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 | BEGIN { eval { require warnings } && warnings->unimport ("uninitialized") } |
39 | use common::sense; |
37 | |
40 | |
38 | use Coro (); |
41 | use Coro (); |
39 | |
42 | |
40 | $VERSION = 1.9; |
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 |
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50 | |
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51 | sub new { |
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52 | bless [defined $_[1] ? $_[1] : 1], $_[0]; |
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53 | } |
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54 | |
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55 | =item $sem->count |
52 | =item $sem->count |
56 | |
53 | |
57 | Returns the current semaphore count. |
54 | Returns the current semaphore count. |
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 | |
55 | |
65 | =item $sem->adjust ($diff) |
56 | =item $sem->adjust ($diff) |
66 | |
57 | |
67 | Atomically adds the amount given to the current semaphore count. If the |
58 | Atomically adds the amount given to the current semaphore count. If the |
68 | count becomes positive, wakes up any waiters. Does not block if the count |
59 | count becomes positive, wakes up any waiters. Does not block if the count |
69 | becomes negative, however. |
60 | becomes negative, however. |
70 | |
61 | |
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 | |
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80 | =item $sem->down |
62 | =item $sem->down |
81 | |
63 | |
82 | Decrement the counter, therefore "locking" the semaphore. This method |
64 | Decrement the counter, therefore "locking" the semaphore. This method |
83 | waits until the semaphore is available if the counter is zero. |
65 | waits until the semaphore is available if the counter is zero. |
84 | |
66 | |
85 | =item $status = $sem->timed_down($timeout) |
67 | =item $sem->wait |
86 | |
68 | |
87 | 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, |
88 | $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). |
89 | |
86 | |
90 | =cut |
87 | =cut |
91 | |
88 | |
92 | sub down { |
89 | #=item $status = $sem->timed_down ($timeout) |
93 | while ($_[0][0] <= 0) { |
90 | # |
94 | push @{$_[0][1]}, $Coro::current; |
91 | #Like C<down>, but returns false if semaphore couldn't be acquired within |
95 | &Coro::schedule; |
92 | #$timeout seconds, otherwise true. |
96 | } |
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97 | --$_[0][0]; |
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98 | } |
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99 | |
93 | |
100 | sub timed_down { |
94 | #sub timed_down { |
101 | require Coro::Timer; |
95 | # require Coro::Timer; |
102 | my $timeout = Coro::Timer::timeout($_[1]); |
96 | # my $timeout = Coro::Timer::timeout ($_[1]); |
103 | |
97 | # |
104 | while ($_[0][0] <= 0) { |
98 | # while ($_[0][0] <= 0) { |
105 | push @{$_[0][1]}, $Coro::current; |
99 | # push @{$_[0][1]}, $Coro::current; |
106 | &Coro::schedule; |
100 | # &Coro::schedule; |
107 | if ($timeout) { |
101 | # if ($timeout) { |
108 | # ugly as hell. slow, too, btw! |
102 | # # ugly as hell. slow, too, btw! |
109 | for (0..$#{$_[0][1]}) { |
103 | # for (0..$#{$_[0][1]}) { |
110 | if ($_[0][1][$_] == $Coro::current) { |
104 | # if ($_[0][1][$_] == $Coro::current) { |
111 | splice @{$_[0][1]}, $_, 1; |
105 | # splice @{$_[0][1]}, $_, 1; |
112 | return; |
106 | # return; |
113 | } |
107 | # } |
114 | } |
108 | # } |
115 | die; |
109 | # die; |
116 | } |
110 | # } |
117 | } |
111 | # } |
118 | |
112 | # |
119 | --$_[0][0]; |
113 | # --$_[0][0]; |
120 | return 1; |
114 | # return 1; |
121 | } |
115 | #} |
122 | |
116 | |
123 | =item $sem->up |
117 | =item $sem->up |
124 | |
118 | |
125 | Unlock the semaphore again. |
119 | Unlock the semaphore again. |
126 | |
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127 | =cut |
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128 | |
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129 | sub up { |
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130 | if (++$_[0][0] > 0) { |
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131 | (shift @{$_[0][1]})->ready if @{$_[0][1]}; |
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132 | } |
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133 | } |
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134 | |
120 | |
135 | =item $sem->try |
121 | =item $sem->try |
136 | |
122 | |
137 | Try to C<down> the semaphore. Returns true when this was possible, |
123 | Try to C<down> the semaphore. Returns true when this was possible, |
138 | otherwise return false and leave the semaphore unchanged. |
124 | otherwise return false and leave the semaphore unchanged. |
139 | |
125 | |
140 | =cut |
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141 | |
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142 | sub try { |
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143 | if ($_[0][0] > 0) { |
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144 | --$_[0][0]; |
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145 | return 1; |
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146 | } else { |
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147 | return 0; |
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148 | } |
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149 | } |
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150 | |
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151 | =item $sem->waiters |
126 | =item $sem->waiters |
152 | |
127 | |
153 | In scalar context, returns the number of coroutines waiting for this |
128 | In scalar context, returns the number of threads waiting for this |
154 | semaphore. |
129 | semaphore. |
155 | |
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156 | =cut |
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157 | |
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158 | sub waiters { |
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159 | @{$_[0][1]}; |
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160 | } |
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161 | |
130 | |
162 | =item $guard = $sem->guard |
131 | =item $guard = $sem->guard |
163 | |
132 | |
164 | 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 |
165 | object is destroyed it automatically calls C<up>. |
134 | object is destroyed it automatically calls C<up>. |
166 | |
135 | |
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 | $timeout seconds, otherwise the guard object. |
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171 | |
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172 | =cut |
136 | =cut |
173 | |
137 | |
174 | sub guard { |
138 | sub guard { |
175 | &down; |
139 | &down; |
176 | # double indirection because bless works on the referenced |
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177 | # object, not (only) on the reference itself. |
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178 | bless \\$_[0], Coro::Semaphore::guard::; |
140 | bless [$_[0]], Coro::Semaphore::guard:: |
179 | } |
141 | } |
180 | |
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 | #$timeout seconds, otherwise the guard object. |
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147 | |
181 | sub timed_guard { |
148 | #sub timed_guard { |
182 | &timed_down |
149 | # &timed_down |
183 | ? bless \\$_[0], Coro::Semaphore::guard:: |
150 | # ? bless \\$_[0], Coro::Semaphore::guard:: |
184 | : (); |
151 | # : (); |
185 | } |
152 | #} |
186 | |
153 | |
187 | sub Coro::Semaphore::guard::DESTROY { |
154 | sub Coro::Semaphore::guard::DESTROY { |
188 | &up(${${$_[0]}}); |
155 | &up($_[0][0]); |
189 | } |
156 | } |
190 | |
157 | |
191 | =back |
158 | =back |
192 | |
159 | |
193 | =head1 AUTHOR |
160 | =head1 AUTHOR |