As many of you know, I have been struggling with a lightweight RPC module. This module was originally written by Sriram in Advanced Perl Programming. It was meant to be used in conjuction with subs, not OO code. Unfortunately, the codebase I was working on is OO based. So, I went about deconstructing the RPC module, looking at the way the code was frozen (using FreezeThaw) and thawed out (again, using FreezeThaw). After a week or two of struggling, I accomplished the code rewrite.

The rewritten RPC module is modeled for client-server use. The code (which can be improved) is:

package RPC_OO;
use Msg;
use strict;
use Carp;
use vars qw(@ISA);
@ISA = qw(Msg);
use FreezeThaw qw(freeze thaw);

#-----------------------------------------------------------------
# Server side
sub new_server {
    my ($pkg, $my_host, $my_port) = @_;
    return $pkg->SUPER::new_server($my_host, $my_port, sub {$pkg->_log
+in(@_)});
}

sub _login {
    return \&_event_dispatcher;
}

sub _event_dispatcher {
    my ($conn, $msg, $err) = @_;
    return if ($err);   # Need better error handling.
    return unless defined($msg);
    my ($dir, $id, $gimme, $obj, $method, @params) = thaw ($msg);
    my ($result, @results);
    if ($dir eq '>') {
        # Incoming msg. (outgoing msg from client, that is)
        eval {
            no strict 'refs';  # Because we call the subroutine using
                               # a symbolic reference
            if ($gimme eq 'a') {  # Want an array back
                @results = $obj->$method(@params); 
            } else {
                $result = $obj->$method(@params);
            }
        };
        if ($@) {
            $msg = bless \$@, "RPC::Error";
            $msg = freeze('<', $id, $msg);
        } elsif ($gimme eq 'a') {
            $msg = freeze('<', $id, @results);
        } else {
            $msg = freeze('<', $id, $result);
        }
        $conn->send_later($msg);
    }
    else {
        #Someone tried to send a bogus command...
        $conn->disconnect();
   }

}


#-----------------------------------------------------------------
# Client side
sub connect {
   my ($pkg, $host, $port) = @_;
   my $conn = $pkg->SUPER::connect($host,$port, \&_response);
   return $conn;
}

my $send_err = 0;
sub handle_send_err {
   $send_err = $!;
}

my $g_msg_id = 0;
sub rpc {
    my $conn = shift;
    my $obj = shift;
    my $method = shift;
    my $gimme;
    $gimme = wantarray ? 'a' : 's';
    my $msg_id = ++$g_msg_id;
    my $serialized_msg = freeze ('>', $msg_id, $gimme, $obj, $method, 
+@_);
    # Send and Receive
    $conn->send_later ($serialized_msg);
    if ($send_err) {
        die "RPC Error: $!\n";
    }

    do {
        Msg->event_loop(1); # Dispatch other messages until we get a r
+esponse
    } until (exists $conn->{rcvd}->{$msg_id} || $send_err);
 
    # Dequeue message
    my $rl_retargs = delete $conn->{rcvd}->{$msg_id}; # ref to list
    if (ref($rl_retargs->[0]) eq 'RPC::Error') {
        die ${$rl_retargs->[0]};
    }
    wantarray ? @$rl_retargs : $rl_retargs->[0];
}

sub _response {
    my ($conn, $msg, $err) = @_;
    return if ($err);   # Need better error handling.
    return unless defined($msg);
    my ($dir, $id, @data) = thaw ($msg);
    $conn->{rcvd}->{$id} = [@data];
}


1;
[download]

I decided to use the same Msg.pm library that Sriram developed in Advanced Perl Programming. Some of the code even has comments from the original RPC module. When I develop better socket programming skills, I'll go and write my own Msg.pm library with more features and such. I just wanted to know what the monks here think of this module. Is it CPAN worthy? Should I just email Sriram with this newer module and ask him to include it in a reprint of Advanced Perl Programming? Or should I just stick this module in my backpack and pull out as needed? Also, any constructive criticism on how to make this module a little better is appreciated.

Theodore Charles III
Network Administrator
Los Angeles Senior High
4650 W. Olympic Blvd.
Los Angeles, CA 90019
323-937-3210 ext. 224
email->secon_kun@hotmail.com

Update: Fixed a small typo in copying the module into the form at line 6 of the code.

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