1package Thread::Queue;
2
3use threads::shared;
4use strict;
5
6our $VERSION = '2.00';
7
8=head1 NAME
9
10Thread::Queue - thread-safe queues
11
12=head1 SYNOPSIS
13
14    use Thread::Queue;
15    my $q = new Thread::Queue;
16    $q->enqueue("foo", "bar");
17    my $foo = $q->dequeue;    # The "bar" is still in the queue.
18    my $foo = $q->dequeue_nb; # returns "bar", or undef if the queue was empty
19    my $left = $q->pending;   # returns the number of items still in the queue
20
21=head1 DESCRIPTION
22
23A queue, as implemented by C<Thread::Queue> is a thread-safe
24data structure much like a list.  Any number of threads can safely
25add elements to the end of the list, or remove elements from the head
26of the list. (Queues don't permit adding or removing elements from
27the middle of the list).
28
29=head1 FUNCTIONS AND METHODS
30
31=over 8
32
33=item new
34
35The C<new> function creates a new empty queue.
36
37=item enqueue LIST
38
39The C<enqueue> method adds a list of scalars on to the end of the queue.
40The queue will grow as needed to accommodate the list.
41
42=item dequeue
43
44The C<dequeue> method removes a scalar from the head of the queue and
45returns it. If the queue is currently empty, C<dequeue> will block the
46thread until another thread C<enqueue>s a scalar.
47
48=item dequeue_nb
49
50The C<dequeue_nb> method, like the C<dequeue> method, removes a scalar from
51the head of the queue and returns it. Unlike C<dequeue>, though,
52C<dequeue_nb> won't block if the queue is empty, instead returning
53C<undef>.
54
55=item pending
56
57The C<pending> method returns the number of items still in the queue.
58
59=back
60
61=head1 SEE ALSO
62
63L<threads>, L<threads::shared>
64
65=cut
66
67sub new {
68    my $class = shift;
69    my @q : shared = @_;
70    return bless \@q, $class;
71}
72
73sub dequeue  {
74    my $q = shift;
75    lock(@$q);
76    cond_wait @$q until @$q;
77    cond_signal @$q if @$q > 1;
78    return shift @$q;
79}
80
81sub dequeue_nb {
82    my $q = shift;
83    lock(@$q);
84    return shift @$q;
85}
86
87sub enqueue {
88    my $q = shift;
89    lock(@$q);
90    push @$q, @_  and cond_signal @$q;
91}
92
93sub pending  {
94    my $q = shift;
95    lock(@$q);
96    return scalar(@$q);
97}
98
991;
100
101
102