NAME

Thread::Queue - thread-safe queues

SYNOPSIS

    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

DESCRIPTION

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

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;

DISCLAIMER

We are painfully aware that these documents may contain incorrect links and misformatted HTML. Such bugs lie in the automatic translation process that automatically created the hundreds and hundreds of separate documents that you find here. Please do not report link or formatting bugs, because we cannot fix per-document problems. The only bug reports that will help us are those that supply working patches to the installhtml or pod2html programs, or to the Pod::HTML module itself, for which I and the entire Perl community will shower you with thanks and praises.

If rather than formatting bugs, you encounter substantive content errors in these documents, such as mistakes in the explanations or code, please use the perlbug utility included with the Perl distribution.

--Tom Christiansen, Perl Documentation Compiler and Editor

Return to the Perl Documentation Index.
Return to the Perl Home Page.