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

--  This package provides various routines for conversion between Ada and Unix
--  time models - Time, Duration, struct tm and struct timespec.

with Interfaces.C;

package Ada.Calendar.Conversions is

   function To_Ada_Time (Unix_Time : Interfaces.C.long) return Time;
   --  Convert a time value represented as number of seconds since the Unix
   --  Epoch to a time value relative to an Ada implementation-defined Epoch.
   --  The units of the result are 100 nanoseconds on VMS and nanoseconds on
   --  all other targets. Raises Time_Error if the result cannot fit into a
   --  Time value.

   function To_Ada_Time
     (tm_year  : Interfaces.C.int;
      tm_mon   : Interfaces.C.int;
      tm_day   : Interfaces.C.int;
      tm_hour  : Interfaces.C.int;
      tm_min   : Interfaces.C.int;
      tm_sec   : Interfaces.C.int;
      tm_isdst : Interfaces.C.int) return Time;
   --  Convert a time value expressed in Unix-like fields of struct tm into
   --  a Time value relative to the Ada Epoch. The ranges of the formals are
   --  as follows:

   --     tm_year   --  years since 1900
   --     tm_mon    --  months since January [0 .. 11]
   --     tm_day    --  day of the month [1 .. 31]
   --     tm_hour   --  hours since midnight [0 .. 24]
   --     tm_min    --  minutes after the hour [0 .. 59]
   --     tm_sec    --  seconds after the minute [0 .. 60]
   --     tm_isdst  --  Daylight Savings Time flag [-1 .. 1]

   --  The returned value is in UTC and may or may not contain leap seconds
   --  depending on whether binder flag "-y" was used. Raises Time_Error if
   --  the input values are out of the defined ranges or if tm_sec equals 60
   --  and the instance in time is not a leap second occurrence.

   function To_Duration
     (tv_sec  : Interfaces.C.long;
      tv_nsec : Interfaces.C.long) return Duration;
   --  Convert an elapsed time value expressed in Unix-like fields of struct
   --  timespec into a Duration value. The expected ranges are:

   --     tv_sec   -  seconds
   --     tv_nsec  -  nanoseconds

   procedure To_Struct_Timespec
     (D       : Duration;
      tv_sec  : out Interfaces.C.long;
      tv_nsec : out Interfaces.C.long);
   --  Convert a Duration value into the constituents of struct timespec.
   --  Formal tv_sec denotes seconds and tv_nsecs denotes nanoseconds.

   procedure To_Struct_Tm
     (T       : Time;
      tm_year : out Interfaces.C.int;
      tm_mon  : out Interfaces.C.int;
      tm_day  : out Interfaces.C.int;
      tm_hour : out Interfaces.C.int;
      tm_min  : out Interfaces.C.int;
      tm_sec  : out Interfaces.C.int);
   --  Convert a Time value set in the Ada Epoch into the constituents of
   --  struct tm. The ranges of the out formals are as follows:

   --     tm_year   --  years since 1900
   --     tm_mon    --  months since January [0 .. 11]
   --     tm_day    --  day of the month [1 .. 31]
   --     tm_hour   --  hours since midnight [0 .. 24]
   --     tm_min    --  minutes after the hour [0 .. 59]
   --     tm_sec    --  seconds after the minute [0 .. 60]
   --     tm_isdst  --  Daylight Savings Time flag [-1 .. 1]

   --  The input date is considered to be in UTC

   function To_Unix_Time (Ada_Time : Time) return Interfaces.C.long;
   --  Convert a time value represented as number of time units since the Ada
   --  implementation-defined Epoch to a value relative to the Unix Epoch. The
   --  units of the result are seconds. Raises Time_Error if the result cannot
   --  fit into a Time value.

end Ada.Calendar.Conversions;