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 consumer.join
static VALUE
rb_queue_initialize(VALUE self)
{
struct rb_queue *q = queue_ptr(self);
RB_OBJ_WRITE(self, &q->que, ary_buf_new());
list_head_init(queue_waitq(q));
return self;
}
Creates a new queue instance.
static VALUE
rb_queue_clear(VALUE self)
{
struct rb_queue *q = queue_ptr(self);
rb_ary_clear(check_array(self, q->que));
return self;
}
Removes all objects from the queue.
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;
}
Closes the queue. A closed queue cannot be re-opened.
After the call to close completes, the following are true:
-
closed?will return true -
closewill be ignored. -
calling enq/push/<< will raise a
ClosedQueueError. -
when
empty?is false, calling deq/pop/shift will return an object from the queue as usual. -
when
empty?is true, deq(false) will not suspend the thread and will return nil. deq(true) will raise aThreadError.
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_closed_p(VALUE self)
{
return queue_closed_p(self) ? Qtrue : Qfalse;
}
Returns true if the queue is closed.
static VALUE
rb_queue_empty_p(VALUE self)
{
return queue_length(self, queue_ptr(self)) == 0 ? Qtrue : Qfalse;
}
Returns true if the queue is empty.
static VALUE
rb_queue_length(VALUE self)
{
return LONG2NUM(queue_length(self, queue_ptr(self)));
}
Returns the length of the queue.
static VALUE
rb_queue_num_waiting(VALUE self)
{
struct rb_queue *q = queue_ptr(self);
return INT2NUM(q->num_waiting);
}
Returns the number of threads waiting on the queue.
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);
}
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_push(VALUE self, VALUE obj)
{
return queue_do_push(self, queue_ptr(self), obj);
}
Pushes the given object to the queue.