Re: PerlIO::via FILL subroutine question

thor,
I am not sure where you are running into the newline problem. I am betting it is with <>/readline. That is because they define a record by looking at $/ (see perldoc perlvar). PerlIO::via allows you to define your own buffering methods, but readline is still going to return records from the buffer by looking at $/. I don't think you are going to be able to use PerlIO::via to change that behavior. Notice the comment:

package rdw;
use strict;
use warnings;

sub PUSHED { bless \*PUSHED,$_[0] }
sub FILL {
    my ($length, $record);
    read $_[1], $length, 1;
    return undef if eof $_[1];
    read $_[1], $record, $length;
    # uncomment next line to see it is actually working
    # print "$record\n";
    return $record;
}
sub WRITE { return undef }

package main;

open( my $in, '<:via(rdw)', 'foo.txt' ) or die $!;
while ( <$in> ) {
    print "$_\n";
}
__END__
# foo.txt - output is aababc
1a2ab3abc
[download]

If I guessed correctly, there are other ways to do it - speak up.

Cheers - L~R

Comment on Re: PerlIO::via FILL subroutine question Download Code

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Re^2: PerlIO::via FILL subroutine question by thor (Priest) on Oct 04, 2004 at 22:31 UTC
Yeah, that's the gist of it (the rdw's are packed shorts, but that's a detail that doesn't matter). So, is there some way to implement readline so that I can provide perl with what my notion of a line is? At first, that's what I thought that FILL did, but I guess I was mistaken... thor `Feel the white light, the light within Be your own disciple, fan the sparks of will For all of us waiting, your kingdom will come`	[reply]
Re^3: PerlIO::via FILL subroutine question by Limbic~Region (Chancellor) on Oct 05, 2004 at 00:53 UTC
thor, You can look at subclassing IO::File, but that is going to end up giving you a different OO interface. The other option is to tie the filehandle. I was disappointed that Tie::FileHandle::Base didn't do more in the way of giving you default methods to inherit. Here is a very rough proof of concept. package rdw; use Carp; sub TIEHANDLE { my ($class, $file) = @_; open ( my $file , '<', $file ) or croak "Unable to open $file : $! +"; return bless \$file , $class; } sub READLINE { my $self = shift; my ($length, $record); read $$self, $length, 1; return undef if eof $$self; read $$self, $record, $length; return $record; } 42; # and a script that uses it #!/usr/bin/perl use strict; use warnings; use rdw; tie fh, 'rdw', 'foo.rdw' or die "Unable to tie : $!"; while ( <fh> ) { print "$_\n"; } __END__ # foo.rdw - outputs "a\nab\nabc\nabcd\n" as desired 1a2ab3abc4abcd [download] See perldoc perltie* for more information Cheers - L~R	[reply] [d/l]