The Queue
class implements multi-producer, multi-consumer queues. It is especially useful in threaded programming when information must be exchanged safely between multiple threads. The Queue
class implements all the required locking semantics.
The class implements FIFO type of queue. In a FIFO queue, the first tasks added are the first retrieved.
Example:
queue = Queue.new producer = Thread.new do 5.times do |i| sleep rand(i) # simulate expense queue << i puts "#{i} produced" end end consumer = Thread.new do 5.times do |i| value = queue.pop sleep rand(i/2) # simulate expense puts "consumed #{value}" end end
Removes all objects from the queue.
static VALUE rb_queue_clear(VALUE self) { struct rb_queue *q = queue_ptr(self); rb_ary_clear(check_array(self, q->que)); return self; }
Closes the queue. A closed queue cannot be re-opened.
After the call to close completes, the following are true:
closed?
will return true
close
will be ignored.
calling enq/push/<< will raise an exception.
when empty?
is false, calling deq/pop/shift will return an object from the queue as usual.
ClosedQueueError
is inherited from StopIteration
, so that you can break loop block.
Example: q = Queue.new Thread.new{ while e = q.deq # wait for nil to break loop # ... end } q.close
static VALUE rb_queue_close(VALUE self) { struct rb_queue *q = queue_ptr(self); if (!queue_closed_p(self)) { FL_SET(self, QUEUE_CLOSED); wakeup_all(queue_waitq(q)); } return self; }
Returns true
if the queue is closed.
static VALUE rb_queue_closed_p(VALUE self) { return queue_closed_p(self) ? Qtrue : Qfalse; }
Returns true
if the queue is empty.
static VALUE rb_queue_empty_p(VALUE self) { return queue_length(self, queue_ptr(self)) == 0 ? Qtrue : Qfalse; }
Returns the length of the queue.
static VALUE rb_queue_length(VALUE self) { return LONG2NUM(queue_length(self, queue_ptr(self))); }
Returns the number of threads waiting on the queue.
static VALUE rb_queue_num_waiting(VALUE self) { struct rb_queue *q = queue_ptr(self); return INT2NUM(q->num_waiting); }
Retrieves data from the queue.
If the queue is empty, the calling thread is suspended until data is pushed onto the queue. If non_block
is true, the thread isn't suspended, and ThreadError
is raised.
static VALUE rb_queue_pop(int argc, VALUE *argv, VALUE self) { int should_block = queue_pop_should_block(argc, argv); return queue_do_pop(self, queue_ptr(self), should_block); }