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Comparing Coro/Coro/Semaphore.pm (file contents):
Revision 1.17 by root, Thu Aug 30 03:35:55 2001 UTC vs.
Revision 1.112 by root, Sat Feb 19 06:51:23 2011 UTC

1=head1 NAME 1=head1 NAME
2 2
3Coro::Semaphore - non-binary semaphores 3Coro::Semaphore - counting semaphores
4 4
5=head1 SYNOPSIS 5=head1 SYNOPSIS
6 6
7 use Coro::Semaphore; 7 use Coro;
8 8
9 $sig = new Coro::Semaphore [initial value]; 9 $sig = new Coro::Semaphore [initial value];
10 10
11 $sig->down; # wait for signal 11 $sig->down; # wait for signal
12 12
… …
17=head1 DESCRIPTION 17=head1 DESCRIPTION
18 18
19This module implements counting semaphores. You can initialize a mutex 19This module implements counting semaphores. You can initialize a mutex
20with any level of parallel users, that is, you can intialize a sempahore 20with any level of parallel users, that is, you can intialize a sempahore
21that can be C<down>ed more than once until it blocks. There is no owner 21that can be C<down>ed more than once until it blocks. There is no owner
22associated with semaphores, so one coroutine can C<down> it while another 22associated with semaphores, so one thread can C<down> it while another
23can C<up> it. 23can C<up> it.
24 24
25Counting semaphores are typically used to coordinate access to 25Counting semaphores are typically used to coordinate access to
26resources, with the semaphore count initialized to the number of free 26resources, with the semaphore count initialized to the number of free
27resources. Coroutines then increment the count when resources are added 27resources. Threads then increment the count when resources are added
28and decrement the count when resources are removed. 28and decrement the count when resources are removed.
29
30You don't have to load C<Coro::Semaphore> manually, it will be loaded
31automatically when you C<use Coro> and call the C<new> constructor.
29 32
30=over 4 33=over 4
31 34
32=cut 35=cut
33 36
34package Coro::Semaphore; 37package Coro::Semaphore;
35 38
39use common::sense;
40
36use Coro (); 41use Coro ();
37 42
38$VERSION = 0.45; 43our $VERSION = 5.37;
39 44
40=item new [inital count] 45=item new [inital count]
41 46
42Creates a new sempahore object with the given initial lock count. The 47Creates 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 48default 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 49negative values) are also allowed, in which case the semaphore is locked
45by default. 50by default.
46 51
47=cut 52=item $sem->count
48 53
49sub new { 54Returns the current semaphore count.
50 bless [defined $_[1] ? $_[1] : 1], $_[0]; 55
51} 56=item $sem->adjust ($diff)
57
58Atomically adds the amount given to the current semaphore count. If the
59count becomes positive, wakes up any waiters. Does not block if the count
60becomes negative, however.
52 61
53=item $sem->down 62=item $sem->down
54 63
55Decrement the counter, therefore "locking" the semaphore. This method 64Decrement the counter, therefore "locking" the semaphore. This method
56waits until the semaphore is available if the counter is zero. 65waits until the semaphore is available if the counter is zero.
57 66
67=item $sem->wait
68
69Similar to C<down>, but does not actually decrement the counter. Instead,
70when this function returns, a following call to C<down> or C<try> is
71guaranteed to succeed without blocking, until the next thread switch
72(C<cede> etc.).
73
74Note that using C<wait> is much less efficient than using C<down>, so try
75to prefer C<down> whenever possible.
76
77=item $sem->wait ($callback)
78
79If you pass a callback argument to C<wait>, it will not wait, but
80immediately return. The callback will be called as soon as the semaphore
81becomes available (which might be instantly), and gets passed the
82semaphore as first argument.
83
84The callback might C<down> the semaphore exactly once, might wake up other
85threads, but is I<NOT> allowed to block (switch to other threads).
86
58=cut 87=cut
59 88
60sub down { 89#=item $status = $sem->timed_down ($timeout)
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#
61 while ($_[0][0] <= 0) { 98# while ($_[0][0] <= 0) {
62 push @{$_[0][1]}, $Coro::current; 99# push @{$_[0][1]}, $Coro::current;
63 Coro::schedule; 100# &Coro::schedule;
101# if ($timeout) {
102# # ugly as hell. slow, too, btw!
103# for (0..$#{$_[0][1]}) {
104# if ($_[0][1][$_] == $Coro::current) {
105# splice @{$_[0][1]}, $_, 1;
106# return;
107# }
108# }
109# die;
110# }
64 } 111# }
112#
65 --$_[0][0]; 113# --$_[0][0];
66} 114# return 1;
115#}
67 116
68=item $sem->up 117=item $sem->up
69 118
70Unlock the semaphore again. 119Unlock the semaphore again.
71
72=cut
73
74sub up {
75 if (++$_[0][0] > 0) {
76 (shift @{$_[0][1]})->ready if @{$_[0][1]};
77 }
78}
79 120
80=item $sem->try 121=item $sem->try
81 122
82Try to C<down> the semaphore. Returns true when this was possible, 123Try to C<down> the semaphore. Returns true when this was possible,
83otherwise return false and leave the semaphore unchanged. 124otherwise return false and leave the semaphore unchanged.
84 125
85=cut
86
87sub try {
88 if ($_[0][0] > 0) {
89 --$_[0][0];
90 return 1;
91 } else {
92 return 0;
93 }
94}
95
96=item $sem->waiters 126=item $sem->waiters
97 127
98In scalar context, returns the number of coroutines waiting for this 128In scalar context, returns the number of threads waiting for this
99semaphore. 129semaphore.
100
101=cut
102
103sub waiters {
104 @{$_[0][1]};
105}
106 130
107=item $guard = $sem->guard 131=item $guard = $sem->guard
108 132
109This method calls C<down> and then creates a guard object. When the guard 133This method calls C<down> and then creates a guard object. When the guard
110object is destroyed it automatically calls C<up>. 134object is destroyed it automatically calls C<up>.
111 135
112=cut 136=cut
113 137
114sub guard { 138sub guard {
115 &down; 139 &down;
116 # double indirection because bless works on the referenced
117 # object, not (only) on the reference itself.
118 bless \\$_[0], Coro::Semaphore::Guard::; 140 bless [$_[0]], Coro::Semaphore::guard::
119} 141}
120 142
143#=item $guard = $sem->timed_guard ($timeout)
144#
145#Like C<guard>, but returns undef if semaphore couldn't be acquired within
146#$timeout seconds, otherwise the guard object.
147
148#sub timed_guard {
149# &timed_down
150# ? bless \\$_[0], Coro::Semaphore::guard::
151# : ();
152#}
153
121sub Coro::Semaphore::Guard::DESTROY { 154sub Coro::Semaphore::guard::DESTROY {
122 &up(${${$_[0]}}); 155 &up($_[0][0]);
123} 156}
124
1251;
126 157
127=back 158=back
128 159
129=head1 AUTHOR 160=head1 AUTHOR
130 161
131 Marc Lehmann <pcg@goof.com> 162 Marc Lehmann <schmorp@schmorp.de>
132 http://www.goof.com/pcg/marc/ 163 http://home.schmorp.de/
133 164
134=cut 165=cut
135 166
1671
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