my $boundary_index;
    for (my @tmp = @v; @tmp;) {
	my($k, $v) = splice(@tmp, 0, 2);
	if ($k eq "boundary") {
	    $boundary = $v;
	    $boundary_index = @v - @tmp - 1;
	    last;
	}
    }

    my @parts = map $_->as_string($CRLF), @{$self->{_parts}};

    my $bno = 0;
    $boundary = _boundary() unless defined $boundary;
 CHECK_BOUNDARY:
    {
	for (@parts) {
	    if (index($_, $boundary) >= 0) {
		# must have a better boundary
		$boundary = _boundary(++$bno);
		redo CHECK_BOUNDARY;
	    }
	}
    }

    if ($boundary_index) {
	$v[$boundary_index] = $boundary;
    }
    else {
	push(@v, boundary => $boundary);
    }

    $ct = HTTP::Headers::Util::join_header_words(@v);
    $self->header("Content-Type", $ct);

    _set_content($self, "--$boundary$CRLF" .
	                join("$CRLF--$boundary$CRLF", @parts) .
			"$CRLF--$boundary--$CRLF",
                        1);
}


sub _boundary
{
    my $size = shift || return "xYzZY";
    require MIME::Base64;
    my $b = MIME::Base64::encode(join("", map chr(rand(256)), 1..$size*3), "");
    $b =~ s/[\W]/X/g;  # ensure alnum only
    $b;
}


1;


__END__

=head1 NAME

HTTP::Message - HTTP style message (base class)

=head1 SYNOPSIS

 use base 'HTTP::Message';

=head1 DESCRIPTION

An C<HTTP::Message> object contains some headers and a content body.
The following methods are available:

=over 4

=item $mess = HTTP::Message->new

=item $mess = HTTP::Message->new( $headers )

=item $mess = HTTP::Message->new( $headers, $content )

This constructs a new message object.  Normally you would want
construct C<HTTP::Request> or C<HTTP::Response> objects instead.

The optional $header argument should be a reference to an
C<HTTP::Headers> object or a plain array reference of key/value pairs.
If an C<HTTP::Headers> object is provided then a copy of it will be
embedded into the constructed message, i.e. it will not be owned and
can be modified afterwards without affecting the message.

The optional $content argument should be a string of bytes.

=item $mess = HTTP::Message->parse( $str )

This constructs a new message object by parsing the given string.

=item $mess->headers

Returns the embedded C<HTTP::Headers> object.

=item $mess->headers_as_string

=item $mess->headers_as_string( $eol )