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package PerlIO::Via;
our $VERSION = '0.01';
use XSLoader ();
XSLoader::load 'PerlIO::Via';
1;
__END__
=head1 NAME
PerlIO::Via - Helper class for PerlIO layers implemented in perl
=head1 SYNOPSIS
use Some::Package;
open($fh,"<:Via(Some::Package)",...);
=head1 DESCRIPTION
The package to be used as a layer should implement at least some of the
following methods. 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. (Compare TIEHANDLE.)
Mandatory.
=item $obj->POPPED([$fh])
Optional - layer is about to be removed.
=item $class->OPEN($path,$mode[,$fh])
Not yet in use.
=item $class->FDOPEN($fd)
Not yet in use.
=item $class->SYSOPEN($path,$imode,$perm,$fh)
Not yet in use.
=item $obj->FILENO($fh)
Returns a numeric value for Unix-like file descriptor. Return -1
if there isn't one.
Optional -default is fileno($fh).
=item $obj->READ($buffer,$len,$fh)
Returns the number of octets placed in $buffer (must be less that $len).
Optional - default is to use FILL instead.
=item $obj->WRITE($buffer,$fh)
Returns the number of octets from buffer that have been sucessfully written.
=item $obj->FILL($fh)
Should return a string to be placed in the buffer.
Optional. If not provided must provide READ or reject handles open for
reading in PUSHED.
=item $obj->CLOSE($fh)
Should return 0 on success, -1 on error.
Optional.
=item $obj->SEEK($posn,$whence,$fh)
Should return 0 on success, -1 on error.
Optional. Default is to fail, but that is likely to be changed.
=item $obj->TELL($fh)
Returns file postion.
Optional. Default to be determined.
=item $obj->UNREAD($buffer,$fh)
Returns the number of octets from buffer that have been sucessfully saved
to be returned on future FILL/READ calls.
Optional. Default is to push data into a temporary layer above this one.
=item $obj->FLUSH($fh)
Flush any buffered write data.
May possibly be called on readable handles too.
Should return 0 on success, -1 on error.
=item $obj->SETLINEBUF($fh)
Optional. No return.
=item $obj->CLEARERR($fh)
Optional. No return.
=item $obj->ERROR($fh)
Optional. Returns error state. Default is no error until a mechanism
to signal error (die?) is worked out.
=item $obj->EOF($fh)
Optional. Returns end-of-file state. Default is function of return value of FILL
or READ.
=back
=cut
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