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--                                                                          --

--                         GNAT RUN-TIME COMPONENTS                         --

--                                                                          --

--                         A D A . C A L E N D A R                          --

--                                                                          --

--                                 S p e c                                  --

--                                                                          --

--          Copyright (C) 1992-2009, Free Software Foundation, Inc.         --

--                                                                          --

-- This specification is derived from the Ada Reference Manual for use with --

-- GNAT. The copyright notice above, and the license provisions that follow --

-- apply solely to the  contents of the part following the private keyword. --

--                                                                          --

-- GNAT is free software;  you can  redistribute it  and/or modify it under --

-- terms of the  GNU General Public License as published  by the Free Soft- --

-- ware  Foundation;  either version 3,  or (at your option) any later ver- --

-- sion.  GNAT is distributed in the hope that it will be useful, but WITH- --

-- OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY --

-- or FITNESS FOR A PARTICULAR PURPOSE.                                     --

--                                                                          --

-- As a special exception under Section 7 of GPL version 3, you are granted --

-- additional permissions described in the GCC Runtime Library Exception,   --

-- version 3.1, as published by the Free Software Foundation.               --

--                                                                          --

-- You should have received a copy of the GNU General Public License and    --

-- a copy of the GCC Runtime Library Exception along with this program;     --

-- see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see    --

-- <http://www.gnu.org/licenses/>.                                          --

--                                                                          --

-- GNAT was originally developed  by the GNAT team at  New York University. --

-- Extensive contributions were provided by Ada Core Technologies Inc.      --

--                                                                          --

------------------------------------------------------------------------------

package Ada.Calendar is

   type Time is private;

   --  Declarations representing limits of allowed local time values. Note that

   --  these do NOT constrain the possible stored values of time which may well

   --  permit a larger range of times (this is explicitly allowed in Ada 95).

   subtype Year_Number  is Integer range 1901 .. 2399;

   subtype Month_Number is Integer range 1 .. 12;

   subtype Day_Number   is Integer range 1 .. 31;

   --  A Day_Duration value of 86_400.0 designates a new day

   subtype Day_Duration is Duration range 0.0 .. 86_400.0;

   function Clock return Time;

   --  The returned time value is the number of nanoseconds since the start

   --  of Ada time (1901-01-01 00:00:00.0 UTC). If leap seconds are enabled,

   --  the result will contain all elapsed leap seconds since the start of

   --  Ada time until now.

   function Year    (Date : Time) return Year_Number;

   function Month   (Date : Time) return Month_Number;

   function Day     (Date : Time) return Day_Number;

   function Seconds (Date : Time) return Day_Duration;

   procedure Split

     (Date    : Time;

      Year    : out Year_Number;

      Month   : out Month_Number;

      Day     : out Day_Number;

      Seconds : out Day_Duration);

   --  Break down a time value into its date components set in the current

   --  time zone. If Split is called on a time value created using Ada 2005

   --  Time_Of in some arbitrary time zone, the input value will always be

   --  interpreted as relative to the local time zone.

   function Time_Of

     (Year    : Year_Number;

      Month   : Month_Number;

      Day     : Day_Number;

      Seconds : Day_Duration := 0.0) return Time;

   --  GNAT Note: Normally when procedure Split is called on a Time value

   --  result of a call to function Time_Of, the out parameters of procedure

   --  Split are identical to the in parameters of function Time_Of. However,

   --  when a non-existent time of day is specified, the values for Seconds

   --  may or may not be different. This may happen when Daylight Saving Time

   --  (DST) is in effect, on the day when switching to DST, if Seconds

   --  specifies a time of day in the hour that does not exist. For example,

   --  in New York:

   --

   --    Time_Of (Year => 1998, Month => 4, Day => 5, Seconds => 10740.0)

   --

   --  will return a Time value T. If Split is called on T, the resulting

   --  Seconds may be 14340.0 (3:59:00) instead of 10740.0 (2:59:00 being

   --  a time that not exist).

   function "+" (Left : Time;     Right : Duration) return Time;

   function "+" (Left : Duration; Right : Time)     return Time;

   function "-" (Left : Time;     Right : Duration) return Time;

   function "-" (Left : Time;     Right : Time)     return Duration;

   --  The first three functions will raise Time_Error if the resulting time

   --  value is less than the start of Ada time in UTC or greater than the

   --  end of Ada time in UTC. The last function will raise Time_Error if the

   --  resulting difference cannot fit into a duration value.

   function "<"  (Left, Right : Time) return Boolean;

   function "<=" (Left, Right : Time) return Boolean;

   function ">"  (Left, Right : Time) return Boolean;

   function ">=" (Left, Right : Time) return Boolean;

   Time_Error : exception;

private

   pragma Inline (Clock);

   pragma Inline (Year);

   pragma Inline (Month);

   pragma Inline (Day);

   pragma Inline ("+");

   pragma Inline ("-");

   pragma Inline ("<");

   pragma Inline ("<=");

   pragma Inline (">");

   pragma Inline (">=");

   --  The units used in this version of Ada.Calendar are nanoseconds. The

   --  following constants provide values used in conversions of seconds or

   --  days to the underlying units.

   Nano         : constant := 1_000_000_000;

   Nano_F       : constant := 1_000_000_000.0;

   Nanos_In_Day : constant := 86_400_000_000_000;

   Secs_In_Day  : constant := 86_400;

   ----------------------------

   -- Implementation of Time --

   ----------------------------

   --  Time is represented as a signed 64 bit integer count of nanoseconds

   --  since the start of Ada time (1901-01-01 00:00:00.0 UTC). Time values

   --  produced by Time_Of are internally normalized to UTC regardless of their

   --  local time zone. This representation ensures correct handling of leap

   --  seconds as well as performing arithmetic. In Ada 95, Split and Time_Of

   --  will treat a time value as being in the local time zone, in Ada 2005,

   --  Split and Time_Of will treat a time value as being in the designated

   --  time zone by the formal parameter or in UTC by default. The size of the

   --  type is large enough to cover the Ada 2005 range of time (1901-01-01

   --  00:00:00.0 UTC - 2399-12-31-23:59:59.999999999 UTC).

   ------------------

   -- Leap seconds --

   ------------------

   --  Due to Earth's slowdown, the astronomical time is not as precise as the

   --  International Atomic Time. To compensate for this inaccuracy, a single

   --  leap second is added after the last day of June or December. The count

   --  of seconds during those occurrences becomes:

   --    ... 58, 59, leap second 60, 0, 1, 2 ...

   --  Unlike leap days, leap seconds occur simultaneously around the world.

   --  In other words, if a leap second occurs at 23:59:60 UTC, it also occurs

   --  on 18:59:60 -5 the same day or 2:59:60 +2 on the next day.

   --  Leap seconds do not follow a formula. The International Earth Rotation

   --  and Reference System Service decides when to add one. Leap seconds are

   --  included in the representation of time in Ada 95 mode. As a result,

   --  the following two time values will differ by two seconds:

   --    1972-06-30 23:59:59.0

   --    1972-07-01 00:00:00.0

   --  When a new leap second is introduced, the following steps must be

   --  carried out:

   --     1) Increment Leap_Seconds_Count in a-calend.adb by one

   --     2) Increment LS_Count in xleaps.adb by one

   --     3) Add the new date to the aggregate of array LS_Dates in

   --        xleaps.adb

   --     4) Compile and execute xleaps

   --     5) Replace the values of Leap_Second_Times in a-calend.adb with the

   --        aggregate generated by xleaps

   --  The algorithms that build the actual leap second values and discover

   --  how many leap seconds have occurred between two dates do not need any

   --  modification.

   ------------------------------

   -- Non-leap centennial years --

   ------------------------------

   --  Over the range of Ada time, centennial years 2100, 2200 and 2300 are

   --  non-leap. As a consequence, seven non-leap years occur over the period

   --  of year - 4 to year + 4. Internally, routines Split and Time_Of add or

   --  subtract a "fake" February 29 to facilitate the arithmetic involved.

   --  The underlying type of Time has been chosen to be a 64 bit signed

   --  integer number since it allows for easier processing of sub seconds

   --  and arithmetic.

   type Time_Rep is range -2 ** 63 .. +2 ** 63 - 1;

   type Time is new Time_Rep;

   Days_In_Month : constant array (Month_Number) of Day_Number :=

                     (31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31);

   Invalid_Time_Zone_Offset : Long_Integer;

   pragma Import (C, Invalid_Time_Zone_Offset, "__gnat_invalid_tzoff");

   function Is_Leap (Year : Year_Number) return Boolean;

   --  Determine whether a given year is leap

   --  The following packages provide a target independent interface to the

   --  children of Calendar - Arithmetic, Conversions, Delays, Formatting and

   --  Time_Zones.

   ---------------------------

   -- Arithmetic_Operations --

   ---------------------------

   package Arithmetic_Operations is

      function Add (Date : Time; Days : Long_Integer) return Time;

      --  Add a certain number of days to a time value

      procedure Difference

        (Left         : Time;

         Right        : Time;

         Days         : out Long_Integer;

         Seconds      : out Duration;

         Leap_Seconds : out Integer);

      --  Calculate the difference between two time values in terms of days,

      --  seconds and leap seconds elapsed. The leap seconds are not included

      --  in the seconds returned. If Left is greater than Right, the returned

      --  values are positive, negative otherwise.

      function Subtract (Date : Time; Days : Long_Integer) return Time;

      --  Subtract a certain number of days from a time value

   end Arithmetic_Operations;

   ---------------------------

   -- Conversion_Operations --

   ---------------------------

   package Conversion_Operations is

      function To_Ada_Time (Unix_Time : Long_Integer) return Time;

      --  Unix to Ada Epoch conversion

      function To_Ada_Time

        (tm_year  : Integer;

         tm_mon   : Integer;

         tm_day   : Integer;

         tm_hour  : Integer;

         tm_min   : Integer;

         tm_sec   : Integer;

         tm_isdst : Integer) return Time;

      --  Struct tm to Ada Epoch conversion

      function To_Duration

        (tv_sec  : Long_Integer;

         tv_nsec : Long_Integer) return Duration;

      --  Struct timespec to Duration conversion

      procedure To_Struct_Timespec

        (D       : Duration;

         tv_sec  : out Long_Integer;

         tv_nsec : out Long_Integer);

      --  Duration to struct timespec conversion

      procedure To_Struct_Tm

        (T       : Time;

         tm_year : out Integer;

         tm_mon  : out Integer;

         tm_day  : out Integer;

         tm_hour : out Integer;

         tm_min  : out Integer;

         tm_sec  : out Integer);

      --  Time to struct tm conversion

      function To_Unix_Time (Ada_Time : Time) return Long_Integer;

      --  Ada to Unix Epoch conversion

   end Conversion_Operations;

   ----------------------

   -- Delay_Operations --

   ----------------------

   package Delay_Operations is

      function To_Duration (Date : Time) return Duration;

      --  Given a time value in nanoseconds since 1901, convert it into a

      --  duration value giving the number of nanoseconds since the Unix Epoch.

   end Delay_Operations;

   ---------------------------

   -- Formatting_Operations --

   ---------------------------

   package Formatting_Operations is

      function Day_Of_Week (Date : Time) return Integer;

      --  Determine which day of week Date falls on. The returned values are

      --  within the range of 0 .. 6 (Monday .. Sunday).

      procedure Split

        (Date      : Time;

         Year      : out Year_Number;

         Month     : out Month_Number;

         Day       : out Day_Number;

         Day_Secs  : out Day_Duration;

         Hour      : out Integer;

         Minute    : out Integer;

         Second    : out Integer;

         Sub_Sec   : out Duration;

         Leap_Sec  : out Boolean;

         Is_Ada_05 : Boolean;

         Time_Zone : Long_Integer);

      --  Split a time value into its components. Set Is_Ada_05 to use the

      --  local time zone (the value in Time_Zone is ignored) when splitting

      --  a time value.

      function Time_Of

        (Year         : Year_Number;

         Month        : Month_Number;

         Day          : Day_Number;

         Day_Secs     : Day_Duration;

         Hour         : Integer;

         Minute       : Integer;

         Second       : Integer;

         Sub_Sec      : Duration;

         Leap_Sec     : Boolean := False;

         Use_Day_Secs : Boolean := False;

         Is_Ada_05    : Boolean := False;

         Time_Zone    : Long_Integer := 0) return Time;

      --  Given all the components of a date, return the corresponding time

      --  value. Set Use_Day_Secs to use the value in Day_Secs, otherwise the

      --  day duration will be calculated from Hour, Minute, Second and Sub_

      --  Sec. Set Is_Ada_05 to use the local time zone (the value in formal

      --  Time_Zone is ignored) when building a time value and to verify the

      --  validity of a requested leap second.

   end Formatting_Operations;

   ---------------------------

   -- Time_Zones_Operations --

   ---------------------------

   package Time_Zones_Operations is

      function UTC_Time_Offset (Date : Time) return Long_Integer;

      --  Return the offset in seconds from UTC

   end Time_Zones_Operations;

end Ada.Calendar;