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;

BEGIN { eval { require warnings } && warnings->unimport ("uninitialized") }

use Coro ();

$VERSION = 0.97;

=item new [inital count]

Creates a new sempahore 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 {
   my $sem = ($_[0][1]{$_[1]} ||= [$_[0][0]]);
   while ($sem->[0] <= 0) {
      push @{$sem->[1]}, $Coro::current;
      Coro::schedule;
   }
   --$sem->[0];
}

sub timed_down {
   require Coro::Timer;
   my $timeout = Coro::Timer::timeout($_[2]);

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

=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];
}

=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 {
   @{$_[0][1]{$_[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 <pcg@goof.com>
 http://www.goof.com/pcg/marc/

=cut

Revision:	1.24
Committed:	Fri May 14 13:25:09 2004 UTC (20 years ago) by pcg
Branch:	MAIN
Changes since 1.23:	+1 -1 lines
Log Message:	* empty log message *
#	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	pcg	1.20	BEGIN { eval { require warnings } && warnings->unimport ("uninitialized") }
34	root	1.4
35	root	1.1	use Coro ();
36
37	pcg	1.24	$VERSION = 0.97;
38	root	1.1
39			=item new [inital count]
40
41			Creates a new sempahore set with the given initial lock count for each
42			individual semaphore. See L<Coro::Semaphore>.
43
44			=cut
45
46			sub new {
47			bless [defined $_[1] ? $_[1] : 1], $_[0];
48			}
49
50			=item $sem->down($id)
51
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	1.8	=item $status = $sem->timed_down($id, $timeout)
56
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			my $sem = ($_[0][1]{$_[1]} \|\|= [$_[0][0]]);
64			while ($sem->[0] <= 0) {
65			push @{$sem->[1]}, $Coro::current;
66			Coro::schedule;
67			}
68			--$sem->[0];
69	root	1.8	}
70
71			sub timed_down {
72			require Coro::Timer;
73			my $timeout = Coro::Timer::timeout($_[2]);
74
75			my $sem = ($_[0][1]{$_[1]} \|\|= [$_[0][0]]);
76			while ($sem->[0] <= 0) {
77			push @{$sem->[1]}, $Coro::current;
78			Coro::schedule;
79	root	1.10	if ($timeout) {
80	root	1.11	# ugly as hell.
81			for (0..$#{$sem->[1]}) {
82			if ($sem->[1][$_] == $Coro::current) {
83			splice @{$sem->[1]}, $_, 1;
84	root	1.10	return;
85			}
86			}
87			die;
88			}
89	root	1.8	}
90			--$sem->[0];
91			return 1;
92	root	1.1	}
93
94			=item $sem->up($id)
95
96			Unlock the semaphore again.
97
98			=cut
99
100			sub up {
101			my $sem = $_[0][1]{$_[1]};
102			if (++$sem->[0] > 0) {
103			(shift @{$sem->[1]})->ready if @{$sem->[1]};
104			}
105			delete $_[0][1]{$_[1]} if $sem->[0] == $_[0][0];
106			}
107
108			=item $sem->try
109
110			Try to C<down> the semaphore. Returns true when this was possible,
111			otherwise return false and leave the semaphore unchanged.
112
113			=cut
114
115			sub try {
116			my $sem = ($_[0][1]{$_[1]} \|\|= [$_[0][0]]);
117			if ($sem->[0] > 0) {
118			--$sem->[0];
119			return 1;
120			} else {
121			return 0;
122			}
123			}
124
125			=item $sem->waiters($id)
126
127			In scalar context, returns the number of coroutines waiting for this
128			semaphore.
129
130			=cut
131
132			sub waiters {
133			@{$_[0][1]{$_[1]}};
134			}
135
136			=item $guard = $sem->guard($id)
137
138			This method calls C<down> and then creates a guard object. When the guard
139			object is destroyed it automatically calls C<up>.
140
141	root	1.9	=item $guard = $sem->timed_guard($id, $timeout)
142
143			Like C<guard>, but returns undef if semaphore couldn't be acquired within
144			$timeout seconds, otherwise the guard object.
145
146	root	1.1	=cut
147
148			sub guard {
149			&down;
150	root	1.10	bless [@_], Coro::SemaphoreSet::guard::;
151	root	1.9	}
152
153	root	1.15	sub timed_guard {
154	root	1.9	&timed_down
155	root	1.10	? bless [$_[0], $_[1]], Coro::SemaphoreSet::guard::
156	root	1.9	: ();
157	root	1.1	}
158
159	root	1.9	sub Coro::SemaphoreSet::guard::DESTROY {
160	root	1.1	&up(@{$_[0]});
161			}
162
163			1;
164
165			=back
166
167			=head1 AUTHOR
168
169			Marc Lehmann <pcg@goof.com>
170			http://www.goof.com/pcg/marc/
171
172			=cut
173