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) 1992-2015, 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 with
  37   SPARK_Mode,
  38   Abstract_State => (Clock_Time with Synchronous,
  39                                      External => (Async_Readers,
  40                                                   Async_Writers)),
  41   Initializes    => Clock_Time
  42 is
  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
 118 private
 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
 395 end Ada.Calendar;