Thread::Queue - thread-safe queues
use Thread::Queue; my $q = new Thread::Queue; $q->enqueue("foo", "bar"); my $foo = $q->dequeue; # The "bar" is still in the queue. my $foo = $q->dequeue_nb; # returns "bar", or undef if the queue was # empty my $left = $q->pending; # returns the number of items still in the queue
A queue, as implemented by Thread::Queue
is a thread-safe data structure much like a list. Any number of threads can
safely add elements to the end of the list, or remove elements from the
head of the list. (Queues don't permit adding or removing elements from the
middle of the list)
The new function creates a new empty queue.
The enqueue method adds a list of scalars on to the end of the queue. The queue will grow as needed to accomodate the list.
The dequeue method removes a scalar from the head of the queue and returns it. If the queue is currently empty, dequeue will block the thread until another thread enqueues a scalar.
The dequeue_nb method, like the dequeue method, removes a scalar from the head of the queue and returns it. Unlike dequeue, though, dequeue_nb won't block if the queue is empty, instead returning undef.
The pending method returns the number of items still in the queue. (If there can be multiple readers on the queue it's best to lock the queue before checking to make sure that it stays in a consistent state)
the Thread manpage =cut
sub new { my $class = shift; return bless [@_], $class; }
sub dequeue { use attrs qw(locked
method); my $q = shift; cond_wait $q until
@$q; return shift @$q; }
sub dequeue_nb { use attrs qw(locked
method); my $q = shift; if (@$q) { return shift @$q; } else {
return undef; } }
sub enqueue { use attrs qw(locked
method); my $q = shift; push(@$q,
@_) and
cond_broadcast $q; }
sub pending { use attrs qw(locked
method); my $q = shift; return scalar(@$q);
}
1;