Commit | Line | Data |
83272a45 |
1 | package Thread::Queue; |
2 | use Thread qw(cond_wait cond_broadcast); |
3 | |
4 | =head1 NAME |
5 | |
6 | Thread::Queue - thread-safe queues (5.005-threads) |
7 | |
8 | =head1 CAVEAT |
9 | |
10 | This Perl installation is using the old unsupported "5.005 threads". |
11 | Use of the old threads model is discouraged. |
12 | |
13 | For the whole story about the development of threads in Perl, and why |
14 | you should B<not> be using "old threads" unless you know what you're |
15 | doing, see the CAVEAT of the C<Thread> module. |
16 | |
17 | =head1 SYNOPSIS |
18 | |
19 | use Thread::Queue; |
20 | my $q = new Thread::Queue; |
21 | $q->enqueue("foo", "bar"); |
22 | my $foo = $q->dequeue; # The "bar" is still in the queue. |
23 | my $foo = $q->dequeue_nb; # returns "bar", or undef if the queue was |
24 | # empty |
25 | my $left = $q->pending; # returns the number of items still in the queue |
26 | |
27 | =head1 DESCRIPTION |
28 | |
29 | A queue, as implemented by C<Thread::Queue> is a thread-safe data structure |
30 | much like a list. Any number of threads can safely add elements to the end |
31 | of the list, or remove elements from the head of the list. (Queues don't |
32 | permit adding or removing elements from the middle of the list) |
33 | |
34 | =head1 FUNCTIONS AND METHODS |
35 | |
36 | =over 8 |
37 | |
38 | =item new |
39 | |
40 | The C<new> function creates a new empty queue. |
41 | |
42 | =item enqueue LIST |
43 | |
44 | The C<enqueue> method adds a list of scalars on to the end of the queue. |
45 | The queue will grow as needed to accomodate the list. |
46 | |
47 | =item dequeue |
48 | |
49 | The C<dequeue> method removes a scalar from the head of the queue and |
50 | returns it. If the queue is currently empty, C<dequeue> will block the |
51 | thread until another thread C<enqueue>s a scalar. |
52 | |
53 | =item dequeue_nb |
54 | |
55 | The C<dequeue_nb> method, like the C<dequeue> method, removes a scalar from |
56 | the head of the queue and returns it. Unlike C<dequeue>, though, |
57 | C<dequeue_nb> won't block if the queue is empty, instead returning |
58 | C<undef>. |
59 | |
60 | =item pending |
61 | |
62 | The C<pending> method returns the number of items still in the queue. (If |
63 | there can be multiple readers on the queue it's best to lock the queue |
64 | before checking to make sure that it stays in a consistent state) |
65 | |
66 | =back |
67 | |
68 | =head1 SEE ALSO |
69 | |
70 | L<Thread> |
71 | |
72 | =cut |
73 | |
74 | sub new { |
75 | my $class = shift; |
76 | return bless [@_], $class; |
77 | } |
78 | |
79 | sub dequeue : locked : method { |
80 | my $q = shift; |
81 | cond_wait $q until @$q; |
82 | return shift @$q; |
83 | } |
84 | |
85 | sub dequeue_nb : locked : method { |
86 | my $q = shift; |
87 | if (@$q) { |
88 | return shift @$q; |
89 | } else { |
90 | return undef; |
91 | } |
92 | } |
93 | |
94 | sub enqueue : locked : method { |
95 | my $q = shift; |
96 | push(@$q, @_) and cond_broadcast $q; |
97 | } |
98 | |
99 | sub pending : locked : method { |
100 | my $q = shift; |
101 | return scalar(@$q); |
102 | } |
103 | |
104 | 1; |