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Comparing Coro/Coro/Semaphore.pm (file contents):
Revision 1.15 by root, Wed Aug 29 01:32:50 2001 UTC vs.
Revision 1.82 by root, Wed Nov 19 11:11:10 2008 UTC

… …
14 14
15 $sig->up; 15 $sig->up;
16 16
17=head1 DESCRIPTION 17=head1 DESCRIPTION
18 18
19This module implements counted semaphores. You can initialize a mutex 19This module implements counting semaphores. You can initialize a mutex
20with any level of parallel users, that is, you can intialize a sempahore 20with any level of parallel users, that is, you can intialize a sempahore
21that can be C<down>ed more than once until it blocks. There is no owner 21that can be C<down>ed more than once until it blocks. There is no owner
22associated with semaphores, so one coroutine can C<down> it while another 22associated with semaphores, so one coroutine can C<down> it while another
23can C<up> it. 23can C<up> it.
24 24
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31 31
32=cut 32=cut
33 33
34package Coro::Semaphore; 34package Coro::Semaphore;
35 35
36no warnings;
37
36use Coro (); 38use Coro ();
37 39
38$VERSION = 0.45; 40$VERSION = 5.0;
39 41
40=item new [inital count, default one] 42=item new [inital count]
41 43
42Creates a new sempahore object with the given initial lock count. The 44Creates a new sempahore object with the given initial lock count. The
43default lock count is 1, which means it is unlocked by default. Zero (or 45default 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 46negative values) are also allowed, in which case the semaphore is locked
45by default. 47by default.
46 48
47=cut 49=item $sem->count
48 50
49sub new { 51Returns the current semaphore count.
50 bless [defined $_[1] ? $_[1] : 1], $_[0]; 52
51} 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.
52 58
53=item $sem->down 59=item $sem->down
54 60
55Decrement the counter, therefore "locking" the semaphore. This method 61Decrement the counter, therefore "locking" the semaphore. This method
56waits until the semaphore is available if the counter is zero. 62waits until the semaphore is available if the counter is zero.
57 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
58=cut 87=cut
59 88
60sub down { 89#=item $status = $sem->timed_down ($timeout)
61 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#
62 while ($self->[0] <= 0) { 98# while ($_[0][0] <= 0) {
63 push @{$self->[1]}, $Coro::current; 99# push @{$_[0][1]}, $Coro::current;
64 Coro::schedule; 100# &Coro::schedule;
101# if ($timeout) {
102# # ugly as hell. slow, too, btw!
103# for (0..$#{$_[0][1]}) {
104# if ($_[0][1][$_] == $Coro::current) {
105# splice @{$_[0][1]}, $_, 1;
106# return;
107# }
108# }
109# die;
110# }
65 } 111# }
66 --$self->[0]; 112#
67} 113# --$_[0][0];
114# return 1;
115#}
68 116
69=item $sem->up 117=item $sem->up
70 118
71Unlock the semaphore again. 119Unlock the semaphore again.
72
73=cut
74
75sub up {
76 my $self = shift;
77 if (++$self->[0] > 0) {
78 (shift @{$self->[1]})->ready if @{$self->[1]};
79 }
80}
81 120
82=item $sem->try 121=item $sem->try
83 122
84Try to C<down> the semaphore. Returns true when this was possible, 123Try to C<down> the semaphore. Returns true when this was possible,
85otherwise return false and leave the semaphore unchanged. 124otherwise return false and leave the semaphore unchanged.
86 125
87=cut
88
89sub try {
90 my $self = shift;
91 if ($self->[0] > 0) {
92 --$self->[0];
93 return 1;
94 } else {
95 return 0;
96 }
97}
98
99=item $sem->waiters 126=item $sem->waiters
100 127
101In scalar context, returns the number of coroutines waiting for this 128In scalar context, returns the number of coroutines waiting for this
102semaphore. 129semaphore.
103
104=cut
105
106sub waiters {
107 @{$_[0][1]};
108}
109 130
110=item $guard = $sem->guard 131=item $guard = $sem->guard
111 132
112This method calls C<down> and then creates a guard object. When the guard 133This method calls C<down> and then creates a guard object. When the guard
113object is destroyed it automatically calls C<up>. 134object is destroyed it automatically calls C<up>.
114 135
115=cut 136=cut
116 137
117sub guard { 138sub guard {
118 $_[0]->down; 139 &down;
119 # double indirection because bless works on the referenced 140 # double indirection because bless works on the referenced
120 # object, not (only) on the reference itself. 141 # object, not (only) on the reference itself.
121 bless \\$_[0], Coro::Semaphore::Guard::; 142 bless \\$_[0], Coro::Semaphore::guard::;
122} 143}
123 144
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
124sub Coro::Semaphore::Guard::DESTROY { 156sub Coro::Semaphore::guard::DESTROY {
125 ${${$_[0]}}->up; 157 &up(${${$_[0]}});
126} 158}
127
1281;
129 159
130=back 160=back
131 161
132=head1 AUTHOR 162=head1 AUTHOR
133 163
134 Marc Lehmann <pcg@goof.com> 164 Marc Lehmann <schmorp@schmorp.de>
135 http://www.goof.com/pcg/marc/ 165 http://home.schmorp.de/
136 166
137=cut 167=cut
138 168
1691
170

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