211 lines
4.7 KiB
Perl
211 lines
4.7 KiB
Perl
package DateTime::LeapSecond;
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use strict;
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use warnings;
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use namespace::autoclean;
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our $VERSION = '1.54';
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our ( @RD, @LEAP_SECONDS, %RD_LENGTH );
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use DateTime;
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# Generates a Perl binary decision tree
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sub _make_utx {
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my ( $beg, $end, $tab, $op ) = @_;
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my $step = int( ( $end - $beg ) / 2 );
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my $tmp;
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if ( $step <= 0 ) {
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$tmp = "${tab}return $LEAP_SECONDS[$beg + 1];\n";
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return $tmp;
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}
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$tmp = "${tab}if (\$val < " . $RD[ $beg + $step ] . ") {\n";
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$tmp .= _make_utx( $beg, $beg + $step, $tab . q{ }, $op );
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$tmp .= "${tab}}\n";
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$tmp .= "${tab}else {\n";
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$tmp .= _make_utx( $beg + $step, $end, $tab . q{ }, $op );
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$tmp .= "${tab}}\n";
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return $tmp;
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}
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# Process BEGIN data and write binary tree decision table
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sub _init {
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my $value = -1;
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while (@_) {
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my ( $year, $mon, $mday, $leap_seconds )
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= ( shift, shift, shift, shift );
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# print "$year,$mon,$mday\n";
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## no critic (Subroutines::ProtectPrivateSubs)
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my $utc_epoch
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= DateTime->_ymd2rd( $year, ( $mon =~ /Jan/i ? 1 : 7 ), $mday );
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$value++;
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push @LEAP_SECONDS, $value;
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push @RD, $utc_epoch;
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$RD_LENGTH{ $utc_epoch - 1 } = $leap_seconds;
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# warn "$year,$mon,$mday = $utc_epoch +$value";
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}
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push @LEAP_SECONDS, ++$value;
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my $tmp;
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# write binary tree decision table
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$tmp = "sub leap_seconds {\n";
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$tmp .= " my \$val = shift;\n";
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$tmp .= _make_utx( -1, 1 + $#RD, q{ }, '+' );
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$tmp .= "}; 1\n";
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# NOTE: uncomment the line below to see the code:
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#warn $tmp;
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## no critic (BuiltinFunctions::ProhibitStringyEval)
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eval $tmp or die $@;
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}
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sub extra_seconds {
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exists $RD_LENGTH{ $_[0] } ? $RD_LENGTH{ $_[0] } : 0;
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}
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sub day_length {
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exists $RD_LENGTH{ $_[0] } ? 86400 + $RD_LENGTH{ $_[0] } : 86400;
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}
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sub _initialize {
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# There are no leap seconds before 1972, because that's the
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# year this system was implemented.
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#
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# year month day number-of-leapseconds
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#
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_init(
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qw(
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1972 Jul. 1 +1
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1973 Jan. 1 +1
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1974 Jan. 1 +1
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1975 Jan. 1 +1
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1976 Jan. 1 +1
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1977 Jan. 1 +1
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1978 Jan. 1 +1
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1979 Jan. 1 +1
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1980 Jan. 1 +1
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1981 Jul. 1 +1
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1982 Jul. 1 +1
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1983 Jul. 1 +1
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1985 Jul. 1 +1
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1988 Jan. 1 +1
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1990 Jan. 1 +1
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1991 Jan. 1 +1
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1992 Jul. 1 +1
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1993 Jul. 1 +1
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1994 Jul. 1 +1
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1996 Jan. 1 +1
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1997 Jul. 1 +1
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1999 Jan. 1 +1
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2006 Jan. 1 +1
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2009 Jan. 1 +1
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2012 Jul. 1 +1
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2015 Jul. 1 +1
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2017 Jan. 1 +1
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)
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);
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}
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__PACKAGE__->_initialize();
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1;
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# ABSTRACT: leap seconds table and utilities
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__END__
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=pod
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=encoding UTF-8
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=head1 NAME
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DateTime::LeapSecond - leap seconds table and utilities
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=head1 VERSION
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version 1.54
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=head1 SYNOPSIS
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use DateTime;
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use DateTime::LeapSecond;
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print "Leap seconds between years 1990 and 2000 are ";
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print DateTime::Leapsecond::leap_seconds($utc_rd_2000)
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- DateTime::Leapsecond::leap_seconds($utc_rd_1990);
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=head1 DESCRIPTION
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This module is used to calculate leap seconds for a given Rata Die day. It is
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used when L<DateTime> cannot compile the XS version of this code.
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This library is known to be accurate for dates until Jun 2020.
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There are no leap seconds before 1972, because that's the year this
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system was implemented.
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=over 4
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=item * leap_seconds($rd)
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Returns the number of accumulated leap seconds for a given day.
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=item * extra_seconds($rd)
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Returns the number of leap seconds for a given day,
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in the range -2 .. 2.
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=item * day_length($rd)
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Returns the number of seconds for a given day,
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in the range 86398 .. 86402.
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=back
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=head1 SEE ALSO
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L<http://hpiers.obspm.fr/eop-pc/earthor/utc/leapsecond.html>
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http://datetime.perl.org
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=head1 SUPPORT
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Bugs may be submitted at L<https://github.com/houseabsolute/DateTime.pm/issues>.
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There is a mailing list available for users of this distribution,
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L<mailto:datetime@perl.org>.
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I am also usually active on IRC as 'autarch' on C<irc://irc.perl.org>.
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=head1 SOURCE
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The source code repository for DateTime can be found at L<https://github.com/houseabsolute/DateTime.pm>.
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=head1 AUTHOR
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Dave Rolsky <autarch@urth.org>
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=head1 COPYRIGHT AND LICENSE
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This software is Copyright (c) 2003 - 2020 by Dave Rolsky.
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This is free software, licensed under:
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The Artistic License 2.0 (GPL Compatible)
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The full text of the license can be found in the
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F<LICENSE> file included with this distribution.
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=cut
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