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// 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.
#include "time_zone_fixed.h"
#include <algorithm>
#include <cassert>
#include <chrono>
#include <cstring>
#include <string>
namespace cctz {
namespace {
// The prefix used for the internal names of fixed-offset zones.
const char kFixedZonePrefix[] = "Fixed/UTC";
const char kDigits[] = "0123456789";
char* Format02d(char* p, int v) {
*p++ = kDigits[(v / 10) % 10];
*p++ = kDigits[v % 10];
return p;
}
int Parse02d(const char* p) {
if (const char* ap = std::strchr(kDigits, *p)) {
int v = static_cast<int>(ap - kDigits);
if (const char* bp = std::strchr(kDigits, *++p)) {
return (v * 10) + static_cast<int>(bp - kDigits);
}
}
return -1;
}
} // namespace
bool FixedOffsetFromName(const std::string& name, seconds* offset) {
if (name == "UTC" || name == "UTC0") {
*offset = seconds::zero();
return true;
}
const std::size_t prefix_len = sizeof(kFixedZonePrefix) - 1;
const char* const ep = kFixedZonePrefix + prefix_len;
if (name.size() != prefix_len + 9) // <prefix>+99:99:99
return false;
if (!std::equal(kFixedZonePrefix, ep, name.begin()))
return false;
const char* np = name.data() + prefix_len;
if (np[0] != '+' && np[0] != '-')
return false;
if (np[3] != ':' || np[6] != ':') // see note below about large offsets
return false;
int hours = Parse02d(np + 1);
if (hours == -1) return false;
int mins = Parse02d(np + 4);
if (mins == -1) return false;
int secs = Parse02d(np + 7);
if (secs == -1) return false;
secs += ((hours * 60) + mins) * 60;
if (secs > 24 * 60 * 60) return false; // outside supported offset range
*offset = seconds(secs * (np[0] == '-' ? -1 : 1)); // "-" means west
return true;
}
std::string FixedOffsetToName(const seconds& offset) {
if (offset == seconds::zero()) return "UTC";
if (offset < std::chrono::hours(-24) || offset > std::chrono::hours(24)) {
// We don't support fixed-offset zones more than 24 hours
// away from UTC to avoid complications in rendering such
// offsets and to (somewhat) limit the total number of zones.
return "UTC";
}
int offset_seconds = static_cast<int>(offset.count());
const char sign = (offset_seconds < 0 ? '-' : '+');
int offset_minutes = offset_seconds / 60;
offset_seconds %= 60;
if (sign == '-') {
if (offset_seconds > 0) {
offset_seconds -= 60;
offset_minutes += 1;
}
offset_seconds = -offset_seconds;
offset_minutes = -offset_minutes;
}
int offset_hours = offset_minutes / 60;
offset_minutes %= 60;
const std::size_t prefix_len = sizeof(kFixedZonePrefix) - 1;
char buf[prefix_len + sizeof("-24:00:00")];
char* ep = std::copy(kFixedZonePrefix, kFixedZonePrefix + prefix_len, buf);
*ep++ = sign;
ep = Format02d(ep, offset_hours);
*ep++ = ':';
ep = Format02d(ep, offset_minutes);
*ep++ = ':';
ep = Format02d(ep, offset_seconds);
*ep++ = '\0';
assert(ep == buf + sizeof(buf));
return buf;
}
std::string FixedOffsetToAbbr(const seconds& offset) {
std::string abbr = FixedOffsetToName(offset);
const std::size_t prefix_len = sizeof(kFixedZonePrefix) - 1;
if (abbr.size() == prefix_len + 9) { // <prefix>+99:99:99
abbr.erase(0, prefix_len); // +99:99:99
abbr.erase(6, 1); // +99:9999
abbr.erase(3, 1); // +999999
if (abbr[5] == '0' && abbr[6] == '0') { // +999900
abbr.erase(5, 2); // +9999
if (abbr[3] == '0' && abbr[4] == '0') { // +9900
abbr.erase(3, 2); // +99
}
}
}
return abbr;
}
} // namespace cctz
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