Re: Direct I/O

Thomas Munro <thomas.munro@gmail.com> writes:

> I think I have that working OK.  Any Perl hackers want to comment on
> my use of IO::File (copied from examples on the internet that showed
> how to use O_DIRECT)?  I am not much of a perl hacker but according to
> my package manager, IO/File.pm came with perl itself.

Indeed, and it has been since perl 5.003_07, released in 1996.  And Fcntl
has known about O_DIRECT since perl 5.6.0, released in 2000, so we can
safely use both.

> And the Fcntl eval trick that I copied from File::stat, and the
> perl-critic suppression that requires?
[…]
> +    no strict 'refs';    ## no critic (ProhibitNoStrict)
> +    my $val = eval { &{'Fcntl::O_DIRECT'} };
> +    if (defined $val)

This trick is only needed in File::stat because it's constructing the
symbol name dynamically.  And because Fcntl by default exports all the
O_* and F_* constants it knows about, we can simply do:

       if (defined &O_DIRECT)
> +    {
> +        use Fcntl qw(O_DIRECT);

The `use Fcntl;` above will already have imported this, so this is
redundant.

- ilmari