| … | |
… | |
| 14 | |
14 | |
| 15 | $sig->up; |
15 | $sig->up; |
| 16 | |
16 | |
| 17 | =head1 DESCRIPTION |
17 | =head1 DESCRIPTION |
| 18 | |
18 | |
|
|
19 | This module implements counting semaphores. You can initialize a mutex |
|
|
20 | with any level of parallel users, that is, you can intialize a sempahore |
|
|
21 | that can be C<down>ed more than once until it blocks. There is no owner |
|
|
22 | associated with semaphores, so one coroutine can C<down> it while another |
|
|
23 | can C<up> it. |
|
|
24 | |
|
|
25 | Counting semaphores are typically used to coordinate access to |
|
|
26 | resources, with the semaphore count initialized to the number of free |
|
|
27 | resources. Coroutines then increment the count when resources are added |
|
|
28 | and decrement the count when resources are removed. |
|
|
29 | |
| 19 | =over 4 |
30 | =over 4 |
| 20 | |
31 | |
| 21 | =cut |
32 | =cut |
| 22 | |
33 | |
| 23 | package Coro::Semaphore; |
34 | package Coro::Semaphore; |
| 24 | |
35 | |
|
|
36 | BEGIN { eval { require warnings } && warnings->unimport ("uninitialized") } |
|
|
37 | |
| 25 | use Coro (); |
38 | use Coro (); |
| 26 | |
39 | |
| 27 | $VERSION = 0.10; |
40 | $VERSION = 1.9; |
| 28 | |
41 | |
| 29 | =item new [inital count, default zero] |
42 | =item new [inital count] |
| 30 | |
43 | |
| 31 | Creates a new sempahore object with the given initial lock count. The |
44 | Creates a new sempahore object with the given initial lock count. The |
| 32 | default lock count is 1, which means it is unlocked by default. |
45 | default lock count is 1, which means it is unlocked by default. Zero (or |
|
|
46 | negative values) are also allowed, in which case the semaphore is locked |
|
|
47 | by default. |
| 33 | |
48 | |
| 34 | =cut |
49 | =cut |
| 35 | |
50 | |
| 36 | sub new { |
51 | sub new { |
| 37 | bless [defined $_[1] ? $_[1] : 1], $_[0]; |
52 | bless [defined $_[1] ? $_[1] : 1], $_[0]; |
| … | |
… | |
| 40 | =item $sem->down |
55 | =item $sem->down |
| 41 | |
56 | |
| 42 | Decrement the counter, therefore "locking" the semaphore. This method |
57 | Decrement the counter, therefore "locking" the semaphore. This method |
| 43 | waits until the semaphore is available if the counter is zero. |
58 | waits until the semaphore is available if the counter is zero. |
| 44 | |
59 | |
|
|
60 | =item $status = $sem->timed_down($timeout) |
|
|
61 | |
|
|
62 | Like C<down>, but returns false if semaphore couldn't be acquired within |
|
|
63 | $timeout seconds, otherwise true. |
|
|
64 | |
| 45 | =cut |
65 | =cut |
| 46 | |
66 | |
| 47 | sub down { |
67 | sub down { |
| 48 | my $self = shift; |
|
|
| 49 | while ($self->[0] <= 0) { |
68 | while ($_[0][0] <= 0) { |
| 50 | push @{$self->[1]}, $Coro::current; |
69 | push @{$_[0][1]}, $Coro::current; |
| 51 | Coro::schedule; |
70 | Coro::schedule; |
| 52 | } |
71 | } |
| 53 | --$self->[0]; |
72 | --$_[0][0]; |
|
|
73 | } |
|
|
74 | |
|
|
75 | sub timed_down { |
|
|
76 | require Coro::Timer; |
|
|
77 | my $timeout = Coro::Timer::timeout($_[1]); |
|
|
78 | |
|
|
79 | while ($_[0][0] <= 0) { |
|
|
80 | push @{$_[0][1]}, $Coro::current; |
|
|
81 | Coro::schedule; |
|
|
82 | if ($timeout) { |
|
|
83 | # ugly as hell. slow, too, btw! |
|
|
84 | for (0..$#{$_[0][1]}) { |
|
|
85 | if ($_[0][1][$_] == $Coro::current) { |
|
|
86 | splice @{$_[0][1]}, $_, 1; |
|
|
87 | return; |
|
|
88 | } |
|
|
89 | } |
|
|
90 | die; |
|
|
91 | } |
|
|
92 | } |
|
|
93 | |
|
|
94 | --$_[0][0]; |
|
|
95 | return 1; |
| 54 | } |
96 | } |
| 55 | |
97 | |
| 56 | =item $sem->up |
98 | =item $sem->up |
| 57 | |
99 | |
| 58 | Unlock the semaphore again. |
100 | Unlock the semaphore again. |
| 59 | |
101 | |
| 60 | =cut |
102 | =cut |
| 61 | |
103 | |
| 62 | sub up { |
104 | sub up { |
| 63 | my $self = shift; |
|
|
| 64 | if (++$self->[0] > 0) { |
105 | if (++$_[0][0] > 0) { |
| 65 | (shift @{$self->[1]})->ready if @{$self->[1]}; |
106 | (shift @{$_[0][1]})->ready if @{$_[0][1]}; |
| 66 | } |
107 | } |
| 67 | } |
108 | } |
| 68 | |
109 | |
| 69 | =item $sem->try |
110 | =item $sem->try |
| 70 | |
111 | |
| … | |
… | |
| 72 | otherwise return false and leave the semaphore unchanged. |
113 | otherwise return false and leave the semaphore unchanged. |
| 73 | |
114 | |
| 74 | =cut |
115 | =cut |
| 75 | |
116 | |
| 76 | sub try { |
117 | sub try { |
| 77 | my $self = shift; |
|
|
| 78 | if ($self->[0] > 0) { |
118 | if ($_[0][0] > 0) { |
| 79 | --$self->[0]; |
119 | --$_[0][0]; |
| 80 | return 1; |
120 | return 1; |
| 81 | } else { |
121 | } else { |
| 82 | return 0; |
122 | return 0; |
| 83 | } |
123 | } |
| 84 | } |
124 | } |
| 85 | |
125 | |
| 86 | 1; |
126 | =item $sem->waiters |
|
|
127 | |
|
|
128 | In scalar context, returns the number of coroutines waiting for this |
|
|
129 | semaphore. |
|
|
130 | |
|
|
131 | =cut |
|
|
132 | |
|
|
133 | sub waiters { |
|
|
134 | @{$_[0][1]}; |
|
|
135 | } |
|
|
136 | |
|
|
137 | =item $guard = $sem->guard |
|
|
138 | |
|
|
139 | This method calls C<down> and then creates a guard object. When the guard |
|
|
140 | object is destroyed it automatically calls C<up>. |
|
|
141 | |
|
|
142 | =item $guard = $sem->timed_guard($timeout) |
|
|
143 | |
|
|
144 | Like C<guard>, but returns undef if semaphore couldn't be acquired within |
|
|
145 | $timeout seconds, otherwise the guard object. |
|
|
146 | |
|
|
147 | =cut |
|
|
148 | |
|
|
149 | sub guard { |
|
|
150 | &down; |
|
|
151 | # double indirection because bless works on the referenced |
|
|
152 | # object, not (only) on the reference itself. |
|
|
153 | bless \\$_[0], Coro::Semaphore::guard::; |
|
|
154 | } |
|
|
155 | |
|
|
156 | sub timed_guard { |
|
|
157 | &timed_down |
|
|
158 | ? bless \\$_[0], Coro::Semaphore::guard:: |
|
|
159 | : (); |
|
|
160 | } |
|
|
161 | |
|
|
162 | sub Coro::Semaphore::guard::DESTROY { |
|
|
163 | &up(${${$_[0]}}); |
|
|
164 | } |
| 87 | |
165 | |
| 88 | =back |
166 | =back |
| 89 | |
167 | |
| 90 | =head1 AUTHOR |
168 | =head1 AUTHOR |
| 91 | |
169 | |
| 92 | Marc Lehmann <pcg@goof.com> |
170 | Marc Lehmann <schmorp@schmorp.de> |
| 93 | http://www.goof.com/pcg/marc/ |
171 | http://home.schmorp.de/ |
| 94 | |
172 | |
| 95 | =cut |
173 | =cut |
| 96 | |
174 | |
|
|
175 | 1 |
|
|
176 | |
