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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.
#
# $Id$
# $FML$
#
package File::RingBuffer;
use strict;
use vars qw(@ISA @EXPORT @EXPORT_OK $AUTOLOAD);
use Carp;
use IO::File;
=head1 NAME
File::RingBuffer - IO operations to ring buffer which consists of files
=head1 SYNOPSIS
... lock e.g. by flock(2) ...
use File::RingBuffer;
$obj = new File::RingBuffer {
directory => '/some/where'
};
$fh = $obj->open;
print $fh "some message";
$fh->close;
... unlock ...
The buffer directory has files with the name C<0>, C<1>, ...
You can specify C<file_name> parameter.
$obj = new File::RingBuffer {
directory => '/some/where',
file_name => '_smtplog',
};
If so, the file names become _smtplog.0, _smtplog.1, ...
=head1 DESCRIPTION
To log messages but up to some limit, it may be useful to use filenames
in cyclic way.
The file to write is chosen among a set of files allocated as a buffer.
Consider several files under a directory C<ring/>
where the unit of the ring is 5 here.
C<ring/> may have 5 files in it.
0 1 2 3 4
To log a message is to write it to one of them.
At the first time the message is logged to the file C<0>,
and next time to C<1> and so on.
If all 5 files are used, it reuses and overwrites the oldest one C<0>.
So we use a file in cyclic way as follows:
0 -> 1 -> 2 -> 3 -> 4 -> 0 -> 1 -> ...
We expire the old data.
A file name is a number for simplicity.
The latest number is holded in C<ring/.seq> file (C<.seq> in that
direcotry by default) and truncated to 0 by the modulus C<5>.
=head1 METHODS
=head2 C<open()>
no argument.
=head2 C<close()>
no argument.
=cut
require Exporter;
@ISA = qw(IO::File);
BEGIN {}
END {}
# Descriptions: constructor
# forward new() request to superclass (IO::File)
# Arguments: $class_name
# Side Effects: none
# Return Value: class object
# XXX $self is blessed file handle.
sub new
{
my ($self, $args) = @_;
my $me = $self->SUPER::new();
_take_file_name($me, $args);
$me;
}
# Descriptions: determine the file name to write into
# Arguments: $self $args
# Side Effects: increment $sequence_file_name
# set the file name at ${*$self}{ _file }
# Return Value: none
sub _take_file_name
{
my ($self, $args) = @_;
my $file_name = $args->{ file_name } || '';
my $sequence_file_name = $args->{ sequence_file_name } || '.seq';
my $modulus = $args->{ modulus } || 128;
use File::Spec;
my $seq_file =
File::Spec->catfile($args->{ directory }, $sequence_file_name);
use File::Sequence;
my $sfh = new File::Sequence {
sequence_file => $seq_file,
modulus => $modulus,
};
my $id = $sfh->increment_id;
my $file = File::Spec->catfile($args->{ directory }, $file_name.$id);
${*$self}{ _file } = $file;
}
# Descriptions: open() a file in the buffer
# Arguments: $self
# XXX $self is blessed file handle.
# Side Effects: create ${ *$self } hash to save status information
# Return Value: write file handle (for $file.new.$$)
sub open
{
my ($self) = @_;
# temporary file
my $file = ${*$self}{ _file};
# real open with $mode
$self->autoflush;
$self->SUPER::open($file, "w") ? $self : undef;
}
# Descriptions: forward close() to SUPER class
# Arguments: $self
# Side Effects: none
# Return Value: value returned by SUPER::close()
sub close
{
my ($self) = @_;
$self->SUPER::close();
}
=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::RingBuffer appeared in fml5 mailing list driver package.
See C<http://www.fml.org/> for more details.
=cut
1;
|
