File Coverage

blib/lib/Date/Hijri.pm

Criterion	Covered	Total	%
statement	49	54	90.7
branch	6	10	60.0
condition	4	9	44.4
subroutine	12	13	92.3
pod	0	9	0.0
total	71	95	74.7

#!/usr/bin/perl

############################################################
# Date::Hijri
# module for converting islamic (hijri) and gregorian dates
# (c) zeitform Internet Dienste 2003 - [e-mail]
# This program is free software; you can redistribute it and/or
# modify it under the same terms as Perl itself.
#
# based on kcalendarsystemhijri.cpp
#   Copyright (c) 2002-2003 Carlos Moro
#   Copyright (c) 2002-2003 Hans Petter Bieker
#
#   This library is free software; you can redistribute it and/or
#   modify it under the terms of the GNU Library General Public
#   License as published by the Free Software Foundation; either
#   version 2 of the License, or (at your option) any later version.
#
#   This library 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
#   Library General Public License for more details.
#
#   You should have received a copy of the GNU Library General Public License
#   along with this library; see the file COPYING.LIB.  If not, write to
#   the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
#   Boston, MA 02111-1307, USA.
#
# kcalendarsystemhijri.cpp
#   [...] is translated from the Lisp code
#   in ``Calendrical Calculations'' by Nachum Dershowitz and
#   Edward M. Reingold, Software---Practice & Experience,
#   vol. 20, no. 9 (September, 1990), pp. 899--928.
#
#   This code is in the public domain, but any use of it
#   should publically acknowledge its source.
#
# Example usage:
#
# use Date::Hijri;
#
# print join("-", g2h(22,8,2003));  # prints 23-6-1424
# print join("-", h2g(23,6,1424));  # prints 22-8-2003
#
############################################################

package Date::Hijri;
use strict;
use warnings;
use vars qw($VERSION @ISA @EXPORT);
require Exporter;

@ISA = qw(Exporter);
@EXPORT = qw(h2g g2h);

$VERSION = '0.02';

############################################################

use constant IslamicEpoch => 227014;

############################################################

sub g2h
  {
    my ($day, $month, $year) = @_;
    return Absolute2Islamic(Gregorian2Absolute($day, $month, $year));
  }

sub h2g
  {
    my ($day, $month, $year) = @_;
    return Absolute2Gregorian(Islamic2Absolute($day, $month, $year));
  }

sub lastDayOfGregorianMonth
  {
    # Compute the last date of the month for the Gregorian calendar.
    my ($month, $year) = @_;
    if ($month == 2)
      {
	return 29 if ($year % 4 == 0 && $year % 100 != 0) || ($year % 400 == 0);
      }
    return (31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31)[$month - 1];
  }

sub Gregorian2Absolute
  {
    # Computes the absolute date from the Gregorian date.
    my ($day, $month, $year) = @_;
    my $N = $day;                          # days this month
    for (my $m = $month - 1; $m > 0; $m--) # days in prior months this year
      {
	$N += lastDayOfGregorianMonth($m, $year);
      }
    return int($N                        # days this year
               + 365 * ($year - 1)       # days in previous years ignoring leap days
	       + ($year - 1) / 4         # Julian leap days before this year...
	       - ($year - 1) / 100       # ...minus prior century years...
	       + ($year - 1) / 400);     # ...plus prior years divisible by 400
  }

sub Absolute2Gregorian
  {
    # Computes the Gregorian date from the absolute date.
    my ($d) = @_;
    # Search forward year by year from approximate year
    my $year = int($d / 366 + 0.5);
    while ($d >= Gregorian2Absolute(1,1,$year+1)) { $year++; }
    # Search forward month by month from January
    my $month = 1;
    while ($d > Gregorian2Absolute(lastDayOfGregorianMonth($month, $year), $month, $year)) { $month++; }
    my $day = $d - Gregorian2Absolute(1, $month, $year) + 1;

    return ($day, $month, $year);
  }

sub IslamicLeapYear
  {
    # True if year is an Islamic leap year
    my ($year) = @_;
    return ((((11 * $year) + 14) % 30) < 11) ? 1 : 0;
  }

sub lastDayOfIslamicMonth
  {
    # Last day in month during year on the Islamic calendar.
    my ($month, $year) = @_;
    return ($month % 2 == 1) || ($month == 12 && IslamicLeapYear($year)) ? 30 : 29;
  }

sub Islamic2Absolute
  {
    # Computes the absolute date from the Islamic date.
    my ($day, $month, $year) = @_;
    return int($day                      # days so far this month
               + 29 * ($month - 1)       # days so far...
               + int($month /2)          # ...this year
               + 354 * ($year - 1)       # non-leap days in prior years
               + (3 + (11 * $year)) / 30 # leap days in prior years
               + IslamicEpoch);          # days before start of calendar
  }

sub Absolute2Islamic
  {
    # Computes the Islamic date from the absolute date.
    my ($d) = @_;
    my ($day, $month, $year);
    if ($d <= IslamicEpoch)
      {
        # Date is pre-Islamic
	$month = 0;
	$day = 0;
	$year = 0;
      }
    else
      {
	# Search forward year by year from approximate year
	$year = int(($d - IslamicEpoch) / 355);
	while ($d >= Islamic2Absolute(1,1,$year+1)) { $year++; }
	# Search forward month by month from Muharram
        $month = 1;
	while ($d > Islamic2Absolute(lastDayOfIslamicMonth($month,$year), $month, $year)) { $month++ }
	$day = $d - Islamic2Absolute(1, $month, $year) + 1;
    }
    return ($day, $month, $year);

  }

1;
__END__