100 lines
2.9 KiB
Perl
100 lines
2.9 KiB
Perl
package SocketActivation;
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# vim:ts=4:sw=4:expandtab
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use IO::Socket::UNIX; # core
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use Cwd qw(abs_path); # core
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use POSIX; # core
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use AnyEvent::Handle; # not core
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use Exporter 'import';
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use v5.10;
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our @EXPORT = qw(activate_i3);
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#
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# Starts i3 using socket activation. Creates a listening socket (with bind +
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# listen) which is then passed to i3, who in turn calls accept and handles the
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# requests.
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#
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# Since the kernel buffers the connect, the parent process can connect to the
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# socket immediately after forking. It then sends a request and waits until it
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# gets an answer. Obviously, i3 has to be initialized to actually answer the
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# request.
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#
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# This way, we can wait *precisely* the amount of time which i3 waits to get
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# ready, which is a *HUGE* speed gain (and a lot more robust) in comparison to
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# using sleep() with a fixed amount of time.
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#
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# unix_socket_path: Location of the socket to use for the activation
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# display: X11 $ENV{DISPLAY}
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# configfile: path to the configuration file to use
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# logpath: path to the logfile to which i3 will append
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# cv: an AnyEvent->condvar which will be triggered once i3 is ready
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#
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sub activate_i3 {
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my %args = @_;
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# remove the old unix socket
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unlink($args{unix_socket_path});
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# pass all file descriptors up to three to the children.
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# we need to set this flag before opening the socket.
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open(my $fdtest, '<', '/dev/null');
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$^F = fileno($fdtest);
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close($fdtest);
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my $socket = IO::Socket::UNIX->new(
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Listen => 1,
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Local => $args{unix_socket_path},
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);
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my $pid = fork;
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if (!defined($pid)) {
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die "could not fork()";
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}
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if ($pid == 0) {
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$ENV{LISTEN_PID} = $$;
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$ENV{LISTEN_FDS} = 1;
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$ENV{DISPLAY} = $args{display};
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$^F = 3;
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POSIX::close(3);
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POSIX::dup2(fileno($socket), 3);
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# now execute i3
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my $i3cmd = abs_path("../i3") . " -V -d all --disable-signalhandler";
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my $cmd = "exec $i3cmd -c $args{configfile} >$args{logpath} 2>&1";
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exec "/bin/sh", '-c', $cmd;
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# if we are still here, i3 could not be found or exec failed. bail out.
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exit 1;
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}
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# close the socket, the child process should be the only one which keeps a file
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# descriptor on the listening socket.
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$socket->close;
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# We now connect (will succeed immediately) and send a request afterwards.
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# As soon as the reply is there, i3 is considered ready.
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my $cl = IO::Socket::UNIX->new(Peer => $args{unix_socket_path});
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my $hdl;
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$hdl = AnyEvent::Handle->new(
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fh => $cl,
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on_error => sub {
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$hdl->destroy;
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$args{cv}->send(0);
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});
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# send a get_tree message without payload
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$hdl->push_write('i3-ipc' . pack("LL", 0, 4));
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# wait for the reply
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$hdl->push_read(chunk => 1, => sub {
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my ($h, $line) = @_;
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$args{cv}->send(1);
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undef $hdl;
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});
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return $pid;
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}
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1
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