1------------------------------------------------------------------------------
2--                                                                          --
3--                         GNAT RUN-TIME COMPONENTS                         --
4--                                                                          --
5--                         A D A . C A L E N D A R                          --
6--                                                                          --
7--                                 S p e c                                  --
8--                                                                          --
9--          Copyright (C) 1992-2018, Free Software Foundation, Inc.         --
10--                                                                          --
11-- This specification is derived from the Ada Reference Manual for use with --
12-- GNAT. The copyright notice above, and the license provisions that follow --
13-- apply solely to the  contents of the part following the private keyword. --
14--                                                                          --
15-- GNAT is free software;  you can  redistribute it  and/or modify it under --
16-- terms of the  GNU General Public License as published  by the Free Soft- --
17-- ware  Foundation;  either version 3,  or (at your option) any later ver- --
18-- sion.  GNAT is distributed in the hope that it will be useful, but WITH- --
19-- OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY --
20-- or FITNESS FOR A PARTICULAR PURPOSE.                                     --
21--                                                                          --
22-- As a special exception under Section 7 of GPL version 3, you are granted --
23-- additional permissions described in the GCC Runtime Library Exception,   --
24-- version 3.1, as published by the Free Software Foundation.               --
25--                                                                          --
26-- You should have received a copy of the GNU General Public License and    --
27-- a copy of the GCC Runtime Library Exception along with this program;     --
28-- see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see    --
29-- <http://www.gnu.org/licenses/>.                                          --
30--                                                                          --
31-- GNAT was originally developed  by the GNAT team at  New York University. --
32-- Extensive contributions were provided by Ada Core Technologies Inc.      --
33--                                                                          --
34------------------------------------------------------------------------------
35
36package Ada.Calendar with
37  SPARK_Mode,
38  Abstract_State => (Clock_Time with Synchronous,
39                                     External => (Async_Readers,
40                                                  Async_Writers)),
41  Initializes    => Clock_Time
42is
43
44   type Time is private;
45
46   --  Declarations representing limits of allowed local time values. Note that
47   --  these do NOT constrain the possible stored values of time which may well
48   --  permit a larger range of times (this is explicitly allowed in Ada 95).
49
50   subtype Year_Number  is Integer range 1901 .. 2399;
51   subtype Month_Number is Integer range 1 .. 12;
52   subtype Day_Number   is Integer range 1 .. 31;
53
54   --  A Day_Duration value of 86_400.0 designates a new day
55
56   subtype Day_Duration is Duration range 0.0 .. 86_400.0;
57
58   function Clock return Time with
59     Volatile_Function,
60     Global => Clock_Time;
61   --  The returned time value is the number of nanoseconds since the start
62   --  of Ada time (1901-01-01 00:00:00.0 UTC). If leap seconds are enabled,
63   --  the result will contain all elapsed leap seconds since the start of
64   --  Ada time until now.
65
66   function Year    (Date : Time) return Year_Number;
67   function Month   (Date : Time) return Month_Number;
68   function Day     (Date : Time) return Day_Number;
69   function Seconds (Date : Time) return Day_Duration;
70
71   procedure Split
72     (Date    : Time;
73      Year    : out Year_Number;
74      Month   : out Month_Number;
75      Day     : out Day_Number;
76      Seconds : out Day_Duration);
77   --  Break down a time value into its date components set in the current
78   --  time zone. If Split is called on a time value created using Ada 2005
79   --  Time_Of in some arbitrary time zone, the input value will always be
80   --  interpreted as relative to the local time zone.
81
82   function Time_Of
83     (Year    : Year_Number;
84      Month   : Month_Number;
85      Day     : Day_Number;
86      Seconds : Day_Duration := 0.0) return Time;
87   --  GNAT Note: Normally when procedure Split is called on a Time value
88   --  result of a call to function Time_Of, the out parameters of procedure
89   --  Split are identical to the in parameters of function Time_Of. However,
90   --  when a non-existent time of day is specified, the values for Seconds
91   --  may or may not be different. This may happen when Daylight Saving Time
92   --  (DST) is in effect, on the day when switching to DST, if Seconds
93   --  specifies a time of day in the hour that does not exist. For example,
94   --  in New York:
95   --
96   --    Time_Of (Year => 1998, Month => 4, Day => 5, Seconds => 10740.0)
97   --
98   --  will return a Time value T. If Split is called on T, the resulting
99   --  Seconds may be 14340.0 (3:59:00) instead of 10740.0 (2:59:00 being
100   --  a time that not exist).
101
102   function "+" (Left : Time;     Right : Duration) return Time;
103   function "+" (Left : Duration; Right : Time)     return Time;
104   function "-" (Left : Time;     Right : Duration) return Time;
105   function "-" (Left : Time;     Right : Time)     return Duration;
106   --  The first three functions will raise Time_Error if the resulting time
107   --  value is less than the start of Ada time in UTC or greater than the
108   --  end of Ada time in UTC. The last function will raise Time_Error if the
109   --  resulting difference cannot fit into a duration value.
110
111   function "<"  (Left, Right : Time) return Boolean;
112   function "<=" (Left, Right : Time) return Boolean;
113   function ">"  (Left, Right : Time) return Boolean;
114   function ">=" (Left, Right : Time) return Boolean;
115
116   Time_Error : exception;
117
118private
119   --  Mark the private part as SPARK_Mode Off to avoid accounting for variable
120   --  Invalid_Time_Zone_Offset in abstract state.
121
122   pragma SPARK_Mode (Off);
123
124   pragma Inline (Clock);
125
126   pragma Inline (Year);
127   pragma Inline (Month);
128   pragma Inline (Day);
129
130   pragma Inline ("+");
131   pragma Inline ("-");
132
133   pragma Inline ("<");
134   pragma Inline ("<=");
135   pragma Inline (">");
136   pragma Inline (">=");
137
138   --  The units used in this version of Ada.Calendar are nanoseconds. The
139   --  following constants provide values used in conversions of seconds or
140   --  days to the underlying units.
141
142   Nano         : constant := 1_000_000_000;
143   Nano_F       : constant := 1_000_000_000.0;
144   Nanos_In_Day : constant := 86_400_000_000_000;
145   Secs_In_Day  : constant := 86_400;
146
147   ----------------------------
148   -- Implementation of Time --
149   ----------------------------
150
151   --  Time is represented as a signed 64 bit integer count of nanoseconds
152   --  since the start of Ada time (1901-01-01 00:00:00.0 UTC). Time values
153   --  produced by Time_Of are internally normalized to UTC regardless of their
154   --  local time zone. This representation ensures correct handling of leap
155   --  seconds as well as performing arithmetic. In Ada 95, Split and Time_Of
156   --  will treat a time value as being in the local time zone, in Ada 2005,
157   --  Split and Time_Of will treat a time value as being in the designated
158   --  time zone by the formal parameter or in UTC by default. The size of the
159   --  type is large enough to cover the Ada 2005 range of time (1901-01-01
160   --  00:00:00.0 UTC - 2399-12-31-23:59:59.999999999 UTC).
161
162   ------------------
163   -- Leap Seconds --
164   ------------------
165
166   --  Due to Earth's slowdown, the astronomical time is not as precise as the
167   --  International Atomic Time. To compensate for this inaccuracy, a single
168   --  leap second is added after the last day of June or December. The count
169   --  of seconds during those occurrences becomes:
170
171   --    ... 58, 59, leap second 60, 0, 1, 2 ...
172
173   --  Unlike leap days, leap seconds occur simultaneously around the world.
174   --  In other words, if a leap second occurs at 23:59:60 UTC, it also occurs
175   --  on 18:59:60 -5 the same day or 2:59:60 +2 on the next day.
176
177   --  Leap seconds do not follow a formula. The International Earth Rotation
178   --  and Reference System Service decides when to add one. Leap seconds are
179   --  included in the representation of time in Ada 95 mode. As a result,
180   --  the following two time values will differ by two seconds:
181
182   --    1972-06-30 23:59:59.0
183   --    1972-07-01 00:00:00.0
184
185   --  When a new leap second is introduced, the following steps must be
186   --  carried out:
187
188   --     1) Increment Leap_Seconds_Count in a-calend.adb by one
189   --     2) Increment LS_Count in xleaps.adb by one
190   --     3) Add the new date to the aggregate of array LS_Dates in
191   --        xleaps.adb
192   --     4) Compile and execute xleaps
193   --     5) Replace the values of Leap_Second_Times in a-calend.adb with the
194   --        aggregate generated by xleaps
195
196   --  The algorithms that build the actual leap second values and discover
197   --  how many leap seconds have occurred between two dates do not need any
198   --  modification.
199
200   ------------------------------
201   -- Non-leap Centennial Years --
202   ------------------------------
203
204   --  Over the range of Ada time, centennial years 2100, 2200 and 2300 are
205   --  non-leap. As a consequence, seven non-leap years occur over the period
206   --  of year - 4 to year + 4. Internally, routines Split and Time_Of add or
207   --  subtract a "fake" February 29 to facilitate the arithmetic involved.
208
209   ------------------------
210   -- Local Declarations --
211   ------------------------
212
213   type Time_Rep is new Long_Long_Integer;
214   type Time is new Time_Rep;
215   --  The underlying type of Time has been chosen to be a 64 bit signed
216   --  integer number since it allows for easier processing of sub-seconds
217   --  and arithmetic. We use Long_Long_Integer to allow this unit to compile
218   --  when using custom target configuration files where the max integer is
219   --  32 bits. This is useful for static analysis tools such as SPARK or
220   --  CodePeer.
221   --
222   --  Note: the reason we have two separate types here is to avoid problems
223   --  with overloading ambiguities in the body if we tried to use Time as an
224   --  internal computational type.
225
226   Days_In_Month : constant array (Month_Number) of Day_Number :=
227                     (31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31);
228   --  Days in month for non-leap year, leap year case is adjusted in code
229
230   Invalid_Time_Zone_Offset : Long_Integer;
231   pragma Import (C, Invalid_Time_Zone_Offset, "__gnat_invalid_tzoff");
232
233   function Is_Leap (Year : Year_Number) return Boolean;
234   --  Determine whether a given year is leap
235
236   ----------------------------------------------------------
237   -- Target-Independent Interface to Children of Calendar --
238   ----------------------------------------------------------
239
240   --  The following packages provide a target-independent interface to the
241   --  children of Calendar - Arithmetic, Conversions, Delays, Formatting and
242   --  Time_Zones.
243
244   ---------------------------
245   -- Arithmetic_Operations --
246   ---------------------------
247
248   package Arithmetic_Operations is
249
250      function Add (Date : Time; Days : Long_Integer) return Time;
251      --  Add a certain number of days to a time value
252
253      procedure Difference
254        (Left         : Time;
255         Right        : Time;
256         Days         : out Long_Integer;
257         Seconds      : out Duration;
258         Leap_Seconds : out Integer);
259      --  Calculate the difference between two time values in terms of days,
260      --  seconds and leap seconds elapsed. The leap seconds are not included
261      --  in the seconds returned. If Left is greater than Right, the returned
262      --  values are positive, negative otherwise.
263
264      function Subtract (Date : Time; Days : Long_Integer) return Time;
265      --  Subtract a certain number of days from a time value
266
267   end Arithmetic_Operations;
268
269   ---------------------------
270   -- Conversion_Operations --
271   ---------------------------
272
273   package Conversion_Operations is
274
275      function To_Ada_Time (Unix_Time : Long_Integer) return Time;
276      --  Unix to Ada Epoch conversion
277
278      function To_Ada_Time
279        (tm_year  : Integer;
280         tm_mon   : Integer;
281         tm_day   : Integer;
282         tm_hour  : Integer;
283         tm_min   : Integer;
284         tm_sec   : Integer;
285         tm_isdst : Integer) return Time;
286      --  Struct tm to Ada Epoch conversion
287
288      function To_Duration
289        (tv_sec  : Long_Integer;
290         tv_nsec : Long_Integer) return Duration;
291      --  Struct timespec to Duration conversion
292
293      procedure To_Struct_Timespec
294        (D       : Duration;
295         tv_sec  : out Long_Integer;
296         tv_nsec : out Long_Integer);
297      --  Duration to struct timespec conversion
298
299      procedure To_Struct_Tm
300        (T       : Time;
301         tm_year : out Integer;
302         tm_mon  : out Integer;
303         tm_day  : out Integer;
304         tm_hour : out Integer;
305         tm_min  : out Integer;
306         tm_sec  : out Integer);
307      --  Time to struct tm conversion
308
309      function To_Unix_Time (Ada_Time : Time) return Long_Integer;
310      --  Ada to Unix Epoch conversion
311
312   end Conversion_Operations;
313
314   ----------------------
315   -- Delay_Operations --
316   ----------------------
317
318   package Delay_Operations is
319
320      function To_Duration (Date : Time) return Duration;
321      --  Given a time value in nanoseconds since 1901, convert it into a
322      --  duration value giving the number of nanoseconds since the Unix Epoch.
323
324   end Delay_Operations;
325
326   ---------------------------
327   -- Formatting_Operations --
328   ---------------------------
329
330   package Formatting_Operations is
331
332      function Day_Of_Week (Date : Time) return Integer;
333      --  Determine which day of week Date falls on. The returned values are
334      --  within the range of 0 .. 6 (Monday .. Sunday).
335
336      procedure Split
337        (Date        : Time;
338         Year        : out Year_Number;
339         Month       : out Month_Number;
340         Day         : out Day_Number;
341         Day_Secs    : out Day_Duration;
342         Hour        : out Integer;
343         Minute      : out Integer;
344         Second      : out Integer;
345         Sub_Sec     : out Duration;
346         Leap_Sec    : out Boolean;
347         Use_TZ      : Boolean;
348         Is_Historic : Boolean;
349         Time_Zone   : Long_Integer);
350      pragma Export (Ada, Split, "__gnat_split");
351      --  Split a time value into its components. If flag Is_Historic is set,
352      --  this routine would try to use to the best of the OS's abilities the
353      --  time zone offset that was or will be in effect on Date. Set Use_TZ
354      --  to use the local time zone (the value in Time_Zone is ignored) when
355      --  splitting a time value.
356
357      function Time_Of
358        (Year         : Year_Number;
359         Month        : Month_Number;
360         Day          : Day_Number;
361         Day_Secs     : Day_Duration;
362         Hour         : Integer;
363         Minute       : Integer;
364         Second       : Integer;
365         Sub_Sec      : Duration;
366         Leap_Sec     : Boolean;
367         Use_Day_Secs : Boolean;
368         Use_TZ       : Boolean;
369         Is_Historic  : Boolean;
370         Time_Zone    : Long_Integer) return Time;
371      pragma Export (Ada, Time_Of, "__gnat_time_of");
372      --  Given all the components of a date, return the corresponding time
373      --  value. Set Use_Day_Secs to use the value in Day_Secs, otherwise the
374      --  day duration will be calculated from Hour, Minute, Second and Sub_
375      --  Sec. If flag Is_Historic is set, this routine would try to use to the
376      --  best of the OS's abilities the time zone offset that was or will be
377      --  in effect on the input date. Set Use_TZ to use the local time zone
378      --  (the value in formal Time_Zone is ignored) when building a time value
379      --  and to verify the validity of a requested leap second.
380
381   end Formatting_Operations;
382
383   ---------------------------
384   -- Time_Zones_Operations --
385   ---------------------------
386
387   package Time_Zones_Operations is
388
389      function UTC_Time_Offset (Date : Time) return Long_Integer;
390      --  Return (in seconds) the difference between the local time zone and
391      --  UTC time at a specific historic date.
392
393   end Time_Zones_Operations;
394
395end Ada.Calendar;
396