[fpc-pascal]Week Day

[Marco van de Voort]

> Does anyone know how to get the actual day (mon, tues, wed, etc) that a
> file was created? The datetime record doesn't seem to have that info,
> nor does the searchrec. Is there a way to get this information from a
> packed date?

No, but you can simply calculate it. 

FUNCTION LeapYr( Year : LONGINT) : BOOLEAN; ASSEMBLER;

asm
                push    %ebx            // ease calls from other procedures
                push    %ecx
                push    %edx
                movl    Year,%eax
                testl    $3,%eax
                jne     .LLeapEnd
                movl    $100,%ebx

                  cltd
                idivl   %ebx
                testb   %dl,%dl
                jne     .LLeapTrue
                and     $3,%eax
                je      .LLeapTrue
 .LLeapEnd:     setb    %al
                jmp     .LLeapExit
 .LLeapTrue:    movl   $1,%ax
 .LLeapExit:    pop     %edx
                pop     %ecx
                pop     %ebx
                and     $1,%al
end ['EAX'];  // procedure saves %ebx..%edx, for internal calling.

{ Calculates daynumber, January 1st =1. incl leapyear(LeapYr()) 
correction }
FUNCTION DayNr( Day, Month, Year: LONGINT) : LONGINT; 
ASSEMBLER;
TYPE DyNr=ARRAY[0..11] OF LONGINT;

CONST MonthDays : 
DyNr=(0,31,59,90,120,151,181,212,243,273,304,334);

ASM
                        movl    Month,%ebx
                        movl    Day,%ecx
                        cmp     $2,%ebx
                        jbe     .LDayNr2
             .LDayNr1:  push    Year
                        call    LeapYr
                        add     %eax,%ecx
              .LDayNr2: decl    %ebx
                        movl    MonthDays(,%ebx,4),%eax
                        add     %ecx,%eax
END ['EAX','EBX','ECX'];

TYPE  Arr12     =       ARRAY[0..11] OF BYTE;
      TabType=ARRAY[0..3] OF BYTE;

CONST TabCent   : TabType = (0,6,4,2);          { Century correction}
      TabMonth  : Arr12   = (0,3,3,6,1,4,6,2,5,0,3,5); {Month indices}


FUNCTION DOW( Year,Month,Day:LONGINT): LONGINT; 
ASSEMBLER;
  {  DOW( a Sunday)=0; DOW( a Monday)=1
      Ultrafast since it works with tables. }


     ASM

                xorl   %ecx,%ecx
                mov    Year,%eax
                cmp    $2000,%eax
                jb     .LBelow2000
                cmp    $3,Month
                jb     .LBelow2000
                incl   %ecx

.LBelow2000:    movl   $100,%ebx

                  cltd

                idivl  %ebx
                incl   %eax
                andl   $3,%eax

                movzbl TabCent(,%eax),%ebx
                                 // ebx contains century correction
                mov    Day,%eax
                addl   %eax,%ebx      // Add Day
                addl   %edx,%ebx      // Add Year MOD 100
                shrl   $2,%edx
                addl   %edx,%ebx      //  Add (Year MOD 100) SHR 2
                mov    Month,%eax  // Month
                decl   %eax
                movzbl TabMonth(,%eax),%edx // is index
                addl   %edx,%ebx      //  Add TabMonth[Month]
                movl   $7,%eax
                xchgl  %eax,%ebx
                addl   %ecx,%eax
                incl   %eax

                  cltd

                idivl  %ebx           // Divide total by 7
                movl   %edx,%eax
END ['EAX','EBX','ECX','EDX'];

begin
end.


Marco van de Voort (MarcoV at Stack.nl or marco at freepascal.org)