Coro/Coro/SemaphoreSet.pm

=head1 NAME

Coro::SemaphoreSet - hash of semaphores.

=head1 SYNOPSIS

 use Coro::SemaphoreSet;

 $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.

=over 4

=cut

package Coro::SemaphoreSet;

no warnings;

use Coro ();

$VERSION = 4.802;

=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 $sem->down ($id)

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

=item $status = $sem->timed_down ($id, $timeout)

Like C<down>, but returns false if semaphore couldn't be acquired within
$timeout seconds, otherwise true.

=cut

sub down {
   while () {
      my $sem = ($_[0][1]{$_[1]} ||= [$_[0][0]]);

      if ($sem->[0] > 0) {
         --$sem->[0];
         return 1;
      }

      push @{$sem->[1]}, $Coro::current;
      &Coro::schedule;
   }
}

sub 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 $sem->up ($id)

Unlock the semaphore again.

=cut

sub up {
   my $sem = $_[0][1]{$_[1]};

   if (++$sem->[0] > 0) {
      (shift @{$sem->[1]})->ready if @{$sem->[1]};
   }

   delete $_[0][1]{$_[1]} if $sem->[0] == $_[0][0] && !@{$sem->[1] || []};
}

=item $sem->try

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

=cut

sub try {
   my $sem = ($_[0][1]{$_[1]} ||= [$_[0][0]]);
   if ($sem->[0] > 0) {
      --$sem->[0];
      return 1;
   } else {
      return 0;
   }
}

=item $sem->waiters ($id)

In scalar context, returns the number of coroutines waiting for this
semaphore.

=cut

sub waiters {
   my $sem = $_[0][1]{$_[1]}
      or return;
   @{ $_[0][1]{$_[1]}[1] || []}
}

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

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

=item $guard = $sem->timed_guard ($id, $timeout)

Like C<guard>, but returns undef if semaphore couldn't be acquired within
$timeout seconds, otherwise the guard object.

=cut

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

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

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

1;

=back

=head1 AUTHOR

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

=cut

Revision:	1.60
Committed:	Thu Oct 30 09:57:01 2008 UTC (15 years, 7 months ago) by root
Branch:	MAIN
CVS Tags:	rel-4_802
Changes since 1.59:	+1 -1 lines
Log Message:	4.802
#	User	Rev	Content
1	root	1.1	=head1 NAME
2
3			Coro::SemaphoreSet - hash of semaphores.
4
5			=head1 SYNOPSIS
6
7			use Coro::SemaphoreSet;
8
9			$sig = new Coro::SemaphoreSet [initial value];
10
11			$sig->down("semaphoreid"); # wait for signal
12
13			# ... some other "thread"
14
15			$sig->up("semaphoreid");
16
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			=over 4
28
29			=cut
30
31			package Coro::SemaphoreSet;
32
33	root	1.48	no warnings;
34	root	1.4
35	root	1.1	use Coro ();
36
37	root	1.60	$VERSION = 4.802;
38	root	1.1
39			=item new [inital count]
40
41	root	1.36	Creates a new semaphore set with the given initial lock count for each
42	root	1.1	individual semaphore. See L<Coro::Semaphore>.
43
44			=cut
45
46			sub new {
47			bless [defined $_[1] ? $_[1] : 1], $_[0];
48			}
49
50	root	1.31	=item $sem->down ($id)
51	root	1.1
52			Decrement the counter, therefore "locking" the named semaphore. This
53			method waits until the semaphore is available if the counter is zero.
54
55	root	1.31	=item $status = $sem->timed_down ($id, $timeout)
56	root	1.8
57			Like C<down>, but returns false if semaphore couldn't be acquired within
58			$timeout seconds, otherwise true.
59
60	root	1.1	=cut
61
62			sub down {
63	root	1.29	while () {
64			my $sem = ($_[0][1]{$_[1]} \|\|= [$_[0][0]]);
65	root	1.31
66	root	1.30	if ($sem->[0] > 0) {
67			--$sem->[0];
68	root	1.31	return 1;
69	root	1.30	}
70	root	1.31
71	root	1.1	push @{$sem->[1]}, $Coro::current;
72	root	1.45	&Coro::schedule;
73	root	1.1	}
74	root	1.8	}
75
76			sub timed_down {
77			require Coro::Timer;
78	root	1.31	my $timeout = Coro::Timer::timeout ($_[2]);
79
80			while () {
81			my $sem = ($_[0][1]{$_[1]} \|\|= [$_[0][0]]);
82
83			if ($sem->[0] > 0) {
84			--$sem->[0];
85			return 1;
86			}
87	root	1.8
88	root	1.10	if ($timeout) {
89	root	1.11	# ugly as hell.
90			for (0..$#{$sem->[1]}) {
91			if ($sem->[1][$_] == $Coro::current) {
92			splice @{$sem->[1]}, $_, 1;
93	root	1.31	return 0;
94	root	1.10	}
95			}
96			die;
97			}
98	root	1.31
99			push @{$sem->[1]}, $Coro::current;
100	root	1.45	&Coro::schedule;
101	root	1.8	}
102	root	1.1	}
103
104	root	1.31	=item $sem->up ($id)
105	root	1.1
106			Unlock the semaphore again.
107
108			=cut
109
110			sub up {
111			my $sem = $_[0][1]{$_[1]};
112	root	1.35
113	root	1.1	if (++$sem->[0] > 0) {
114			(shift @{$sem->[1]})->ready if @{$sem->[1]};
115			}
116	root	1.35
117			delete $_[0][1]{$_[1]} if $sem->[0] == $_[0][0] && !@{$sem->[1] \|\| []};
118	root	1.1	}
119
120			=item $sem->try
121
122			Try to C<down> the semaphore. Returns true when this was possible,
123			otherwise return false and leave the semaphore unchanged.
124
125			=cut
126
127			sub try {
128			my $sem = ($_[0][1]{$_[1]} \|\|= [$_[0][0]]);
129			if ($sem->[0] > 0) {
130			--$sem->[0];
131			return 1;
132			} else {
133			return 0;
134			}
135			}
136
137	root	1.31	=item $sem->waiters ($id)
138	root	1.1
139			In scalar context, returns the number of coroutines waiting for this
140			semaphore.
141
142			=cut
143
144			sub waiters {
145	root	1.33	my $sem = $_[0][1]{$_[1]}
146	root	1.32	or return;
147	root	1.33	@{ $_[0][1]{$_[1]}[1] \|\| []}
148	root	1.1	}
149
150	root	1.31	=item $guard = $sem->guard ($id)
151	root	1.1
152			This method calls C<down> and then creates a guard object. When the guard
153			object is destroyed it automatically calls C<up>.
154
155	root	1.31	=item $guard = $sem->timed_guard ($id, $timeout)
156	root	1.9
157			Like C<guard>, but returns undef if semaphore couldn't be acquired within
158			$timeout seconds, otherwise the guard object.
159
160	root	1.1	=cut
161
162			sub guard {
163			&down;
164	root	1.10	bless [@_], Coro::SemaphoreSet::guard::;
165	root	1.9	}
166
167	root	1.15	sub timed_guard {
168	root	1.9	&timed_down
169	root	1.10	? bless [$_[0], $_[1]], Coro::SemaphoreSet::guard::
170	root	1.9	: ();
171	root	1.1	}
172
173	root	1.9	sub Coro::SemaphoreSet::guard::DESTROY {
174	root	1.1	&up(@{$_[0]});
175			}
176
177			1;
178
179			=back
180
181			=head1 AUTHOR
182
183	root	1.28	Marc Lehmann <schmorp@schmorp.de>
184	root	1.26	http://home.schmorp.de/
185	root	1.1
186			=cut
187