1 | =head1 NAME |
1 | =head1 NAME |
2 | |
2 | |
3 | Coro - create and manage simple coroutines |
3 | Coro - coroutine process abstraction |
4 | |
4 | |
5 | =head1 SYNOPSIS |
5 | =head1 SYNOPSIS |
6 | |
6 | |
7 | use Coro; |
7 | use Coro; |
8 | |
8 | |
9 | $new = new Coro sub { |
9 | async { |
10 | print "in coroutine, switching back\n"; |
10 | # some asynchronous thread of execution |
11 | $new->transfer($main); |
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12 | print "in coroutine again, switching back\n"; |
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13 | $new->transfer($main); |
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14 | }; |
11 | }; |
15 | |
12 | |
16 | $main = new Coro; |
13 | # alternatively create an async coroutine like this: |
17 | |
14 | |
18 | print "in main, switching to coroutine\n"; |
15 | sub some_func : Coro { |
19 | $main->transfer($new); |
16 | # some more async code |
20 | print "back in main, switch to coroutine again\n"; |
17 | } |
21 | $main->transfer($new); |
18 | |
22 | print "back in main\n"; |
19 | cede; |
23 | |
20 | |
24 | =head1 DESCRIPTION |
21 | =head1 DESCRIPTION |
25 | |
22 | |
26 | This module implements coroutines. Coroutines, similar to continuations, |
23 | This module collection manages coroutines. Coroutines are similar to |
27 | allow you to run more than one "thread of execution" in parallel. Unlike |
24 | threads but don't run in parallel. |
28 | threads this, only voluntary switching is used so locking problems are |
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29 | greatly reduced. |
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30 | |
25 | |
31 | Although this is the "main" module of the Coro family it provides only |
26 | In this module, coroutines are defined as "callchain + lexical variables |
32 | low-level functionality. See L<Coro::Process> and related modules for a |
27 | + @_ + $_ + $@ + $^W + C stack), that is, a coroutine has it's own |
33 | more useful process abstraction including scheduling. |
28 | callchain, it's own set of lexicals and it's own set of perl's most |
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29 | important global variables. |
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30 | |
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31 | =cut |
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32 | |
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33 | package Coro; |
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34 | |
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35 | use strict; |
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36 | no warnings "uninitialized"; |
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37 | |
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38 | use Coro::State; |
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39 | |
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40 | use base qw(Coro::State Exporter); |
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41 | |
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42 | our $idle; # idle handler |
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43 | our $main; # main coroutine |
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44 | our $current; # current coroutine |
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45 | |
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46 | our $VERSION = '3.01'; |
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47 | |
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48 | our @EXPORT = qw(async cede schedule terminate current unblock_sub); |
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49 | our %EXPORT_TAGS = ( |
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50 | prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)], |
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51 | ); |
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52 | our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready)); |
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53 | |
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54 | { |
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55 | my @async; |
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56 | my $init; |
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57 | |
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58 | # this way of handling attributes simply is NOT scalable ;() |
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59 | sub import { |
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60 | no strict 'refs'; |
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61 | |
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62 | Coro->export_to_level (1, @_); |
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63 | |
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64 | my $old = *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"}{CODE}; |
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65 | *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"} = sub { |
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66 | my ($package, $ref) = (shift, shift); |
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67 | my @attrs; |
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68 | for (@_) { |
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69 | if ($_ eq "Coro") { |
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70 | push @async, $ref; |
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71 | unless ($init++) { |
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72 | eval q{ |
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73 | sub INIT { |
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74 | &async(pop @async) while @async; |
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75 | } |
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76 | }; |
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77 | } |
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78 | } else { |
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79 | push @attrs, $_; |
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80 | } |
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81 | } |
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82 | return $old ? $old->($package, $ref, @attrs) : @attrs; |
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83 | }; |
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84 | } |
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85 | |
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86 | } |
34 | |
87 | |
35 | =over 4 |
88 | =over 4 |
36 | |
89 | |
37 | =cut |
90 | =item $main |
38 | |
91 | |
39 | package Coro; |
92 | This coroutine represents the main program. |
40 | |
93 | |
41 | BEGIN { |
94 | =cut |
42 | $VERSION = 0.03; |
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43 | |
95 | |
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96 | $main = new Coro; |
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97 | |
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98 | =item $current (or as function: current) |
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99 | |
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100 | The current coroutine (the last coroutine switched to). The initial value |
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101 | is C<$main> (of course). |
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102 | |
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103 | This variable is B<strictly> I<read-only>. It is provided for performance |
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104 | reasons. If performance is not essentiel you are encouraged to use the |
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105 | C<Coro::current> function instead. |
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106 | |
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107 | =cut |
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108 | |
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109 | # maybe some other module used Coro::Specific before... |
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110 | $main->{specific} = $current->{specific} |
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111 | if $current; |
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112 | |
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113 | _set_current $main; |
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114 | |
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115 | sub current() { $current } |
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116 | |
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117 | =item $idle |
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118 | |
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119 | A callback that is called whenever the scheduler finds no ready coroutines |
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120 | to run. The default implementation prints "FATAL: deadlock detected" and |
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121 | exits, because the program has no other way to continue. |
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122 | |
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123 | This hook is overwritten by modules such as C<Coro::Timer> and |
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124 | C<Coro::Event> to wait on an external event that hopefully wake up a |
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125 | coroutine so the scheduler can run it. |
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126 | |
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127 | Please note that if your callback recursively invokes perl (e.g. for event |
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128 | handlers), then it must be prepared to be called recursively. |
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129 | |
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130 | =cut |
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131 | |
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132 | $idle = sub { |
44 | require XSLoader; |
133 | require Carp; |
45 | XSLoader::load Coro, $VERSION; |
134 | Carp::croak ("FATAL: deadlock detected"); |
46 | } |
135 | }; |
47 | |
136 | |
48 | =item $coro = new [$coderef [, @args]] |
137 | # this coroutine is necessary because a coroutine |
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138 | # cannot destroy itself. |
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139 | my @destroy; |
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140 | my $manager; $manager = new Coro sub { |
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141 | while () { |
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142 | # by overwriting the state object with the manager we destroy it |
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143 | # while still being able to schedule this coroutine (in case it has |
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144 | # been readied multiple times. this is harmless since the manager |
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145 | # can be called as many times as neccessary and will always |
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146 | # remove itself from the runqueue |
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147 | while (@destroy) { |
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148 | my $coro = pop @destroy; |
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149 | $coro->{status} ||= []; |
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150 | $_->ready for @{delete $coro->{join} || []}; |
49 | |
151 | |
50 | Create a new coroutine and return it. The first C<transfer> call to this |
152 | # the next line destroys the coro state, but keeps the |
51 | coroutine will start execution at the given coderef. If, the subroutine |
153 | # coroutine itself intact (we basically make it a zombie |
52 | returns it will be executed again. |
154 | # coroutine that always runs the manager thread, so it's possible |
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155 | # to transfer() to this coroutine). |
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156 | $coro->_clone_state_from ($manager); |
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157 | } |
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158 | &schedule; |
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159 | } |
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160 | }; |
53 | |
161 | |
54 | If the coderef is omitted this function will create a new "empty" |
162 | # static methods. not really. |
55 | coroutine, i.e. a coroutine that cannot be transfered to but can be used |
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56 | to save the current coroutine in. |
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57 | |
163 | |
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164 | =back |
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165 | |
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166 | =head2 STATIC METHODS |
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167 | |
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168 | Static methods are actually functions that operate on the current coroutine only. |
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169 | |
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170 | =over 4 |
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171 | |
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172 | =item async { ... } [@args...] |
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173 | |
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174 | Create a new asynchronous coroutine and return it's coroutine object |
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175 | (usually unused). When the sub returns the new coroutine is automatically |
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176 | terminated. |
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177 | |
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178 | Calling C<exit> in a coroutine will not work correctly, so do not do that. |
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179 | |
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180 | When the coroutine dies, the program will exit, just as in the main |
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181 | program. |
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182 | |
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183 | # create a new coroutine that just prints its arguments |
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184 | async { |
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185 | print "@_\n"; |
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186 | } 1,2,3,4; |
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187 | |
58 | =cut |
188 | =cut |
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189 | |
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190 | sub async(&@) { |
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191 | my $pid = new Coro @_; |
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192 | $pid->ready; |
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193 | $pid |
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194 | } |
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195 | |
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196 | =item schedule |
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197 | |
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198 | Calls the scheduler. Please note that the current coroutine will not be put |
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199 | into the ready queue, so calling this function usually means you will |
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200 | never be called again unless something else (e.g. an event handler) calls |
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201 | ready. |
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202 | |
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203 | The canonical way to wait on external events is this: |
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204 | |
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205 | { |
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206 | # remember current coroutine |
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207 | my $current = $Coro::current; |
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208 | |
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209 | # register a hypothetical event handler |
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210 | on_event_invoke sub { |
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211 | # wake up sleeping coroutine |
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212 | $current->ready; |
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213 | undef $current; |
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214 | }; |
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215 | |
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216 | # call schedule until event occured. |
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217 | # in case we are woken up for other reasons |
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218 | # (current still defined), loop. |
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219 | Coro::schedule while $current; |
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220 | } |
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221 | |
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222 | =item cede |
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223 | |
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224 | "Cede" to other coroutines. This function puts the current coroutine into the |
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225 | ready queue and calls C<schedule>, which has the effect of giving up the |
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226 | current "timeslice" to other coroutines of the same or higher priority. |
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227 | |
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228 | =item terminate [arg...] |
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229 | |
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230 | Terminates the current coroutine with the given status values (see L<cancel>). |
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231 | |
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232 | =cut |
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233 | |
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234 | sub terminate { |
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235 | $current->cancel (@_); |
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236 | } |
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237 | |
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238 | =back |
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239 | |
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240 | # dynamic methods |
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241 | |
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242 | =head2 COROUTINE METHODS |
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243 | |
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244 | These are the methods you can call on coroutine objects. |
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245 | |
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246 | =over 4 |
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247 | |
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248 | =item new Coro \&sub [, @args...] |
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249 | |
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250 | Create a new coroutine and return it. When the sub returns the coroutine |
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251 | automatically terminates as if C<terminate> with the returned values were |
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252 | called. To make the coroutine run you must first put it into the ready queue |
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253 | by calling the ready method. |
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254 | |
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255 | Calling C<exit> in a coroutine will not work correctly, so do not do that. |
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256 | |
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257 | =cut |
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258 | |
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259 | sub _run_coro { |
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260 | terminate &{+shift}; |
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261 | } |
59 | |
262 | |
60 | sub new { |
263 | sub new { |
61 | my $class = $_[0]; |
264 | my $class = shift; |
62 | my $proc = $_[1] || sub { die "tried to transfer to an empty coroutine" }; |
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63 | bless _newprocess { |
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64 | do { |
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65 | eval { &$proc }; |
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66 | if ($@) { |
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67 | $error_msg = $@; |
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68 | $error_coro = _newprocess { }; |
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69 | &transfer($error_coro, $error); |
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70 | } |
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71 | } while (1); |
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72 | }, $class; |
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73 | } |
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74 | |
265 | |
75 | =item $prev->transfer($next) |
266 | $class->SUPER::new (\&_run_coro, @_) |
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267 | } |
76 | |
268 | |
77 | Save the state of the current subroutine in C<$prev> and switch to the |
269 | =item $success = $coroutine->ready |
78 | coroutine saved in C<$next>. |
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79 | |
270 | |
80 | The "state" of a subroutine only ever includes scope, i.e. lexical |
271 | Put the given coroutine into the ready queue (according to it's priority) |
81 | variables and the current execution state. It does not save/restore any |
272 | and return true. If the coroutine is already in the ready queue, do nothing |
82 | global variables such as C<$_> or C<$@> or any other special or non |
273 | and return false. |
83 | special variables. So remember that every function call that might call |
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84 | C<transfer> (such as C<Coro::Channel::put>) might clobber any global |
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85 | and/or special variables. Yes, this is by design ;) You cna always create |
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86 | your own process abstraction model that saves these variables. |
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87 | |
274 | |
88 | The easiest way to do this is to create your own scheduling primitive like this: |
275 | =item $is_ready = $coroutine->is_ready |
89 | |
276 | |
90 | sub schedule { |
277 | Return wether the coroutine is currently the ready queue or not, |
91 | local ($_, $@, ...); |
278 | |
92 | $old->transfer($new); |
279 | =item $coroutine->cancel (arg...) |
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280 | |
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281 | Terminates the given coroutine and makes it return the given arguments as |
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282 | status (default: the empty list). |
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283 | |
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284 | =cut |
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285 | |
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286 | sub cancel { |
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287 | my $self = shift; |
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288 | $self->{status} = [@_]; |
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289 | push @destroy, $self; |
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290 | $manager->ready; |
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291 | &schedule if $current == $self; |
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292 | } |
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293 | |
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294 | =item $coroutine->join |
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295 | |
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296 | Wait until the coroutine terminates and return any values given to the |
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297 | C<terminate> or C<cancel> functions. C<join> can be called multiple times |
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298 | from multiple coroutine. |
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299 | |
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300 | =cut |
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301 | |
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302 | sub join { |
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303 | my $self = shift; |
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304 | unless ($self->{status}) { |
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305 | push @{$self->{join}}, $current; |
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306 | &schedule; |
93 | } |
307 | } |
94 | |
308 | wantarray ? @{$self->{status}} : $self->{status}[0]; |
95 | =cut |
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96 | |
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97 | # I call the _transfer function from a perl function |
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98 | # because that way perl saves all important things on |
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99 | # the stack. Actually, I'd do it from within XS, but |
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100 | # I couldn't get it to work. |
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101 | sub transfer { |
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102 | _transfer($_[0], $_[1]); |
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103 | } |
309 | } |
104 | |
310 | |
105 | =item $error, $error_msg, $error_coro |
311 | =item $oldprio = $coroutine->prio ($newprio) |
106 | |
312 | |
107 | This coroutine will be called on fatal errors. C<$error_msg> and |
313 | Sets (or gets, if the argument is missing) the priority of the |
108 | C<$error_coro> return the error message and the error-causing coroutine |
314 | coroutine. Higher priority coroutines get run before lower priority |
109 | (NOT an object) respectively. This API might change. |
315 | coroutines. Priorities are small signed integers (currently -4 .. +3), |
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316 | that you can refer to using PRIO_xxx constants (use the import tag :prio |
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317 | to get then): |
110 | |
318 | |
111 | =cut |
319 | PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN |
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320 | 3 > 1 > 0 > -1 > -3 > -4 |
112 | |
321 | |
113 | $error_msg = |
322 | # set priority to HIGH |
114 | $error_coro = undef; |
323 | current->prio(PRIO_HIGH); |
115 | |
324 | |
116 | $error = _newprocess { |
325 | The idle coroutine ($Coro::idle) always has a lower priority than any |
117 | print STDERR "FATAL: $error_msg\nprogram aborted\n"; |
326 | existing coroutine. |
118 | exit 50; |
327 | |
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328 | Changing the priority of the current coroutine will take effect immediately, |
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329 | but changing the priority of coroutines in the ready queue (but not |
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330 | running) will only take effect after the next schedule (of that |
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331 | coroutine). This is a bug that will be fixed in some future version. |
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332 | |
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333 | =item $newprio = $coroutine->nice ($change) |
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334 | |
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335 | Similar to C<prio>, but subtract the given value from the priority (i.e. |
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336 | higher values mean lower priority, just as in unix). |
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337 | |
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338 | =item $olddesc = $coroutine->desc ($newdesc) |
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339 | |
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340 | Sets (or gets in case the argument is missing) the description for this |
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341 | coroutine. This is just a free-form string you can associate with a coroutine. |
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342 | |
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343 | =cut |
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344 | |
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345 | sub desc { |
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346 | my $old = $_[0]{desc}; |
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347 | $_[0]{desc} = $_[1] if @_ > 1; |
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348 | $old; |
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349 | } |
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350 | |
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351 | =back |
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352 | |
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353 | =head2 GLOBAL FUNCTIONS |
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354 | |
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355 | =over 4 |
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356 | |
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357 | =item Coro::nready |
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358 | |
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359 | Returns the number of coroutines that are currently in the ready state, |
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360 | i.e. that can be swicthed to. The value C<0> means that the only runnable |
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361 | coroutine is the currently running one, so C<cede> would have no effect, |
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362 | and C<schedule> would cause a deadlock unless there is an idle handler |
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363 | that wakes up some coroutines. |
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364 | |
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365 | =item unblock_sub { ... } |
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366 | |
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367 | This utility function takes a BLOCK or code reference and "unblocks" it, |
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368 | returning the new coderef. This means that the new coderef will return |
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369 | immediately without blocking, returning nothing, while the original code |
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370 | ref will be called (with parameters) from within its own coroutine. |
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371 | |
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372 | The reason this fucntion exists is that many event libraries (such as the |
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373 | venerable L<Event|Event> module) are not coroutine-safe (a weaker form |
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374 | of thread-safety). This means you must not block within event callbacks, |
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375 | otherwise you might suffer from crashes or worse. |
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376 | |
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377 | This function allows your callbacks to block by executing them in another |
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378 | coroutine where it is safe to block. One example where blocking is handy |
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379 | is when you use the L<Coro::AIO|Coro::AIO> functions to save results to |
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380 | disk. |
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381 | |
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382 | In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when |
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383 | creating event callbacks that want to block. |
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384 | |
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385 | =cut |
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386 | |
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387 | our @unblock_pool; |
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388 | our @unblock_queue; |
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389 | our $UNBLOCK_POOL_SIZE = 2; |
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390 | |
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391 | sub unblock_handler_ { |
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392 | while () { |
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393 | my ($cb, @arg) = @{ delete $Coro::current->{arg} }; |
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394 | $cb->(@arg); |
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395 | |
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396 | last if @unblock_pool >= $UNBLOCK_POOL_SIZE; |
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397 | push @unblock_pool, $Coro::current; |
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398 | schedule; |
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399 | } |
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400 | } |
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401 | |
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402 | our $unblock_scheduler = async { |
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403 | while () { |
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404 | while (my $cb = pop @unblock_queue) { |
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405 | my $handler = (pop @unblock_pool or new Coro \&unblock_handler_); |
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406 | $handler->{arg} = $cb; |
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407 | $handler->ready; |
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408 | cede; |
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409 | } |
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410 | |
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411 | schedule; |
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412 | } |
119 | }; |
413 | }; |
120 | |
414 | |
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415 | sub unblock_sub(&) { |
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416 | my $cb = shift; |
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417 | |
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418 | sub { |
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419 | push @unblock_queue, [$cb, @_]; |
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420 | $unblock_scheduler->ready; |
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421 | } |
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422 | } |
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423 | |
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424 | =back |
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425 | |
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426 | =cut |
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427 | |
121 | 1; |
428 | 1; |
122 | |
429 | |
123 | =back |
430 | =head1 BUGS/LIMITATIONS |
124 | |
431 | |
125 | =head1 BUGS |
432 | - you must make very sure that no coro is still active on global |
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433 | destruction. very bad things might happen otherwise (usually segfaults). |
126 | |
434 | |
127 | This module has not yet been extensively tested. |
435 | - this module is not thread-safe. You should only ever use this module |
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436 | from the same thread (this requirement might be losened in the future |
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437 | to allow per-thread schedulers, but Coro::State does not yet allow |
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438 | this). |
128 | |
439 | |
129 | =head1 SEE ALSO |
440 | =head1 SEE ALSO |
130 | |
441 | |
131 | L<Coro::Process>, L<Coro::Signal>. |
442 | Support/Utility: L<Coro::Cont>, L<Coro::Specific>, L<Coro::State>, L<Coro::Util>. |
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443 | |
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444 | Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>. |
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445 | |
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446 | Event/IO: L<Coro::Timer>, L<Coro::Event>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::Select>. |
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447 | |
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448 | Embedding: L<Coro:MakeMaker> |
132 | |
449 | |
133 | =head1 AUTHOR |
450 | =head1 AUTHOR |
134 | |
451 | |
135 | Marc Lehmann <pcg@goof.com> |
452 | Marc Lehmann <schmorp@schmorp.de> |
136 | http://www.goof.com/pcg/marc/ |
453 | http://home.schmorp.de/ |
137 | |
454 | |
138 | =cut |
455 | =cut |
139 | |
456 | |