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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 | |
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36 | no warnings; |
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37 | |
25 | use Coro (); |
38 | use Coro (); |
26 | |
39 | |
27 | $VERSION = 0.12; |
40 | $VERSION = 4.741; |
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 |
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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]; |
38 | } |
53 | } |
39 | |
54 | |
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55 | =item $sem->count |
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56 | |
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57 | Returns the current semaphore count. |
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58 | |
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59 | =cut |
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60 | |
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61 | sub count { |
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62 | $_[0][0] |
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63 | } |
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64 | |
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65 | =item $sem->adjust ($diff) |
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66 | |
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67 | Atomically adds the amount given to the current semaphore count. If the |
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68 | count becomes positive, wakes up any waiters. Does not block if the count |
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69 | becomes negative, however. |
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70 | |
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71 | =cut |
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72 | |
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73 | sub adjust { |
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74 | # basically a weird copy of up |
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75 | if (($_[0][0] += $_[1]) > 0) { |
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76 | (shift @{$_[0][1]})->ready if @{$_[0][1]}; |
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77 | } |
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78 | } |
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79 | |
40 | =item $sem->down |
80 | =item $sem->down |
41 | |
81 | |
42 | Decrement the counter, therefore "locking" the semaphore. This method |
82 | Decrement the counter, therefore "locking" the semaphore. This method |
43 | waits until the semaphore is available if the counter is zero. |
83 | waits until the semaphore is available if the counter is zero. |
44 | |
84 | |
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85 | =item $status = $sem->timed_down ($timeout) |
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86 | |
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87 | Like C<down>, but returns false if semaphore couldn't be acquired within |
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88 | $timeout seconds, otherwise true. |
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89 | |
45 | =cut |
90 | =cut |
46 | |
91 | |
47 | sub down { |
92 | sub down { |
48 | my $self = shift; |
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49 | while ($self->[0] <= 0) { |
93 | while ($_[0][0] <= 0) { |
50 | push @{$self->[1]}, $Coro::current; |
94 | push @{$_[0][1]}, $Coro::current; |
51 | Coro::schedule; |
95 | &Coro::schedule; |
52 | } |
96 | } |
53 | --$self->[0]; |
97 | --$_[0][0]; |
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98 | } |
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99 | |
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100 | sub timed_down { |
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101 | require Coro::Timer; |
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102 | my $timeout = Coro::Timer::timeout ($_[1]); |
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103 | |
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104 | while ($_[0][0] <= 0) { |
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105 | push @{$_[0][1]}, $Coro::current; |
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106 | &Coro::schedule; |
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107 | if ($timeout) { |
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108 | # ugly as hell. slow, too, btw! |
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109 | for (0..$#{$_[0][1]}) { |
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110 | if ($_[0][1][$_] == $Coro::current) { |
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111 | splice @{$_[0][1]}, $_, 1; |
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112 | return; |
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113 | } |
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114 | } |
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115 | die; |
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116 | } |
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117 | } |
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118 | |
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119 | --$_[0][0]; |
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120 | return 1; |
54 | } |
121 | } |
55 | |
122 | |
56 | =item $sem->up |
123 | =item $sem->up |
57 | |
124 | |
58 | Unlock the semaphore again. |
125 | Unlock the semaphore again. |
59 | |
126 | |
60 | =cut |
127 | =cut |
61 | |
128 | |
62 | sub up { |
129 | sub up { |
63 | my $self = shift; |
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64 | if (++$self->[0] > 0) { |
130 | if (++$_[0][0] > 0) { |
65 | (shift @{$self->[1]})->ready if @{$self->[1]}; |
131 | (shift @{$_[0][1]})->ready if @{$_[0][1]}; |
66 | } |
132 | } |
67 | } |
133 | } |
68 | |
134 | |
69 | =item $sem->try |
135 | =item $sem->try |
70 | |
136 | |
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72 | otherwise return false and leave the semaphore unchanged. |
138 | otherwise return false and leave the semaphore unchanged. |
73 | |
139 | |
74 | =cut |
140 | =cut |
75 | |
141 | |
76 | sub try { |
142 | sub try { |
77 | my $self = shift; |
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78 | if ($self->[0] > 0) { |
143 | if ($_[0][0] > 0) { |
79 | --$self->[0]; |
144 | --$_[0][0]; |
80 | return 1; |
145 | return 1; |
81 | } else { |
146 | } else { |
82 | return 0; |
147 | return 0; |
83 | } |
148 | } |
84 | } |
149 | } |
85 | |
150 | |
86 | 1; |
151 | =item $sem->waiters |
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152 | |
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153 | In scalar context, returns the number of coroutines waiting for this |
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154 | semaphore. |
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155 | |
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156 | =cut |
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157 | |
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158 | sub waiters { |
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159 | @{$_[0][1]}; |
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160 | } |
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161 | |
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162 | =item $guard = $sem->guard |
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163 | |
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164 | This method calls C<down> and then creates a guard object. When the guard |
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165 | object is destroyed it automatically calls C<up>. |
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166 | |
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167 | =item $guard = $sem->timed_guard ($timeout) |
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168 | |
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169 | Like C<guard>, but returns undef if semaphore couldn't be acquired within |
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170 | $timeout seconds, otherwise the guard object. |
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171 | |
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172 | =cut |
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173 | |
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174 | sub guard { |
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175 | &down; |
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176 | # double indirection because bless works on the referenced |
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177 | # object, not (only) on the reference itself. |
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178 | bless \\$_[0], Coro::Semaphore::guard::; |
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179 | } |
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180 | |
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181 | sub timed_guard { |
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182 | &timed_down |
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183 | ? bless \\$_[0], Coro::Semaphore::guard:: |
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184 | : (); |
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185 | } |
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186 | |
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187 | sub Coro::Semaphore::guard::DESTROY { |
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188 | &up(${${$_[0]}}); |
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189 | } |
87 | |
190 | |
88 | =back |
191 | =back |
89 | |
192 | |
90 | =head1 AUTHOR |
193 | =head1 AUTHOR |
91 | |
194 | |
92 | Marc Lehmann <pcg@goof.com> |
195 | Marc Lehmann <schmorp@schmorp.de> |
93 | http://www.goof.com/pcg/marc/ |
196 | http://home.schmorp.de/ |
94 | |
197 | |
95 | =cut |
198 | =cut |
96 | |
199 | |
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200 | 1 |
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201 | |