gcc/ada/a-calend.ads

   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) 1992-2009, 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
  36 package Ada.Calendar is
  37
  38    type Time is private;
  39
  40    --  Declarations representing limits of allowed local time values. Note that
  41    --  these do NOT constrain the possible stored values of time which may well
  42    --  permit a larger range of times (this is explicitly allowed in Ada 95).
  43
  44    subtype Year_Number  is Integer range 1901 .. 2399;
  45    subtype Month_Number is Integer range 1 .. 12;
  46    subtype Day_Number   is Integer range 1 .. 31;
  47
  48    --  A Day_Duration value of 86_400.0 designates a new day
  49
  50    subtype Day_Duration is Duration range 0.0 .. 86_400.0;
  51
  52    function Clock return Time;
  53    --  The returned time value is the number of nanoseconds since the start
  54    --  of Ada time (1901-01-01 00:00:00.0 UTC). If leap seconds are enabled,
  55    --  the result will contain all elapsed leap seconds since the start of
  56    --  Ada time until now.
  57
  58    function Year    (Date : Time) return Year_Number;
  59    function Month   (Date : Time) return Month_Number;
  60    function Day     (Date : Time) return Day_Number;
  61    function Seconds (Date : Time) return Day_Duration;
  62
  63    procedure Split
  64      (Date    : Time;
  65       Year    : out Year_Number;
  66       Month   : out Month_Number;
  67       Day     : out Day_Number;
  68       Seconds : out Day_Duration);
  69    --  Break down a time value into its date components set in the current
  70    --  time zone. If Split is called on a time value created using Ada 2005
  71    --  Time_Of in some arbitrary time zone, the input value will always be
  72    --  interpreted as relative to the local time zone.
  73
  74    function Time_Of
  75      (Year    : Year_Number;
  76       Month   : Month_Number;
  77       Day     : Day_Number;
  78       Seconds : Day_Duration := 0.0) return Time;
  79    --  GNAT Note: Normally when procedure Split is called on a Time value
  80    --  result of a call to function Time_Of, the out parameters of procedure
  81    --  Split are identical to the in parameters of function Time_Of. However,
  82    --  when a non-existent time of day is specified, the values for Seconds
  83    --  may or may not be different. This may happen when Daylight Saving Time
  84    --  (DST) is in effect, on the day when switching to DST, if Seconds
  85    --  specifies a time of day in the hour that does not exist. For example,
  86    --  in New York:
  87    --
  88    --    Time_Of (Year => 1998, Month => 4, Day => 5, Seconds => 10740.0)
  89    --
  90    --  will return a Time value T. If Split is called on T, the resulting
  91    --  Seconds may be 14340.0 (3:59:00) instead of 10740.0 (2:59:00 being
  92    --  a time that not exist).
  93
  94    function "+" (Left : Time;     Right : Duration) return Time;
  95    function "+" (Left : Duration; Right : Time)     return Time;
  96    function "-" (Left : Time;     Right : Duration) return Time;
  97    function "-" (Left : Time;     Right : Time)     return Duration;
  98    --  The first three functions will raise Time_Error if the resulting time
  99    --  value is less than the start of Ada time in UTC or greater than the
 100    --  end of Ada time in UTC. The last function will raise Time_Error if the
 101    --  resulting difference cannot fit into a duration value.
 102
 103    function "<"  (Left, Right : Time) return Boolean;
 104    function "<=" (Left, Right : Time) return Boolean;
 105    function ">"  (Left, Right : Time) return Boolean;
 106    function ">=" (Left, Right : Time) return Boolean;
 107
 108    Time_Error : exception;
 109
 110 private
 111    pragma Inline (Clock);
 112
 113    pragma Inline (Year);
 114    pragma Inline (Month);
 115    pragma Inline (Day);
 116
 117    pragma Inline ("+");
 118    pragma Inline ("-");
 119
 120    pragma Inline ("<");
 121    pragma Inline ("<=");
 122    pragma Inline (">");
 123    pragma Inline (">=");
 124
 125    --  The units used in this version of Ada.Calendar are nanoseconds. The
 126    --  following constants provide values used in conversions of seconds or
 127    --  days to the underlying units.
 128
 129    Nano         : constant := 1_000_000_000;
 130    Nano_F       : constant := 1_000_000_000.0;
 131    Nanos_In_Day : constant := 86_400_000_000_000;
 132    Secs_In_Day  : constant := 86_400;
 133
 134    ----------------------------
 135    -- Implementation of Time --
 136    ----------------------------
 137
 138    --  Time is represented as a signed 64 bit integer count of nanoseconds
 139    --  since the start of Ada time (1901-01-01 00:00:00.0 UTC). Time values
 140    --  produced by Time_Of are internally normalized to UTC regardless of their
 141    --  local time zone. This representation ensures correct handling of leap
 142    --  seconds as well as performing arithmetic. In Ada 95, Split and Time_Of
 143    --  will treat a time value as being in the local time zone, in Ada 2005,
 144    --  Split and Time_Of will treat a time value as being in the designated
 145    --  time zone by the formal parameter or in UTC by default. The size of the
 146    --  type is large enough to cover the Ada 2005 range of time (1901-01-01
 147    --  00:00:00.0 UTC - 2399-12-31-23:59:59.999999999 UTC).
 148
 149    ------------------
 150    -- Leap seconds --
 151    ------------------
 152
 153    --  Due to Earth's slowdown, the astronomical time is not as precise as the
 154    --  International Atomic Time. To compensate for this inaccuracy, a single
 155    --  leap second is added after the last day of June or December. The count
 156    --  of seconds during those occurrences becomes:
 157
 158    --    ... 58, 59, leap second 60, 0, 1, 2 ...
 159
 160    --  Unlike leap days, leap seconds occur simultaneously around the world.
 161    --  In other words, if a leap second occurs at 23:59:60 UTC, it also occurs
 162    --  on 18:59:60 -5 the same day or 2:59:60 +2 on the next day.
 163
 164    --  Leap seconds do not follow a formula. The International Earth Rotation
 165    --  and Reference System Service decides when to add one. Leap seconds are
 166    --  included in the representation of time in Ada 95 mode. As a result,
 167    --  the following two time values will differ by two seconds:
 168
 169    --    1972-06-30 23:59:59.0
 170    --    1972-07-01 00:00:00.0
 171
 172    --  When a new leap second is introduced, the following steps must be
 173    --  carried out:
 174
 175    --     1) Increment Leap_Seconds_Count in a-calend.adb by one
 176    --     2) Increment LS_Count in xleaps.adb by one
 177    --     3) Add the new date to the aggregate of array LS_Dates in
 178    --        xleaps.adb
 179    --     4) Compile and execute xleaps
 180    --     5) Replace the values of Leap_Second_Times in a-calend.adb with the
 181    --        aggregate generated by xleaps
 182
 183    --  The algorithms that build the actual leap second values and discover
 184    --  how many leap seconds have occurred between two dates do not need any
 185    --  modification.
 186
 187    ------------------------------
 188    -- Non-leap centennial years --
 189    ------------------------------
 190
 191    --  Over the range of Ada time, centennial years 2100, 2200 and 2300 are
 192    --  non-leap. As a consequence, seven non-leap years occur over the period
 193    --  of year - 4 to year + 4. Internally, routines Split and Time_Of add or
 194    --  subtract a "fake" February 29 to facilitate the arithmetic involved.
 195
 196    --  The underlying type of Time has been chosen to be a 64 bit signed
 197    --  integer number since it allows for easier processing of sub seconds
 198    --  and arithmetic.
 199
 200    type Time_Rep is range -2 ** 63 .. +2 ** 63 - 1;
 201    type Time is new Time_Rep;
 202
 203    Days_In_Month : constant array (Month_Number) of Day_Number :=
 204                      (31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31);
 205
 206    Invalid_Time_Zone_Offset : Long_Integer;
 207    pragma Import (C, Invalid_Time_Zone_Offset, "__gnat_invalid_tzoff");
 208
 209    function Is_Leap (Year : Year_Number) return Boolean;
 210    --  Determine whether a given year is leap
 211
 212    --  The following packages provide a target independent interface to the
 213    --  children of Calendar - Arithmetic, Conversions, Delays, Formatting and
 214    --  Time_Zones.
 215
 216    ---------------------------
 217    -- Arithmetic_Operations --
 218    ---------------------------
 219
 220    package Arithmetic_Operations is
 221
 222       function Add (Date : Time; Days : Long_Integer) return Time;
 223       --  Add a certain number of days to a time value
 224
 225       procedure Difference
 226         (Left         : Time;
 227          Right        : Time;
 228          Days         : out Long_Integer;
 229          Seconds      : out Duration;
 230          Leap_Seconds : out Integer);
 231       --  Calculate the difference between two time values in terms of days,
 232       --  seconds and leap seconds elapsed. The leap seconds are not included
 233       --  in the seconds returned. If Left is greater than Right, the returned
 234       --  values are positive, negative otherwise.
 235
 236       function Subtract (Date : Time; Days : Long_Integer) return Time;
 237       --  Subtract a certain number of days from a time value
 238
 239    end Arithmetic_Operations;
 240
 241    ---------------------------
 242    -- Conversion_Operations --
 243    ---------------------------
 244
 245    package Conversion_Operations is
 246
 247       function To_Ada_Time (Unix_Time : Long_Integer) return Time;
 248       --  Unix to Ada Epoch conversion
 249
 250       function To_Ada_Time
 251         (tm_year  : Integer;
 252          tm_mon   : Integer;
 253          tm_day   : Integer;
 254          tm_hour  : Integer;
 255          tm_min   : Integer;
 256          tm_sec   : Integer;
 257          tm_isdst : Integer) return Time;
 258       --  Struct tm to Ada Epoch conversion
 259
 260       function To_Duration
 261         (tv_sec  : Long_Integer;
 262          tv_nsec : Long_Integer) return Duration;
 263       --  Struct timespec to Duration conversion
 264
 265       procedure To_Struct_Timespec
 266         (D       : Duration;
 267          tv_sec  : out Long_Integer;
 268          tv_nsec : out Long_Integer);
 269       --  Duration to struct timespec conversion
 270
 271       procedure To_Struct_Tm
 272         (T       : Time;
 273          tm_year : out Integer;
 274          tm_mon  : out Integer;
 275          tm_day  : out Integer;
 276          tm_hour : out Integer;
 277          tm_min  : out Integer;
 278          tm_sec  : out Integer);
 279       --  Time to struct tm conversion
 280
 281       function To_Unix_Time (Ada_Time : Time) return Long_Integer;
 282       --  Ada to Unix Epoch conversion
 283
 284    end Conversion_Operations;
 285
 286    ----------------------
 287    -- Delay_Operations --
 288    ----------------------
 289
 290    package Delay_Operations is
 291
 292       function To_Duration (Date : Time) return Duration;
 293       --  Given a time value in nanoseconds since 1901, convert it into a
 294       --  duration value giving the number of nanoseconds since the Unix Epoch.
 295
 296    end Delay_Operations;
 297
 298    ---------------------------
 299    -- Formatting_Operations --
 300    ---------------------------
 301
 302    package Formatting_Operations is
 303
 304       function Day_Of_Week (Date : Time) return Integer;
 305       --  Determine which day of week Date falls on. The returned values are
 306       --  within the range of 0 .. 6 (Monday .. Sunday).
 307
 308       procedure Split
 309         (Date      : Time;
 310          Year      : out Year_Number;
 311          Month     : out Month_Number;
 312          Day       : out Day_Number;
 313          Day_Secs  : out Day_Duration;
 314          Hour      : out Integer;
 315          Minute    : out Integer;
 316          Second    : out Integer;
 317          Sub_Sec   : out Duration;
 318          Leap_Sec  : out Boolean;
 319          Is_Ada_05 : Boolean;
 320          Time_Zone : Long_Integer);
 321       --  Split a time value into its components. Set Is_Ada_05 to use the
 322       --  local time zone (the value in Time_Zone is ignored) when splitting
 323       --  a time value.
 324
 325       function Time_Of
 326         (Year         : Year_Number;
 327          Month        : Month_Number;
 328          Day          : Day_Number;
 329          Day_Secs     : Day_Duration;
 330          Hour         : Integer;
 331          Minute       : Integer;
 332          Second       : Integer;
 333          Sub_Sec      : Duration;
 334          Leap_Sec     : Boolean := False;
 335          Use_Day_Secs : Boolean := False;
 336          Is_Ada_05    : Boolean := False;
 337          Time_Zone    : Long_Integer := 0) return Time;
 338       --  Given all the components of a date, return the corresponding time
 339       --  value. Set Use_Day_Secs to use the value in Day_Secs, otherwise the
 340       --  day duration will be calculated from Hour, Minute, Second and Sub_
 341       --  Sec. Set Is_Ada_05 to use the local time zone (the value in formal
 342       --  Time_Zone is ignored) when building a time value and to verify the
 343       --  validity of a requested leap second.
 344
 345    end Formatting_Operations;
 346
 347    ---------------------------
 348    -- Time_Zones_Operations --
 349    ---------------------------
 350
 351    package Time_Zones_Operations is
 352
 353       function UTC_Time_Offset (Date : Time) return Long_Integer;
 354       --  Return the offset in seconds from UTC
 355
 356    end Time_Zones_Operations;
 357
 358 end Ada.Calendar;