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Comparing Coro/Coro/Semaphore.pm (file contents):
Revision 1.67 by root, Wed Jul 23 22:15:25 2008 UTC vs.
Revision 1.99 by root, Wed Jul 22 03:02:07 2009 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::Semaphore;
8 8
… …
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 29
30=over 4 30=over 4
31 31
32=cut 32=cut
… …
35 35
36no warnings; 36no warnings;
37 37
38use Coro (); 38use Coro ();
39 39
40$VERSION = 4.745; 40$VERSION = 5.161;
41 41
42=item new [inital count] 42=item new [inital count]
43 43
44Creates a new sempahore object with the given initial lock count. The 44Creates 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 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 46negative values) are also allowed, in which case the semaphore is locked
47by default. 47by default.
48 48
49=cut
50
51sub new {
52 bless [defined $_[1] ? $_[1] : 1], $_[0];
53}
54
55=item $sem->count 49=item $sem->count
56 50
57Returns the current semaphore count. 51Returns the current semaphore count.
58
59=cut
60
61sub count {
62 $_[0][0]
63}
64 52
65=item $sem->adjust ($diff) 53=item $sem->adjust ($diff)
66 54
67Atomically adds the amount given to the current semaphore count. If the 55Atomically adds the amount given to the current semaphore count. If the
68count becomes positive, wakes up any waiters. Does not block if the count 56count becomes positive, wakes up any waiters. Does not block if the count
69becomes negative, however. 57becomes negative, however.
70 58
71=cut
72
73sub adjust {
74 # basically a weird copy of up
75 if (($_[0][0] += $_[1]) > 0) {
76 (shift @{$_[0][1]})->ready if @{$_[0][1]};
77 }
78}
79
80=item $sem->down 59=item $sem->down
81 60
82Decrement the counter, therefore "locking" the semaphore. This method 61Decrement the counter, therefore "locking" the semaphore. This method
83waits until the semaphore is available if the counter is zero. 62waits until the semaphore is available if the counter is zero.
84 63
85=item $status = $sem->timed_down ($timeout) 64=item $sem->wait
86 65
87Like C<down>, but returns false if semaphore couldn't be acquired within 66Similar to C<down>, but does not actually decrement the counter. Instead,
88$timeout seconds, otherwise true. 67when this function returns, a following call to C<down> or C<try> is
68guaranteed to succeed without blocking, until the next thread 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
82threads, but is I<NOT> allowed to block (switch to other threads).
89 83
90=cut 84=cut
91 85
92sub down { 86#=item $status = $sem->timed_down ($timeout)
93 while ($_[0][0] <= 0) { 87#
94 push @{$_[0][1]}, $Coro::current; 88#Like C<down>, but returns false if semaphore couldn't be acquired within
95 &Coro::schedule; 89#$timeout seconds, otherwise true.
96 }
97 --$_[0][0];
98}
99 90
100sub timed_down { 91#sub timed_down {
101 require Coro::Timer; 92# require Coro::Timer;
102 my $timeout = Coro::Timer::timeout ($_[1]); 93# my $timeout = Coro::Timer::timeout ($_[1]);
103 94#
104 while ($_[0][0] <= 0) { 95# while ($_[0][0] <= 0) {
105 push @{$_[0][1]}, $Coro::current; 96# push @{$_[0][1]}, $Coro::current;
106 &Coro::schedule; 97# &Coro::schedule;
107 if ($timeout) { 98# if ($timeout) {
108 # ugly as hell. slow, too, btw! 99# # ugly as hell. slow, too, btw!
109 for (0..$#{$_[0][1]}) { 100# for (0..$#{$_[0][1]}) {
110 if ($_[0][1][$_] == $Coro::current) { 101# if ($_[0][1][$_] == $Coro::current) {
111 splice @{$_[0][1]}, $_, 1; 102# splice @{$_[0][1]}, $_, 1;
112 return; 103# return;
113 } 104# }
114 } 105# }
115 die; 106# die;
116 } 107# }
117 } 108# }
118 109#
119 --$_[0][0]; 110# --$_[0][0];
120 return 1; 111# return 1;
121} 112#}
122 113
123=item $sem->up 114=item $sem->up
124 115
125Unlock the semaphore again. 116Unlock the semaphore again.
126
127=cut
128
129sub up {
130 if (++$_[0][0] > 0) {
131 (shift @{$_[0][1]})->ready if @{$_[0][1]};
132 }
133}
134 117
135=item $sem->try 118=item $sem->try
136 119
137Try to C<down> the semaphore. Returns true when this was possible, 120Try to C<down> the semaphore. Returns true when this was possible,
138otherwise return false and leave the semaphore unchanged. 121otherwise return false and leave the semaphore unchanged.
139 122
140=cut
141
142sub try {
143 if ($_[0][0] > 0) {
144 --$_[0][0];
145 return 1;
146 } else {
147 return 0;
148 }
149}
150
151=item $sem->waiters 123=item $sem->waiters
152 124
153In scalar context, returns the number of coroutines waiting for this 125In scalar context, returns the number of threads waiting for this
154semaphore. 126semaphore.
155
156=cut
157
158sub waiters {
159 @{$_[0][1]};
160}
161 127
162=item $guard = $sem->guard 128=item $guard = $sem->guard
163 129
164This method calls C<down> and then creates a guard object. When the guard 130This method calls C<down> and then creates a guard object. When the guard
165object is destroyed it automatically calls C<up>. 131object is destroyed it automatically calls C<up>.
166 132
167=item $guard = $sem->timed_guard ($timeout)
168
169Like C<guard>, but returns undef if semaphore couldn't be acquired within
170$timeout seconds, otherwise the guard object.
171
172=cut 133=cut
173 134
174sub guard { 135sub guard {
175 &down; 136 &down;
176 # double indirection because bless works on the referenced
177 # object, not (only) on the reference itself.
178 bless \\$_[0], Coro::Semaphore::guard::; 137 bless [$_[0]], Coro::Semaphore::guard::
179} 138}
180 139
140#=item $guard = $sem->timed_guard ($timeout)
141#
142#Like C<guard>, but returns undef if semaphore couldn't be acquired within
143#$timeout seconds, otherwise the guard object.
144
181sub timed_guard { 145#sub timed_guard {
182 &timed_down 146# &timed_down
183 ? bless \\$_[0], Coro::Semaphore::guard:: 147# ? bless \\$_[0], Coro::Semaphore::guard::
184 : (); 148# : ();
185} 149#}
186 150
187sub Coro::Semaphore::guard::DESTROY { 151sub Coro::Semaphore::guard::DESTROY {
188 &up(${${$_[0]}}); 152 &up($_[0][0]);
189} 153}
190 154
191=back 155=back
192 156
193=head1 AUTHOR 157=head1 AUTHOR

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