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(* $Id: Time.Mod,v 1.5 1999/09/02 13:27:32 acken Exp $ *)
MODULE Time;
(*
Time - time and time interval manipulation.
Copyright (C) 1996 Michael Griebling
This module is free software; you can redistribute it and/or modify
it under the terms of the GNU Lesser General Public License as
published by the Free Software Foundation; either version 2 of the
License, or (at your option) any later version.
This module is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*)
IMPORT SysClock;
CONST
msecPerSec* = 1000;
msecPerMin* = msecPerSec*60;
msecPerHour* = msecPerMin*60;
msecPerDay * = msecPerHour*24;
TYPE
(* The TimeStamp is a compressed date/time format with the
advantage over the Unix time stamp of being able to
represent any date/time in the DateTime type. The
fields are defined as follows:
days = Modified Julian days since 17 Nov 1858.
This quantity can be negative to represent
dates occuring before day zero.
msecs = Milliseconds since 00:00.
NOTE: TimeStamp is in UTC or local time when time zones
are not supported by the local operating system.
*)
TimeStamp * =
RECORD
days-: LONGINT;
msecs-: LONGINT
END;
(* The Interval is a delta time measure which can be used
to increment a Time or find the time difference between
two Times. The fields are defined as follows:
dayInt = numbers of days in this interval
msecInt = the number of milliseconds in this interval
The maximum number of milliseconds in an interval will
be the value `msecPerDay' *)
Interval * =
RECORD
dayInt-: LONGINT;
msecInt-: LONGINT
END;
(* ------------------------------------------------------------- *)
(* TimeStamp functions *)
PROCEDURE InitTimeStamp* (VAR t: TimeStamp; days, msecs: LONGINT);
(* Initialize the TimeStamp `t' with `days' days and `msecs' mS.
Pre: msecs>=0 *)
BEGIN
t.msecs:=msecs MOD msecPerDay;
t.days:=days + msecs DIV msecPerDay
END InitTimeStamp;
PROCEDURE GetTime* (VAR t: TimeStamp);
(* Set `t' to the current time of day. In case of failure (i.e. if
SysClock.CanGetClock() is FALSE) the time 00:00 UTC on Jan 1 1970 is
returned. This procedure is typically much faster than doing
SysClock.GetClock followed by Calendar.SetTimeStamp. *)
VAR
res, sec, usec: LONGINT;
BEGIN
res := SysClock.GetTimeOfDay (sec, usec);
t. days := 40587+sec DIV 86400;
t. msecs := (sec MOD 86400)*msecPerSec + usec DIV 1000
END GetTime;
PROCEDURE (VAR a: TimeStamp) Add* (b: Interval);
(* Adds the interval `b' to the time stamp `a'. *)
BEGIN
INC(a.msecs, b.msecInt);
INC(a.days, b.dayInt);
IF a.msecs>=msecPerDay THEN
DEC(a.msecs, msecPerDay); INC(a.days)
END
END Add;
PROCEDURE (VAR a: TimeStamp) Sub* (b: Interval);
(* Subtracts the interval `b' from the time stamp `a'. *)
BEGIN
DEC(a.msecs, b.msecInt);
DEC(a.days, b.dayInt);
IF a.msecs<0 THEN INC(a.msecs, msecPerDay); DEC(a.days) END
END Sub;
PROCEDURE (VAR a: TimeStamp) Delta* (b: TimeStamp; VAR c: Interval);
(* Post: c = a - b *)
BEGIN
c.msecInt:=a.msecs-b.msecs;
c.dayInt:=a.days-b.days;
IF c.msecInt<0 THEN
INC(c.msecInt, msecPerDay); DEC(c.dayInt)
END
END Delta;
PROCEDURE (VAR a: TimeStamp) Cmp* (b: TimeStamp) : SHORTINT;
(* Compares 'a' to 'b'. Result: -1: a<b; 0: a=b; 1: a>b
Above convention makes more sense since the comparison
can be directly extrapolated to a comparison between the
two numbers e.g.,
Cmp(a,b)<0 then a<b
Cmp(a,b)=0 then a=b
Cmp(a,b)>0 then a>b
Cmp(a,b)>=0 then a>=b
*)
BEGIN
IF (a.days>b.days) OR (a.days=b.days) & (a.msecs>b.msecs) THEN RETURN 1
ELSIF (a.days=b.days) & (a.msecs=b.msecs) THEN RETURN 0
ELSE RETURN -1
END
END Cmp;
(* ------------------------------------------------------------- *)
(* Interval functions *)
PROCEDURE InitInterval* (VAR int: Interval; days, msecs: LONGINT);
(* Initialize the Interval `int' with `days' days and `msecs' mS.
Pre: msecs>=0 *)
BEGIN
int.dayInt:=days + msecs DIV msecPerDay;
int.msecInt:=msecs MOD msecPerDay
END InitInterval;
PROCEDURE (VAR a: Interval) Add* (b: Interval);
(* Post: a = a + b *)
BEGIN
INC(a.msecInt, b.msecInt);
INC(a.dayInt, b.dayInt);
IF a.msecInt>=msecPerDay THEN
DEC(a.msecInt, msecPerDay); INC(a.dayInt)
END
END Add;
PROCEDURE (VAR a: Interval) Sub* (b: Interval);
(* Post: a = a - b *)
BEGIN
DEC(a.msecInt, b.msecInt);
DEC(a.dayInt, b.dayInt);
IF a.msecInt<0 THEN
INC(a.msecInt, msecPerDay); DEC(a.dayInt)
END
END Sub;
PROCEDURE (VAR a: Interval) Cmp* (b: Interval) : SHORTINT;
(* Compares 'a' to 'b'. Result: -1: a<b; 0: a=b; 1: a>b
Above convention makes more sense since the comparison
can be directly extrapolated to a comparison between the
two numbers e.g.,
Cmp(a,b)<0 then a<b
Cmp(a,b)=0 then a=b
Cmp(a,b)>0 then a>b
Cmp(a,b)>=0 then a>=b
*)
BEGIN
IF (a.dayInt>b.dayInt) OR (a.dayInt=b.dayInt)&(a.msecInt>b.msecInt) THEN RETURN 1
ELSIF (a.dayInt=b.dayInt) & (a.msecInt=b.msecInt) THEN RETURN 0
ELSE RETURN -1
END
END Cmp;
PROCEDURE (VAR a: Interval) Scale* (b: LONGREAL);
(* Pre: b>=0; Post: a := a*b *)
VAR
si: LONGREAL;
BEGIN
si:=(a.dayInt+a.msecInt/msecPerDay)*b;
a.dayInt:=ENTIER(si);
a.msecInt:=ENTIER((si-a.dayInt)*msecPerDay+0.5D0)
END Scale;
PROCEDURE (VAR a: Interval) Fraction* (b: Interval) : LONGREAL;
(* Pre: b<>0; Post: RETURN a/b *)
BEGIN
RETURN (a.dayInt+a.msecInt/msecPerDay)/(b.dayInt+b.msecInt/msecPerDay)
END Fraction;
END Time.
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