#!/usr/bin/env perl
use strict;
use warnings;
use feature 'say';
use IPC::SysV qw/IPC_PRIVATE S_IRUSR S_IWUSR IPC_NOWAIT/;
use IPC::Msg;
$|++;

use constant MSG_BYTES => 1024;

my $q = IPC::Msg->new(IPC_PRIVATE,S_IRUSR|S_IWUSR);

sub quit { $q->remove; }
$SIG{INT} = \&quit;

sub enqueue {
    my $msg = shift;
    my $msg_type = shift // 1; # Used for message selection, see msgsnd(2)
    $q->snd($msg_type,$msg,IPC_NOWAIT) || die $!;
}

sub dequeue {
    my $type = shift // 1; # See msgop(2)
    my $msg;
    $q->rcv($msg,MSG_BYTES,$type,IPC_NOWAIT);
    #if ($!) { warn "$$ - $!" }
    return $msg // undef;
}

sub dequeue_block {
    my $msg;
    my $type = shift // 1; # See msgop(2)
    $q->rcv($msg,MSG_BYTES,$type);
    #if ($!) { warn "$$ - $!" }
    return $msg // undef;
}

sub isEmpty {
    my $stat = $q->stat;
    return $stat->qnum == 0;
}

sub isPrime {
    my $num = shift;
    return 1 if ($num < 4);
    return 0 if ($num %2 == 0);
    for (my $i=3; $i <= sqrt($num); $i+=2) {
        return 0 if $num % $i == 0;
    }
    return 1;
}

my $n_workers = shift // die ;

enqueue($_) for (1..2_000_000);

my $parent = $$;

for (my $i=1; $i<$n_workers && $$ == $parent; $i++) {
	fork // die;
}

while (my $data = dequeue()) {
    if (isPrime($data)) {
        print "Prime: $data\n";
    }
}

END {
    if ($$ == $parent) {
       1 until wait == -1;
       quit;
    }
}