1package Thread::Queue;
2use Thread qw(cond_wait cond_broadcast);
3
4use vars qw($VERSION);
5$VERSION = '1.00';
6
7=head1 NAME
8
9Thread::Queue - thread-safe queues (5.005-threads)
10
11=head1 CAVEAT
12
13This Perl installation is using the old unsupported "5.005 threads".
14Use of the old threads model is discouraged.
15
16For the whole story about the development of threads in Perl, and why
17you should B<not> be using "old threads" unless you know what you're
18doing, see the CAVEAT of the C<Thread> module.
19
20=head1 SYNOPSIS
21
22    use Thread::Queue;
23    my $q = new Thread::Queue;
24    $q->enqueue("foo", "bar");
25    my $foo = $q->dequeue;    # The "bar" is still in the queue.
26    my $foo = $q->dequeue_nb; # returns "bar", or undef if the queue was
27                              # empty
28    my $left = $q->pending;   # returns the number of items still in the queue
29
30=head1 DESCRIPTION
31
32A queue, as implemented by C<Thread::Queue> is a thread-safe data structure
33much like a list. Any number of threads can safely add elements to the end
34of the list, or remove elements from the head of the list. (Queues don't
35permit adding or removing elements from the middle of the list)
36
37=head1 FUNCTIONS AND METHODS
38
39=over 8
40
41=item new
42
43The C<new> function creates a new empty queue.
44
45=item enqueue LIST
46
47The C<enqueue> method adds a list of scalars on to the end of the queue.
48The queue will grow as needed to accomodate the list.
49
50=item dequeue
51
52The C<dequeue> method removes a scalar from the head of the queue and
53returns it. If the queue is currently empty, C<dequeue> will block the
54thread until another thread C<enqueue>s a scalar.
55
56=item dequeue_nb
57
58The C<dequeue_nb> method, like the C<dequeue> method, removes a scalar from
59the head of the queue and returns it. Unlike C<dequeue>, though,
60C<dequeue_nb> won't block if the queue is empty, instead returning
61C<undef>.
62
63=item pending
64
65The C<pending> method returns the number of items still in the queue.  (If
66there can be multiple readers on the queue it's best to lock the queue
67before checking to make sure that it stays in a consistent state)
68
69=back
70
71=head1 SEE ALSO
72
73L<Thread>
74
75=cut
76
77sub new {
78    my $class = shift;
79    return bless [@_], $class;
80}
81
82sub dequeue : locked : method {
83    my $q = shift;
84    cond_wait $q until @$q;
85    return shift @$q;
86}
87
88sub dequeue_nb : locked : method {
89  my $q = shift;
90  if (@$q) {
91    return shift @$q;
92  } else {
93    return undef;
94  }
95}
96
97sub enqueue : locked : method {
98    my $q = shift;
99    push(@$q, @_) and cond_broadcast $q;
100}
101
102sub pending : locked : method {
103  my $q = shift;
104  return scalar(@$q);
105}
106
1071;
108