| 1 |
=head1 NAME |
| 2 |
|
| 3 |
Coro::SemaphoreSet - efficient set of counting 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 |
use strict qw(vars subs); |
| 34 |
no warnings; |
| 35 |
|
| 36 |
our $VERSION = 5.17; |
| 37 |
|
| 38 |
use Coro::Semaphore (); |
| 39 |
|
| 40 |
=item new [inital count] |
| 41 |
|
| 42 |
Creates a new semaphore set with the given initial lock count for each |
| 43 |
individual semaphore. See L<Coro::Semaphore>. |
| 44 |
|
| 45 |
=cut |
| 46 |
|
| 47 |
sub new { |
| 48 |
bless [defined $_[1] ? $_[1] : 1], $_[0] |
| 49 |
} |
| 50 |
|
| 51 |
=item $semset->down ($id) |
| 52 |
|
| 53 |
Decrement the counter, therefore "locking" the named semaphore. This |
| 54 |
method waits until the semaphore is available if the counter is zero. |
| 55 |
|
| 56 |
=cut |
| 57 |
|
| 58 |
sub down { |
| 59 |
# Coro::Semaphore::down increases the refcount, which we check in _may_delete |
| 60 |
Coro::Semaphore::down ($_[0][1]{$_[1]} ||= Coro::Semaphore::_alloc $_[0][0]); |
| 61 |
} |
| 62 |
|
| 63 |
#ub timed_down { |
| 64 |
# require Coro::Timer; |
| 65 |
# my $timeout = Coro::Timer::timeout ($_[2]); |
| 66 |
# |
| 67 |
# while () { |
| 68 |
# my $sem = ($_[0][1]{$_[1]} ||= [$_[0][0]]); |
| 69 |
# |
| 70 |
# if ($sem->[0] > 0) { |
| 71 |
# --$sem->[0]; |
| 72 |
# return 1; |
| 73 |
# } |
| 74 |
# |
| 75 |
# if ($timeout) { |
| 76 |
# # ugly as hell. |
| 77 |
# for (0..$#{$sem->[1]}) { |
| 78 |
# if ($sem->[1][$_] == $Coro::current) { |
| 79 |
# splice @{$sem->[1]}, $_, 1; |
| 80 |
# return 0; |
| 81 |
# } |
| 82 |
# } |
| 83 |
# die; |
| 84 |
# } |
| 85 |
# |
| 86 |
# push @{$sem->[1]}, $Coro::current; |
| 87 |
# &Coro::schedule; |
| 88 |
# } |
| 89 |
# |
| 90 |
|
| 91 |
=item $semset->up ($id) |
| 92 |
|
| 93 |
Unlock the semaphore again. If the semaphore reaches the default count for |
| 94 |
this set and has no waiters, the space allocated for it will be freed. |
| 95 |
|
| 96 |
=cut |
| 97 |
|
| 98 |
sub up { |
| 99 |
my ($self, $id) = @_; |
| 100 |
|
| 101 |
my $sem = $self->[1]{$id} ||= Coro::Semaphore::_alloc $self->[0]; |
| 102 |
|
| 103 |
Coro::Semaphore::up $sem; |
| 104 |
|
| 105 |
delete $self->[1]{$id} |
| 106 |
if _may_delete $sem, $self->[0], 1; |
| 107 |
} |
| 108 |
|
| 109 |
=item $semset->try ($id) |
| 110 |
|
| 111 |
Try to C<down> the semaphore. Returns true when this was possible, |
| 112 |
otherwise return false and leave the semaphore unchanged. |
| 113 |
|
| 114 |
=cut |
| 115 |
|
| 116 |
sub try { |
| 117 |
Coro::Semaphore::try ($_[0][1]{$_[1]} || return $_[0][0] > 0) |
| 118 |
} |
| 119 |
|
| 120 |
=item $semset->count ($id) |
| 121 |
|
| 122 |
Return the current semaphore count for the specified semaphore. |
| 123 |
|
| 124 |
=cut |
| 125 |
|
| 126 |
sub count { |
| 127 |
Coro::Semaphore::count ($_[0][1]{$_[1]} || return $_[0][0]); |
| 128 |
} |
| 129 |
|
| 130 |
=item $semset->waiters ($id) |
| 131 |
|
| 132 |
Returns the number (in scalar context) or list (in list context) of |
| 133 |
waiters waiting on the specified semaphore. |
| 134 |
|
| 135 |
=cut |
| 136 |
|
| 137 |
sub waiters { |
| 138 |
Coro::Semaphore::waiters ($_[0][1]{$_[1]} || return); |
| 139 |
} |
| 140 |
|
| 141 |
=item $semset->wait ($id) |
| 142 |
|
| 143 |
Same as Coro::Semaphore::wait on the specified semaphore. |
| 144 |
|
| 145 |
=cut |
| 146 |
|
| 147 |
sub wait { |
| 148 |
Coro::Semaphore::wait ($_[0][1]{$_[1]} || return); |
| 149 |
} |
| 150 |
|
| 151 |
=item $guard = $semset->guard ($id) |
| 152 |
|
| 153 |
This method calls C<down> and then creates a guard object. When the guard |
| 154 |
object is destroyed it automatically calls C<up>. |
| 155 |
|
| 156 |
=cut |
| 157 |
|
| 158 |
sub guard { |
| 159 |
&down; |
| 160 |
bless [@_], Coro::SemaphoreSet::guard:: |
| 161 |
} |
| 162 |
|
| 163 |
#ub timed_guard { |
| 164 |
# &timed_down |
| 165 |
# ? bless [$_[0], $_[1]], Coro::SemaphoreSet::guard:: |
| 166 |
# : (); |
| 167 |
# |
| 168 |
|
| 169 |
sub Coro::SemaphoreSet::guard::DESTROY { |
| 170 |
up @{$_[0]}; |
| 171 |
} |
| 172 |
|
| 173 |
=item $semaphore = $semset->sem ($id) |
| 174 |
|
| 175 |
This SemaphoreSet version is based on Coro::Semaphore's. This function |
| 176 |
creates (if necessary) the underlying Coro::Semaphore object and returns |
| 177 |
it. You may legally call any Coro::Semaphore method on it, but note that |
| 178 |
calling C<< $semset->up >> can invalidate the returned semaphore. |
| 179 |
|
| 180 |
=cut |
| 181 |
|
| 182 |
sub sem { |
| 183 |
bless +($_[0][1]{$_[1]} ||= Coro::Semaphore::_alloc $_[0][0]), |
| 184 |
Coro::Semaphore::; |
| 185 |
} |
| 186 |
|
| 187 |
1; |
| 188 |
|
| 189 |
=back |
| 190 |
|
| 191 |
=head1 AUTHOR |
| 192 |
|
| 193 |
Marc Lehmann <schmorp@schmorp.de> |
| 194 |
http://home.schmorp.de/ |
| 195 |
|
| 196 |
=cut |
| 197 |
|
