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perlman:Thread::Queue

by root (Scribe)
on Dec 23, 1999 at 00:53 UTC ( #1259=perlfunc: print w/ replies, xml ) Need Help??

Thread::Queue

See the current Perl documentation for Thread::Queue.

Here is our local, out-dated (pre-5.6) version:


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",
    

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)


FUNCTIONS AND METHODS

new

The new function creates a new empty queue.

enqueue LIST

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.

dequeue

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.

dequeue_nb

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.

pending

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)


SEE ALSO

Thread =cut

sub new { my $class = shift; return bless [@_], $class; }

sub dequeue { use attrs qw(locked method); my $q = shift; cond_wait perlop until @$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 perlop = shift; push(@$q, @_) and cond_broadcast $q; }

sub pending { use attrs qw(locked method); my perlop = shift; return scalar(@$q); }

1;


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