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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 counting 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::Process (); |
36 | no warnings qw(uninitialized); |
| 26 | |
37 | |
| 27 | $VERSION = 0.01; |
38 | use Coro (); |
| 28 | |
39 | |
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40 | $VERSION = 0.52; |
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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 |
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46 | negative values) are also allowed, in which case the semaphore is locked |
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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]; |
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| 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 | |
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60 | =item $status = $sem->timed_down($timeout) |
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61 | |
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62 | Like C<down>, but returns false if semaphore couldn't be acquired within |
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63 | $timeout seconds, otherwise true. |
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64 | |
| 45 | =cut |
65 | =cut |
| 46 | |
66 | |
| 47 | sub down { |
67 | sub down { |
| 48 | my $self = shift; |
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| 49 | while ($self->[0] <= 0) { |
68 | while ($_[0][0] <= 0) { |
| 50 | push @{$self->[1]}, $Coro::Process::current; |
69 | push @{$_[0][1]}, $Coro::current; |
| 51 | Coro::Process::schedule; |
70 | Coro::schedule; |
| 52 | } |
71 | } |
| 53 | --$self->[0]; |
72 | --$_[0][0]; |
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73 | } |
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74 | |
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75 | sub timed_down { |
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76 | require Coro::Timer; |
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77 | my $timeout = Coro::Timer::timeout($_[1]); |
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78 | |
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79 | while ($_[0][0] <= 0) { |
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80 | push @{$_[0][1]}, $Coro::current; |
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81 | Coro::schedule; |
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82 | $timeout and return; |
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83 | } |
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84 | |
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85 | --$_[0][0]; |
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86 | return 1; |
| 54 | } |
87 | } |
| 55 | |
88 | |
| 56 | =item $sem->up |
89 | =item $sem->up |
| 57 | |
90 | |
| 58 | Unlock the semaphore again. |
91 | Unlock the semaphore again. |
| 59 | |
92 | |
| 60 | =cut |
93 | =cut |
| 61 | |
94 | |
| 62 | sub up { |
95 | sub up { |
| 63 | my $self = shift; |
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| 64 | if (++$self->[0] > 0) { |
96 | if (++$_[0][0] > 0) { |
| 65 | (shift @{$self->[1]})->ready if @{$self->[1]}; |
97 | (shift @{$_[0][1]})->ready if @{$_[0][1]}; |
| 66 | } |
98 | } |
| 67 | } |
99 | } |
| 68 | |
100 | |
| 69 | =item $sem->try |
101 | =item $sem->try |
| 70 | |
102 | |
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| 72 | otherwise return false and leave the semaphore unchanged. |
104 | otherwise return false and leave the semaphore unchanged. |
| 73 | |
105 | |
| 74 | =cut |
106 | =cut |
| 75 | |
107 | |
| 76 | sub try { |
108 | sub try { |
| 77 | my $self = shift; |
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| 78 | if ($self->[0] > 0) { |
109 | if ($_[0][0] > 0) { |
| 79 | --$self->[0]; |
110 | --$_[0][0]; |
| 80 | return 1; |
111 | return 1; |
| 81 | } else { |
112 | } else { |
| 82 | return 0; |
113 | return 0; |
| 83 | } |
114 | } |
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115 | } |
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116 | |
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117 | =item $sem->waiters |
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118 | |
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119 | In scalar context, returns the number of coroutines waiting for this |
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120 | semaphore. |
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121 | |
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122 | =cut |
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123 | |
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124 | sub waiters { |
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125 | @{$_[0][1]}; |
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126 | } |
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127 | |
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128 | =item $guard = $sem->guard |
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129 | |
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130 | This method calls C<down> and then creates a guard object. When the guard |
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131 | object is destroyed it automatically calls C<up>. |
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132 | |
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133 | =item $guard = $sem->timed_guard($timeout) |
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134 | |
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135 | Like C<guard>, but returns undef if semaphore couldn't be acquired within |
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136 | $timeout seconds, otherwise the guard object. |
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137 | |
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138 | =cut |
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139 | |
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140 | sub guard { |
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141 | &down; |
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142 | # double indirection because bless works on the referenced |
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143 | # object, not (only) on the reference itself. |
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144 | bless \\$_[0], Coro::Semaphore::guard; |
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145 | } |
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146 | |
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147 | sub timed_guard { |
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148 | &timed_down |
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149 | ? bless \\$_[0], Coro::Semaphore::guard |
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150 | : (); |
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151 | } |
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152 | |
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153 | sub Coro::Semaphore::guard::DESTROY { |
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154 | &up(${${$_[0]}}); |
| 84 | } |
155 | } |
| 85 | |
156 | |
| 86 | 1; |
157 | 1; |
| 87 | |
158 | |
| 88 | =back |
159 | =back |
