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Coro/RWLock.pm  view on Meta::CPAN

=head1 NAME

Coro::RWLock - reader/write locks

=head1 SYNOPSIS

 use Coro;

 $lck = new Coro::RWLock;

 $lck->rdlock; # acquire read lock
 $lck->unlock; # unlock lock again

 # or:
 $lck->wrlock; # acquire write lock
 $lck->tryrdlock; # try a readlock
 $lck->trywrlock; # try a write lock


=head1 DESCRIPTION

This module implements reader/write locks. A read can be acquired for
read by many coroutines in parallel as long as no writer has locked it
(shared access). A single write lock can be acquired when no readers
exist. RWLocks basically allow many concurrent readers (without writers)
OR a single writer (but no readers).

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

=over 4

=cut

package Coro::RWLock;

use common::sense;

use Coro ();

our $VERSION = 6.514;

=item $l = new Coro::RWLock;

Create a new reader/writer lock.

=cut

sub new {
   # [rdcount, [readqueue], wrcount, [writequeue]]
   bless [0, [], 0, []], $_[0];
}

=item $l->rdlock

Acquire a read lock.

=item $l->tryrdlock

Try to acquire a read lock.

=cut

sub rdlock {
   while ($_[0][0]) {
      push @{$_[0][3]}, $Coro::current;
      &Coro::schedule;
   }
   ++$_[0][2];
}

sub tryrdlock {
   return if $_[0][0];
   ++$_[0][2];
}

=item $l->wrlock

Acquire a write lock.

=item $l->trywrlock

Try to acquire a write lock.