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 #ifndef ABSL_TIME_INTERNAL_CCTZ_TIME_ZONE_INFO_H_
16 #define ABSL_TIME_INTERNAL_CCTZ_TIME_ZONE_INFO_H_
17 
18 #include <atomic>
19 #include <cstddef>
20 #include <cstdint>
21 #include <string>
22 #include <vector>
23 
24 #include "absl/base/config.h"
25 #include "absl/time/internal/cctz/include/cctz/civil_time.h"
26 #include "absl/time/internal/cctz/include/cctz/time_zone.h"
27 #include "absl/time/internal/cctz/include/cctz/zone_info_source.h"
28 #include "time_zone_if.h"
29 #include "tzfile.h"
30 
31 namespace absl {
32 ABSL_NAMESPACE_BEGIN
33 namespace time_internal {
34 namespace cctz {
35 
36 // A transition to a new UTC offset.
37 struct Transition {
38   std::int_least64_t unix_time;   // the instant of this transition
39   std::uint_least8_t type_index;  // index of the transition type
40   civil_second civil_sec;         // local civil time of transition
41   civil_second prev_civil_sec;    // local civil time one second earlier
42 
43   struct ByUnixTime {
operatorTransition::ByUnixTime44     inline bool operator()(const Transition& lhs, const Transition& rhs) const {
45       return lhs.unix_time < rhs.unix_time;
46     }
47   };
48   struct ByCivilTime {
operatorTransition::ByCivilTime49     inline bool operator()(const Transition& lhs, const Transition& rhs) const {
50       return lhs.civil_sec < rhs.civil_sec;
51     }
52   };
53 };
54 
55 // The characteristics of a particular transition.
56 struct TransitionType {
57   std::int_least32_t utc_offset;  // the new prevailing UTC offset
58   civil_second civil_max;         // max convertible civil time for offset
59   civil_second civil_min;         // min convertible civil time for offset
60   bool is_dst;                    // did we move into daylight-saving time
61   std::uint_least8_t abbr_index;  // index of the new abbreviation
62 };
63 
64 // A time zone backed by the IANA Time Zone Database (zoneinfo).
65 class TimeZoneInfo : public TimeZoneIf {
66  public:
67   TimeZoneInfo() = default;
68   TimeZoneInfo(const TimeZoneInfo&) = delete;
69   TimeZoneInfo& operator=(const TimeZoneInfo&) = delete;
70 
71   // Loads the zoneinfo for the given name, returning true if successful.
72   bool Load(const std::string& name);
73 
74   // TimeZoneIf implementations.
75   time_zone::absolute_lookup BreakTime(
76       const time_point<seconds>& tp) const override;
77   time_zone::civil_lookup MakeTime(const civil_second& cs) const override;
78   bool NextTransition(const time_point<seconds>& tp,
79                       time_zone::civil_transition* trans) const override;
80   bool PrevTransition(const time_point<seconds>& tp,
81                       time_zone::civil_transition* trans) const override;
82   std::string Version() const override;
83   std::string Description() const override;
84 
85  private:
86   struct Header {            // counts of:
87     std::size_t timecnt;     // transition times
88     std::size_t typecnt;     // transition types
89     std::size_t charcnt;     // zone abbreviation characters
90     std::size_t leapcnt;     // leap seconds (we expect none)
91     std::size_t ttisstdcnt;  // UTC/local indicators (unused)
92     std::size_t ttisutcnt;   // standard/wall indicators (unused)
93 
94     bool Build(const tzhead& tzh);
95     std::size_t DataLength(std::size_t time_len) const;
96   };
97 
98   bool GetTransitionType(std::int_fast32_t utc_offset, bool is_dst,
99                          const std::string& abbr, std::uint_least8_t* index);
100   bool EquivTransitions(std::uint_fast8_t tt1_index,
101                         std::uint_fast8_t tt2_index) const;
102   bool ExtendTransitions();
103 
104   bool ResetToBuiltinUTC(const seconds& offset);
105   bool Load(ZoneInfoSource* zip);
106 
107   // Helpers for BreakTime() and MakeTime().
108   time_zone::absolute_lookup LocalTime(std::int_fast64_t unix_time,
109                                        const TransitionType& tt) const;
110   time_zone::absolute_lookup LocalTime(std::int_fast64_t unix_time,
111                                        const Transition& tr) const;
112   time_zone::civil_lookup TimeLocal(const civil_second& cs,
113                                     year_t c4_shift) const;
114 
115   std::vector<Transition> transitions_;  // ordered by unix_time and civil_sec
116   std::vector<TransitionType> transition_types_;  // distinct transition types
117   std::uint_fast8_t default_transition_type_;     // for before first transition
118   std::string abbreviations_;  // all the NUL-terminated abbreviations
119 
120   std::string version_;      // the tzdata version if available
121   std::string future_spec_;  // for after the last zic transition
122   bool extended_;            // future_spec_ was used to generate transitions
123   year_t last_year_;         // the final year of the generated transitions
124 
125   // We remember the transitions found during the last BreakTime() and
126   // MakeTime() calls. If the next request is for the same transition we
127   // will avoid re-searching.
128   mutable std::atomic<std::size_t> local_time_hint_ = {};  // BreakTime() hint
129   mutable std::atomic<std::size_t> time_local_hint_ = {};  // MakeTime() hint
130 };
131 
132 }  // namespace cctz
133 }  // namespace time_internal
134 ABSL_NAMESPACE_END
135 }  // namespace absl
136 
137 #endif  // ABSL_TIME_INTERNAL_CCTZ_TIME_ZONE_INFO_H_
138