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=head1 NAME |
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Coro::SemaphoreSet - efficient set of counting semaphores |
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=head1 SYNOPSIS |
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use Coro; |
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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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You don't have to load C<Coro::SemaphoreSet> manually, it will be loaded |
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automatically when you C<use Coro> and call the C<new> constructor. |
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=over 4 |
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=cut |
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package Coro::SemaphoreSet; |
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use common::sense; |
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our $VERSION = 6.57; |
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use Coro::Semaphore (); |
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=item new [initial count] |
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Creates a new semaphore 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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sub new { |
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bless [defined $_[1] ? $_[1] : 1], $_[0] |
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} |
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=item $semset->down ($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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# Coro::Semaphore::down increases the refcount, which we check in _may_delete |
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Coro::Semaphore::down ($_[0][1]{$_[1]} ||= Coro::Semaphore::_alloc $_[0][0]); |
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} |
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#ub timed_down { |
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# require Coro::Timer; |
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# my $timeout = Coro::Timer::timeout ($_[2]); |
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# |
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# while () { |
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# my $sem = ($_[0][1]{$_[1]} ||= [$_[0][0]]); |
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# |
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# if ($sem->[0] > 0) { |
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# --$sem->[0]; |
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# return 1; |
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# } |
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# |
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# if ($timeout) { |
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# # ugly as hell. |
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# for (0..$#{$sem->[1]}) { |
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# if ($sem->[1][$_] == $Coro::current) { |
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# splice @{$sem->[1]}, $_, 1; |
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# return 0; |
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# } |
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# } |
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# die; |
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# } |
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# |
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# push @{$sem->[1]}, $Coro::current; |
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# &Coro::schedule; |
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# } |
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# |
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=item $semset->up ($id) |
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Unlock the semaphore again. If the semaphore reaches the default count for |
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this set and has no waiters, the space allocated for it will be freed. |
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=cut |
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sub up { |
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my ($self, $id) = @_; |
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my $sem = $self->[1]{$id} ||= Coro::Semaphore::_alloc $self->[0]; |
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Coro::Semaphore::up $sem; |
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delete $self->[1]{$id} |
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if _may_delete $sem, $self->[0], 1; |
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} |
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=item $semset->try ($id) |
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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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Coro::Semaphore::try ( |
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$_[0][1]{$_[1]} ||= $_[0][0] > 0 |
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? Coro::Semaphore::_alloc $_[0][0] |
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: return 0 |
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) |
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} |
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=item $semset->count ($id) |
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Return the current semaphore count for the specified semaphore. |
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=cut |
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sub count { |
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Coro::Semaphore::count ($_[0][1]{$_[1]} || return $_[0][0]); |
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} |
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=item $semset->waiters ($id) |
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Returns the number (in scalar context) or list (in list context) of |
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waiters waiting on the specified semaphore. |
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=cut |
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sub waiters { |
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Coro::Semaphore::waiters ($_[0][1]{$_[1]} || return); |
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} |
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=item $semset->wait ($id) |
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Same as Coro::Semaphore::wait on the specified semaphore. |
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=cut |
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sub wait { |
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Coro::Semaphore::wait ($_[0][1]{$_[1]} || return); |
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} |
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=item $guard = $semset->guard ($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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sub guard { |
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&down; |
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bless [@_], Coro::SemaphoreSet::guard:: |
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} |
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#ub timed_guard { |
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# &timed_down |
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# ? bless [$_[0], $_[1]], Coro::SemaphoreSet::guard:: |
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# : (); |
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# |
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sub Coro::SemaphoreSet::guard::DESTROY { |
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up @{$_[0]}; |
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} |
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=item $semaphore = $semset->sem ($id) |
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This SemaphoreSet version is based on Coro::Semaphore's. This function |
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creates (if necessary) the underlying Coro::Semaphore object and returns |
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it. You may legally call any Coro::Semaphore method on it, but note that |
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calling C<< $semset->up >> can invalidate the returned semaphore. |
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=cut |
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sub sem { |
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bless +($_[0][1]{$_[1]} ||= Coro::Semaphore::_alloc $_[0][0]), |
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Coro::Semaphore::; |
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} |
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1; |
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=back |
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=head1 AUTHOR/SUPPORT/CONTACT |
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Marc A. Lehmann <schmorp@schmorp.de> |
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http://software.schmorp.de/pkg/Coro.html |
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=cut |
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