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#-*- perl -*-
#
# Copyright (C) 2001 Ken'ichi Fukamachi
# All rights reserved. This program is free software; you can
# redistribute it and/or modify it under the same terms as Perl itself.
#
# $FML: Sequence.pm,v 1.8 2001/05/27 14:27:55 fukachan Exp $
#
package File::Sequence;
use strict;
use vars qw(@ISA @EXPORT @EXPORT_OK);
use Carp;
use ErrorStatus qw(error_set error error_clear);
=head1 NAME
File::Sequence - maintain the sequence number
=head1 SYNOPSIS
To get the latest $article_id,
use File::Sequence;
my $sfh = new File::Sequence { sequence_file => $seq_file };
my $id = $sfh->et_id;
if ($sfh->error) { use Carp; carp( $sfh->error ); }
to increment $article_id and get it
use File::Sequence;
my $sfh = new File::Sequence { sequence_file => $seq_file };
my $id = $sfh->increment_id;
if ($sfh->error) { use Carp; carp( $sfh->error ); }
If you divide the $id by some modulus, use
my $sfh = new File::Sequence {
sequence_file => $seq_file,
modulus => $modules,
};
my $id = $sfh->increment_id;
For example, if you do new() with modulus 3,
my $sfh = new File::Sequence {
sequence_file => $seq_file,
modulus => 3,
};
$id becomes 0, 1, 2, 0, 1, 2...
=head1 DESCRIPTION
File::Sequence module maintains the sequence number for something,
for example, the article number typically.
As an extension, you can generate a cyclic number by this module.
Please specify C<modulus> parameter in new() method if you want to get
a cyclic number.
=head2 C<new($args)>
$args->{ sequence_file } is the file holding the current sequence
number.
$args->{ modulus } is the modulus when you want to get a cyclic
number.
=head2 C<increment_id([$file])>
increment the sequence number.
=head2 C<get_id([$file])>
get the sequence number from specified C<$file>.
=cut
# Descriptions: constructor
# Arguments: $self $args
# Side Effects: object itself holds a few local _variables
# Return Value: object
sub new
{
my ($self, $args) = @_;
my ($type) = ref($self) || $self;
my $me = {};
$me->{ _sequence_file } = $args->{ sequence_file };
$me->{ _modulus } = $args->{ modulus };
return bless $me, $type;
}
# Descriptions: increment sequence
# Arguments: $self [$file]
# If $file is not specified,
# the sequence_file parameter in new().
# Side Effects: the number holded in $file is incremented
# Return Value: number (sequence number)
sub increment_id
{
my ($self, $file) = @_;
my $id = 0;
my $seq_file = $file || $self->{ _sequence_file };
unless ($seq_file) {
$self->error_set("the sequence file is not specified");
return 0;
};
# touch the sequence file if it does not exist.
unless (-f $seq_file) {
use File::Utils qw(touch);
touch($seq_file);
};
use IO::File::Atomic;
my ($rh, $wh) = IO::File::Atomic->rw_open($seq_file);
# read the current sequence number
if (defined $rh) {
$id = $rh->getline;
$rh->close;
}
else {
$self->error_set("cannot open the sequence file");
return 0;
}
# compute the modulus
if (defined $self->{ _modulus }) {
my $modulus = $self->{ _modulus };
$id++;
$id = $id % $modulus;
}
# increment $id. The incremented number is the current article ID.
else {
$id++;
}
# save $id
print $wh $id, "\n";
$wh->close;
$id;
}
# Descriptions: get sequence
# Arguments: $self [$file]
# If $file is not specified,
# the sequence_file parameter in new().
# Side Effects: the number holded in $file is incremented
# Return Value: number (sequence number)
sub get_id
{
my ($self, $file) = @_;
my $id = 0;
my $seq_file = $file || $self->{ _sequence_file };
unless ($seq_file) {
$self->error_set("the sequence file is not specified");
return 0;
};
# touch the sequence file if it does not exist.
unless (-f $seq_file) {
return 0;
};
use IO::File::Atomic;
my ($rh, $wh) = IO::File::Atomic->rw_open($seq_file);
# read the current sequence number
if (defined $rh) {
$id = $rh->getline;
$rh->close;
}
else {
$self->error_set("cannot open the sequence file");
return 0;
}
return $id;
}
=head1 AUTHOR
Ken'ichi Fukamachi
=head1 COPYRIGHT
Copyright (C) 2001 Ken'ichi Fukamachi
All rights reserved. This program is free software; you can
redistribute it and/or modify it under the same terms as Perl itself.
=head1 HISTORY
File::Sequence appeared in fml5 mailing list driver package.
See C<http://www.fml.org/> for more details.
=cut
1;
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