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1 | package threads::shared; |
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2 | |
3 | use 5.007_003; |
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4 | use strict; |
5 | use warnings; |
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6 | BEGIN { |
7 | require Exporter; |
8 | our @ISA = qw(Exporter); |
9 | our @EXPORT = qw(share cond_wait cond_broadcast cond_signal); |
10 | our $VERSION = '0.90'; |
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11 | |
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12 | if ($threads::threads) { |
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13 | *cond_wait = \&cond_wait_enabled; |
14 | *cond_signal = \&cond_signal_enabled; |
15 | *cond_broadcast = \&cond_broadcast_enabled; |
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16 | require XSLoader; |
17 | XSLoader::load('threads::shared',$VERSION); |
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18 | push @EXPORT,'bless'; |
19 | } |
20 | else { |
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21 | *share = \&share_disabled; |
22 | *cond_wait = \&cond_wait_disabled; |
23 | *cond_signal = \&cond_signal_disabled; |
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24 | *cond_broadcast = \&cond_broadcast_disabled; |
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25 | } |
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26 | } |
27 | |
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28 | |
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29 | sub cond_wait_disabled (\[$@%]) { undef } |
30 | sub cond_signal_disabled (\[$@%]) { undef } |
31 | sub cond_broadcast_disabled (\[$@%]) { undef } |
32 | sub share_disabled (\[$@%]) { return $_[0] } |
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33 | |
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34 | $threads::shared::threads_shared = 1; |
35 | |
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36 | |
37 | sub threads::shared::tie::SPLICE |
38 | { |
39 | die "Splice not implemented for shared arrays"; |
40 | } |
41 | |
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42 | __END__ |
43 | |
44 | =head1 NAME |
45 | |
46 | threads::shared - Perl extension for sharing data structures between threads |
47 | |
48 | =head1 SYNOPSIS |
49 | |
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50 | use threads; |
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51 | use threads::shared; |
52 | |
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53 | my $var : shared; |
54 | |
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55 | my($scalar, @array, %hash); |
56 | share($scalar); |
57 | share(@array); |
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58 | share(%hash); |
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59 | my $bar = &share([]); |
60 | $hash{bar} = &share({}); |
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61 | |
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62 | { lock(%hash); ... } |
63 | |
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64 | cond_wait($scalar); |
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65 | cond_broadcast(@array); |
66 | cond_signal(%hash); |
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67 | |
68 | =head1 DESCRIPTION |
69 | |
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70 | By default, variables are private to each thread, and each newly created |
71 | thread gets a private copy of each existing variable. This module allows |
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72 | you to share variables across different threads (and pseudoforks on Win32). |
73 | It is used together with the threads module. |
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74 | |
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75 | =head1 EXPORT |
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76 | |
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77 | C<share>, C<cond_wait>, C<cond_signal>, C<cond_broadcast> |
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78 | |
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79 | Note that if this module is imported when C<threads> has not yet been |
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80 | loaded, then these functions all become no-ops. This makes it possible |
81 | to write modules that will work in both threaded and non-threaded |
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82 | environments. |
83 | |
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84 | =head1 FUNCTIONS |
85 | |
86 | =over 4 |
87 | |
88 | =item share VARIABLE |
89 | |
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90 | C<share> takes a value and marks it as shared. You can share a scalar, |
91 | array, hash, scalar ref, array ref or hash ref. C<share> will return |
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92 | the shared rvalue but always as a reference. |
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93 | |
94 | C<share> will traverse up references exactly I<one> level. |
95 | C<share(\$a)> is equivalent to C<share($a)>, while C<share(\\$a)> is not. |
96 | |
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97 | A variable can also be marked as shared at compile time by using the |
98 | C<shared> attribute: C<my $var : shared>. |
99 | |
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100 | If you want to share a newly created reference unfortunately you |
101 | need to use C<&share([])> and C<&share({})> syntax due to problems |
102 | with Perl's prototyping. |
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103 | |
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104 | =item lock VARIABLE |
105 | |
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106 | C<lock> places a lock on a variable until the lock goes out of scope. |
107 | If the variable is locked by another thread, the C<lock> call will |
108 | block until it's available. C<lock> is recursive, so multiple calls |
109 | to C<lock> are safe -- the variable will remain locked until the |
110 | outermost lock on the variable goes out of scope. |
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111 | |
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112 | If a container object, such as a hash or array, is locked, all the |
113 | elements of that container are not locked. For example, if a thread |
114 | does a C<lock @a>, any other thread doing a C<lock($a[12])> won't block. |
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115 | |
116 | C<lock> will traverse up references exactly I<one> level. |
117 | C<lock(\$a)> is equivalent to C<lock($a)>, while C<lock(\\$a)> is not. |
118 | |
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119 | Note that you cannot explicitly unlock a variable; you can only wait |
120 | for the lock to go out of scope. If you need more fine-grained |
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121 | control, see L<Thread::Semaphore>. |
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122 | |
123 | =item cond_wait VARIABLE |
124 | |
125 | The C<cond_wait> function takes a B<locked> variable as a parameter, |
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126 | unlocks the variable, and blocks until another thread does a |
127 | C<cond_signal> or C<cond_broadcast> for that same locked variable. |
128 | The variable that C<cond_wait> blocked on is relocked after the |
129 | C<cond_wait> is satisfied. If there are multiple threads |
130 | C<cond_wait>ing on the same variable, all but one will reblock waiting |
131 | to reacquire the lock on the variable. (So if you're only using |
132 | C<cond_wait> for synchronisation, give up the lock as soon as |
133 | possible). The two actions of unlocking the variable and entering the |
134 | blocked wait state are atomic, The two actions of exiting from the |
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135 | blocked wait state and relocking the variable are not. |
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136 | |
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137 | It is important to note that the variable can be notified even if |
138 | no thread C<cond_signal> or C<cond_broadcast> on the variable. |
139 | It is therefore important to check the value of the variable and |
140 | go back to waiting if the requirement is not fulfilled. |
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141 | |
142 | =item cond_signal VARIABLE |
143 | |
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144 | The C<cond_signal> function takes a B<locked> variable as a parameter |
145 | and unblocks one thread that's C<cond_wait>ing on that variable. If |
146 | more than one thread is blocked in a C<cond_wait> on that variable, |
147 | only one (and which one is indeterminate) will be unblocked. |
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148 | |
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149 | If there are no threads blocked in a C<cond_wait> on the variable, |
150 | the signal is discarded. By always locking before signaling, you can |
151 | (with care), avoid signaling before another thread has entered cond_wait(). |
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152 | |
153 | C<cond_signal> will normally generate a warning if you attempt to use it |
154 | on an unlocked variable. On the rare occasions where doing this may be |
155 | sensible, you can skip the warning with |
156 | |
157 | { no warnings 'threads'; cond_signal($foo) } |
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158 | |
159 | =item cond_broadcast VARIABLE |
160 | |
161 | The C<cond_broadcast> function works similarly to C<cond_signal>. |
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162 | C<cond_broadcast>, though, will unblock B<all> the threads that are |
163 | blocked in a C<cond_wait> on the locked variable, rather than only one. |
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164 | |
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165 | =back |
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166 | |
167 | =head1 NOTES |
168 | |
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169 | threads::shared is designed to disable itself silently if threads are |
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170 | not available. If you want access to threads, you must C<use threads> |
171 | before you C<use threads::shared>. threads will emit a warning if you |
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172 | use it after threads::shared. |
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173 | |
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174 | =head1 BUGS |
175 | |
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176 | C<bless> is not supported on shared references. In the current version, |
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177 | C<bless> will only bless the thread local reference and the blessing |
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178 | will not propagate to the other threads. This is expected to be |
179 | implemented in a future version of Perl. |
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180 | |
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181 | Does not support splice on arrays! |
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182 | |
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183 | Taking references to the elements of shared arrays and hashes does not |
184 | autovivify the elements, and neither does slicing a shared array/hash |
185 | over non-existent indices/keys autovivify the elements. |
186 | |
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187 | share() allows you to C<< share $hashref->{key} >> without giving any error |
188 | message. But the C<< $hashref->{key} >> is B<not> shared, causing the error |
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189 | "locking can only be used on shared values" to occur when you attempt to |
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190 | C<< lock $hasref->{key} >>. |
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191 | |
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192 | =head1 AUTHOR |
193 | |
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194 | Arthur Bergman E<lt>arthur at contiller.seE<gt> |
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195 | |
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196 | threads::shared is released under the same license as Perl |
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197 | |
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198 | Documentation borrowed from the old Thread.pm |
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199 | |
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200 | =head1 SEE ALSO |
201 | |
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202 | L<threads>, L<perlthrtut>, L<http://www.perl.com/pub/a/2002/06/11/threads.html> |
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203 | |
204 | =cut |