my $len = $n >= 0xFC ? 5
    : $n >= 0xF8 ? 4
    : $n >= 0xF0 ? 3
    : $n >= 0xE0 ? 2
    : $n >= 0xC0 ? 1
    : throw XML::SAX::Exception::Parse(
        Message => sprintf("Invalid character 0x%x", $n),
            ColumnNumber => $self->column,
            LineNumber => $self->line,
            PublicId => $self->public_id,
            SystemId => $self->system_id,
      );

if ($len <= length($self->[BUFFER])) {
    $current .= substr($self->[BUFFER], 0, $len, '');
    $self->[CURRENT] = substr($self->[BUFFER], -1);
}
else {
    $len -= length($self->[BUFFER]);
    $current .= $self->[BUFFER];
    $self->[BUFFER] = '';
    while (-1 < --$len) {
        next($self);
        $current .= $self->[CURRENT];
    }
}