Commit | Line | Data |
83272a45 |
1 | package Thread::Queue; |
2 | use Thread qw(cond_wait cond_broadcast); |
3 | |
f7229ad3 |
4 | use vars qw($VERSION); |
5 | $VERSION = '1.00'; |
6 | |
83272a45 |
7 | =head1 NAME |
8 | |
9 | Thread::Queue - thread-safe queues (5.005-threads) |
10 | |
11 | =head1 CAVEAT |
12 | |
13 | This Perl installation is using the old unsupported "5.005 threads". |
14 | Use of the old threads model is discouraged. |
15 | |
16 | For the whole story about the development of threads in Perl, and why |
17 | you should B<not> be using "old threads" unless you know what you're |
18 | doing, 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 | |
32 | A queue, as implemented by C<Thread::Queue> is a thread-safe data structure |
33 | much like a list. Any number of threads can safely add elements to the end |
34 | of the list, or remove elements from the head of the list. (Queues don't |
35 | permit 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 | |
43 | The C<new> function creates a new empty queue. |
44 | |
45 | =item enqueue LIST |
46 | |
47 | The C<enqueue> method adds a list of scalars on to the end of the queue. |
48 | The queue will grow as needed to accomodate the list. |
49 | |
50 | =item dequeue |
51 | |
52 | The C<dequeue> method removes a scalar from the head of the queue and |
53 | returns it. If the queue is currently empty, C<dequeue> will block the |
54 | thread until another thread C<enqueue>s a scalar. |
55 | |
56 | =item dequeue_nb |
57 | |
58 | The C<dequeue_nb> method, like the C<dequeue> method, removes a scalar from |
59 | the head of the queue and returns it. Unlike C<dequeue>, though, |
60 | C<dequeue_nb> won't block if the queue is empty, instead returning |
61 | C<undef>. |
62 | |
63 | =item pending |
64 | |
65 | The C<pending> method returns the number of items still in the queue. (If |
66 | there can be multiple readers on the queue it's best to lock the queue |
67 | before checking to make sure that it stays in a consistent state) |
68 | |
69 | =back |
70 | |
71 | =head1 SEE ALSO |
72 | |
73 | L<Thread> |
74 | |
75 | =cut |
76 | |
77 | sub new { |
78 | my $class = shift; |
79 | return bless [@_], $class; |
80 | } |
81 | |
82 | sub dequeue : locked : method { |
83 | my $q = shift; |
84 | cond_wait $q until @$q; |
85 | return shift @$q; |
86 | } |
87 | |
88 | sub dequeue_nb : locked : method { |
89 | my $q = shift; |
90 | if (@$q) { |
91 | return shift @$q; |
92 | } else { |
93 | return undef; |
94 | } |
95 | } |
96 | |
97 | sub enqueue : locked : method { |
98 | my $q = shift; |
99 | push(@$q, @_) and cond_broadcast $q; |
100 | } |
101 | |
102 | sub pending : locked : method { |
103 | my $q = shift; |
104 | return scalar(@$q); |
105 | } |
106 | |
107 | 1; |