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14 | |
14 | |
15 | $sig->up; |
15 | $sig->up; |
16 | |
16 | |
17 | =head1 DESCRIPTION |
17 | =head1 DESCRIPTION |
18 | |
18 | |
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19 | This module implements counted semaphores. You can initialize a mutex |
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20 | with any level of parallel users, that is, you can intialize a sempahore |
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21 | that can be C<down>ed more than once until it blocks. There is no owner |
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22 | associated with semaphores, so one coroutine can C<down> it while another |
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23 | can C<up> it. |
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24 | |
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25 | Counting semaphores are typically used to coordinate access to |
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26 | resources, with the semaphore count initialized to the number of free |
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27 | resources. Coroutines then increment the count when resources are added |
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28 | and decrement the count when resources are removed. |
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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 | |
25 | use Coro (); |
36 | use Coro (); |
26 | |
37 | |
27 | $VERSION = 0.12; |
38 | $VERSION = 0.45; |
28 | |
39 | |
29 | =item new [inital count, default zero] |
40 | =item new [inital count, default one] |
30 | |
41 | |
31 | Creates a new sempahore object with the given initial lock count. The |
42 | 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. |
43 | default lock count is 1, which means it is unlocked by default. Zero (or |
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44 | negative values) are also allowed, in which case the semaphore is locked |
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45 | by default. |
33 | |
46 | |
34 | =cut |
47 | =cut |
35 | |
48 | |
36 | sub new { |
49 | sub new { |
37 | bless [defined $_[1] ? $_[1] : 1], $_[0]; |
50 | bless [defined $_[1] ? $_[1] : 1], $_[0]; |
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81 | } else { |
94 | } else { |
82 | return 0; |
95 | return 0; |
83 | } |
96 | } |
84 | } |
97 | } |
85 | |
98 | |
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99 | =item $guard = $sem->guard |
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100 | |
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101 | This method calls C<down> and then creates a guard object. When the guard |
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102 | object is destroyed it automatically calls C<up>. |
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103 | |
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104 | =cut |
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105 | |
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106 | sub guard { |
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107 | $_[0]->down; |
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108 | # double indirection because bless works on the referenced |
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109 | # object, not (only) on the reference itself. |
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110 | bless \\$_[0], Coro::Semaphore::Guard::; |
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111 | } |
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112 | |
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113 | sub Coro::Semaphore::Guard::DESTROY { |
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114 | ${${$_[0]}}->up; |
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115 | } |
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116 | |
86 | 1; |
117 | 1; |
87 | |
118 | |
88 | =back |
119 | =back |
89 | |
120 | |
90 | =head1 AUTHOR |
121 | =head1 AUTHOR |