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Comparing Coro/Coro/Semaphore.pm (file contents):
Revision 1.10 by root, Wed Jul 25 04:14:38 2001 UTC vs.
Revision 1.82 by root, Wed Nov 19 11:11:10 2008 UTC

… …
14 14
15 $sig->up; 15 $sig->up;
16 16
17=head1 DESCRIPTION 17=head1 DESCRIPTION
18 18
19This module implements counting semaphores. You can initialize a mutex
20with any level of parallel users, that is, you can intialize a sempahore
21that can be C<down>ed more than once until it blocks. There is no owner
22associated with semaphores, so one coroutine can C<down> it while another
23can C<up> it.
24
25Counting semaphores are typically used to coordinate access to
26resources, with the semaphore count initialized to the number of free
27resources. Coroutines then increment the count when resources are added
28and decrement the count when resources are removed.
29
19=over 4 30=over 4
20 31
21=cut 32=cut
22 33
23package Coro::Semaphore; 34package Coro::Semaphore;
24 35
36no warnings;
37
25use Coro (); 38use Coro ();
26 39
27$VERSION = 0.12; 40$VERSION = 5.0;
28 41
29=item new [inital count, default zero] 42=item new [inital count]
30 43
31Creates a new sempahore object with the given initial lock count. The 44Creates a new sempahore object with the given initial lock count. The
32default lock count is 1, which means it is unlocked by default. 45default lock count is 1, which means it is unlocked by default. Zero (or
46negative values) are also allowed, in which case the semaphore is locked
47by default.
33 48
34=cut 49=item $sem->count
35 50
36sub new { 51Returns the current semaphore count.
37 bless [defined $_[1] ? $_[1] : 1], $_[0]; 52
38} 53=item $sem->adjust ($diff)
54
55Atomically adds the amount given to the current semaphore count. If the
56count becomes positive, wakes up any waiters. Does not block if the count
57becomes negative, however.
39 58
40=item $sem->down 59=item $sem->down
41 60
42Decrement the counter, therefore "locking" the semaphore. This method 61Decrement the counter, therefore "locking" the semaphore. This method
43waits until the semaphore is available if the counter is zero. 62waits until the semaphore is available if the counter is zero.
44 63
64=item $sem->wait
65
66Similar to C<down>, but does not actually decrement the counter. Instead,
67when this function returns, a following call to C<down> or C<try> is
68guaranteed to succeed without blocking, until the next coroutine switch
69(C<cede> etc.).
70
71Note that using C<wait> is much less efficient than using C<down>, so try
72to prefer C<down> whenever possible.
73
74=item $sem->wait ($callback)
75
76If you pass a callback argument to C<wait>, it will not wait, but
77immediately return. The callback will be called as soon as the semaphore
78becomes available (which might be instantly), and gets passed the
79semaphore as first argument.
80
81The callback might C<down> the semaphore exactly once, might wake up other
82coroutines, but is I<NOT> allowed to block (switch to other coroutines).
83
84This is considered a rather experimental interface, and is subject to
85change.
86
45=cut 87=cut
46 88
47sub down { 89#=item $status = $sem->timed_down ($timeout)
48 my $self = shift; 90#
91#Like C<down>, but returns false if semaphore couldn't be acquired within
92#$timeout seconds, otherwise true.
93
94#sub timed_down {
95# require Coro::Timer;
96# my $timeout = Coro::Timer::timeout ($_[1]);
97#
49 while ($self->[0] <= 0) { 98# while ($_[0][0] <= 0) {
50 push @{$self->[1]}, $Coro::current; 99# push @{$_[0][1]}, $Coro::current;
51 Coro::schedule; 100# &Coro::schedule;
101# if ($timeout) {
102# # ugly as hell. slow, too, btw!
103# for (0..$#{$_[0][1]}) {
104# if ($_[0][1][$_] == $Coro::current) {
105# splice @{$_[0][1]}, $_, 1;
106# return;
107# }
108# }
109# die;
110# }
52 } 111# }
53 --$self->[0]; 112#
54} 113# --$_[0][0];
114# return 1;
115#}
55 116
56=item $sem->up 117=item $sem->up
57 118
58Unlock the semaphore again. 119Unlock the semaphore again.
59
60=cut
61
62sub up {
63 my $self = shift;
64 if (++$self->[0] > 0) {
65 (shift @{$self->[1]})->ready if @{$self->[1]};
66 }
67}
68 120
69=item $sem->try 121=item $sem->try
70 122
71Try to C<down> the semaphore. Returns true when this was possible, 123Try to C<down> the semaphore. Returns true when this was possible,
72otherwise return false and leave the semaphore unchanged. 124otherwise return false and leave the semaphore unchanged.
73 125
126=item $sem->waiters
127
128In scalar context, returns the number of coroutines waiting for this
129semaphore.
130
131=item $guard = $sem->guard
132
133This method calls C<down> and then creates a guard object. When the guard
134object is destroyed it automatically calls C<up>.
135
74=cut 136=cut
75 137
76sub try { 138sub guard {
77 my $self = shift; 139 &down;
78 if ($self->[0] > 0) { 140 # double indirection because bless works on the referenced
79 --$self->[0]; 141 # object, not (only) on the reference itself.
80 return 1; 142 bless \\$_[0], Coro::Semaphore::guard::;
81 } else {
82 return 0;
83 }
84} 143}
85 144
861; 145#=item $guard = $sem->timed_guard ($timeout)
146#
147#Like C<guard>, but returns undef if semaphore couldn't be acquired within
148#$timeout seconds, otherwise the guard object.
149
150#sub timed_guard {
151# &timed_down
152# ? bless \\$_[0], Coro::Semaphore::guard::
153# : ();
154#}
155
156sub Coro::Semaphore::guard::DESTROY {
157 &up(${${$_[0]}});
158}
87 159
88=back 160=back
89 161
90=head1 AUTHOR 162=head1 AUTHOR
91 163
92 Marc Lehmann <pcg@goof.com> 164 Marc Lehmann <schmorp@schmorp.de>
93 http://www.goof.com/pcg/marc/ 165 http://home.schmorp.de/
94 166
95=cut 167=cut
96 168
1691
170

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