bounded-channel.p6

class BoundedChannel is Channel {
    has $!lock = Lock.new;
    has $!send-cond = $!lock.condition;
    has $.limit is required;

    method send(|c) {
        $!lock.lock();
        LEAVE $!lock.unlock();
        while $!limit == 0 {
            $!send-cond.wait();
        }
        $!limit--;
        nextsame();
    }

    method receive() {
        my \got = callsame();
        self!received();
        got
    }

    method poll() {
        my \got = callsame();
        unless got === Nil {
            self!received();
        }
        got
    }

    method !received() {
        $!lock.lock();
        LEAVE $!lock.unlock();
        $!limit++;
        if $!limit == 1 {
            $!send-cond.signal();
        }
    }
}

my $bc = BoundedChannel.new(limit => 5);
start {
    loop {
        say "Got $bc.receive()";
        sleep 1;
    }
    CATCH { say $_ }
}
for 1..* {
    say "Sending $_";
    $bc.send($_);
}