PC World 2003 March/PCWorld_2003-03_cd.bin/Software/Topware/activeperl/ActivePerl/Perl/lib/Digest/MD5.pm

Perl POD Document | 2002-06-19 | 7.2 KB | 280 lines

package Digest::MD5;

use strict;
use vars qw($VERSION @ISA @EXPORT_OK);

$VERSION = '2.20';  # $Date: 2002/05/06 05:15:09 $

require Exporter;
*import = \&Exporter::import;
@EXPORT_OK = qw(md5 md5_hex md5_base64);

require DynaLoader;
@ISA=qw(DynaLoader);

eval {
    Digest::MD5->bootstrap($VERSION);
};
if ($@) {
    my $olderr = $@;
    eval {
    # Try to load the pure perl version
    require Digest::Perl::MD5;

    Digest::Perl::MD5->import(qw(md5 md5_hex md5_base64));
    push(@ISA, "Digest::Perl::MD5");  # make OO interface work
    };
    if ($@) {
    # restore the original error
    die $olderr;
    }
}
else {
    *reset = \&new;
}

1;
__END__

=head1 NAME

Digest::MD5 - Perl interface to the MD5 Algorithm

=head1 SYNOPSIS

 # Functional style
 use Digest::MD5  qw(md5 md5_hex md5_base64);

 $digest = md5($data);
 $digest = md5_hex($data);
 $digest = md5_base64($data);

 # OO style
 use Digest::MD5;

 $ctx = Digest::MD5->new;

 $ctx->add($data);
 $ctx->addfile(*FILE);

 $digest = $ctx->digest;
 $digest = $ctx->hexdigest;
 $digest = $ctx->b64digest;

=head1 DESCRIPTION

The C<Digest::MD5> module allows you to use the RSA Data Security
Inc. MD5 Message Digest algorithm from within Perl programs.  The
algorithm takes as input a message of arbitrary length and produces as
output a 128-bit "fingerprint" or "message digest" of the input.

The C<Digest::MD5> module provide a procedural interface for simple
use, as well as an object oriented interface that can handle messages
of arbitrary length and which can read files directly.

A binary digest will be 16 bytes long.  A hex digest will be 32
characters long.  A base64 digest will be 22 characters long.

=head1 FUNCTIONS

The following functions can be exported from the C<Digest::MD5>
module.  No functions are exported by default.

=over 4

=item md5($data,...)

This function will concatenate all arguments, calculate the MD5 digest
of this "message", and return it in binary form.

=item md5_hex($data,...)

Same as md5(), but will return the digest in hexadecimal form.

=item md5_base64($data,...)

Same as md5(), but will return the digest as a base64 encoded string.

The base64 encoded string returned is not padded to be a multiple of 4
bytes long.  If you want interoperability with other base64 encoded
md5 digests you might want to append the string "==" to the result.

=back

=head1 METHODS

The following methods are available:

=over 4

=item $md5 = Digest::MD5->new

The constructor returns a new C<Digest::MD5> object which encapsulate
the state of the MD5 message-digest algorithm.  You can add data to
the object and finally ask for the digest.

If called as an instance method (i.e. $md5->new) it will just reset the
state the object to the state of a newly created object.  No new
object is created in this case.

=item $md5->reset

This is just an alias for $md5->new.

=item $md5->add($data,...)

The $data provided as argument are appended to the message we
calculate the digest for.  The return value is the $md5 object itself.

=item $md5->addfile($io_handle)

The $io_handle is read until EOF and the content is appended to the
message we calculate the digest for.  The return value is the $md5
object itself.

In most cases you want to make sure that the $io_handle is set up to
be in binmode().

=item $md5->digest

Return the binary digest for the message.

Note that the C<digest> operation is effectively a destructive,
read-once operation. Once it has been performed, the C<Digest::MD5>
object is automatically C<reset> and can be used to calculate another
digest value.

=item $md5->hexdigest

Same as $md5->digest, but will return the digest in hexadecimal form.

=item $md5->b64digest

Same as $md5->digest, but will return the digest as a base64 encoded
string.

The base64 encoded string returned is not padded to be a multiple of 4
bytes long.  If you want interoperability with other base64 encoded
md5 digests you might want to append the string "==" to the result.

=back


=head1 EXAMPLES

The simplest way to use this library is to import the md5_hex()
function (or one of its cousins):

    use Digest::MD5 qw(md5_hex);
    print "Digest is ", md5_hex("foobarbaz"), "\n";

The above example would print out the message

    Digest is 6df23dc03f9b54cc38a0fc1483df6e21

provided that the implementation is working correctly.  The same
checksum can also be calculated in OO style:

    use Digest::MD5;

    $md5 = Digest::MD5->new;
    $md5->add('foo', 'bar');
    $md5->add('baz');
    $digest = $md5->hexdigest;

    print "Digest is $digest\n";

With OO style you can break the message arbitrary.  This means that we
are no longer limited to have space for the whole message in memory, i.e.
we can handle messages of any size.

This is useful when calculating checksum for files:

    use Digest::MD5;

    my $file = shift || "/etc/passwd";
    open(FILE, $file) or die "Can't open '$file': $!";
    binmode(FILE);

    $md5 = Digest::MD5->new;
    while (<FILE>) {
        $md5->add($_);
    }
    close(FILE);
    print $md5->b64digest, " $file\n";

Or we can use the builtin addfile method for more efficient reading of
the file:

    use Digest::MD5;

    my $file = shift || "/etc/passwd";
    open(FILE, $file) or die "Can't open '$file': $!";
    binmode(FILE);

    print Digest::MD5->new->addfile(*FILE)->hexdigest, " $file\n";

=head1 SEE ALSO

L<Digest>,
L<Digest::MD2>,
L<Digest::SHA1>,
L<Digest::HMAC>

L<md5sum(1)>

RFC 1321

=head1 COPYRIGHT

This library is free software; you can redistribute it and/or
modify it under the same terms as Perl itself.

 Copyright 1998-2002 Gisle Aas.
 Copyright 1995-1996 Neil Winton.
 Copyright 1991-1992 RSA Data Security, Inc.

The MD5 algorithm is defined in RFC 1321. The basic C code
implementing the algorithm is derived from that in the RFC and is
covered by the following copyright:

=over 4

=item

Copyright (C) 1991-2, RSA Data Security, Inc. Created 1991. All
rights reserved.

License to copy and use this software is granted provided that it
is identified as the "RSA Data Security, Inc. MD5 Message-Digest
Algorithm" in all material mentioning or referencing this software
or this function.

License is also granted to make and use derivative works provided
that such works are identified as "derived from the RSA Data
Security, Inc. MD5 Message-Digest Algorithm" in all material
mentioning or referencing the derived work.

RSA Data Security, Inc. makes no representations concerning either
the merchantability of this software or the suitability of this
software for any particular purpose. It is provided "as is"
without express or implied warranty of any kind.

These notices must be retained in any copies of any part of this
documentation and/or software.

=back

This copyright does not prohibit distribution of any version of Perl
containing this extension under the terms of the GNU or Artistic
licenses.

=head1 AUTHORS

The original MD5 interface was written by Neil Winton
(C<[e-mail]>).

This release was made by Gisle Aas <[e-mail]>

=cut