[p5sagit/p5-mst-13.2.git] / ext / PerlIO / Via / Via.pm

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
Commit	Line	Data
e7a1fdd7	1	package PerlIO::Via;
	2	our $VERSION = '0.01';
	3	use XSLoader ();
	4	XSLoader::load 'PerlIO::Via';
	5	1;
	6	__END__
	7
	8	=head1 NAME
	9
	10	PerlIO::Via - Helper class for PerlIO layers implemented in perl
	11
	12	=head1 SYNOPSIS
	13
	14	use Some::Package;
	15
	16	open($fh,"<:Via(Some::Package)",...);
	17
	18	=head1 DESCRIPTION
	19
	20	The package to be used as a layer should implement at least some of the
	21	following methods. In the method descriptions below I<$fh> will be
	22	a reference to a glob which can be treated as a perl file handle.
	23	It refers to the layer below. I<$fh> is not passed if the layer
	24	is at the bottom of the stack, for this reason and to maintain
	25	some level of "compatibility" with TIEHANDLE classes it is passed
	26	last.
	27
	28	=over 4
	29
	30	=item $class->PUSHED([$mode][,$fh])
	31
	32	Should return an object or the class. (Compare TIEHANDLE.)
	33	Mandatory.
	34
	35	=item $obj->POPPED([$fh])
	36
	37	Optional - layer is about to be removed.
	38
	39	=item $class->OPEN($path,$mode[,$fh])
	40
	41	Not yet in use.
	42
	43	=item $class->FDOPEN($fd)
	44
	45	Not yet in use.
	46
	47	=item $class->SYSOPEN($path,$imode,$perm,$fh)
	48
	49	Not yet in use.
	50
	51	=item $obj->FILENO($fh)
	52
47bfe92f	53	Returns a numeric value for Unix-like file descriptor. Return -1 if
47bfe92f	54	there isn't one. Optional. Default is fileno($fh).
e7a1fdd7	55
	56	=item $obj->READ($buffer,$len,$fh)
	57
	58	Returns the number of octets placed in $buffer (must be less that $len).
47bfe92f	59	Optional. Default is to use FILL instead.
e7a1fdd7	60
	61	=item $obj->WRITE($buffer,$fh)
	62
	63	Returns the number of octets from buffer that have been sucessfully written.
	64
	65	=item $obj->FILL($fh)
	66
47bfe92f	67	Should return a string to be placed in the buffer. Optional. If not
	68	provided must provide READ or reject handles open for reading in
	69	PUSHED.
e7a1fdd7	70
	71	=item $obj->CLOSE($fh)
	72
	73	Should return 0 on success, -1 on error.
	74	Optional.
	75
	76	=item $obj->SEEK($posn,$whence,$fh)
	77
	78	Should return 0 on success, -1 on error.
	79	Optional. Default is to fail, but that is likely to be changed.
	80
	81	=item $obj->TELL($fh)
	82
	83	Returns file postion.
	84	Optional. Default to be determined.
	85
	86	=item $obj->UNREAD($buffer,$fh)
	87
47bfe92f	88	Returns the number of octets from buffer that have been sucessfully
	89	saved to be returned on future FILL/READ calls. Optional. Default is
	90	to push data into a temporary layer above this one.
e7a1fdd7	91
	92	=item $obj->FLUSH($fh)
	93
47bfe92f	94	Flush any buffered write data. May possibly be called on readable
47bfe92f	95	handles too. Should return 0 on success, -1 on error.
e7a1fdd7	96
	97	=item $obj->SETLINEBUF($fh)
	98
	99	Optional. No return.
	100
	101	=item $obj->CLEARERR($fh)
	102
	103	Optional. No return.
	104
	105	=item $obj->ERROR($fh)
	106
	107	Optional. Returns error state. Default is no error until a mechanism
	108	to signal error (die?) is worked out.
	109
	110	=item $obj->EOF($fh)
	111
47bfe92f	112	Optional. Returns end-of-file state. Default is function of return
47bfe92f	113	value of FILL or READ.
e7a1fdd7	114
	115	=back
	116
	117	=cut
	118
	119