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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) 1992-2007, 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 2, 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. See the GNU General Public License --
21 -- for more details. You should have received a copy of the GNU General --
22 -- Public License distributed with GNAT; see file COPYING. If not, write --
23 -- to the Free Software Foundation, 51 Franklin Street, Fifth Floor, --
24 -- Boston, MA 02110-1301, USA. --
25 -- --
26 -- As a special exception, if other files instantiate generics from this --
27 -- unit, or you link this unit with other files to produce an executable, --
28 -- this unit does not by itself cause the resulting executable to be --
29 -- covered by the GNU General Public License. This exception does not --
30 -- however invalidate any other reasons why the executable file might be --
31 -- covered by the GNU Public License. --
32 -- --
33 -- GNAT was originally developed by the GNAT team at New York University. --
34 -- Extensive contributions were provided by Ada Core Technologies Inc. --
35 -- --
36 ------------------------------------------------------------------------------
38 package Ada.Calendar is
40 type Time is private;
42 -- Declarations representing limits of allowed local time values. Note that
43 -- these do NOT constrain the possible stored values of time which may well
44 -- permit a larger range of times (this is explicitly allowed in Ada 95).
46 subtype Year_Number is Integer range 1901 .. 2399;
47 subtype Month_Number is Integer range 1 .. 12;
48 subtype Day_Number is Integer range 1 .. 31;
50 -- A Day_Duration value of 86_400.0 designates a new day
52 subtype Day_Duration is Duration range 0.0 .. 86_400.0;
54 function Clock return Time;
55 -- The returned time value is the number of nanoseconds since the start
56 -- of Ada time (1901-01-01 00:00:00.0 UTC). If leap seconds are enabled,
57 -- the result will contain all elapsed leap seconds since the start of
58 -- Ada time until now.
60 function Year (Date : Time) return Year_Number;
61 function Month (Date : Time) return Month_Number;
62 function Day (Date : Time) return Day_Number;
63 function Seconds (Date : Time) return Day_Duration;
65 procedure Split
66 (Date : Time;
67 Year : out Year_Number;
68 Month : out Month_Number;
69 Day : out Day_Number;
70 Seconds : out Day_Duration);
71 -- Break down a time value into its date components set in the current
72 -- time zone. If Split is called on a time value created using Ada 2005
73 -- Time_Of in some arbitrary time zone, the input value will always be
74 -- interpreted as relative to the local time zone.
76 function Time_Of
77 (Year : Year_Number;
78 Month : Month_Number;
79 Day : Day_Number;
80 Seconds : Day_Duration := 0.0) return Time;
81 -- GNAT Note: Normally when procedure Split is called on a Time value
82 -- result of a call to function Time_Of, the out parameters of procedure
83 -- Split are identical to the in parameters of function Time_Of. However,
84 -- when a non-existent time of day is specified, the values for Seconds
85 -- may or may not be different. This may happen when Daylight Saving Time
86 -- (DST) is in effect, on the day when switching to DST, if Seconds
87 -- specifies a time of day in the hour that does not exist. For example,
88 -- in New York:
90 -- Time_Of (Year => 1998, Month => 4, Day => 5, Seconds => 10740.0)
92 -- will return a Time value T. If Split is called on T, the resulting
93 -- Seconds may be 14340.0 (3:59:00) instead of 10740.0 (2:59:00 being
94 -- a time that not exist).
96 function "+" (Left : Time; Right : Duration) return Time;
97 function "+" (Left : Duration; Right : Time) return Time;
98 function "-" (Left : Time; Right : Duration) return Time;
99 function "-" (Left : Time; Right : Time) return Duration;
100 -- The first three functions will raise Time_Error if the resulting time
101 -- value is less than the start of Ada time in UTC or greater than the
102 -- end of Ada time in UTC. The last function will raise Time_Error if the
103 -- resulting difference cannot fit into a duration value.
105 function "<" (Left, Right : Time) return Boolean;
106 function "<=" (Left, Right : Time) return Boolean;
107 function ">" (Left, Right : Time) return Boolean;
108 function ">=" (Left, Right : Time) return Boolean;
110 Time_Error : exception;
112 private
113 pragma Inline (Clock);
115 pragma Inline (Year);
116 pragma Inline (Month);
117 pragma Inline (Day);
119 pragma Inline ("+");
120 pragma Inline ("-");
122 pragma Inline ("<");
123 pragma Inline ("<=");
124 pragma Inline (">");
125 pragma Inline (">=");
127 -- The units used in this version of Ada.Calendar are nanoseconds. The
128 -- following constants provide values used in conversions of seconds or
129 -- days to the underlying units.
131 Nano : constant := 1_000_000_000;
132 Nano_F : constant := 1_000_000_000.0;
133 Nanos_In_Day : constant := 86_400_000_000_000;
134 Secs_In_Day : constant := 86_400;
136 ----------------------------
137 -- Implementation of Time --
138 ----------------------------
140 -- Time is represented as a signed 64 bit integer count of nanoseconds
141 -- since the start of Ada time (1901-01-01 00:00:00.0 UTC). Time values
142 -- produced by Time_Of are internaly normalized to UTC regardless of their
143 -- local time zone. This representation ensures correct handling of leap
144 -- seconds as well as performing arithmetic. In Ada 95, Split and Time_Of
145 -- will treat a time value as being in the local time zone, in Ada 2005,
146 -- Split and Time_Of will treat a time value as being in the designated
147 -- time zone by the formal parameter or in UTC by default. The size of the
148 -- type is large enough to cover the Ada 2005 range of time (1901-01-01
149 -- 00:00:00.0 UTC - 2399-12-31-23:59:59.999999999 UTC).
151 ------------------
152 -- Leap seconds --
153 ------------------
155 -- Due to Earth's slowdown, the astronomical time is not as precise as the
156 -- International Atomic Time. To compensate for this inaccuracy, a single
157 -- leap second is added after the last day of June or December. The count
158 -- of seconds during those occurences becomes:
160 -- ... 58, 59, leap second 60, 0, 1, 2 ...
162 -- Unlike leap days, leap seconds occur simultaneously around the world.
163 -- In other words, if a leap second occurs at 23:59:60 UTC, it also occurs
164 -- on 18:59:60 -5 the same day or 2:59:60 +2 on the next day.
166 -- Leap seconds do not follow a formula. The International Earth Rotation
167 -- and Reference System Service decides when to add one. Leap seconds are
168 -- included in the representation of time in Ada 95 mode. As a result,
169 -- the following two time values will differ by two seconds:
171 -- 1972-06-30 23:59:59.0
172 -- 1972-07-01 00:00:00.0
174 -- When a new leap second is introduced, the following steps must be
175 -- carried out:
177 -- 1) Increment Leap_Seconds_Count in a-calend.adb by one
178 -- 2) Increment LS_Count in xleaps.adb by one
179 -- 3) Add the new date to the aggregate of array LS_Dates in
180 -- xleaps.adb
181 -- 4) Compile and execute xleaps
182 -- 5) Replace the values of Leap_Second_Times in a-calend.adb with the
183 -- aggregate generated by xleaps
185 -- The algorithms that build the actual leap second values and discover
186 -- how many leap seconds have occured between two dates do not need any
187 -- modification.
189 ------------------------------
190 -- Non-leap centenial years --
191 ------------------------------
193 -- Over the range of Ada time, centenial years 2100, 2200 and 2300 are
194 -- non-leap. As a consequence, seven non-leap years occur over the period
195 -- of year - 4 to year + 4. Internaly, routines Split and Time_Of add or
196 -- subtract a "fake" February 29 to facilitate the arithmetic involved.
198 -- The underlying type of Time has been chosen to be a 64 bit signed
199 -- integer number since it allows for easier processing of sub seconds
200 -- and arithmetic.
202 type Time_Rep is range -2 ** 63 .. +2 ** 63 - 1;
203 type Time is new Time_Rep;
205 Days_In_Month : constant array (Month_Number) of Day_Number :=
206 (31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31);
208 Invalid_Time_Zone_Offset : Long_Integer;
209 pragma Import (C, Invalid_Time_Zone_Offset, "__gnat_invalid_tzoff");
211 function Is_Leap (Year : Year_Number) return Boolean;
212 -- Determine whether a given year is leap
214 -- The following packages provide a target independent interface to the
215 -- children of Calendar - Arithmetic, Delays, Formatting and Time_Zones.
217 package Arithmetic_Operations is
218 function Add (Date : Time; Days : Long_Integer) return Time;
219 -- Add a certain number of days to a time value
221 procedure Difference
222 (Left : Time;
223 Right : Time;
224 Days : out Long_Integer;
225 Seconds : out Duration;
226 Leap_Seconds : out Integer);
227 -- Calculate the difference between two time values in terms of days,
228 -- seconds and leap seconds elapsed. The leap seconds are not included
229 -- in the seconds returned. If Left is greater than Right, the returned
230 -- values are positive, negative otherwise.
232 function Subtract (Date : Time; Days : Long_Integer) return Time;
233 -- Subtract a certain number of days from a time value
234 end Arithmetic_Operations;
236 package Delays_Operations is
237 function To_Duration (Date : Time) return Duration;
238 -- Given a time value in nanoseconds since 1901, convert it into a
239 -- duration value giving the number of nanoseconds since the Unix Epoch.
240 end Delays_Operations;
242 package Formatting_Operations is
243 function Day_Of_Week (Date : Time) return Integer;
244 -- Determine which day of week Date falls on. The returned values are
245 -- within the range of 0 .. 6 (Monday .. Sunday).
247 procedure Split
248 (Date : Time;
249 Year : out Year_Number;
250 Month : out Month_Number;
251 Day : out Day_Number;
252 Day_Secs : out Day_Duration;
253 Hour : out Integer;
254 Minute : out Integer;
255 Second : out Integer;
256 Sub_Sec : out Duration;
257 Leap_Sec : out Boolean;
258 Is_Ada_05 : Boolean;
259 Time_Zone : Long_Integer);
260 -- Split a time value into its components. Set Is_Ada_05 to use the
261 -- local time zone (the value in Time_Zone is ignored) when splitting
262 -- a time value.
264 function Time_Of
265 (Year : Year_Number;
266 Month : Month_Number;
267 Day : Day_Number;
268 Day_Secs : Day_Duration;
269 Hour : Integer;
270 Minute : Integer;
271 Second : Integer;
272 Sub_Sec : Duration;
273 Leap_Sec : Boolean;
274 Use_Day_Secs : Boolean;
275 Is_Ada_05 : Boolean;
276 Time_Zone : Long_Integer) return Time;
277 -- Given all the components of a date, return the corresponding time
278 -- value. Set Use_Day_Secs to use the value in Day_Secs, otherwise the
279 -- day duration will be calculated from Hour, Minute, Second and Sub_
280 -- Sec. Set Is_Ada_05 to use the local time zone (the value in formal
281 -- Time_Zone is ignored) when building a time value and to verify the
282 -- validity of a requested leap second.
283 end Formatting_Operations;
285 package Time_Zones_Operations is
286 function UTC_Time_Offset (Date : Time) return Long_Integer;
287 -- Return the offset in seconds from UTC
288 end Time_Zones_Operations;
290 end Ada.Calendar;