Re: C date package

[Robert Dewar <robert_dewar@my-deja.com>]

In article <3918BB77.693C70D6@research.canon.com.au>,
  Geoff Bull <geoff@research.canon.com.au> wrote:
> Oops, I posted to comp.lang.ada by mistake!
> This was a thread on team-ada discussing which started with
> the "2038 bug".

> Fair enough, weak was probably the wrong word (maybe I should
> used "basic")
> - it doesn't even split out hours and minutes.

By the way, have a look at the package GNAT.Calendar in GNAT
3.13 which fills in some of the gaps. In fact let me post the
spec here. There is also a GNAT.Calendar.Time_IO that allows
flexible output of times


--  This package extends Ada.Calendar to handle Hour, Minute,
Second,
--  Second_Duration and Day_Of_Week and Day_In_Year from
Calendar.Time.
--  Second_Duration precision depends on the target clock
precision.
--
--  GNAT.Calendar provides the same kind of abstraction found in
--  Ada.Calendar. It provides Split and Time_Of to build and
split a Time
--  data. And it provides accessor functions to get only one of
Hour, Minute,
--  Second, Second_Duration. Other functions are to access more
advanced
--  valueas like Day_Of_Week, Day_In_Year and Week_In_Year.

with Ada.Calendar;
with Interfaces.C;

package GNAT.Calendar is

   type Day_Name is
     (Monday, Tuesday, Wednesday, Thursday, Friday, Saturday,
Sunday);

   subtype Hour_Number         is Natural range 0 .. 23;
   subtype Minute_Number       is Natural range 0 .. 59;
   subtype Second_Number       is Natural range 0 .. 59;
   subtype Second_Duration     is Ada.Calendar.Day_Duration
range 0.0 .. 1.0;
   subtype Day_In_Year_Number  is Positive range 1 .. 366;
   subtype Week_In_Year_Number is Positive range 1 .. 53;

   function Hour        (Date : Ada.Calendar.Time) return
Hour_Number;
   function Minute      (Date : Ada.Calendar.Time) return
Minute_Number;
   function Second      (Date : Ada.Calendar.Time) return
Second_Number;
   function Sub_Second  (Date : Ada.Calendar.Time) return
Second_Duration;
   --  Hour, Minute, Sedond and Sub_Second returns the complete
time data for
   --  the Date (H:M:S.SS). See Ada.Calendar for Year, Month,
Day accessors.
   --  Second_Duration precision depends on the target clock
precision.

   function Day_Of_Week (Date : Ada.Calendar.Time) return
Day_Name;
   --  Return the day name.

   function Day_In_Year (Date : Ada.Calendar.Time) return
Day_In_Year_Number;
   --  Returns the day number in the year. (1st January is day 1
and 31st
   --  December is day 365 or 366 for leap year).

   function Week_In_Year (Date : Ada.Calendar.Time) return
Week_In_Year_Number;
   --  Returns the week number in the year with Monday as first
day of week

   procedure Split
     (Date       : Ada.Calendar.Time;
      Year       : out Ada.Calendar.Year_Number;
      Month      : out Ada.Calendar.Month_Number;
      Day        : out Ada.Calendar.Day_Number;
      Hour       : out Hour_Number;
      Minute     : out Minute_Number;
      Second     : out Second_Number;
      Sub_Second : out Second_Duration);
   --  Split the standard Ada.Calendar.Time data in date data
(Year, Month,
   --  Day) and Time data (Hour, Minute, Second, Sub_Second)

   function Time_Of
     (Year       : Ada.Calendar.Year_Number;
      Month      : Ada.Calendar.Month_Number;
      Day        : Ada.Calendar.Day_Number;
      Hour       : Hour_Number;
      Minute     : Minute_Number;
      Second     : Second_Number;
      Sub_Second : Second_Duration := 0.0)
      return Ada.Calendar.Time;
   --  Returns an Ada.Calendar.Time data built from the date and
time values.

   --  C timeval conversion

   --  C timeval represent a duration (used in Select for
example). This
   --  structure is composed of a number of seconds and a number
of micro
   --  seconds. The timeval structure is not exposed here
because its
   --  definition is target dependent. Interface to C programs
is done via a
   --  pointer to timeval structure.

   type timeval is private;

   function To_Duration (T : access timeval) return Duration;
   function To_Timeval  (D : Duration) return timeval;

private
   --  This is a dummy declaration that should be the largest
possible timeval
   --  structure of all supported targets.

   type timeval is array (1 .. 2) of Interfaces.C.long;

   function Julian_Day
     (Year  : Ada.Calendar.Year_Number;
      Month : Ada.Calendar.Month_Number;
      Day   : Ada.Calendar.Day_Number)
      return  Integer;
   --  Compute Julian day number.
   --
   --  The code of this function is a modified version of
algorithm
   --  199 from the Collected Algorithms of the ACM.
   --  The author of algorithm 199 is Robert G. Tantzen.
end GNAT.Calendar;


--  This package augments standard Ada.Text_IO with facilities
for input
--  and output of time values in standardized format.

package GNAT.Calendar.Time_IO is

   Picture_Error : exception;

   type Picture_String is new String;

   --  This is a string to describe date and time output format.
The string is
   --  a set of standard character and special tag that are
replaced by the
   --  corresponding values. It follows the GNU Date
specification. Here are
   --  the recognized directives :
   --
   --          %    a literal %
   --          n    a newline
   --          t    a horizontal tab
   --
   --          Time fields:
   --
   --          %H   hour (00..23)
   --          %I   hour (01..12)
   --          %k   hour ( 0..23)
   --          %l   hour ( 1..12)
   --          %M   minute (00..59)
   --          %p   locale's AM or PM
   --          %r   time, 12-hour (hh:mm:ss [AP]M)
   --          %s   seconds  since 1970-01-01  00:00:00 UTC
   --                (a nonstandard extension)
   --          %S   second (00..59)
   --          %T   time, 24-hour (hh:mm:ss)
   --
   --          Date fields:
   --
   --          %a   locale's abbreviated weekday name (Sun..Sat)
   --          %A   locale's    full   weekday   name,
variable   length
   --                  (Sunday..Saturday)
   --          %b   locale's abbreviated month name (Jan..Dec)
   --          %B   locale's    full    month    name,
variable    length
   --                  (January..December)
   --          %c   locale's date and time (Sat Nov 04 12:02:33
EST 1989)
   --          %d   day of month (01..31)
   --          %D   date (mm/dd/yy)
   --          %h   same as %b
   --          %j   day of year (001..366)
   --          %m   month (01..12)
   --          %U   week number  of year with  Sunday as first
day  of week
   --                  (00..53)
   --          %w   day of week (0..6) with 0 corresponding to
Sunday
   --          %W   week number  of year with  Monday as first
day  of week
   --                  (00..53)
   --          %x   locale's date representation (mm/dd/yy)
   --          %y   last two digits of year (00..99)
   --          %Y   year (1970...)
   --
   --          By default,  date pads numeric fields with
zeroes.  GNU date
   --          recognizes the following nonstandard numeric
modifiers:
   --
   --          -    (hyphen) do not pad the field
   --          _    (underscore) pad the field with spaces


   ISO_Date      : constant Picture_String;
   US_Date       : constant Picture_String;
   European_Date : constant Picture_String;

   function Image
     (Date    : Ada.Calendar.Time;
      Picture : Picture_String)
      return    String;
   --  Return Date as a string with format Picture.
   --  raise Picture_Error if picture string is wrong

   procedure Put_Time
     (Date    : Ada.Calendar.Time;
      Picture : Picture_String);
   --  Put Date with format Picture.
   --  raise Picture_Error if picture string is wrong

private
   ISO_Date      : constant Picture_String := "%Y/%m/%d";
   US_Date       : constant Picture_String := "%m/%d/%y";
   European_Date : constant Picture_String := "%d/%m/%y";

end GNAT.Calendar.Time_IO;



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