------------------------------------------------------------------------------ -- -- -- GNAT RUN-TIME COMPONENTS -- -- -- -- A D A . C A L E N D A R -- -- -- -- B o d y -- -- -- -- Copyright (C) 1992-2005, Free Software Foundation, Inc. -- -- -- -- 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 2, 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. See the GNU General Public License -- -- for more details. You should have received a copy of the GNU General -- -- Public License distributed with GNAT; see file COPYING. If not, write -- -- to the Free Software Foundation, 51 Franklin Street, Fifth Floor, -- -- Boston, MA 02110-1301, USA. -- -- -- -- As a special exception, if other files instantiate generics from this -- -- unit, or you link this unit with other files to produce an executable, -- -- this unit does not by itself cause the resulting executable to be -- -- covered by the GNU General Public License. This exception does not -- -- however invalidate any other reasons why the executable file might be -- -- covered by the GNU Public License. -- -- -- -- GNAT was originally developed by the GNAT team at New York University. -- -- Extensive contributions were provided by Ada Core Technologies Inc. -- -- -- ------------------------------------------------------------------------------ with Unchecked_Conversion; with System.OS_Primitives; -- used for Clock package body Ada.Calendar is ------------------------------ -- Use of Pragma Unsuppress -- ------------------------------ -- This implementation of Calendar takes advantage of the permission in -- Ada 95 of using arithmetic overflow checks to check for out of bounds -- time values. This means that we must catch the constraint error that -- results from arithmetic overflow, so we use pragma Unsuppress to make -- sure that overflow is enabled, using software overflow checking if -- necessary. That way, compiling Calendar with options to suppress this -- checking will not affect its correctness. ------------------------ -- Local Declarations -- ------------------------ type Char_Pointer is access Character; subtype int is Integer; subtype long is Long_Integer; -- Synonyms for C types. We don't want to get them from Interfaces.C -- because there is no point in loading that unit just for calendar. type tm is record tm_sec : int; -- seconds after the minute (0 .. 60) tm_min : int; -- minutes after the hour (0 .. 59) tm_hour : int; -- hours since midnight (0 .. 24) tm_mday : int; -- day of the month (1 .. 31) tm_mon : int; -- months since January (0 .. 11) tm_year : int; -- years since 1900 tm_wday : int; -- days since Sunday (0 .. 6) tm_yday : int; -- days since January 1 (0 .. 365) tm_isdst : int; -- Daylight Savings Time flag (-1 .. +1) tm_gmtoff : long; -- offset from CUT in seconds tm_zone : Char_Pointer; -- timezone abbreviation end record; type tm_Pointer is access all tm; subtype time_t is long; type time_t_Pointer is access all time_t; procedure localtime_r (C : time_t_Pointer; res : tm_Pointer); pragma Import (C, localtime_r, "__gnat_localtime_r"); function mktime (TM : tm_Pointer) return time_t; pragma Import (C, mktime); -- mktime returns -1 in case the calendar time given by components of -- TM.all cannot be represented. -- The following constants are used in adjusting Ada dates so that they -- fit into a 56 year range that can be handled by Unix (1970 included - -- 2026 excluded). Dates that are not in this 56 year range are shifted -- by multiples of 56 years to fit in this range. -- The trick is that the number of days in any four year period in the Ada -- range of years (1901 - 2099) has a constant number of days. This is -- because we have the special case of 2000 which, contrary to the normal -- exception for centuries, is a leap year after all. 56 has been chosen, -- because it is not only a multiple of 4, but also a multiple of 7. Thus -- two dates 56 years apart fall on the same day of the week, and the -- Daylight Saving Time change dates are usually the same for these two -- years. Unix_Year_Min : constant := 1970; Unix_Year_Max : constant := 2026; Ada_Year_Min : constant := 1901; Ada_Year_Max : constant := 2099; -- Some basic constants used throughout Days_In_Month : constant array (Month_Number) of Day_Number := (31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31); Days_In_4_Years : constant := 365 * 3 + 366; Seconds_In_4_Years : constant := 86_400 * Days_In_4_Years; Seconds_In_56_Years : constant := Seconds_In_4_Years * 14; Seconds_In_56_YearsD : constant := Duration (Seconds_In_56_Years); --------- -- "+" -- --------- function "+" (Left : Time; Right : Duration) return Time is pragma Unsuppress (Overflow_Check); begin return (Left + Time (Right)); exception when Constraint_Error => raise Time_Error; end "+"; function "+" (Left : Duration; Right : Time) return Time is pragma Unsuppress (Overflow_Check); begin return (Time (Left) + Right); exception when Constraint_Error => raise Time_Error; end "+"; --------- -- "-" -- --------- function "-" (Left : Time; Right : Duration) return Time is pragma Unsuppress (Overflow_Check); begin return Left - Time (Right); exception when Constraint_Error => raise Time_Error; end "-"; function "-" (Left : Time; Right : Time) return Duration is pragma Unsuppress (Overflow_Check); begin return Duration (Left) - Duration (Right); exception when Constraint_Error => raise Time_Error; end "-"; --------- -- "<" -- --------- function "<" (Left, Right : Time) return Boolean is begin return Duration (Left) < Duration (Right); end "<"; ---------- -- "<=" -- ---------- function "<=" (Left, Right : Time) return Boolean is begin return Duration (Left) <= Duration (Right); end "<="; --------- -- ">" -- --------- function ">" (Left, Right : Time) return Boolean is begin return Duration (Left) > Duration (Right); end ">"; ---------- -- ">=" -- ---------- function ">=" (Left, Right : Time) return Boolean is begin return Duration (Left) >= Duration (Right); end ">="; ----------- -- Clock -- ----------- function Clock return Time is begin return Time (System.OS_Primitives.Clock); end Clock; --------- -- Day -- --------- function Day (Date : Time) return Day_Number is DY : Year_Number; DM : Month_Number; DD : Day_Number; DS : Day_Duration; begin Split (Date, DY, DM, DD, DS); return DD; end Day; ----------- -- Month -- ----------- function Month (Date : Time) return Month_Number is DY : Year_Number; DM : Month_Number; DD : Day_Number; DS : Day_Duration; begin Split (Date, DY, DM, DD, DS); return DM; end Month; ------------- -- Seconds -- ------------- function Seconds (Date : Time) return Day_Duration is DY : Year_Number; DM : Month_Number; DD : Day_Number; DS : Day_Duration; begin Split (Date, DY, DM, DD, DS); return DS; end Seconds; ----------- -- Split -- ----------- procedure Split (Date : Time; Year : out Year_Number; Month : out Month_Number; Day : out Day_Number; Seconds : out Day_Duration) is -- The following declare bounds for duration that are comfortably -- wider than the maximum allowed output result for the Ada range -- of representable split values. These are used for a quick check -- that the value is not wildly out of range. Low : constant := (Ada_Year_Min - Unix_Year_Min - 2) * 365 * 86_400; High : constant := (Ada_Year_Max - Unix_Year_Min + 2) * 365 * 86_400; LowD : constant Duration := Duration (Low); HighD : constant Duration := Duration (High); -- Finally the actual variables used in the computation D : Duration; Frac_Sec : Duration; Year_Val : Integer; Adjusted_Seconds : aliased time_t; Tm_Val : aliased tm; begin -- For us a time is simply a signed duration value, so we work with -- this duration value directly. Note that it can be negative. D := Duration (Date); -- First of all, filter out completely ludicrous values. Remember that -- we use the full stored range of duration values, which may be -- significantly larger than the allowed range of Ada times. Note that -- these checks are wider than required to make absolutely sure that -- there are no end effects from time zone differences. if D < LowD or else D > HighD then raise Time_Error; end if; -- The unix localtime_r function is more or less exactly what we need -- here. The less comes from the fact that it does not support the -- required range of years (the guaranteed range available is only -- EPOCH through EPOCH + N seconds). N is in practice 2 ** 31 - 1. -- If we have a value outside this range, then we first adjust it to be -- in the required range by adding multiples of 56 years. For the range -- we are interested in, the number of days in any consecutive 56 year -- period is constant. Then we do the split on the adjusted value, and -- readjust the years value accordingly. Year_Val := 0; while D < 0.0 loop D := D + Seconds_In_56_YearsD; Year_Val := Year_Val - 56; end loop; while D >= Seconds_In_56_YearsD loop D := D - Seconds_In_56_YearsD; Year_Val := Year_Val + 56; end loop; -- Now we need to take the value D, which is now non-negative, and -- break it down into seconds (to pass to the localtime_r function) and -- fractions of seconds (for the adjustment below). -- Surprisingly there is no easy way to do this in Ada, and certainly -- no easy way to do it and generate efficient code. Therefore we do it -- at a low level, knowing that it is really represented as an integer -- with units of Small declare type D_Int is range 0 .. 2 ** (Duration'Size - 1) - 1; for D_Int'Size use Duration'Size; Small_Div : constant D_Int := D_Int (1.0 / Duration'Small); D_As_Int : D_Int; function To_D_As_Int is new Unchecked_Conversion (Duration, D_Int); function To_Duration is new Unchecked_Conversion (D_Int, Duration); begin D_As_Int := To_D_As_Int (D); Adjusted_Seconds := time_t (D_As_Int / Small_Div); Frac_Sec := To_Duration (D_As_Int rem Small_Div); end; localtime_r (Adjusted_Seconds'Unchecked_Access, Tm_Val'Unchecked_Access); Year_Val := Tm_Val.tm_year + 1900 + Year_Val; Month := Tm_Val.tm_mon + 1; Day := Tm_Val.tm_mday; -- The Seconds value is a little complex. The localtime function -- returns the integral number of seconds, which is what we want, but -- we want to retain the fractional part from the original Time value, -- since this is typically stored more accurately. Seconds := Duration (Tm_Val.tm_hour * 3600 + Tm_Val.tm_min * 60 + Tm_Val.tm_sec) + Frac_Sec; -- Note: the above expression is pretty horrible, one of these days we -- should stop using time_of and do everything ourselves to avoid these -- unnecessary divides and multiplies???. -- The Year may still be out of range, since our entry test was -- deliberately crude. Trying to make this entry test accurate is -- tricky due to time zone adjustment issues affecting the exact -- boundary. It is interesting to note that whether or not a given -- Calendar.Time value gets Time_Error when split depends on the -- current time zone setting. if Year_Val not in Ada_Year_Min .. Ada_Year_Max then raise Time_Error; else Year := Year_Val; end if; end Split; ------------- -- Time_Of -- ------------- function Time_Of (Year : Year_Number; Month : Month_Number; Day : Day_Number; Seconds : Day_Duration := 0.0) return Time is Result_Secs : aliased time_t; TM_Val : aliased tm; Int_Secs : constant Integer := Integer (Seconds); Year_Val : Integer := Year; Duration_Adjust : Duration := 0.0; begin -- The following checks are redundant with respect to the constraint -- error checks that should normally be made on parameters, but we -- decide to raise Constraint_Error in any case if bad values come in -- (as a result of checks being off in the caller, or for other -- erroneous or bounded error cases). if not Year 'Valid or else not Month 'Valid or else not Day 'Valid or else not Seconds'Valid then raise Constraint_Error; end if; -- Check for Day value too large (one might expect mktime to do this -- check, as well as the basic checks we did with 'Valid, but it seems -- that at least on some systems, this built-in check is too weak). if Day > Days_In_Month (Month) and then (Day /= 29 or Month /= 2 or Year mod 4 /= 0) then raise Time_Error; end if; TM_Val.tm_sec := Int_Secs mod 60; TM_Val.tm_min := (Int_Secs / 60) mod 60; TM_Val.tm_hour := (Int_Secs / 60) / 60; TM_Val.tm_mday := Day; TM_Val.tm_mon := Month - 1; -- For the year, we have to adjust it to a year that Unix can handle. -- We do this in 56 year steps, since the number of days in 56 years is -- constant, so the timezone effect on the conversion from local time -- to GMT is unaffected; also the DST change dates are usually not -- modified. while Year_Val < Unix_Year_Min loop Year_Val := Year_Val + 56; Duration_Adjust := Duration_Adjust - Seconds_In_56_YearsD; end loop; while Year_Val >= Unix_Year_Max loop Year_Val := Year_Val - 56; Duration_Adjust := Duration_Adjust + Seconds_In_56_YearsD; end loop; TM_Val.tm_year := Year_Val - 1900; -- Since we do not have information on daylight savings, rely on the -- default information. TM_Val.tm_isdst := -1; Result_Secs := mktime (TM_Val'Unchecked_Access); -- That gives us the basic value in seconds. Two adjustments are -- needed. First we must undo the year adjustment carried out above. -- Second we put back the fraction seconds value since in general the -- Day_Duration value we received has additional precision which we do -- not want to lose in the constructed result. return Time (Duration (Result_Secs) + Duration_Adjust + (Seconds - Duration (Int_Secs))); end Time_Of; ---------- -- Year -- ---------- function Year (Date : Time) return Year_Number is DY : Year_Number; DM : Month_Number; DD : Day_Number; DS : Day_Duration; begin Split (Date, DY, DM, DD, DS); return DY; end Year; begin System.OS_Primitives.Initialize; end Ada.Calendar;