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Comparing Coro/Coro/Semaphore.pm (file contents):
Revision 1.44 by root, Thu Mar 3 17:20:31 2005 UTC vs.
Revision 1.119 by root, Wed Aug 3 14:52:19 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 $sig->down; # wait for signal
12 12
… …
17=head1 DESCRIPTION 17=head1 DESCRIPTION
18 18
19This module implements counting semaphores. You can initialize a mutex 19This module implements counting semaphores. You can initialize a mutex
20with any level of parallel users, that is, you can intialize a sempahore 20with any level of parallel users, that is, you can intialize a sempahore
21that can be C<down>ed more than once until it blocks. There is no owner 21that can be C<down>ed more than once until it blocks. There is no owner
22associated with semaphores, so one coroutine can C<down> it while another 22associated with semaphores, so one thread can C<down> it while another
23can C<up> it. 23can C<up> it.
24 24
25Counting semaphores are typically used to coordinate access to 25Counting semaphores are typically used to coordinate access to
26resources, with the semaphore count initialized to the number of free 26resources, with the semaphore count initialized to the number of free
27resources. Coroutines then increment the count when resources are added 27resources. Threads then increment the count when resources are added
28and decrement the count when resources are removed. 28and decrement the count when resources are removed.
29
30You don't have to load C<Coro::Semaphore> manually, it will be loaded
31automatically when you C<use Coro> and call the C<new> constructor.
29 32
30=over 4 33=over 4
31 34
32=cut 35=cut
33 36
34package Coro::Semaphore; 37package Coro::Semaphore;
35 38
36BEGIN { eval { require warnings } && warnings->unimport ("uninitialized") } 39use common::sense;
37 40
38use Coro (); 41use Coro ();
39 42
40$VERSION = 1.11; 43our $VERSION = 6.04;
41 44
42=item new [inital count] 45=item new [inital count]
43 46
44Creates a new sempahore object with the given initial lock count. The 47Creates a new sempahore object with the given initial lock count. The
45default 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
46negative values) are also allowed, in which case the semaphore is locked 49negative values) are also allowed, in which case the semaphore is locked
47by default. 50by default.
48 51
49=cut 52=item $sem->count
50 53
51sub new { 54Returns the current semaphore count.
52 bless [defined $_[1] ? $_[1] : 1], $_[0]; 55
53} 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.
54 61
55=item $sem->down 62=item $sem->down
56 63
57Decrement the counter, therefore "locking" the semaphore. This method 64Decrement the counter, therefore "locking" the semaphore. This method
58waits until the semaphore is available if the counter is zero. 65waits until the semaphore is available if the counter is zero.
59 66
60=item $status = $sem->timed_down($timeout) 67=item $sem->wait
61 68
62Like C<down>, but returns false if semaphore couldn't be acquired within 69Similar to C<down>, but does not actually decrement the counter. Instead,
63$timeout seconds, otherwise true. 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).
64 86
65=cut 87=cut
66 88
67sub down { 89#=item $status = $sem->timed_down ($timeout)
68 while ($_[0][0] <= 0) { 90#
69 push @{$_[0][1]}, $Coro::current; 91#Like C<down>, but returns false if semaphore couldn't be acquired within
70 Coro::schedule; 92#$timeout seconds, otherwise true.
71 }
72 --$_[0][0];
73}
74 93
75sub timed_down { 94#sub timed_down {
76 require Coro::Timer; 95# require Coro::Timer;
77 my $timeout = Coro::Timer::timeout($_[1]); 96# my $timeout = Coro::Timer::timeout ($_[1]);
78 97#
79 while ($_[0][0] <= 0) { 98# while ($_[0][0] <= 0) {
80 push @{$_[0][1]}, $Coro::current; 99# push @{$_[0][1]}, $Coro::current;
81 Coro::schedule; 100# &Coro::schedule;
82 if ($timeout) { 101# if ($timeout) {
83 # ugly as hell. slow, too, btw! 102# # ugly as hell. slow, too, btw!
84 for (0..$#{$_[0][1]}) { 103# for (0..$#{$_[0][1]}) {
85 if ($_[0][1][$_] == $Coro::current) { 104# if ($_[0][1][$_] == $Coro::current) {
86 splice @{$_[0][1]}, $_, 1; 105# splice @{$_[0][1]}, $_, 1;
87 return; 106# return;
88 } 107# }
89 } 108# }
90 die; 109# die;
91 } 110# }
92 } 111# }
93 112#
94 --$_[0][0]; 113# --$_[0][0];
95 return 1; 114# return 1;
96} 115#}
97 116
98=item $sem->up 117=item $sem->up
99 118
100Unlock the semaphore again. 119Unlock the semaphore again.
101
102=cut
103
104sub up {
105 if (++$_[0][0] > 0) {
106 (shift @{$_[0][1]})->ready if @{$_[0][1]};
107 }
108}
109 120
110=item $sem->try 121=item $sem->try
111 122
112Try to C<down> the semaphore. Returns true when this was possible, 123Try to C<down> the semaphore. Returns true when this was possible,
113otherwise return false and leave the semaphore unchanged. 124otherwise return false and leave the semaphore unchanged.
114 125
115=cut
116
117sub try {
118 if ($_[0][0] > 0) {
119 --$_[0][0];
120 return 1;
121 } else {
122 return 0;
123 }
124}
125
126=item $sem->waiters 126=item $sem->waiters
127 127
128In scalar context, returns the number of coroutines waiting for this 128In scalar context, returns the number of threads waiting for this
129semaphore. 129semaphore.
130
131=cut
132
133sub waiters {
134 @{$_[0][1]};
135}
136 130
137=item $guard = $sem->guard 131=item $guard = $sem->guard
138 132
139This 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
140object is destroyed it automatically calls C<up>. 134object is destroyed it automatically calls C<up>.
141 135
142=item $guard = $sem->timed_guard($timeout)
143
144Like C<guard>, but returns undef if semaphore couldn't be acquired within
145$timeout seconds, otherwise the guard object.
146
147=cut 136=cut
148 137
149sub guard { 138sub guard {
150 &down; 139 &down;
151 # double indirection because bless works on the referenced
152 # object, not (only) on the reference itself.
153 bless \\$_[0], Coro::Semaphore::guard::; 140 bless [$_[0]], Coro::Semaphore::guard::
154} 141}
155 142
143#=item $guard = $sem->timed_guard ($timeout)
144#
145#Like C<guard>, but returns undef if semaphore couldn't be acquired within
146#$timeout seconds, otherwise the guard object.
147
156sub timed_guard { 148#sub timed_guard {
157 &timed_down 149# &timed_down
158 ? bless \\$_[0], Coro::Semaphore::guard:: 150# ? bless \\$_[0], Coro::Semaphore::guard::
159 : (); 151# : ();
160} 152#}
161 153
162sub Coro::Semaphore::guard::DESTROY { 154sub Coro::Semaphore::guard::DESTROY {
163 &up(${${$_[0]}}); 155 &up($_[0][0]);
164} 156}
165
1661;
167 157
168=back 158=back
169 159
170=head1 AUTHOR 160=head1 AUTHOR
171 161
172 Marc Lehmann <schmorp@schmorp.de> 162 Marc Lehmann <schmorp@schmorp.de>
173 http://home.schmorp.de/ 163 http://home.schmorp.de/
174 164
175=cut 165=cut
176 166
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