) {
if (offset >= str.size())
return std::nullopt;
time_t day_of_year;
if (str[offset] == 'J') {
++offset;
auto julian_day = read_num(str, offset);
if (!julian_day || julian_day.value() < 1 || julian_day.value() > 365)
return std::nullopt;
day_of_year = julian_day.value() - 1;
if (leap_year(local_year) && julian_day.value() >= 60)
++day_of_year;
} else if (str[offset] == 'M') {
++offset;
auto month = read_num(str, offset);
if (!month || month.value() < 1 || month.value() > 12)
return std::nullopt;
if (offset >= str.size() || str[offset] != '.')
return std::nullopt;
++offset;
auto week_of_month = read_num(str, offset);
if (!week_of_month || week_of_month.value() < 1 ||
week_of_month.value() > 5)
return std::nullopt;
if (offset >= str.size() || str[offset] != '.')
return std::nullopt;
++offset;
auto day_of_week = read_num(str, offset);
if (!day_of_week || day_of_week.value() > 6)
return std::nullopt;
day_of_year = 0;
for (size_t i = 1; i < month; ++i) {
day_of_year += (i <= 7)
? ((i == 2) ? (leap_year(local_year) ? 29 : 28) : (i % 2 ? 31 : 30))
: (i % 2 ? 30 : 31);
}
auto week_day_for_first_day_of_month = week_day_for_day_of_month(
local_year, month.value(), 1);
for (size_t i = 1; i < week_of_month; ++i)
day_of_year += 7;
if (day_of_week.value() < week_day_for_first_day_of_month)
day_of_year += 7 - week_day_for_first_day_of_month - day_of_week.value();
else
day_of_year += day_of_week.value() - week_day_for_first_day_of_month;
} else {
auto julian_day = read_num(str, offset);
if (!julian_day || julian_day.value() > 365)
return std::nullopt;
day_of_year = julian_day.value();
}
time_t ret = day_of_year * 24 * 60 * 60;
if (offset < str.size() && str[offset] == '/') {
++offset;
auto time = read_time(str, offset);
if (!time)
return std::nullopt;
ret += time.value();
} else {
ret += 2 * 60 * 60;
}
return ret;
}
} // namespace
std::optional<time_t> get_local_time(std::string_view tz_str,
time_t utc_time) {
size_t offset = 0;
auto std = read_abbr(tz_str, offset);
if (!std)
return std::nullopt;
auto std_offset = read_offset(tz_str, offset);
if (!std_offset)
return std::nullopt;
auto local_time = utc_time + std_offset.value();
if (offset == tz_str.size())
return local_time;
auto dst = read_abbr(tz_str, offset);
if (!dst)
return std::nullopt;
std::optional<time_t> dst_offset;
if (offset == tz_str.size() || tz_str[offset] == ',') {
dst_offset = std_offset.value() + 60 * 60;
} else {
dst_offset = read_offset(tz_str, offset);
if (!dst_offset)
return std::nullopt;
}
if (offset == tz_str.size()) {
// TODO: Can't figure out what the spec actually says about this.
// They are clearly optional but it doesn't specify what the default
// are. Assume no DST.
return local_time;
}
if (tz_str[offset] != ',')
return std::nullopt;
++offset;
// TODO: This can't be 100% correct
auto local_year = 1970 + local_time / (365.25 * 24 * 60 * 60);
auto start = read_date_and_time(tz_str, local_year, offset);
if (!start)
return std::nullopt;
if (tz_str[offset] != ',')
return std::nullopt;
++offset;
auto end = read_date_and_time(tz_str, local_year, offset);
if (!end)
return std::nullopt;
// TODO: If local_year isn't correct this is definitly not.
auto local_time_in_year =
local_time % static_cast<time_t>((365.25 * 24 * 60 * 60));
if (start.value() <= end.value()) {
if (start.value() < local_time_in_year &&
local_time_in_year < end.value()) {
return utc_time + dst_offset.value();
}
} else {
if (!(end.value() < local_time_in_year &&
local_time_in_year < start.value())) {
return utc_time + dst_offset.value();
}
}
return local_time;
}
} // namespace tz
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