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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 1.18 by root, Sun Sep 2 01:03:53 2001 UTC

… …
14 14
15 $sig->up; 15 $sig->up;
16 16
17=head1 DESCRIPTION 17=head1 DESCRIPTION
18 18
19This module implements counting semaphores. You can initialize a mutex
20with any level of parallel users, that is, you can intialize a sempahore
21that can be C<down>ed more than once until it blocks. There is no owner
22associated with semaphores, so one coroutine can C<down> it while another
23can C<up> it.
24
25Counting semaphores are typically used to coordinate access to
26resources, with the semaphore count initialized to the number of free
27resources. Coroutines then increment the count when resources are added
28and decrement the count when resources are removed.
29
19=over 4 30=over 4
20 31
21=cut 32=cut
22 33
23package Coro::Semaphore; 34package Coro::Semaphore;
24 35
25use Coro (); 36use Coro ();
26 37
27$VERSION = 0.12; 38$VERSION = 0.49;
28 39
29=item new [inital count, default zero] 40=item new [inital count]
30 41
31Creates a new sempahore object with the given initial lock count. The 42Creates a new sempahore object with the given initial lock count. The
32default lock count is 1, which means it is unlocked by default. 43default lock count is 1, which means it is unlocked by default. Zero (or
44negative values) are also allowed, in which case the semaphore is locked
45by default.
33 46
34=cut 47=cut
35 48
36sub new { 49sub new {
37 bless [defined $_[1] ? $_[1] : 1], $_[0]; 50 bless [defined $_[1] ? $_[1] : 1], $_[0];
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43waits until the semaphore is available if the counter is zero. 56waits until the semaphore is available if the counter is zero.
44 57
45=cut 58=cut
46 59
47sub down { 60sub down {
48 my $self = shift;
49 while ($self->[0] <= 0) { 61 while ($_[0][0] <= 0) {
50 push @{$self->[1]}, $Coro::current; 62 push @{$_[0][1]}, $Coro::current;
51 Coro::schedule; 63 Coro::schedule;
52 } 64 }
53 --$self->[0]; 65 --$_[0][0];
54} 66}
55 67
56=item $sem->up 68=item $sem->up
57 69
58Unlock the semaphore again. 70Unlock the semaphore again.
59 71
60=cut 72=cut
61 73
62sub up { 74sub up {
63 my $self = shift;
64 if (++$self->[0] > 0) { 75 if (++$_[0][0] > 0) {
65 (shift @{$self->[1]})->ready if @{$self->[1]}; 76 (shift @{$_[0][1]})->ready if @{$_[0][1]};
66 } 77 }
67} 78}
68 79
69=item $sem->try 80=item $sem->try
70 81
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72otherwise return false and leave the semaphore unchanged. 83otherwise return false and leave the semaphore unchanged.
73 84
74=cut 85=cut
75 86
76sub try { 87sub try {
77 my $self = shift;
78 if ($self->[0] > 0) { 88 if ($_[0][0] > 0) {
79 --$self->[0]; 89 --$_[0][0];
80 return 1; 90 return 1;
81 } else { 91 } else {
82 return 0; 92 return 0;
83 } 93 }
94}
95
96=item $sem->waiters
97
98In scalar context, returns the number of coroutines waiting for this
99semaphore.
100
101=cut
102
103sub waiters {
104 @{$_[0][1]};
105}
106
107=item $guard = $sem->guard
108
109This method calls C<down> and then creates a guard object. When the guard
110object is destroyed it automatically calls C<up>.
111
112=cut
113
114sub guard {
115 &down;
116 # double indirection because bless works on the referenced
117 # object, not (only) on the reference itself.
118 bless \\$_[0], Coro::Semaphore::Guard::;
119}
120
121sub Coro::Semaphore::Guard::DESTROY {
122 &up(${${$_[0]}});
84} 123}
85 124
861; 1251;
87 126
88=back 127=back

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