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365 | rain-er | 1 | package threads::shared; |
2 | |||
3 | use 5.008; |
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4 | |||
5 | use strict; |
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6 | use warnings; |
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7 | |||
8 | use Scalar::Util qw(reftype refaddr blessed); |
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9 | |||
10 | our $VERSION = '1.28'; |
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11 | my $XS_VERSION = $VERSION; |
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12 | $VERSION = eval $VERSION; |
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13 | |||
14 | # Declare that we have been loaded |
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15 | $threads::shared::threads_shared = 1; |
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16 | |||
17 | # Load the XS code, if applicable |
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18 | if ($threads::threads) { |
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19 | require XSLoader; |
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20 | XSLoader::load('threads::shared', $XS_VERSION); |
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21 | |||
22 | *is_shared = \&_id; |
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23 | |||
24 | } else { |
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25 | # String eval is generally evil, but we don't want these subs to |
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26 | # exist at all if 'threads' is not loaded successfully. |
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27 | # Vivifying them conditionally this way saves on average about 4K |
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28 | # of memory per thread. |
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29 | eval <<'_MARKER_'; |
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30 | sub share (\[$@%]) { return $_[0] } |
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31 | sub is_shared (\[$@%]) { undef } |
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32 | sub cond_wait (\[$@%];\[$@%]) { undef } |
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33 | sub cond_timedwait (\[$@%]$;\[$@%]) { undef } |
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34 | sub cond_signal (\[$@%]) { undef } |
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35 | sub cond_broadcast (\[$@%]) { undef } |
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36 | _MARKER_ |
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37 | } |
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38 | |||
39 | |||
40 | ### Export ### |
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41 | |||
42 | sub import |
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43 | { |
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44 | # Exported subroutines |
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45 | my @EXPORT = qw(share is_shared cond_wait cond_timedwait |
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46 | cond_signal cond_broadcast shared_clone); |
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47 | if ($threads::threads) { |
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48 | push(@EXPORT, 'bless'); |
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49 | } |
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50 | |||
51 | # Export subroutine names |
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52 | my $caller = caller(); |
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53 | foreach my $sym (@EXPORT) { |
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54 | no strict 'refs'; |
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55 | *{$caller.'::'.$sym} = \&{$sym}; |
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56 | } |
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57 | } |
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58 | |||
59 | |||
60 | # Predeclarations for internal functions |
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61 | my ($make_shared); |
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62 | |||
63 | |||
64 | ### Methods, etc. ### |
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65 | |||
66 | sub threads::shared::tie::SPLICE |
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67 | { |
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68 | require Carp; |
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69 | Carp::croak('Splice not implemented for shared arrays'); |
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70 | } |
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71 | |||
72 | |||
73 | # Create a thread-shared clone of a complex data structure or object |
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74 | sub shared_clone |
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75 | { |
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76 | if (@_ != 1) { |
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77 | require Carp; |
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78 | Carp::croak('Usage: shared_clone(REF)'); |
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79 | } |
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80 | |||
81 | return $make_shared->(shift, {}); |
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82 | } |
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83 | |||
84 | |||
85 | ### Internal Functions ### |
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86 | |||
87 | # Used by shared_clone() to recursively clone |
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88 | # a complex data structure or object |
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89 | $make_shared = sub { |
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90 | my ($item, $cloned) = @_; |
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91 | |||
92 | # Just return the item if: |
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93 | # 1. Not a ref; |
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94 | # 2. Already shared; or |
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95 | # 3. Not running 'threads'. |
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96 | return $item if (! ref($item) || is_shared($item) || ! $threads::threads); |
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97 | |||
98 | # Check for previously cloned references |
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99 | # (this takes care of circular refs as well) |
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100 | my $addr = refaddr($item); |
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101 | if (exists($cloned->{$addr})) { |
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102 | # Return the already existing clone |
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103 | return $cloned->{$addr}; |
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104 | } |
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105 | |||
106 | # Make copies of array, hash and scalar refs and refs of refs |
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107 | my $copy; |
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108 | my $ref_type = reftype($item); |
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109 | |||
110 | # Copy an array ref |
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111 | if ($ref_type eq 'ARRAY') { |
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112 | # Make empty shared array ref |
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113 | $copy = &share([]); |
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114 | # Add to clone checking hash |
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115 | $cloned->{$addr} = $copy; |
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116 | # Recursively copy and add contents |
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117 | push(@$copy, map { $make_shared->($_, $cloned) } @$item); |
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118 | } |
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119 | |||
120 | # Copy a hash ref |
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121 | elsif ($ref_type eq 'HASH') { |
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122 | # Make empty shared hash ref |
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123 | $copy = &share({}); |
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124 | # Add to clone checking hash |
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125 | $cloned->{$addr} = $copy; |
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126 | # Recursively copy and add contents |
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127 | foreach my $key (keys(%{$item})) { |
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128 | $copy->{$key} = $make_shared->($item->{$key}, $cloned); |
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129 | } |
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130 | } |
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131 | |||
132 | # Copy a scalar ref |
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133 | elsif ($ref_type eq 'SCALAR') { |
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134 | $copy = \do{ my $scalar = $$item; }; |
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135 | share($copy); |
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136 | # Add to clone checking hash |
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137 | $cloned->{$addr} = $copy; |
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138 | } |
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139 | |||
140 | # Copy of a ref of a ref |
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141 | elsif ($ref_type eq 'REF') { |
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142 | # Special handling for $x = \$x |
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143 | if ($addr == refaddr($$item)) { |
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144 | $copy = \$copy; |
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145 | share($copy); |
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146 | $cloned->{$addr} = $copy; |
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147 | } else { |
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148 | my $tmp; |
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149 | $copy = \$tmp; |
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150 | share($copy); |
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151 | # Add to clone checking hash |
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152 | $cloned->{$addr} = $copy; |
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153 | # Recursively copy and add contents |
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154 | $tmp = $make_shared->($$item, $cloned); |
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155 | } |
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156 | |||
157 | } else { |
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158 | require Carp; |
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159 | Carp::croak("Unsupported ref type: ", $ref_type); |
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160 | } |
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161 | |||
162 | # If input item is an object, then bless the copy into the same class |
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163 | if (my $class = blessed($item)) { |
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164 | bless($copy, $class); |
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165 | } |
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166 | |||
167 | # Clone READONLY flag |
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168 | if ($ref_type eq 'SCALAR') { |
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169 | if (Internals::SvREADONLY($$item)) { |
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170 | Internals::SvREADONLY($$copy, 1) if ($] >= 5.008003); |
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171 | } |
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172 | } |
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173 | if (Internals::SvREADONLY($item)) { |
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174 | Internals::SvREADONLY($copy, 1) if ($] >= 5.008003); |
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175 | } |
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176 | |||
177 | return $copy; |
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178 | }; |
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179 | |||
180 | 1; |
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181 | |||
182 | __END__ |
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183 | |||
184 | =head1 NAME |
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185 | |||
186 | threads::shared - Perl extension for sharing data structures between threads |
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187 | |||
188 | =head1 VERSION |
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189 | |||
190 | This document describes threads::shared version 1.28 |
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191 | |||
192 | =head1 SYNOPSIS |
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193 | |||
194 | use threads; |
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195 | use threads::shared; |
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196 | |||
197 | my $var :shared; |
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198 | my %hsh :shared; |
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199 | my @ary :shared; |
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200 | |||
201 | my ($scalar, @array, %hash); |
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202 | share($scalar); |
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203 | share(@array); |
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204 | share(%hash); |
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205 | |||
206 | $var = $scalar_value; |
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207 | $var = $shared_ref_value; |
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208 | $var = shared_clone($non_shared_ref_value); |
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209 | $var = shared_clone({'foo' => [qw/foo bar baz/]}); |
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210 | |||
211 | $hsh{'foo'} = $scalar_value; |
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212 | $hsh{'bar'} = $shared_ref_value; |
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213 | $hsh{'baz'} = shared_clone($non_shared_ref_value); |
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214 | $hsh{'quz'} = shared_clone([1..3]); |
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215 | |||
216 | $ary[0] = $scalar_value; |
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217 | $ary[1] = $shared_ref_value; |
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218 | $ary[2] = shared_clone($non_shared_ref_value); |
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219 | $ary[3] = shared_clone([ {}, [] ]); |
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220 | |||
221 | { lock(%hash); ... } |
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222 | |||
223 | cond_wait($scalar); |
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224 | cond_timedwait($scalar, time() + 30); |
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225 | cond_broadcast(@array); |
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226 | cond_signal(%hash); |
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227 | |||
228 | my $lockvar :shared; |
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229 | # condition var != lock var |
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230 | cond_wait($var, $lockvar); |
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231 | cond_timedwait($var, time()+30, $lockvar); |
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232 | |||
233 | =head1 DESCRIPTION |
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234 | |||
235 | By default, variables are private to each thread, and each newly created |
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236 | thread gets a private copy of each existing variable. This module allows you |
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237 | to share variables across different threads (and pseudo-forks on Win32). It |
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238 | is used together with the L<threads> module. |
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239 | |||
240 | This module supports the sharing of the following data types only: scalars |
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241 | and scalar refs, arrays and array refs, and hashes and hash refs. |
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242 | |||
243 | =head1 EXPORT |
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244 | |||
245 | The following functions are exported by this module: C<share>, |
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246 | C<shared_clone>, C<is_shared>, C<cond_wait>, C<cond_timedwait>, C<cond_signal> |
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247 | and C<cond_broadcast> |
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248 | |||
249 | Note that if this module is imported when L<threads> has not yet been loaded, |
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250 | then these functions all become no-ops. This makes it possible to write |
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251 | modules that will work in both threaded and non-threaded environments. |
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252 | |||
253 | =head1 FUNCTIONS |
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254 | |||
255 | =over 4 |
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256 | |||
257 | =item share VARIABLE |
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258 | |||
259 | C<share> takes a variable and marks it as shared: |
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260 | |||
261 | my ($scalar, @array, %hash); |
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262 | share($scalar); |
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263 | share(@array); |
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264 | share(%hash); |
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265 | |||
266 | C<share> will return the shared rvalue, but always as a reference. |
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267 | |||
268 | Variables can also be marked as shared at compile time by using the |
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269 | C<:shared> attribute: |
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270 | |||
271 | my ($var, %hash, @array) :shared; |
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272 | |||
273 | Shared variables can only store scalars, refs of shared variables, or |
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274 | refs of shared data (discussed in next section): |
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275 | |||
276 | my ($var, %hash, @array) :shared; |
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277 | my $bork; |
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278 | |||
279 | # Storing scalars |
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280 | $var = 1; |
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281 | $hash{'foo'} = 'bar'; |
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282 | $array[0] = 1.5; |
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283 | |||
284 | # Storing shared refs |
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285 | $var = \%hash; |
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286 | $hash{'ary'} = \@array; |
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287 | $array[1] = \$var; |
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288 | |||
289 | # The following are errors: |
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290 | # $var = \$bork; # ref of non-shared variable |
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291 | # $hash{'bork'} = []; # non-shared array ref |
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292 | # push(@array, { 'x' => 1 }); # non-shared hash ref |
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293 | |||
294 | =item shared_clone REF |
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295 | |||
296 | C<shared_clone> takes a reference, and returns a shared version of its |
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297 | argument, performing a deep copy on any non-shared elements. Any shared |
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298 | elements in the argument are used as is (i.e., they are not cloned). |
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299 | |||
300 | my $cpy = shared_clone({'foo' => [qw/foo bar baz/]}); |
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301 | |||
302 | Object status (i.e., the class an object is blessed into) is also cloned. |
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303 | |||
304 | my $obj = {'foo' => [qw/foo bar baz/]}; |
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305 | bless($obj, 'Foo'); |
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306 | my $cpy = shared_clone($obj); |
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307 | print(ref($cpy), "\n"); # Outputs 'Foo' |
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308 | |||
309 | For cloning empty array or hash refs, the following may also be used: |
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310 | |||
311 | $var = &share([]); # Same as $var = shared_clone([]); |
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312 | $var = &share({}); # Same as $var = shared_clone({}); |
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313 | |||
314 | =item is_shared VARIABLE |
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315 | |||
316 | C<is_shared> checks if the specified variable is shared or not. If shared, |
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317 | returns the variable's internal ID (similar to |
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318 | L<refaddr()|Scalar::Util/"refaddr EXPR">). Otherwise, returns C<undef>. |
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319 | |||
320 | if (is_shared($var)) { |
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321 | print("\$var is shared\n"); |
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322 | } else { |
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323 | print("\$var is not shared\n"); |
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324 | } |
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325 | |||
326 | When used on an element of an array or hash, C<is_shared> checks if the |
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327 | specified element belongs to a shared array or hash. (It does not check |
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328 | the contents of that element.) |
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329 | |||
330 | my %hash :shared; |
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331 | if (is_shared(%hash)) { |
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332 | print("\%hash is shared\n"); |
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333 | } |
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334 | |||
335 | $hash{'elem'} = 1; |
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336 | if (is_shared($hash{'elem'})) { |
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337 | print("\$hash{'elem'} is in a shared hash\n"); |
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338 | } |
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339 | |||
340 | =item lock VARIABLE |
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341 | |||
342 | C<lock> places a B<advisory> lock on a variable until the lock goes out of |
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343 | scope. If the variable is locked by another thread, the C<lock> call will |
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344 | block until it's available. Multiple calls to C<lock> by the same thread from |
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345 | within dynamically nested scopes are safe -- the variable will remain locked |
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346 | until the outermost lock on the variable goes out of scope. |
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347 | |||
348 | C<lock> follows references exactly I<one> level: |
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349 | |||
350 | my %hash :shared; |
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351 | my $ref = \%hash; |
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352 | lock($ref); # This is equivalent to lock(%hash) |
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353 | |||
354 | Note that you cannot explicitly unlock a variable; you can only wait for the |
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355 | lock to go out of scope. This is most easily accomplished by locking the |
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356 | variable inside a block. |
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357 | |||
358 | my $var :shared; |
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359 | { |
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360 | lock($var); |
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361 | # $var is locked from here to the end of the block |
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362 | ... |
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363 | } |
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364 | # $var is now unlocked |
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365 | |||
366 | As locks are advisory, they do not prevent data access or modification by |
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367 | another thread that does not itself attempt to obtain a lock on the variable. |
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368 | |||
369 | You cannot lock the individual elements of a container variable: |
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370 | |||
371 | my %hash :shared; |
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372 | $hash{'foo'} = 'bar'; |
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373 | #lock($hash{'foo'}); # Error |
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374 | lock(%hash); # Works |
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375 | |||
376 | If you need more fine-grained control over shared variable access, see |
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377 | L<Thread::Semaphore>. |
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378 | |||
379 | =item cond_wait VARIABLE |
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380 | |||
381 | =item cond_wait CONDVAR, LOCKVAR |
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382 | |||
383 | The C<cond_wait> function takes a B<locked> variable as a parameter, unlocks |
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384 | the variable, and blocks until another thread does a C<cond_signal> or |
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385 | C<cond_broadcast> for that same locked variable. The variable that |
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386 | C<cond_wait> blocked on is relocked after the C<cond_wait> is satisfied. If |
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387 | there are multiple threads C<cond_wait>ing on the same variable, all but one |
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388 | will re-block waiting to reacquire the lock on the variable. (So if you're only |
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389 | using C<cond_wait> for synchronisation, give up the lock as soon as possible). |
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390 | The two actions of unlocking the variable and entering the blocked wait state |
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391 | are atomic, the two actions of exiting from the blocked wait state and |
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392 | re-locking the variable are not. |
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393 | |||
394 | In its second form, C<cond_wait> takes a shared, B<unlocked> variable followed |
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395 | by a shared, B<locked> variable. The second variable is unlocked and thread |
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396 | execution suspended until another thread signals the first variable. |
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397 | |||
398 | It is important to note that the variable can be notified even if no thread |
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399 | C<cond_signal> or C<cond_broadcast> on the variable. It is therefore |
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400 | important to check the value of the variable and go back to waiting if the |
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401 | requirement is not fulfilled. For example, to pause until a shared counter |
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402 | drops to zero: |
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403 | |||
404 | { lock($counter); cond_wait($count) until $counter == 0; } |
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405 | |||
406 | =item cond_timedwait VARIABLE, ABS_TIMEOUT |
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407 | |||
408 | =item cond_timedwait CONDVAR, ABS_TIMEOUT, LOCKVAR |
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409 | |||
410 | In its two-argument form, C<cond_timedwait> takes a B<locked> variable and an |
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411 | absolute timeout as parameters, unlocks the variable, and blocks until the |
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412 | timeout is reached or another thread signals the variable. A false value is |
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413 | returned if the timeout is reached, and a true value otherwise. In either |
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414 | case, the variable is re-locked upon return. |
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415 | |||
416 | Like C<cond_wait>, this function may take a shared, B<locked> variable as an |
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417 | additional parameter; in this case the first parameter is an B<unlocked> |
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418 | condition variable protected by a distinct lock variable. |
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419 | |||
420 | Again like C<cond_wait>, waking up and reacquiring the lock are not atomic, |
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421 | and you should always check your desired condition after this function |
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422 | returns. Since the timeout is an absolute value, however, it does not have to |
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423 | be recalculated with each pass: |
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424 | |||
425 | lock($var); |
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426 | my $abs = time() + 15; |
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427 | until ($ok = desired_condition($var)) { |
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428 | last if !cond_timedwait($var, $abs); |
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429 | } |
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430 | # we got it if $ok, otherwise we timed out! |
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431 | |||
432 | =item cond_signal VARIABLE |
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433 | |||
434 | The C<cond_signal> function takes a B<locked> variable as a parameter and |
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435 | unblocks one thread that's C<cond_wait>ing on that variable. If more than one |
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436 | thread is blocked in a C<cond_wait> on that variable, only one (and which one |
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437 | is indeterminate) will be unblocked. |
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438 | |||
439 | If there are no threads blocked in a C<cond_wait> on the variable, the signal |
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440 | is discarded. By always locking before signaling, you can (with care), avoid |
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441 | signaling before another thread has entered cond_wait(). |
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442 | |||
443 | C<cond_signal> will normally generate a warning if you attempt to use it on an |
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444 | unlocked variable. On the rare occasions where doing this may be sensible, you |
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445 | can suppress the warning with: |
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446 | |||
447 | { no warnings 'threads'; cond_signal($foo); } |
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448 | |||
449 | =item cond_broadcast VARIABLE |
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450 | |||
451 | The C<cond_broadcast> function works similarly to C<cond_signal>. |
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452 | C<cond_broadcast>, though, will unblock B<all> the threads that are blocked in |
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453 | a C<cond_wait> on the locked variable, rather than only one. |
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454 | |||
455 | =back |
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456 | |||
457 | =head1 OBJECTS |
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458 | |||
459 | L<threads::shared> exports a version of L<bless()|perlfunc/"bless REF"> that |
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460 | works on shared objects such that I<blessings> propagate across threads. |
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461 | |||
462 | # Create a shared 'Foo' object |
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463 | my $foo :shared = shared_clone({}); |
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464 | bless($foo, 'Foo'); |
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465 | |||
466 | # Create a shared 'Bar' object |
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467 | my $bar :shared = shared_clone({}); |
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468 | bless($bar, 'Bar'); |
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469 | |||
470 | # Put 'bar' inside 'foo' |
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471 | $foo->{'bar'} = $bar; |
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472 | |||
473 | # Rebless the objects via a thread |
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474 | threads->create(sub { |
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475 | # Rebless the outer object |
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476 | bless($foo, 'Yin'); |
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477 | |||
478 | # Cannot directly rebless the inner object |
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479 | #bless($foo->{'bar'}, 'Yang'); |
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480 | |||
481 | # Retrieve and rebless the inner object |
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482 | my $obj = $foo->{'bar'}; |
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483 | bless($obj, 'Yang'); |
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484 | $foo->{'bar'} = $obj; |
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485 | |||
486 | })->join(); |
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487 | |||
488 | print(ref($foo), "\n"); # Prints 'Yin' |
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489 | print(ref($foo->{'bar'}), "\n"); # Prints 'Yang' |
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490 | print(ref($bar), "\n"); # Also prints 'Yang' |
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491 | |||
492 | =head1 NOTES |
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493 | |||
494 | L<threads::shared> is designed to disable itself silently if threads are not |
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495 | available. This allows you to write modules and packages that can be used |
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496 | in both threaded and non-threaded applications. |
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497 | |||
498 | If you want access to threads, you must C<use threads> before you |
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499 | C<use threads::shared>. L<threads> will emit a warning if you use it after |
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500 | L<threads::shared>. |
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501 | |||
502 | =head1 BUGS AND LIMITATIONS |
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503 | |||
504 | When C<share> is used on arrays, hashes, array refs or hash refs, any data |
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505 | they contain will be lost. |
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506 | |||
507 | my @arr = qw(foo bar baz); |
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508 | share(@arr); |
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509 | # @arr is now empty (i.e., == ()); |
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510 | |||
511 | # Create a 'foo' object |
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512 | my $foo = { 'data' => 99 }; |
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513 | bless($foo, 'foo'); |
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514 | |||
515 | # Share the object |
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516 | share($foo); # Contents are now wiped out |
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517 | print("ERROR: \$foo is empty\n") |
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518 | if (! exists($foo->{'data'})); |
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519 | |||
520 | Therefore, populate such variables B<after> declaring them as shared. (Scalar |
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521 | and scalar refs are not affected by this problem.) |
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522 | |||
523 | It is often not wise to share an object unless the class itself has been |
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524 | written to support sharing. For example, an object's destructor may get |
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525 | called multiple times, once for each thread's scope exit. Another danger is |
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526 | that the contents of hash-based objects will be lost due to the above |
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527 | mentioned limitation. See F<examples/class.pl> (in the CPAN distribution of |
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528 | this module) for how to create a class that supports object sharing. |
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529 | |||
530 | Does not support C<splice> on arrays! |
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531 | |||
532 | Taking references to the elements of shared arrays and hashes does not |
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533 | autovivify the elements, and neither does slicing a shared array/hash over |
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534 | non-existent indices/keys autovivify the elements. |
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535 | |||
536 | C<share()> allows you to C<< share($hashref->{key}) >> and |
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537 | C<< share($arrayref->[idx]) >> without giving any error message. But the |
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538 | C<< $hashref->{key} >> or C<< $arrayref->[idx] >> is B<not> shared, causing |
||
539 | the error "lock can only be used on shared values" to occur when you attempt |
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540 | to C<< lock($hasref->{key}) >> or C<< lock($arrayref->[idx]) >> in another |
||
541 | thread. |
||
542 | |||
543 | Using L<refaddr()|Scalar::Util/"refaddr EXPR">) is unreliable for testing |
||
544 | whether or not two shared references are equivalent (e.g., when testing for |
||
545 | circular references). Use L<is_shared()/"is_shared VARIABLE">, instead: |
||
546 | |||
547 | use threads; |
||
548 | use threads::shared; |
||
549 | use Scalar::Util qw(refaddr); |
||
550 | |||
551 | # If ref is shared, use threads::shared's internal ID. |
||
552 | # Otherwise, use refaddr(). |
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553 | my $addr1 = is_shared($ref1) || refaddr($ref1); |
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554 | my $addr2 = is_shared($ref2) || refaddr($ref2); |
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555 | |||
556 | if ($addr1 == $addr2) { |
||
557 | # The refs are equivalent |
||
558 | } |
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559 | |||
560 | L<each()|perlfunc/"each HASH"> does not work properly on shared references |
||
561 | embedded in shared structures. For example: |
||
562 | |||
563 | my %foo :shared; |
||
564 | $foo{'bar'} = shared_clone({'a'=>'x', 'b'=>'y', 'c'=>'z'}); |
||
565 | |||
566 | while (my ($key, $val) = each(%{$foo{'bar'}})) { |
||
567 | ... |
||
568 | } |
||
569 | |||
570 | Either of the following will work instead: |
||
571 | |||
572 | my $ref = $foo{'bar'}; |
||
573 | while (my ($key, $val) = each(%{$ref})) { |
||
574 | ... |
||
575 | } |
||
576 | |||
577 | foreach my $key (keys(%{$foo{'bar'}})) { |
||
578 | my $val = $foo{'bar'}{$key}; |
||
579 | ... |
||
580 | } |
||
581 | |||
582 | View existing bug reports at, and submit any new bugs, problems, patches, etc. |
||
583 | to: L<http://rt.cpan.org/Public/Dist/Display.html?Name=threads-shared> |
||
584 | |||
585 | =head1 SEE ALSO |
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586 | |||
587 | L<threads::shared> Discussion Forum on CPAN: |
||
588 | L<http://www.cpanforum.com/dist/threads-shared> |
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589 | |||
590 | Annotated POD for L<threads::shared>: |
||
591 | L<http://annocpan.org/~JDHEDDEN/threads-shared-1.28/shared.pm> |
||
592 | |||
593 | Source repository: |
||
594 | L<http://code.google.com/p/threads-shared/> |
||
595 | |||
596 | L<threads>, L<perlthrtut> |
||
597 | |||
598 | L<http://www.perl.com/pub/a/2002/06/11/threads.html> and |
||
599 | L<http://www.perl.com/pub/a/2002/09/04/threads.html> |
||
600 | |||
601 | Perl threads mailing list: |
||
602 | L<http://lists.cpan.org/showlist.cgi?name=iThreads> |
||
603 | |||
604 | =head1 AUTHOR |
||
605 | |||
606 | Artur Bergman E<lt>sky AT crucially DOT netE<gt> |
||
607 | |||
608 | Documentation borrowed from the old Thread.pm. |
||
609 | |||
610 | CPAN version produced by Jerry D. Hedden E<lt>jdhedden AT cpan DOT orgE<gt>. |
||
611 | |||
612 | =head1 LICENSE |
||
613 | |||
614 | threads::shared is released under the same license as Perl. |
||
615 | |||
616 | =cut |