ext/Thread/Queue.pmx

package Thread::Queue;
use Thread qw(cond_wait cond_broadcast);

use vars qw($VERSION);
$VERSION = '1.00';

=head1 NAME

Thread::Queue - thread-safe queues (5.005-threads)

=head1 CAVEAT

This Perl installation is using the old unsupported "5.005 threads".
Use of the old threads model is discouraged.

For the whole story about the development of threads in Perl, and why
you should B<not> be using "old threads" unless you know what you're
doing, see the CAVEAT of the C<Thread> module.

=head1 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

=head1 DESCRIPTION

A queue, as implemented by C<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)

=head1 FUNCTIONS AND METHODS

=over 8

=item new

The C<new> function creates a new empty queue.

=item enqueue LIST

The C<enqueue> method adds a list of scalars on to the end of the queue.
The queue will grow as needed to accomodate the list.

=item dequeue

The C<dequeue> method removes a scalar from the head of the queue and
returns it. If the queue is currently empty, C<dequeue> will block the
thread until another thread C<enqueue>s a scalar.

=item dequeue_nb

The C<dequeue_nb> method, like the C<dequeue> method, removes a scalar from
the head of the queue and returns it. Unlike C<dequeue>, though,
C<dequeue_nb> won't block if the queue is empty, instead returning
C<undef>.

=item pending

The C<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)

=back

=head1 SEE ALSO

L<Thread>
  
=cut

sub new {
    my $class = shift;
    return bless [@_], $class;
}

sub dequeue : locked : method {
    my $q = shift;
    cond_wait $q until @$q;
    return shift @$q;
}

sub dequeue_nb : locked : method {
  my $q = shift;
  if (@$q) {
    return shift @$q;
  } else {
    return undef;
  }
}

sub enqueue : locked : method {
    my $q = shift;
    push(@$q, @_) and cond_broadcast $q;
}

sub pending : locked : method {
  my $q = shift;
  return scalar(@$q);
}

1;
Revision:	1.1
Committed:	Thu Jun 30 14:27:05 2005 UTC (21 years, 3 months ago) by root
Branch:	MAIN
CVS Tags:	PERL-5-8-7, HEAD
Branch point for:	PERL
Log Message:	* empty log message *
#	User	Rev	Content
1	root	1.1	package Thread::Queue;
2			use Thread qw(cond_wait cond_broadcast);
3
4			use vars qw($VERSION);
5			$VERSION = '1.00';
6
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;