[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.

As an example, in Perl release 5.8.0 the MIME::QuotedPrint module
defines the required TIEHANDLE methods so that you can say

	use MIME::QuotedPrint;
	open(my $fh, ">Via(MIME::QuotedPrint)", "qp");

=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 than or
equal to $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
2b8740d8	25	some level of "compatibility" with TIEHANDLE classes it is passed last.
	26
	27	As an example, in Perl release 5.8.0 the MIME::QuotedPrint module
	28	defines the required TIEHANDLE methods so that you can say
	29
	30	use MIME::QuotedPrint;
	31	open(my $fh, ">Via(MIME::QuotedPrint)", "qp");
e7a1fdd7	32
	33	=over 4
	34
	35	=item $class->PUSHED([$mode][,$fh])
	36
	37	Should return an object or the class. (Compare TIEHANDLE.)
	38	Mandatory.
	39
	40	=item $obj->POPPED([$fh])
	41
	42	Optional - layer is about to be removed.
	43
	44	=item $class->OPEN($path,$mode[,$fh])
	45
	46	Not yet in use.
	47
	48	=item $class->FDOPEN($fd)
	49
	50	Not yet in use.
	51
	52	=item $class->SYSOPEN($path,$imode,$perm,$fh)
	53
	54	Not yet in use.
	55
	56	=item $obj->FILENO($fh)
	57
47bfe92f	58	Returns a numeric value for Unix-like file descriptor. Return -1 if
47bfe92f	59	there isn't one. Optional. Default is fileno($fh).
e7a1fdd7	60
	61	=item $obj->READ($buffer,$len,$fh)
	62
6391fff2	63	Returns the number of octets placed in $buffer (must be less than or
6391fff2	64	equal to $len). Optional. Default is to use FILL instead.
e7a1fdd7	65
	66	=item $obj->WRITE($buffer,$fh)
	67
	68	Returns the number of octets from buffer that have been sucessfully written.
	69
	70	=item $obj->FILL($fh)
	71
47bfe92f	72	Should return a string to be placed in the buffer. Optional. If not
	73	provided must provide READ or reject handles open for reading in
	74	PUSHED.
e7a1fdd7	75
	76	=item $obj->CLOSE($fh)
	77
	78	Should return 0 on success, -1 on error.
	79	Optional.
	80
	81	=item $obj->SEEK($posn,$whence,$fh)
	82
	83	Should return 0 on success, -1 on error.
	84	Optional. Default is to fail, but that is likely to be changed.
	85
	86	=item $obj->TELL($fh)
	87
	88	Returns file postion.
	89	Optional. Default to be determined.
	90
	91	=item $obj->UNREAD($buffer,$fh)
	92
47bfe92f	93	Returns the number of octets from buffer that have been sucessfully
	94	saved to be returned on future FILL/READ calls. Optional. Default is
	95	to push data into a temporary layer above this one.
e7a1fdd7	96
	97	=item $obj->FLUSH($fh)
	98
47bfe92f	99	Flush any buffered write data. May possibly be called on readable
47bfe92f	100	handles too. Should return 0 on success, -1 on error.
e7a1fdd7	101
	102	=item $obj->SETLINEBUF($fh)
	103
	104	Optional. No return.
	105
	106	=item $obj->CLEARERR($fh)
	107
	108	Optional. No return.
	109
	110	=item $obj->ERROR($fh)
	111
	112	Optional. Returns error state. Default is no error until a mechanism
	113	to signal error (die?) is worked out.
	114
	115	=item $obj->EOF($fh)
	116
47bfe92f	117	Optional. Returns end-of-file state. Default is function of return
47bfe92f	118	value of FILL or READ.
e7a1fdd7	119
	120	=back
	121
	122	=cut
	123
	124