package Thread::Queue; use strict; use warnings; our $VERSION = '2.11'; use threads::shared 1.21; use Scalar::Util 1.10 qw(looks_like_number blessed reftype refaddr); # Carp errors from threads::shared calls should complain about caller our @CARP_NOT = ("threads::shared"); # Predeclarations for internal functions my ($validate_count, $validate_index); # Create a new queue possibly pre-populated with items sub new { my $class = shift; my @queue :shared = map { shared_clone($_) } @_; return bless(\@queue, $class); } # Add items to the tail of a queue sub enqueue { my $queue = shift; lock(@$queue); push(@$queue, map { shared_clone($_) } @_) and cond_signal(@$queue); } # Return a count of the number of items on a queue sub pending { my $queue = shift; lock(@$queue); return scalar(@$queue); } # Return 1 or more items from the head of a queue, blocking if needed sub dequeue { my $queue = shift; lock(@$queue); my $count = @_ ? $validate_count->(shift) : 1; # Wait for requisite number of items cond_wait(@$queue) until (@$queue >= $count); cond_signal(@$queue) if (@$queue > $count); # Return single item return shift(@$queue) if ($count == 1); # Return multiple items my @items; push(@items, shift(@$queue)) for (1..$count); return @items; } # Return items from the head of a queue with no blocking sub dequeue_nb { my $queue = shift; lock(@$queue); my $count = @_ ? $validate_count->(shift) : 1; # Return single item return shift(@$queue) if ($count == 1); # Return multiple items my @items; for (1..$count) { last if (! @$queue); push(@items, shift(@$queue)); } return @items; } # Return an item without removing it from a queue sub peek { my $queue = shift; lock(@$queue); my $index = @_ ? $validate_index->(shift) : 0; return $$queue[$index]; } # Insert items anywhere into a queue sub insert { my $queue = shift; lock(@$queue); my $index = $validate_index->(shift); return if (! @_); # Nothing to insert # Support negative indices if ($index < 0) { $index += @$queue; if ($index < 0) { $index = 0; } } # Dequeue items from $index onward my @tmp; while (@$queue > $index) { unshift(@tmp, pop(@$queue)) } # Add new items to the queue push(@$queue, map { shared_clone($_) } @_); # Add previous items back onto the queue push(@$queue, @tmp); # Soup's up cond_signal(@$queue); } # Remove items from anywhere in a queue sub extract { my $queue = shift; lock(@$queue); my $index = @_ ? $validate_index->(shift) : 0; my $count = @_ ? $validate_count->(shift) : 1; # Support negative indices if ($index < 0) { $index += @$queue; if ($index < 0) { $count += $index; return if ($count <= 0); # Beyond the head of the queue return $queue->dequeue_nb($count); # Extract from the head } } # Dequeue items from $index+$count onward my @tmp; while (@$queue > ($index+$count)) { unshift(@tmp, pop(@$queue)) } # Extract desired items my @items; unshift(@items, pop(@$queue)) while (@$queue > $index); # Add back any removed items push(@$queue, @tmp); # Return single item return $items[0] if ($count == 1); # Return multiple items return @items; } ### Internal Functions ### # Check value of the requested index $validate_index = sub { my $index = shift; if (! defined($index) || ! looks_like_number($index) || (int($index) != $index)) { require Carp; my ($method) = (caller(1))[3]; $method =~ s/Thread::Queue:://; $index = 'undef' if (! defined($index)); Carp::croak("Invalid 'index' argument ($index) to '$method' method"); } return $index; }; # Check value of the requested count $validate_count = sub { my $count = shift; if (! defined($count) || ! looks_like_number($count) || (int($count) != $count) || ($count < 1)) { require Carp; my ($method) = (caller(1))[3]; $method =~ s/Thread::Queue:://; $count = 'undef' if (! defined($count)); Carp::croak("Invalid 'count' argument ($count) to '$method' method"); } return $count; }; 1; =head1 NAME Thread::Queue - Thread-safe queues =head1 VERSION This document describes Thread::Queue version 2.11 =head1 SYNOPSIS use strict; use warnings; use threads; use Thread::Queue; my $q = Thread::Queue->new(); # A new empty queue # Worker thread my $thr = threads->create(sub { while (my $item = $q->dequeue()) { # Do work on $item } })->detach(); # Send work to the thread $q->enqueue($item1, ...); # Count of items in the queue my $left = $q->pending(); # Non-blocking dequeue if (defined(my $item = $q->dequeue_nb())) { # Work on $item } # Get the second item in the queue without dequeuing anything my $item = $q->peek(1); # Insert two items into the queue just behind the head $q->insert(1, $item1, $item2); # Extract the last two items on the queue my ($item1, $item2) = $q->extract(-2, 2); =head1 DESCRIPTION This module provides thread-safe FIFO queues that can be accessed safely by any number of threads. Any data types supported by L can be passed via queues: =over =item Ordinary scalars =item Array refs =item Hash refs =item Scalar refs =item Objects based on the above =back Ordinary scalars are added to queues as they are. If not already thread-shared, the other complex data types will be cloned (recursively, if needed, and including any Cings and read-only settings) into thread-shared structures before being placed onto a queue. For example, the following would cause L to create a empty, shared array reference via C<&shared([])>, copy the elements 'foo', 'bar' and 'baz' from C<@ary> into it, and then place that shared reference onto the queue: my @ary = qw/foo bar baz/; $q->enqueue(\@ary); However, for the following, the items are already shared, so their references are added directly to the queue, and no cloning takes place: my @ary :shared = qw/foo bar baz/; $q->enqueue(\@ary); my $obj = &shared({}); $$obj{'foo'} = 'bar'; $$obj{'qux'} = 99; bless($obj, 'My::Class'); $q->enqueue($obj); See L for caveats related to passing objects via queues. =head1 QUEUE CREATION =over =item ->new() Creates a new empty queue. =item ->new(LIST) Creates a new queue pre-populated with the provided list of items. =back =head1 BASIC METHODS The following methods deal with queues on a FIFO basis. =over =item ->enqueue(LIST) Adds a list of items onto the end of the queue. =item ->dequeue() =item ->dequeue(COUNT) Removes the requested number of items (default is 1) from the head of the queue, and returns them. If the queue contains fewer than the requested number of items, then the thread will be blocked until the requisite number of items are available (i.e., until other threads more items). =item ->dequeue_nb() =item ->dequeue_nb(COUNT) Removes the requested number of items (default is 1) from the head of the queue, and returns them. If the queue contains fewer than the requested number of items, then it immediately (i.e., non-blocking) returns whatever items there are on the queue. If the queue is empty, then C is returned. =item ->pending() Returns the number of items still in the queue. =back =head1 ADVANCED METHODS The following methods can be used to manipulate items anywhere in a queue. To prevent the contents of a queue from being modified by another thread while it is being examined and/or changed, L the queue inside a local block: { lock($q); # Keep other threads from changing the queue's contents my $item = $q->peek(); if ($item ...) { ... } } # Queue is now unlocked =over =item ->peek() =item ->peek(INDEX) Returns an item from the queue without dequeuing anything. Defaults to the the head of queue (at index position 0) if no index is specified. Negative index values are supported as with L (i.e., -1 is the end of the queue, -2 is next to last, and so on). If no items exists at the specified index (i.e., the queue is empty, or the index is beyond the number of items on the queue), then C is returned. Remember, the returned item is not removed from the queue, so manipulating a Ced at reference affects the item on the queue. =item ->insert(INDEX, LIST) Adds the list of items to the queue at the specified index position (0 is the head of the list). Any existing items at and beyond that position are pushed back past the newly added items: $q->enqueue(1, 2, 3, 4); $q->insert(1, qw/foo bar/); # Queue now contains: 1, foo, bar, 2, 3, 4 Specifying an index position greater than the number of items in the queue just adds the list to the end. Negative index positions are supported: $q->enqueue(1, 2, 3, 4); $q->insert(-2, qw/foo bar/); # Queue now contains: 1, 2, foo, bar, 3, 4 Specifying a negative index position greater than the number of items in the queue adds the list to the head of the queue. =item ->extract() =item ->extract(INDEX) =item ->extract(INDEX, COUNT) Removes and returns the specified number of items (defaults to 1) from the specified index position in the queue (0 is the head of the queue). When called with no arguments, C operates the same as C. This method is non-blocking, and will return only as many items as are available to fulfill the request: $q->enqueue(1, 2, 3, 4); my $item = $q->extract(2) # Returns 3 # Queue now contains: 1, 2, 4 my @items = $q->extract(1, 3) # Returns (2, 4) # Queue now contains: 1 Specifying an index position greater than the number of items in the queue results in C or an empty list being returned. $q->enqueue('foo'); my $nada = $q->extract(3) # Returns undef my @nada = $q->extract(1, 3) # Returns () Negative index positions are supported. Specifying a negative index position greater than the number of items in the queue may return items from the head of the queue (similar to C) if the count overlaps the head of the queue from the specified position (i.e. if queue size + index + count is greater than zero): $q->enqueue(qw/foo bar baz/); my @nada = $q->extract(-6, 2); # Returns () - (3+(-6)+2) <= 0 my @some = $q->extract(-6, 4); # Returns (foo) - (3+(-6)+4) > 0 # Queue now contains: bar, baz my @rest = $q->extract(-3, 4); # Returns (bar, baz) - (2+(-3)+4) > 0 =back =head1 NOTES Queues created by L can be used in both threaded and non-threaded applications. =head1 LIMITATIONS Passing objects on queues may not work if the objects' classes do not support sharing. See L for more. Passing array/hash refs that contain objects may not work for Perl prior to 5.10.0. =head1 SEE ALSO Thread::Queue Discussion Forum on CPAN: L Annotated POD for Thread::Queue: L Source repository: L L, L =head1 MAINTAINER Jerry D. Hedden, Sjdhedden AT cpan DOT orgE> =head1 LICENSE This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself. =cut