Hi All,

I need to replace Perl's built-in open() function. The reason I want to do this is described in detail in another recent post of mine. In a nutshell, I have to do encoding conversions on filename arguments (unicode -> CP932).

Actually, it's not only open() I need to wrap, but open() appears to be the most flexible beast of those, and I'd very much appreciate if some of you wise monks could take a look at what I currently have, and let me know if I've overlooked something...

_____ I18N/Japanese.pm (the 'compatibility' module) _____ 

package I18N::Japanese;

use Encode 'encode';
use Symbol 'qualify_to_ref';

# eventually, determine this dynamically
my $encoding = "cp932";

# this is meant to take effect for whoever uses us
require encoding; encoding->import($encoding);

# override/wrap Perl built-ins that take or return filenames

# (... snippage of all but open()-wrapper)

*CORE::GLOBAL::open = sub (*@) {
    my $fhref = \$_[0];
    my $autov = !defined $_[0];
    my $fh = qualify_to_ref(shift, scalar caller);
    # pass filehandle up to caller when "open my $f, ..."
    $$fhref = $fh if $autov;

    my ($arg2, $arg3, @args) = convert_encoding(@_);

    # need to handle the different prototypes seperately
    if (@_ >= 3) {
        CORE::open $fh, $arg2, $arg3, @args;
    } elsif (@_ == 2) {
        if (defined $arg3) {
            CORE::open $fh, $arg2, $arg3;
        } else {
            # must be undef _syntactically_
            CORE::open $fh, $arg2, undef;
        }
    } elsif (@_ == 1) {
        CORE::open $fh, $arg2;
    } else {
        CORE::open $fh;
    }
};

sub convert_encoding {
    return ( map ref(\$_) eq 'SCALAR' ? encode($encoding, $_) : $_, @_
+ );
}

1;

[download]

_____ using the replaced open() _____ 

use I18N::Japanese;

open F, ">", "myfile"  and print F "foo\n";
open my $f, ">", "myfile" or die $!;
print $f "foo\n";
# ...

[download]

I believe this code is able to handle all various usages of open() ... but please don't hesitate to prove me wrong ;) Otherwise, well, I'd be glad to share this snippet with whoever in need might google this up in the future.

(Note: the encoding conversion aspect is not what I'm worried about at the moment, but rather whether the replaced open() is still behaving like the built-in one, interface-wise)

Thanks,
Almut

In reply to Wrapping the open() built-in by almut

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