[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
	53	Returns a numeric value for Unix-like file descriptor. Return -1
	54	if there isn't one.
	55	Optional -default is fileno($fh).
	56
	57	=item $obj->READ($buffer,$len,$fh)
	58
	59	Returns the number of octets placed in $buffer (must be less that $len).
	60	Optional - default is to use FILL instead.
	61
	62	=item $obj->WRITE($buffer,$fh)
	63
	64	Returns the number of octets from buffer that have been sucessfully written.
65
66	=item $obj->FILL($fh)
67
68	Should return a string to be placed in the buffer.
69	Optional. If not provided must provide READ or reject handles open for
70	reading in PUSHED.
71
72	=item $obj->CLOSE($fh)
73
74	Should return 0 on success, -1 on error.
75	Optional.
76
77	=item $obj->SEEK($posn,$whence,$fh)
78
79	Should return 0 on success, -1 on error.
80	Optional. Default is to fail, but that is likely to be changed.
81
82	=item $obj->TELL($fh)
83
84	Returns file postion.
85	Optional. Default to be determined.
86
87	=item $obj->UNREAD($buffer,$fh)
88
89	Returns the number of octets from buffer that have been sucessfully saved
90	to be returned on future FILL/READ calls.
91	Optional. Default is to push data into a temporary layer above this one.
92
93	=item $obj->FLUSH($fh)
94
95	Flush any buffered write data.
96	May possibly be called on readable handles too.
97	Should return 0 on success, -1 on error.
98
99	=item $obj->SETLINEBUF($fh)
100
101	Optional. No return.
102
103	=item $obj->CLEARERR($fh)
104
105	Optional. No return.
106
107	=item $obj->ERROR($fh)
108
109	Optional. Returns error state. Default is no error until a mechanism
110	to signal error (die?) is worked out.
111
112	=item $obj->EOF($fh)
113
114	Optional. Returns end-of-file state. Default is function of return value of FILL
115	or READ.
116
117	=back
118
119	=cut
120
121