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package Thread::Queue; |
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use Thread qw(cond_wait cond_broadcast); |
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|
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use vars qw($VERSION); |
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$VERSION = '1.00'; |
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|
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=head1 NAME |
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|
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Thread::Queue - thread-safe queues (5.005-threads) |
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|
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=head1 CAVEAT |
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|
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This Perl installation is using the old unsupported "5.005 threads". |
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Use of the old threads model is discouraged. |
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|
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For the whole story about the development of threads in Perl, and why |
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you should B<not> be using "old threads" unless you know what you're |
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doing, see the CAVEAT of the C<Thread> module. |
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|
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=head1 SYNOPSIS |
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|
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use Thread::Queue; |
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my $q = new Thread::Queue; |
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$q->enqueue("foo", "bar"); |
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my $foo = $q->dequeue; # The "bar" is still in the queue. |
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my $foo = $q->dequeue_nb; # returns "bar", or undef if the queue was |
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# empty |
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my $left = $q->pending; # returns the number of items still in the queue |
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|
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=head1 DESCRIPTION |
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|
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A queue, as implemented by C<Thread::Queue> is a thread-safe data structure |
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much like a list. Any number of threads can safely add elements to the end |
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of the list, or remove elements from the head of the list. (Queues don't |
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permit adding or removing elements from the middle of the list) |
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|
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=head1 FUNCTIONS AND METHODS |
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|
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=over 8 |
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|
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=item new |
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|
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The C<new> function creates a new empty queue. |
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|
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=item enqueue LIST |
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|
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The C<enqueue> method adds a list of scalars on to the end of the queue. |
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The queue will grow as needed to accomodate the list. |
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|
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=item dequeue |
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|
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The C<dequeue> method removes a scalar from the head of the queue and |
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returns it. If the queue is currently empty, C<dequeue> will block the |
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thread until another thread C<enqueue>s a scalar. |
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|
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=item dequeue_nb |
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|
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The C<dequeue_nb> method, like the C<dequeue> method, removes a scalar from |
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the head of the queue and returns it. Unlike C<dequeue>, though, |
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C<dequeue_nb> won't block if the queue is empty, instead returning |
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C<undef>. |
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|
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=item pending |
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|
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The C<pending> method returns the number of items still in the queue. (If |
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there can be multiple readers on the queue it's best to lock the queue |
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before checking to make sure that it stays in a consistent state) |
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|
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=back |
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|
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=head1 SEE ALSO |
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|
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L<Thread> |
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|
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=cut |
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|
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sub new { |
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my $class = shift; |
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return bless [@_], $class; |
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} |
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|
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sub dequeue : locked : method { |
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my $q = shift; |
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cond_wait $q until @$q; |
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return shift @$q; |
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} |
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|
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sub dequeue_nb : locked : method { |
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my $q = shift; |
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if (@$q) { |
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return shift @$q; |
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} else { |
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return undef; |
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} |
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} |
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|
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sub enqueue : locked : method { |
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my $q = shift; |
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push(@$q, @_) and cond_broadcast $q; |
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} |
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|
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sub pending : locked : method { |
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my $q = shift; |
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return scalar(@$q); |
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} |
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|
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1; |
