use Time::Local ;
use Math::BigInt ;

sub SysToHex {

    my ($sec,$min,$hour,$mday,$mon,$year)= @_ ;
    my $sectime = timegm($sec,$min,$hour,$mday,$mon,$year) ;
    
    my @hexReg1601  ;  # Result
    
    # Conversion to intervals of 100 nanosecondes since 1970 
    my $secsystime = Math::BigInt -> new( $sectime )  ;
    my $nano100= Math::BigInt -> new(10000000)  ;
    my$nanosecsys = $secsystime -> bmul ( $nano100 ) ;
    
    # 100 ns intervals since 1601 and 1970
    # obtained within windows by manualy
    # entering the date 01/01/1970
    my $hex1970 = '0x019DB1DED53E8000' ;
    my $nano1970 = X2I ( $hex1970 ) ;
    
    # Total number of 100ns intervals
    my $sec1601 = $nano1970 + $nanosecsys ; 
    my $hex1601 = I2X ( $sec1601) ;
    
    # This coma separated format is expected by the registry
    my @liste1601 = split ( "", $hex1601 ) ;
    unshift (@liste1601, "0" ) unless ( @liste1601 % 2 == 0 )  ;
    while (@liste1601)  { 
    push ( @hexReg1601, splice (  @liste1601, -2 ), "," ) 
    }
    pop @hexReg1601 ; # Gets rid of the last coma
    
    return join ( "", @hexReg1601 ) ;

} 

sub X2I {
    my $n = shift;
    $n = '0' x (4 - (length($n) % 4)) . $n;
    my $m = Math::BigInt->new(0);
    while ( my $o = substr($n, 0, 4, '') ) {
        $m = $m * 65536 + hex $o;
    } 
    $m;
}


sub I2X {
    my $i = shift;
    my $hex = '';
        do {
        my $mod = $i % 16;
        $hex .= sprintf("%x", $mod);
        } while $i = $i / 16;
        scalar reverse $hex;
}