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=head1 NAME |
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Coro::SemaphoreSet - hash of semaphores. |
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=head1 SYNOPSIS |
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use Coro::SemaphoreSet; |
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$sig = new Coro::SemaphoreSet [initial value]; |
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$sig->down("semaphoreid"); # wait for signal |
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# ... some other "thread" |
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$sig->up("semaphoreid"); |
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=head1 DESCRIPTION |
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This module implements sets of counting semaphores (see |
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L<Coro::Semaphore>). It is nothing more than a hash with normal semaphores |
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as members, but is more efficiently managed. |
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This is useful if you want to allow parallel tasks to run in parallel but |
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not on the same problem. Just use a SemaphoreSet and lock on the problem |
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identifier. |
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=over 4 |
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=cut |
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|
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package Coro::SemaphoreSet; |
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no warnings qw(uninitialized); |
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|
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use Coro (); |
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$VERSION = 0.5; |
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=item new [inital count] |
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Creates a new sempahore set with the given initial lock count for each |
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individual semaphore. See L<Coro::Semaphore>. |
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=cut |
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|
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sub new { |
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bless [defined $_[1] ? $_[1] : 1], $_[0]; |
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} |
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=item $sem->down($id) |
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Decrement the counter, therefore "locking" the named semaphore. This |
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method waits until the semaphore is available if the counter is zero. |
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=cut |
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sub down { |
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my $sem = ($_[0][1]{$_[1]} ||= [$_[0][0]]); |
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while ($sem->[0] <= 0) { |
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push @{$sem->[1]}, $Coro::current; |
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Coro::schedule; |
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} |
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--$sem->[0]; |
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} |
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=item $sem->up($id) |
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Unlock the semaphore again. |
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=cut |
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sub up { |
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my $sem = $_[0][1]{$_[1]}; |
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if (++$sem->[0] > 0) { |
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(shift @{$sem->[1]})->ready if @{$sem->[1]}; |
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} |
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delete $_[0][1]{$_[1]} if $sem->[0] == $_[0][0]; |
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} |
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=item $sem->try |
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Try to C<down> the semaphore. Returns true when this was possible, |
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otherwise return false and leave the semaphore unchanged. |
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=cut |
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sub try { |
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my $sem = ($_[0][1]{$_[1]} ||= [$_[0][0]]); |
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if ($sem->[0] > 0) { |
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--$sem->[0]; |
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return 1; |
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} else { |
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return 0; |
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} |
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} |
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=item $sem->waiters($id) |
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In scalar context, returns the number of coroutines waiting for this |
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semaphore. |
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=cut |
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sub waiters { |
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@{$_[0][1]{$_[1]}}; |
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} |
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=item $guard = $sem->guard($id) |
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This method calls C<down> and then creates a guard object. When the guard |
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object is destroyed it automatically calls C<up>. |
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=cut |
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|
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sub guard { |
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&down; |
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# double indirection because bless works on the referenced |
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# object, not (only) on the reference itself. |
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bless [@_], Coro::SemaphoreSet::Guard::; |
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} |
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sub Coro::SemaphoreSet::Guard::DESTROY { |
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&up(@{$_[0]}); |
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} |
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1; |
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=back |
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=head1 AUTHOR |
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|
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Marc Lehmann <pcg@goof.com> |
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http://www.goof.com/pcg/marc/ |
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=cut |
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