The Thread::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 Thread::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 = Thread::Queue.new
producer = Thread.new do
5.times do |i|
sleep rand(i)
queue << i
puts "#{i} produced"
end
end
consumer = Thread.new do
5.times do |i|
value = queue.pop
sleep rand(i/2)
puts "consumed #{value}"
end
end
consumer.join
Public Class Methods
Thread::Queue.new → empty_queue click to toggle source
Thread::Queue.new(enumerable) → queue
Creates a new queue instance, optionally using the contents of an enumerable for its initial state.
Example:
q = Thread::Queue.new q.empty? q = Thread::Queue.new([1, 2, 3]) q.empty? q.pop
static VALUE
rb_queue_initialize(int argc, VALUE *argv, VALUE self)
{
VALUE initial;
struct rb_queue *q = queue_ptr(self);
if ((argc = rb_scan_args(argc, argv, "01", &initial)) == 1) {
initial = rb_to_array(initial);
}
RB_OBJ_WRITE(self, &q->que, ary_buf_new());
list_head_init(queue_waitq(q));
if (argc == 1) {
rb_ary_concat(q->que, initial);
}
return self;
} Public Instance Methods
<<(object)
Pushes the given object to the queue.
clear() click to toggle source
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;
}
close click to toggle source
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 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 a ThreadError.
ClosedQueueError is inherited from StopIteration, so that you can break loop block.
Example:
q = Thread::Queue.new
Thread.new{
while e = q.deq
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;
}
closed? click to toggle source
Returns true if the queue is closed.
static VALUE
rb_queue_closed_p(VALUE self)
{
return RBOOL(queue_closed_p(self));
}
deq(non_block=false)
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 isnât suspended, and ThreadError is raised.
empty? click to toggle source
Returns true if the queue is empty.
static VALUE
rb_queue_empty_p(VALUE self)
{
return RBOOL(queue_length(self, queue_ptr(self)) == 0);
}
enq(object)
Pushes the given object to the queue.
length click to toggle source
Returns the length of the queue.
static VALUE
rb_queue_length(VALUE self)
{
return LONG2NUM(queue_length(self, queue_ptr(self)));
}
num_waiting() click to toggle source
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);
}
pop(non_block=false) click to toggle source
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 isnât 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);
}
push(object) click to toggle source
Pushes the given object to the queue.
static VALUE
rb_queue_push(VALUE self, VALUE obj)
{
return queue_do_push(self, queue_ptr(self), obj);
}
Also aliased as:
enq,
<<shift(non_block=false)
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 isnât suspended, and ThreadError is raised.
size
Returns the length of the queue.
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