-- --
-- B o d y --
-- --
--- Copyright (C) 1999-2006, AdaCore --
+-- Copyright (C) 1999-2007, AdaCore --
-- --
-- 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- --
Month : Month_Number;
Day : Day_Number;
Day_Secs : Day_Duration;
-
begin
Split (Date, Year, Month, Day, Day_Secs);
-
return Julian_Day (Year, Month, Day) - Julian_Day (Year, 1, 1) + 1;
end Day_In_Year;
Month : Month_Number;
Day : Day_Number;
Day_Secs : Day_Duration;
-
begin
Split (Date, Year, Month, Day, Day_Secs);
-
return Day_Name'Val ((Julian_Day (Year, Month, Day)) mod 7);
end Day_Of_Week;
Minute : Minute_Number;
Second : Second_Number;
Sub_Second : Second_Duration;
-
begin
Split (Date, Year, Month, Day, Hour, Minute, Second, Sub_Second);
return Hour;
Minute : Minute_Number;
Second : Second_Number;
Sub_Second : Second_Duration;
-
begin
Split (Date, Year, Month, Day, Hour, Minute, Second, Sub_Second);
return Minute;
Minute : Minute_Number;
Second : Second_Number;
Sub_Second : Second_Duration;
-
begin
Split (Date, Year, Month, Day, Hour, Minute, Second, Sub_Second);
return Second;
Minute : Minute_Number;
Second : Second_Number;
Sub_Second : Second_Duration;
-
begin
Split (Date, Year, Month, Day, Hour, Minute, Second, Sub_Second);
return Sub_Second;
Minute : Minute_Number;
Second : Second_Number;
Sub_Second : Second_Duration;
- Offset : Natural;
+ Jan_1 : Day_Name;
+ Shift : Week_In_Year_Number;
+ Start_Week : Week_In_Year_Number;
+
+ function Is_Leap (Year : Year_Number) return Boolean;
+ -- Return True if Year denotes a leap year. Leap centential years are
+ -- properly handled.
+
+ function Jan_1_Day_Of_Week
+ (Jan_1 : Day_Name;
+ Year : Year_Number;
+ Last_Year : Boolean := False;
+ Next_Year : Boolean := False) return Day_Name;
+ -- Given the weekday of January 1 in Year, determine the weekday on
+ -- which January 1 fell last year or will fall next year as set by
+ -- the two flags. This routine does not call Time_Of or Split.
+
+ function Last_Year_Has_53_Weeks
+ (Jan_1 : Day_Name;
+ Year : Year_Number) return Boolean;
+ -- Given the weekday of January 1 in Year, determine whether last year
+ -- has 53 weeks. A False value implies that the year has 52 weeks.
+
+ -------------
+ -- Is_Leap --
+ -------------
+
+ function Is_Leap (Year : Year_Number) return Boolean is
+ begin
+ if Year mod 400 = 0 then
+ return True;
+ elsif Year mod 100 = 0 then
+ return False;
+ else
+ return Year mod 4 = 0;
+ end if;
+ end Is_Leap;
+
+ -----------------------
+ -- Jan_1_Day_Of_Week --
+ -----------------------
+
+ function Jan_1_Day_Of_Week
+ (Jan_1 : Day_Name;
+ Year : Year_Number;
+ Last_Year : Boolean := False;
+ Next_Year : Boolean := False) return Day_Name
+ is
+ Shift : Integer := 0;
+
+ begin
+ if Last_Year then
+ if Is_Leap (Year - 1) then
+ Shift := -2;
+ else
+ Shift := -1;
+ end if;
+
+ elsif Next_Year then
+ if Is_Leap (Year) then
+ Shift := 2;
+ else
+ Shift := 1;
+ end if;
+ end if;
+
+ return Day_Name'Val ((Day_Name'Pos (Jan_1) + Shift) mod 7);
+ end Jan_1_Day_Of_Week;
+
+ ----------------------------
+ -- Last_Year_Has_53_Weeks --
+ ----------------------------
+
+ function Last_Year_Has_53_Weeks
+ (Jan_1 : Day_Name;
+ Year : Year_Number) return Boolean
+ is
+ Last_Jan_1 : constant Day_Name :=
+ Jan_1_Day_Of_Week (Jan_1, Year, Last_Year => True);
+ begin
+ -- These two cases are illustrated in the table below
+
+ return
+ Last_Jan_1 = Thursday
+ or else
+ (Last_Jan_1 = Wednesday
+ and then Is_Leap (Year - 1));
+ end Last_Year_Has_53_Weeks;
+
+ -- Start of processing for Week_In_Year
begin
Split (Date, Year, Month, Day, Hour, Minute, Second, Sub_Second);
- -- Day offset number for the first week of the year
+ -- According to ISO 8601, the first week of year Y is the week that
+ -- contains the first Thursday in year Y. The following table contains
+ -- all possible combinations of years and weekdays along with examples.
+
+ -- +-------+------+-------+---------+
+ -- | Jan 1 | Leap | Weeks | Example |
+ -- +-------+------+-------+---------+
+ -- | Mon | No | 52 | 2007 |
+ -- +-------+------+-------+---------+
+ -- | Mon | Yes | 52 | 1996 |
+ -- +-------+------+-------+---------+
+ -- | Tue | No | 52 | 2002 |
+ -- +-------+------+-------+---------+
+ -- | Tue | Yes | 52 | 1980 |
+ -- +-------+------+-------+---------+
+ -- | Wed | No | 52 | 2003 |
+ -- +-------+------#########---------+
+ -- | Wed | Yes # 53 # 1992 |
+ -- +-------+------#-------#---------+
+ -- | Thu | No # 53 # 1998 |
+ -- +-------+------#-------#---------+
+ -- | Thu | Yes # 53 # 2004 |
+ -- +-------+------#########---------+
+ -- | Fri | No | 52 | 1999 |
+ -- +-------+------+-------+---------+
+ -- | Fri | Yes | 52 | 1988 |
+ -- +-------+------+-------+---------+
+ -- | Sat | No | 52 | 1994 |
+ -- +-------+------+-------+---------+
+ -- | Sat | Yes | 52 | 1972 |
+ -- +-------+------+-------+---------+
+ -- | Sun | No | 52 | 1995 |
+ -- +-------+------+-------+---------+
+ -- | Sun | Yes | 52 | 1956 |
+ -- +-------+------+-------+---------+
+
+ -- A small optimization, the input date is January 1. Note that this
+ -- is a key day since it determines the number of weeks and is used
+ -- when special casing the first week of January and the last week of
+ -- December.
+
+ if Day = 1
+ and then Month = 1
+ then
+ Jan_1 := Day_Of_Week (Date);
+ else
+ Jan_1 := Day_Of_Week (Time_Of (Year, 1, 1, 0.0));
+ end if;
+
+ if Month = 1 then
+
+ -- Special case 1: January 1, 2 and 3. These three days may belong
+ -- to last year's last week which can be week number 52 or 53.
+
+ -- +-----+-----+-----+=====+-----+-----+-----+
+ -- | Mon | Tue | Wed # Thu # Fri | Sat | Sun |
+ -- +-----+-----+-----+-----+-----+-----+-----+
+ -- | 26 | 27 | 28 # 29 # 30 | 31 | 1 |
+ -- +-----+-----+-----+-----+-----+-----+-----+
+ -- | 27 | 28 | 29 # 30 # 31 | 1 | 2 |
+ -- +-----+-----+-----+-----+-----+-----+-----+
+ -- | 28 | 29 | 30 # 31 # 1 | 2 | 3 |
+ -- +-----+-----+-----+=====+-----+-----+-----+
+
+ if (Day = 1 and then Jan_1 in Friday .. Sunday)
+ or else
+ (Day = 2 and then Jan_1 in Friday .. Saturday)
+ or else
+ (Day = 3 and then Jan_1 = Friday)
+ then
+ if Last_Year_Has_53_Weeks (Jan_1, Year) then
+ return 53;
+ else
+ return 52;
+ end if;
+
+ -- Special case 2: January 1, 2, 3, 4, 5 and 6 of the first week. In
+ -- this scenario January 1 does not fall on a Monday.
+
+ -- +-----+-----+-----+=====+-----+-----+-----+
+ -- | Mon | Tue | Wed # Thu # Fri | Sat | Sun |
+ -- +-----+-----+-----+-----+-----+-----+-----+
+ -- | 29 | 30 | 31 # 1 # 2 | 3 | 4 |
+ -- +-----+-----+-----+-----+-----+-----+-----+
+ -- | 30 | 31 | 1 # 2 # 3 | 4 | 5 |
+ -- +-----+-----+-----+-----+-----+-----+-----+
+ -- | 31 | 1 | 2 # 3 # 4 | 5 | 6 |
+ -- +-----+-----+-----+-----+-----+-----+-----+
+
+ elsif (Day <= 4 and then Jan_1 in Tuesday .. Thursday)
+ or else
+ (Day = 5 and then Jan_1 in Tuesday .. Wednesday)
+ or else
+ (Day = 6 and then Jan_1 = Tuesday)
+ then
+ return 1;
+ end if;
+
+ -- Special case 3: December 29, 30 and 31. These days may belong to
+ -- next year's first week.
+
+ -- +-----+-----+-----+=====+-----+-----+-----+
+ -- | Mon | Tue | Wed # Thu # Fri | Sat | Sun |
+ -- +-----+-----+-----+-----+-----+-----+-----+
+ -- | 29 | 30 | 31 # 1 # 2 | 3 | 4 |
+ -- +-----+-----+-----+-----+-----+-----+-----+
+ -- | 30 | 31 | 1 # 2 # 3 | 4 | 5 |
+ -- +-----+-----+-----+-----+-----+-----+-----+
+ -- | 31 | 1 | 2 # 3 # 4 | 5 | 6 |
+ -- +-----+-----+-----+=====+-----+-----+-----+
+
+ elsif Month = 12
+ and then Day > 28
+ then
+ declare
+ Next_Jan_1 : constant Day_Name :=
+ Jan_1_Day_Of_Week (Jan_1, Year, Next_Year => True);
+ begin
+ if (Day = 29 and then Next_Jan_1 = Thursday)
+ or else
+ (Day = 30 and then Next_Jan_1 in Wednesday .. Thursday)
+ or else
+ (Day = 31 and then Next_Jan_1 in Tuesday .. Thursday)
+ then
+ return 1;
+ end if;
+ end;
+ end if;
+
+ -- Determine the week from which to start counting. If January 1 does
+ -- not belong to the first week of the input year, then the next week
+ -- is the first week.
+
+ if Jan_1 in Friday .. Sunday then
+ Start_Week := 1;
+ else
+ Start_Week := 2;
+ end if;
- Offset := Julian_Day (Year, 1, 1) mod 7;
+ -- At this point all special combinations have been accounted for and
+ -- the proper start week has been found. Since January 1 may not fall
+ -- on a Monday, shift 7 - Day_Name'Pos (Jan_1). This action ensures an
+ -- origin which falls on Monday.
- return 1 + ((Day_In_Year (Date) - 1) + Offset) / 7;
+ Shift := 7 - Day_Name'Pos (Jan_1);
+ return Start_Week + (Day_In_Year (Date) - Shift - 1) / 7;
end Week_In_Year;
end GNAT.Calendar;
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