202:0 /li~XEpNF tAo_ub &=LV[(  315_I|Mjq؂ :via(Some::Other::Package)",...); =head1 DESCRIPTION The PerlIO::via module allows you to develop PerlIO layers in Perl, without having to go into the nitty gritty of programming C with XS as the interface to Perl. One example module, L, is included with Perl 5.8.0, and more example modules are available from CPAN, such as L and L. The PerlIO::via::StripHTML module for instance, allows you to say: use PerlIO::via::StripHTML; open( my $fh, "<:via(StripHTML)", "index.html" ); my @line = <$fh>; to obtain the text of an HTML-file in an array with all the HTML-tags automagically removed. Please note that if the layer is created in the PerlIO::via:: namespace, it does B have to be fully qualified. The PerlIO::via module will prefix the PerlIO::via:: namespace if the specified modulename does not exist as a fully qualified module name. =head1 EXPECTED METHODS To create a Perl module that implements a PerlIO layer in Perl (as opposed to in C using XS as the interface to Perl), you need to supply some of the following subroutines. It is recommended to create these Perl modules in the PerlIO::via:: namespace, so that they can easily be located on CPAN and use the default namespace feature of the PerlIO::via module itself. Please note that this is an area of recent development in Perl and that the interface described here is therefore still subject to change (and hopefully will have better documentation and more examples). In the method descriptions below I<$fh> will be a reference to a glob which can be treated as a perl file handle. It refers to the layer below. I<$fh> is not passed if the layer is at the bottom of the stack, for this reason and to maintain some level of "compatibility" with TIEHANDLE classes it is passed last. =over 4 =item $class->PUSHED([$mode,[$fh]]) Should return an object or the class, or -1 on failure. (Compare TIEHANDLE.) The arguments are an optional mode string ("r", "w", "w+", ...) and a filehandle for the PerlIO layer below. Mandatory. When the layer is pushed as part of an C call, C will be called I the actual open occurs, whether that be via C, C, C or by letting a lower layer do the open. =item $obj->POPPED([$fh]) Optional - called when the layer is about to be removed. =item $obj->UTF8($belowFlag,[$fh]) Optional - if present it will be called immediately after PUSHED has returned. It should return a true value if the layer expects data to be UTF-8 encoded. If it returns true, the result is as if the caller had done ":via(YourClass):utf8" If not present or if it returns false, then the stream is left with the UTF-8 flag clear. The I<$belowFlag> argument will be true if there is a layer below and that layer was expecting UTF-8. =item $obj->OPEN($path,$mode,[$fh]) Optional - if not present a lower layer does the open. If present, called for normal opens after the layer is pushed. This function is subject to change as there is no easy way to get a lower layer to do the open and then regain control. =item $obj->BINMODE([$fh]) Optional - if not present the layer is popped on binmode($fh) or when C<:raw> is pushed. If present it should return 0 on success, -1 on error, or undef to pop the layer. =item $obj->FDOPEN($fd,[$fh]) Optional - if not present a lower layer does the open. If present, called after the layer is pushed for opens which pass a numeric file descriptor. This function is subject to change as there is no easy way to get a lower layer to do the open and then regain control. =item $obj->SYSOPEN($path,$imode,$perm,[$fh]) Optional -