Coro/Coro/SemaphoreSet.pm

=head1 NAME

Coro::SemaphoreSet - efficient set of counting semaphores

=head1 SYNOPSIS

 use Coro;

 $sig = new Coro::SemaphoreSet [initial value];

 $sig->down ("semaphoreid"); # wait for signal

 # ... some other "thread"

 $sig->up ("semaphoreid");

=head1 DESCRIPTION

This module implements sets of counting semaphores (see
L<Coro::Semaphore>). It is nothing more than a hash with normal semaphores
as members, but is more efficiently managed.

This is useful if you want to allow parallel tasks to run in parallel but
not on the same problem. Just use a SemaphoreSet and lock on the problem
identifier.

You don't have to load C<Coro::SemaphoreSet> manually, it will be loaded 
automatically when you C<use Coro> and call the C<new> constructor. 

=over 4

=cut

package Coro::SemaphoreSet;

use common::sense;

our $VERSION = 6.03;

use Coro::Semaphore ();

=item new [inital count]

Creates a new semaphore set with the given initial lock count for each
individual semaphore. See L<Coro::Semaphore>.

=cut

sub new {
   bless [defined $_[1] ? $_[1] : 1], $_[0]
}

=item $semset->down ($id)

Decrement the counter, therefore "locking" the named semaphore. This
method waits until the semaphore is available if the counter is zero.

=cut

sub down {
   # Coro::Semaphore::down increases the refcount, which we check in _may_delete
   Coro::Semaphore::down ($_[0][1]{$_[1]} ||= Coro::Semaphore::_alloc $_[0][0]);
}

#ub timed_down {
#  require Coro::Timer;
#  my $timeout = Coro::Timer::timeout ($_[2]);
#
#  while () {
#     my $sem = ($_[0][1]{$_[1]} ||= [$_[0][0]]);
#
#     if ($sem->[0] > 0) {
#        --$sem->[0];
#        return 1;
#     }
#
#     if ($timeout) {
#        # ugly as hell.
#        for (0..$#{$sem->[1]}) {
#           if ($sem->[1][$_] == $Coro::current) {
#              splice @{$sem->[1]}, $_, 1;
#              return 0;
#           }
#        }
#        die;
#     }
#
#     push @{$sem->[1]}, $Coro::current;
#     &Coro::schedule;
#  }
#

=item $semset->up ($id)

Unlock the semaphore again. If the semaphore reaches the default count for
this set and has no waiters, the space allocated for it will be freed.

=cut

sub up {
   my ($self, $id) = @_;

   my $sem = $self->[1]{$id} ||= Coro::Semaphore::_alloc $self->[0];

   Coro::Semaphore::up $sem;

   delete $self->[1]{$id}
      if _may_delete $sem, $self->[0], 1;
}

=item $semset->try ($id)

Try to C<down> the semaphore. Returns true when this was possible,
otherwise return false and leave the semaphore unchanged.

=cut

sub try {
   Coro::Semaphore::try ($_[0][1]{$_[1]} || return $_[0][0] > 0)
}

=item $semset->count ($id)

Return the current semaphore count for the specified semaphore.

=cut

sub count {
   Coro::Semaphore::count ($_[0][1]{$_[1]} || return $_[0][0]);
}

=item $semset->waiters ($id)

Returns the number (in scalar context) or list (in list context) of
waiters waiting on the specified semaphore.

=cut

sub waiters {
   Coro::Semaphore::waiters ($_[0][1]{$_[1]} || return);
}

=item $semset->wait ($id)

Same as Coro::Semaphore::wait on the specified semaphore.

=cut

sub wait {
   Coro::Semaphore::wait ($_[0][1]{$_[1]} || return);
}

=item $guard = $semset->guard ($id)

This method calls C<down> and then creates a guard object. When the guard
object is destroyed it automatically calls C<up>.

=cut

sub guard {
   &down;
   bless [@_], Coro::SemaphoreSet::guard::
}

#ub timed_guard {
#  &timed_down
#     ? bless [$_[0], $_[1]], Coro::SemaphoreSet::guard::
#     : ();
#

sub Coro::SemaphoreSet::guard::DESTROY {
   up @{$_[0]};
}

=item $semaphore = $semset->sem ($id)

This SemaphoreSet version is based on Coro::Semaphore's. This function
creates (if necessary) the underlying Coro::Semaphore object and returns
it. You may legally call any Coro::Semaphore method on it, but note that
calling C<< $semset->up >> can invalidate the returned semaphore.

=cut

sub sem {
   bless +($_[0][1]{$_[1]} ||= Coro::Semaphore::_alloc $_[0][0]),
         Coro::Semaphore::;
}

1;

=back

=head1 AUTHOR

 Marc Lehmann <schmorp@schmorp.de>
 http://home.schmorp.de/

=cut

Revision:	1.105
Committed:	Wed Aug 3 09:43:04 2011 UTC (12 years, 10 months ago) by root
Branch:	MAIN
CVS Tags:	rel-6_03
Changes since 1.104:	+1 -1 lines
Log Message:	* empty log message *
#	User	Rev	Content
1	root	1.1	=head1 NAME
2
3	root	1.70	Coro::SemaphoreSet - efficient set of counting semaphores
4	root	1.1
5			=head1 SYNOPSIS
6
7	root	1.97	use Coro;
8	root	1.1
9			$sig = new Coro::SemaphoreSet [initial value];
10
11	root	1.73	$sig->down ("semaphoreid"); # wait for signal
12	root	1.1
13			# ... some other "thread"
14
15	root	1.73	$sig->up ("semaphoreid");
16	root	1.1
17			=head1 DESCRIPTION
18
19			This module implements sets of counting semaphores (see
20			L<Coro::Semaphore>). It is nothing more than a hash with normal semaphores
21			as members, but is more efficiently managed.
22
23			This is useful if you want to allow parallel tasks to run in parallel but
24			not on the same problem. Just use a SemaphoreSet and lock on the problem
25			identifier.
26
27	root	1.96	You don't have to load C<Coro::SemaphoreSet> manually, it will be loaded
28			automatically when you C<use Coro> and call the C<new> constructor.
29
30	root	1.1	=over 4
31
32			=cut
33
34			package Coro::SemaphoreSet;
35
36	root	1.89	use common::sense;
37	root	1.4
38	root	1.105	our $VERSION = 6.03;
39	root	1.1
40	root	1.68	use Coro::Semaphore ();
41	root	1.1
42			=item new [inital count]
43
44	root	1.36	Creates a new semaphore set with the given initial lock count for each
45	root	1.1	individual semaphore. See L<Coro::Semaphore>.
46
47			=cut
48
49			sub new {
50	root	1.74	bless [defined $_[1] ? $_[1] : 1], $_[0]
51	root	1.1	}
52
53	root	1.68	=item $semset->down ($id)
54	root	1.1
55			Decrement the counter, therefore "locking" the named semaphore. This
56			method waits until the semaphore is available if the counter is zero.
57
58			=cut
59
60			sub down {
61	root	1.77	# Coro::Semaphore::down increases the refcount, which we check in _may_delete
62	root	1.76	Coro::Semaphore::down ($_[0][1]{$_[1]} \|\|= Coro::Semaphore::_alloc $_[0][0]);
63	root	1.1	}
64
65	root	1.68	#ub timed_down {
66			# require Coro::Timer;
67			# my $timeout = Coro::Timer::timeout ($_[2]);
68			#
69			# while () {
70			# my $sem = ($_[0][1]{$_[1]} \|\|= [$_[0][0]]);
71			#
72			# if ($sem->[0] > 0) {
73			# --$sem->[0];
74			# return 1;
75			# }
76			#
77			# if ($timeout) {
78			# # ugly as hell.
79			# for (0..$#{$sem->[1]}) {
80			# if ($sem->[1][$_] == $Coro::current) {
81			# splice @{$sem->[1]}, $_, 1;
82			# return 0;
83			# }
84			# }
85			# die;
86			# }
87			#
88			# push @{$sem->[1]}, $Coro::current;
89			# &Coro::schedule;
90			# }
91			#
92
93			=item $semset->up ($id)
94
95	root	1.77	Unlock the semaphore again. If the semaphore reaches the default count for
96			this set and has no waiters, the space allocated for it will be freed.
97	root	1.1
98			=cut
99
100			sub up {
101	root	1.68	my ($self, $id) = @_;
102
103	root	1.75	my $sem = $self->[1]{$id} \|\|= Coro::Semaphore::_alloc $self->[0];
104	root	1.68
105	root	1.75	Coro::Semaphore::up $sem;
106	root	1.68
107	root	1.75	delete $self->[1]{$id}
108	root	1.77	if _may_delete $sem, $self->[0], 1;
109	root	1.1	}
110
111	root	1.73	=item $semset->try ($id)
112	root	1.1
113			Try to C<down> the semaphore. Returns true when this was possible,
114			otherwise return false and leave the semaphore unchanged.
115
116			=cut
117
118			sub try {
119	root	1.75	Coro::Semaphore::try ($_[0][1]{$_[1]} \|\| return $_[0][0] > 0)
120	root	1.73	}
121
122			=item $semset->count ($id)
123
124			Return the current semaphore count for the specified semaphore.
125
126			=cut
127
128			sub count {
129	root	1.75	Coro::Semaphore::count ($_[0][1]{$_[1]} \|\| return $_[0][0]);
130			}
131
132			=item $semset->waiters ($id)
133
134			Returns the number (in scalar context) or list (in list context) of
135			waiters waiting on the specified semaphore.
136
137			=cut
138
139			sub waiters {
140			Coro::Semaphore::waiters ($_[0][1]{$_[1]} \|\| return);
141	root	1.73	}
142
143			=item $semset->wait ($id)
144
145			Same as Coro::Semaphore::wait on the specified semaphore.
146
147			=cut
148
149			sub wait {
150	root	1.86	Coro::Semaphore::wait ($_[0][1]{$_[1]} \|\| return);
151	root	1.1	}
152
153	root	1.68	=item $guard = $semset->guard ($id)
154	root	1.1
155			This method calls C<down> and then creates a guard object. When the guard
156			object is destroyed it automatically calls C<up>.
157
158			=cut
159
160			sub guard {
161			&down;
162	root	1.79	bless [@_], Coro::SemaphoreSet::guard::
163	root	1.9	}
164
165	root	1.68	#ub timed_guard {
166			# &timed_down
167			# ? bless [$_[0], $_[1]], Coro::SemaphoreSet::guard::
168			# : ();
169			#
170
171			sub Coro::SemaphoreSet::guard::DESTROY {
172			up @{$_[0]};
173	root	1.1	}
174
175	root	1.68	=item $semaphore = $semset->sem ($id)
176
177			This SemaphoreSet version is based on Coro::Semaphore's. This function
178			creates (if necessary) the underlying Coro::Semaphore object and returns
179			it. You may legally call any Coro::Semaphore method on it, but note that
180			calling C<< $semset->up >> can invalidate the returned semaphore.
181
182			=cut
183
184			sub sem {
185	root	1.75	bless +($_[0][1]{$_[1]} \|\|= Coro::Semaphore::_alloc $_[0][0]),
186			Coro::Semaphore::;
187	root	1.1	}
188
189			1;
190
191			=back
192
193			=head1 AUTHOR
194
195	root	1.28	Marc Lehmann <schmorp@schmorp.de>
196	root	1.26	http://home.schmorp.de/
197	root	1.1
198			=cut
199