IO-FDPass/FDPass.pm

=head1 NAME

IO::FDPass - pass a file descriptor over a socket

=head1 SYNOPSIS

   use IO::FDPass;

=head1 DESCRIPTION

This small low-level module only has one purpose: pass a file descriptor
to another process, using a (streaming) unix domain socket (on POSIX
systems) or any (streaming) socket (on WIN32 systems).

=head1 FUNCTIONS

=over 4

=cut

package IO::FDPass;

BEGIN {
   $VERSION = '0.1';

   require XSLoader;
   XSLoader::load (__PACKAGE__, $VERSION);
}

=item $bool = IO::FDPass::send $socket_fd, $fd_to_pass

Sends the file descriptor given by C<$fd_to_pass> over the socket
C<$socket_fd>. Return true if it worked, false otherwise.

Note that I<both> parameters must be file descriptors, not handles.

When used on non-blocking sockets, this function might fail with C<$!>
set to C<EAGAIN> or equivalent, in which case you are free to try. It
should succeed if called on a socket that indicates writability (e.g. via
C<select>).

Example: pass a file handle over an open socket.

   IO::FDPass::send fileno $socket, fileno $fh
      or die "unable to pass file handle: $!";

=item $fd = IO::FDPass::recv $socket_fd

Receive a file descriptor from the socket and return it if successful. On
errors, return C<-1>.

Note that I<both> C<$socket_fd> amd the returned file descriptor are, in
fact, file descriptors, not handles.

When used on non-blocking sockets, this function might fail with C<$!>
set to C<EAGAIN> or equivalent, in which case you are free to try. It
should succeed if called on a socket that indicates readability (e.g. via
C<select>).

Example: receive a file desriptor from a blockign socket and convetr it to
a file handle.

  my $fd = IO::FDPass::recv fileno $socket;
  $fd >= 0 or die "unable to receive file handle: $!";
  open my $fh, "+<&=$fd"
     or die "unable to convert file descriptor to handle: $!";

=back

=head1 PORTABILITY NOTES

This module has been tested on GNU/Linux x86 and amd64, NetBSD 6, OS X
10.5, Windows 2000 ActivePerl 5.10, Solaris 10, OpenBSD 4.4, 4.5, 4.8 and
5.0, DragonFly BSD, FreeBSD 7, 8 and 9, Windows 7 + ActivePerl 5.16.3 32
and 64 bit and Strawberry Perl 5.16.3 32 and 64 bit, and found to work,
although ActivePerl 32 bit needed a newer MinGW version (that supports XP
and higher).

However, windows doesn't support asynchronous file descriptor passing, so
C<send> and C<recv> will have to "rendezvous", that is, they have to wait
for each other. Therefore, on windows, it's advisable to run them at the
same time to avoid any unnecessary delays.

Also, on windows, the passing process must give the receiving process the
PROCESS_DUP_HANDLE access right for this module to work.

Cygwin is not supported at the moment, as file descriptor passing in
cygwin is not supported, and cannot be rolled on your own as cygwin has no
(working) method of opening a handle as fd. That is, it has one, but that
one isn't exposed to programs, and only used for stdin/out/err. Sigh.

=head1 OTHER MODULES

At the time of this writing, the author of this module was aware of two
other file descriptor passing modules on CPAN: L<Linux::FDPasser> and
L<AnyEvent::FDPasser>.

The former hasn't seen any release for over a decade, isn't 64 bit clean
and it's author didn't respond to my mail with the fix. It does, however,
support a snumber of pre-standard unices.

The latter seems to have similar support for antique unices, and doesn't
seem to suffer from 64 bit bugs, but inexplicably has a large perl part,
and requires AnyEvent. Presumably that makes it much more user friendly
than this module.

Neither seems to support native win32 perls.

=head1 AUTHOR

 Marc Lehmann <schmorp@schmorp.de>
 http://home.schmorp.de/

=cut

1

Revision:	1.3
Committed:	Fri Apr 5 05:04:59 2013 UTC (11 years, 1 month ago) by root
Branch:	MAIN
CVS Tags:	rel-0_1
Changes since 1.2:	+14 -9 lines
Log Message:	0.1
#	User	Rev	Content
1	root	1.1	=head1 NAME
2
3			IO::FDPass - pass a file descriptor over a socket
4
5			=head1 SYNOPSIS
6
7			use IO::FDPass;
8
9			=head1 DESCRIPTION
10
11			This small low-level module only has one purpose: pass a file descriptor
12	root	1.3	to another process, using a (streaming) unix domain socket (on POSIX
13			systems) or any (streaming) socket (on WIN32 systems).
14	root	1.1
15			=head1 FUNCTIONS
16
17			=over 4
18
19			=cut
20
21			package IO::FDPass;
22
23			BEGIN {
24	root	1.3	$VERSION = '0.1';
25	root	1.1
26			require XSLoader;
27			XSLoader::load (__PACKAGE__, $VERSION);
28			}
29
30			=item $bool = IO::FDPass::send $socket_fd, $fd_to_pass
31
32			Sends the file descriptor given by C<$fd_to_pass> over the socket
33			C<$socket_fd>. Return true if it worked, false otherwise.
34
35			Note that I<both> parameters must be file descriptors, not handles.
36
37			When used on non-blocking sockets, this function might fail with C<$!>
38			set to C<EAGAIN> or equivalent, in which case you are free to try. It
39			should succeed if called on a socket that indicates writability (e.g. via
40			C<select>).
41
42			Example: pass a file handle over an open socket.
43
44			IO::FDPass::send fileno $socket, fileno $fh
45			or die "unable to pass file handle: $!";
46
47			=item $fd = IO::FDPass::recv $socket_fd
48
49			Receive a file descriptor from the socket and return it if successful. On
50			errors, return C<-1>.
51
52			Note that I<both> C<$socket_fd> amd the returned file descriptor are, in
53			fact, file descriptors, not handles.
54
55			When used on non-blocking sockets, this function might fail with C<$!>
56			set to C<EAGAIN> or equivalent, in which case you are free to try. It
57			should succeed if called on a socket that indicates readability (e.g. via
58			C<select>).
59
60			Example: receive a file desriptor from a blockign socket and convetr it to
61			a file handle.
62
63			my $fd = IO::FDPass::recv fileno $socket;
64			$fd >= 0 or die "unable to receive file handle: $!";
65			open my $fh, "+<&=$fd"
66			or die "unable to convert file descriptor to handle: $!";
67
68			=back
69
70			=head1 PORTABILITY NOTES
71
72	root	1.3	This module has been tested on GNU/Linux x86 and amd64, NetBSD 6, OS X
73			10.5, Windows 2000 ActivePerl 5.10, Solaris 10, OpenBSD 4.4, 4.5, 4.8 and
74			5.0, DragonFly BSD, FreeBSD 7, 8 and 9, Windows 7 + ActivePerl 5.16.3 32
75			and 64 bit and Strawberry Perl 5.16.3 32 and 64 bit, and found to work,
76			although ActivePerl 32 bit needed a newer MinGW version (that supports XP
77			and higher).
78	root	1.1
79			However, windows doesn't support asynchronous file descriptor passing, so
80			C<send> and C<recv> will have to "rendezvous", that is, they have to wait
81			for each other. Therefore, on windows, it's advisable to run them at the
82			same time to avoid any unnecessary delays.
83
84			Also, on windows, the passing process must give the receiving process the
85			PROCESS_DUP_HANDLE access right for this module to work.
86
87	root	1.3	Cygwin is not supported at the moment, as file descriptor passing in
88			cygwin is not supported, and cannot be rolled on your own as cygwin has no
89			(working) method of opening a handle as fd. That is, it has one, but that
90			one isn't exposed to programs, and only used for stdin/out/err. Sigh.
91
92	root	1.1	=head1 OTHER MODULES
93
94			At the time of this writing, the author of this module was aware of two
95			other file descriptor passing modules on CPAN: L<Linux::FDPasser> and
96			L<AnyEvent::FDPasser>.
97
98			The former hasn't seen any release for over a decade, isn't 64 bit clean
99			and it's author didn't respond to my mail with the fix. It does, however,
100			support a snumber of pre-standard unices.
101
102			The latter seems to have similar support for antique unices, and doesn't
103			seem to suffer from 64 bit bugs, but inexplicably has a large perl part,
104			and requires AnyEvent. Presumably that makes it much more user friendly
105			than this module.
106
107			Neither seems to support native win32 perls.
108
109			=head1 AUTHOR
110
111			Marc Lehmann <schmorp@schmorp.de>
112			http://home.schmorp.de/
113
114			=cut
115
116			1
117