1 | =head1 NAME |
1 | =head1 NAME |
2 | |
2 | |
3 | Coro::Semaphore - non-binary semaphores |
3 | Coro::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 | |
19 | This module implements counting semaphores. You can initialize a mutex |
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 |
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 |
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 |
22 | associated with semaphores, so one thread can C<down> it while another |
23 | can C<up> it. |
23 | can C<up> it. |
24 | |
24 | |
25 | Counting semaphores are typically used to coordinate access to |
25 | Counting semaphores are typically used to coordinate access to |
26 | resources, with the semaphore count initialized to the number of free |
26 | resources, with the semaphore count initialized to the number of free |
27 | resources. Coroutines then increment the count when resources are added |
27 | resources. Threads then increment the count when resources are added |
28 | and decrement the count when resources are removed. |
28 | and decrement the count when resources are removed. |
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29 | |
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30 | You don't have to load C<Coro::Semaphore> manually, it will be loaded |
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31 | automatically 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 | |
34 | package Coro::Semaphore; |
37 | package Coro::Semaphore; |
35 | |
38 | |
36 | no warnings qw(uninitialized); |
39 | use common::sense; |
37 | |
40 | |
38 | use Coro (); |
41 | use Coro (); |
39 | |
42 | |
40 | $VERSION = 0.65; |
43 | our $VERSION = 6.04; |
41 | |
44 | |
42 | =item new [inital count] |
45 | =item new [inital count] |
43 | |
46 | |
44 | Creates a new sempahore object with the given initial lock count. The |
47 | Creates a new sempahore object with the given initial lock count. The |
45 | default lock count is 1, which means it is unlocked by default. Zero (or |
48 | 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 |
49 | negative values) are also allowed, in which case the semaphore is locked |
47 | by default. |
50 | by default. |
48 | |
51 | |
49 | =cut |
52 | =item $sem->count |
50 | |
53 | |
51 | sub new { |
54 | Returns the current semaphore count. |
52 | bless [defined $_[1] ? $_[1] : 1], $_[0]; |
55 | |
53 | } |
56 | =item $sem->adjust ($diff) |
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57 | |
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58 | Atomically adds the amount given to the current semaphore count. If the |
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59 | count becomes positive, wakes up any waiters. Does not block if the count |
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60 | becomes negative, however. |
54 | |
61 | |
55 | =item $sem->down |
62 | =item $sem->down |
56 | |
63 | |
57 | Decrement the counter, therefore "locking" the semaphore. This method |
64 | Decrement the counter, therefore "locking" the semaphore. This method |
58 | waits until the semaphore is available if the counter is zero. |
65 | waits 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 | |
62 | Like C<down>, but returns false if semaphore couldn't be acquired within |
69 | Similar to C<down>, but does not actually decrement the counter. Instead, |
63 | $timeout seconds, otherwise true. |
70 | when this function returns, a following call to C<down> or C<try> is |
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71 | guaranteed to succeed without blocking, until the next thread switch |
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72 | (C<cede> etc.). |
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73 | |
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74 | Note that using C<wait> is much less efficient than using C<down>, so try |
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75 | to prefer C<down> whenever possible. |
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76 | |
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77 | =item $sem->wait ($callback) |
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78 | |
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79 | If you pass a callback argument to C<wait>, it will not wait, but |
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80 | immediately return. The callback will be called as soon as the semaphore |
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81 | becomes available (which might be instantly), and gets passed the |
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82 | semaphore as first argument. |
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83 | |
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84 | The callback might C<down> the semaphore exactly once, might wake up other |
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85 | threads, but is I<NOT> allowed to block (switch to other threads). |
64 | |
86 | |
65 | =cut |
87 | =cut |
66 | |
88 | |
67 | sub 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 | } |
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72 | --$_[0][0]; |
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73 | } |
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74 | |
93 | |
75 | sub 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 $sem->up |
99 | |
118 | |
100 | Unlock the semaphore again. |
119 | Unlock the semaphore again. |
101 | |
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102 | =cut |
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103 | |
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104 | sub up { |
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105 | if (++$_[0][0] > 0) { |
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106 | (shift @{$_[0][1]})->ready if @{$_[0][1]}; |
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107 | } |
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108 | } |
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109 | |
120 | |
110 | =item $sem->try |
121 | =item $sem->try |
111 | |
122 | |
112 | Try to C<down> the semaphore. Returns true when this was possible, |
123 | Try to C<down> the semaphore. Returns true when this was possible, |
113 | otherwise return false and leave the semaphore unchanged. |
124 | otherwise return false and leave the semaphore unchanged. |
114 | |
125 | |
115 | =cut |
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116 | |
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117 | sub try { |
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118 | if ($_[0][0] > 0) { |
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119 | --$_[0][0]; |
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120 | return 1; |
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121 | } else { |
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122 | return 0; |
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123 | } |
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124 | } |
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125 | |
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126 | =item $sem->waiters |
126 | =item $sem->waiters |
127 | |
127 | |
128 | In scalar context, returns the number of coroutines waiting for this |
128 | In scalar context, returns the number of threads waiting for this |
129 | semaphore. |
129 | semaphore. |
130 | |
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131 | =cut |
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132 | |
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133 | sub waiters { |
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134 | @{$_[0][1]}; |
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135 | } |
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136 | |
130 | |
137 | =item $guard = $sem->guard |
131 | =item $guard = $sem->guard |
138 | |
132 | |
139 | This method calls C<down> and then creates a guard object. When the guard |
133 | This method calls C<down> and then creates a guard object. When the guard |
140 | object is destroyed it automatically calls C<up>. |
134 | object is destroyed it automatically calls C<up>. |
141 | |
135 | |
142 | =item $guard = $sem->timed_guard($timeout) |
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143 | |
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144 | Like C<guard>, but returns undef if semaphore couldn't be acquired within |
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145 | $timeout seconds, otherwise the guard object. |
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146 | |
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147 | =cut |
136 | =cut |
148 | |
137 | |
149 | sub guard { |
138 | sub guard { |
150 | &down; |
139 | &down; |
151 | # double indirection because bless works on the referenced |
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152 | # object, not (only) on the reference itself. |
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153 | bless \\$_[0], Coro::Semaphore::guard::; |
140 | bless [$_[0]], Coro::Semaphore::guard:: |
154 | } |
141 | } |
155 | |
142 | |
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143 | #=item $guard = $sem->timed_guard ($timeout) |
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144 | # |
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145 | #Like C<guard>, but returns undef if semaphore couldn't be acquired within |
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146 | #$timeout seconds, otherwise the guard object. |
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147 | |
156 | sub timed_guard { |
148 | #sub timed_guard { |
157 | &timed_down |
149 | # &timed_down |
158 | ? bless \\$_[0], Coro::Semaphore::guard:: |
150 | # ? bless \\$_[0], Coro::Semaphore::guard:: |
159 | : (); |
151 | # : (); |
160 | } |
152 | #} |
161 | |
153 | |
162 | sub Coro::Semaphore::guard::DESTROY { |
154 | sub Coro::Semaphore::guard::DESTROY { |
163 | &up(${${$_[0]}}); |
155 | &up($_[0][0]); |
164 | } |
156 | } |
165 | |
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166 | 1; |
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167 | |
157 | |
168 | =back |
158 | =back |
169 | |
159 | |
170 | =head1 AUTHOR |
160 | =head1 AUTHOR |
171 | |
161 | |
172 | Marc Lehmann <pcg@goof.com> |
162 | Marc Lehmann <schmorp@schmorp.de> |
173 | http://www.goof.com/pcg/marc/ |
163 | http://home.schmorp.de/ |
174 | |
164 | |
175 | =cut |
165 | =cut |
176 | |
166 | |
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167 | 1 |
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168 | |