lib/Thread/Queue.pm

package Thread::Queue;

use threads::shared;
use strict;

our $VERSION = '2.00';

=head1 NAME

Thread::Queue - thread-safe queues

=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 accommodate 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.

=back

=head1 SEE ALSO

L<threads>, L<threads::shared>

=cut

sub new {
    my $class = shift;
    my @q : shared = @_;
    return bless \@q, $class;
}

sub dequeue  {
    my $q = shift;
    lock(@$q);
    cond_wait @$q until @$q;
    cond_signal @$q if @$q > 1;
    return shift @$q;
}

sub dequeue_nb {
    my $q = shift;
    lock(@$q);
    return shift @$q;
}

sub enqueue {
    my $q = shift;
    lock(@$q);
    push @$q, @_  and cond_signal @$q;
}

sub pending  {
    my $q = shift;
    lock(@$q);
    return scalar(@$q);
}

1;


Revision:	1.1
Committed:	Thu Jun 30 14:27:16 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
3			use threads::shared;
4			use strict;
5
6			our $VERSION = '2.00';
7
8			=head1 NAME
9
10			Thread::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
23			A queue, as implemented by C<Thread::Queue> is a thread-safe
24			data structure much like a list. Any number of threads can safely
25			add elements to the end of the list, or remove elements from the head
26			of the list. (Queues don't permit adding or removing elements from
27			the middle of the list).
28
29			=head1 FUNCTIONS AND METHODS
30
31			=over 8
32
33			=item new
34
35			The C<new> function creates a new empty queue.
36
37			=item enqueue LIST
38
39			The C<enqueue> method adds a list of scalars on to the end of the queue.
40			The queue will grow as needed to accommodate the list.
41
42			=item dequeue
43
44			The C<dequeue> method removes a scalar from the head of the queue and
45			returns it. If the queue is currently empty, C<dequeue> will block the
46			thread until another thread C<enqueue>s a scalar.
47
48			=item dequeue_nb
49
50			The C<dequeue_nb> method, like the C<dequeue> method, removes a scalar from
51			the head of the queue and returns it. Unlike C<dequeue>, though,
52			C<dequeue_nb> won't block if the queue is empty, instead returning
53			C<undef>.
54
55			=item pending
56
57			The C<pending> method returns the number of items still in the queue.
58
59			=back
60
61			=head1 SEE ALSO
62
63			L<threads>, L<threads::shared>
64
65			=cut
66
67			sub new {
68			my $class = shift;
69			my @q : shared = @_;
70			return bless \@q, $class;
71			}
72
73			sub 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
81			sub dequeue_nb {
82			my $q = shift;
83			lock(@$q);
84			return shift @$q;
85			}
86
87			sub enqueue {
88			my $q = shift;
89			lock(@$q);
90			push @$q, @_ and cond_signal @$q;
91			}
92
93			sub pending {
94			my $q = shift;
95			lock(@$q);
96			return scalar(@$q);
97			}
98
99			1;
100
101