# You may distribute under the terms of either the GNU General Public License # or the Artistic License (the same terms as Perl itself) # # (C) Paul Evans, 2019 -- leonerd@leonerd.org.uk package Future::Queue; use v5.10; use strict; use warnings; our $VERSION = '0.48'; =head1 NAME C - a FIFO queue of values that uses Ls =head1 SYNOPSIS use Future::Queue; my $queue = Future::Queue->new; my $f = repeat { $queue->shift->then(sub { my ( $thing ) = @_; ... }); }; $queue->push( "a thing" ); =head1 DESCRIPTION Objects in this class provide a simple FIFO queue the stores arbitrary perl values. Values may be added into the queue using the L method, and retrieved from it using the L method. Values may be stored within the queue object for C to retrieve later, or if the queue is empty then the future that C returns will be completed once an item becomes available. =cut =head1 CONSTRUCTOR =cut =head2 new $queue = Future::Queue->new Returns a new C instance. =cut sub new { my $class = shift; return bless { items => [], waiters => [], }, $class; } =head2 push $queue->push( $item ) Adds a new item into the queue. If the queue was previously empty and there is at least one C future waiting, then the next one will be completed by this method. =cut sub push :method { my $self = shift; my ( $item ) = @_; push @{ $self->{items} }, $item; ( shift @{ $self->{waiters} } )->done if @{ $self->{waiters} }; } =head2 shift $item = $queue->shift->get Returns a C that will yield the next item from the queue. If there is already an item then this will be taken and the returned future will be immediate. If not, then the returned future will be pending, and the next C method will complete it. =cut sub shift :method { my $self = shift; if( @{ $self->{items} } ) { return Future->done( shift @{ $self->{items} } ); } push @{ $self->{waiters} }, my $f = Future->new; return $f->then(sub { return Future->done( shift @{ $self->{items} } ); }); } =head1 AUTHOR Paul Evans =cut 0x55AA;