1// Copyright 2016 Google Inc. All Rights Reserved.
2//
3// Licensed under the Apache License, Version 2.0 (the "License");
4// you may not use this file except in compliance with the License.
5// You may obtain a copy of the License at
6//
7// https://www.apache.org/licenses/LICENSE-2.0
8//
9// Unless required by applicable law or agreed to in writing, software
10// distributed under the License is distributed on an "AS IS" BASIS,
11// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12// See the License for the specific language governing permissions and
13// limitations under the License.
14
15#include "time_zone_fixed.h"
16
17#include <algorithm>
18#include <cassert>
19#include <chrono>
20#include <cstring>
21#include <string>
22
23namespace absl {
24namespace time_internal {
25namespace cctz {
26
27namespace {
28
29// The prefix used for the internal names of fixed-offset zones.
30const char kFixedZonePrefix[] = "Fixed/UTC";
31
32const char kDigits[] = "0123456789";
33
34char* Format02d(char* p, int v) {
35 *p++ = kDigits[(v / 10) % 10];
36 *p++ = kDigits[v % 10];
37 return p;
38}
39
40int Parse02d(const char* p) {
41 if (const char* ap = std::strchr(kDigits, *p)) {
42 int v = static_cast<int>(ap - kDigits);
43 if (const char* bp = std::strchr(kDigits, *++p)) {
44 return (v * 10) + static_cast<int>(bp - kDigits);
45 }
46 }
47 return -1;
48}
49
50} // namespace
51
52bool FixedOffsetFromName(const std::string& name, seconds* offset) {
53 if (name.compare(0, std::string::npos, "UTC", 3) == 0) {
54 *offset = seconds::zero();
55 return true;
56 }
57
58 const std::size_t prefix_len = sizeof(kFixedZonePrefix) - 1;
59 const char* const ep = kFixedZonePrefix + prefix_len;
60 if (name.size() != prefix_len + 9) // <prefix>+99:99:99
61 return false;
62 if (!std::equal(kFixedZonePrefix, ep, name.begin()))
63 return false;
64 const char* np = name.data() + prefix_len;
65 if (np[0] != '+' && np[0] != '-')
66 return false;
67 if (np[3] != ':' || np[6] != ':') // see note below about large offsets
68 return false;
69
70 int hours = Parse02d(np + 1);
71 if (hours == -1) return false;
72 int mins = Parse02d(np + 4);
73 if (mins == -1) return false;
74 int secs = Parse02d(np + 7);
75 if (secs == -1) return false;
76
77 secs += ((hours * 60) + mins) * 60;
78 if (secs > 24 * 60 * 60) return false; // outside supported offset range
79 *offset = seconds(secs * (np[0] == '-' ? -1 : 1)); // "-" means west
80 return true;
81}
82
83std::string FixedOffsetToName(const seconds& offset) {
84 if (offset == seconds::zero()) return "UTC";
85 if (offset < std::chrono::hours(-24) || offset > std::chrono::hours(24)) {
86 // We don't support fixed-offset zones more than 24 hours
87 // away from UTC to avoid complications in rendering such
88 // offsets and to (somewhat) limit the total number of zones.
89 return "UTC";
90 }
91 int seconds = static_cast<int>(offset.count());
92 const char sign = (seconds < 0 ? '-' : '+');
93 int minutes = seconds / 60;
94 seconds %= 60;
95 if (sign == '-') {
96 if (seconds > 0) {
97 seconds -= 60;
98 minutes += 1;
99 }
100 seconds = -seconds;
101 minutes = -minutes;
102 }
103 int hours = minutes / 60;
104 minutes %= 60;
105 const std::size_t prefix_len = sizeof(kFixedZonePrefix) - 1;
106 char buf[prefix_len + sizeof("-24:00:00")];
107 char* ep = std::copy(kFixedZonePrefix, kFixedZonePrefix + prefix_len, buf);
108 *ep++ = sign;
109 ep = Format02d(ep, hours);
110 *ep++ = ':';
111 ep = Format02d(ep, minutes);
112 *ep++ = ':';
113 ep = Format02d(ep, seconds);
114 *ep++ = '\0';
115 assert(ep == buf + sizeof(buf));
116 return buf;
117}
118
119std::string FixedOffsetToAbbr(const seconds& offset) {
120 std::string abbr = FixedOffsetToName(offset);
121 const std::size_t prefix_len = sizeof(kFixedZonePrefix) - 1;
122 if (abbr.size() == prefix_len + 9) { // <prefix>+99:99:99
123 abbr.erase(0, prefix_len); // +99:99:99
124 abbr.erase(6, 1); // +99:9999
125 abbr.erase(3, 1); // +999999
126 if (abbr[5] == '0' && abbr[6] == '0') { // +999900
127 abbr.erase(5, 2); // +9999
128 if (abbr[3] == '0' && abbr[4] == '0') { // +9900
129 abbr.erase(3, 2); // +99
130 }
131 }
132 }
133 return abbr;
134}
135
136} // namespace cctz
137} // namespace time_internal
138} // namespace absl
139