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1 | NAME |
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2 | AnyEvent - provide framework for multiple event loops |
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3 | |
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4 | Event, Coro, Glib, Tk - various supported event loops |
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5 | |
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6 | SYNOPSIS |
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7 | use AnyEvent; |
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8 | |
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9 | my $w = AnyEvent->io (fh => ..., poll => "[rw]+", cb => sub { |
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10 | my ($poll_got) = @_; |
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11 | ... |
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12 | }); |
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13 | |
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14 | * only one io watcher per $fh and $poll type is allowed (i.e. on a |
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15 | socket you can have one r + one w or one rw watcher, not any more |
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16 | (limitation by Tk). |
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17 | |
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18 | * the $poll_got passed to the handler needs to be checked by looking for |
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19 | single characters (e.g. with a regex), as it can contain more event |
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20 | types than were requested (e.g. a 'w' watcher might generate 'rw' |
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21 | events, limitation by Glib). |
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22 | |
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23 | * AnyEvent will keep filehandles alive, so as long as the watcher |
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24 | exists, the filehandle exists. |
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25 | |
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26 | my $w = AnyEvent->timer (after => $seconds, cb => sub { |
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27 | ... |
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28 | }); |
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29 | |
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30 | * io and time watchers get canceled whenever $w is destroyed, so keep a |
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31 | copy |
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32 | |
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33 | * timers can only be used once and must be recreated for repeated |
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34 | operation (limitation by Glib and Tk). |
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35 | |
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36 | my $w = AnyEvent->condvar; # kind of main loop replacement |
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37 | $w->wait; # enters main loop till $condvar gets ->broadcast |
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38 | $w->broadcast; # wake up current and all future wait's |
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39 | |
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40 | * condvars are used to give blocking behaviour when neccessary. Create a |
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41 | condvar for any "request" or "event" your module might create, |
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42 | "->broadcast" it when the event happens and provide a function that |
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43 | calls "->wait" for it. See the examples below. |
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44 | |
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45 | DESCRIPTION |
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46 | AnyEvent provides an identical interface to multiple event loops. This |
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47 | allows module authors to utilizy an event loop without forcing module |
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48 | users to use the same event loop (as only a single event loop can |
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49 | coexist peacefully at any one time). |
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50 | |
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51 | The interface itself is vaguely similar but not identical to the Event |
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52 | module. |
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53 | |
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54 | On the first call of any method, the module tries to detect the |
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55 | currently loaded event loop by probing wether any of the following |
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56 | modules is loaded: Coro::Event, Event, Glib, Tk. The first one found is |
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57 | used. If none is found, the module tries to load these modules in the |
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58 | order given. The first one that could be successfully loaded will be |
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59 | used. If still none could be found, it will issue an error. |
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60 | |
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61 | ENVIRONMENT VARIABLES |
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62 | The following environment variables are used by this module: |
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63 | |
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64 | "PERL_ANYEVENT_VERBOSE" when set to 2 or higher, reports which event |
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65 | model gets used. |
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66 | |
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67 | EXAMPLE |
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68 | The following program uses an io watcher to read data from stdin, a |
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69 | timer to display a message once per second, and a condvar to exit the |
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70 | program when the user enters quit: |
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71 | |
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72 | use AnyEvent; |
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73 | |
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74 | my $cv = AnyEvent->condvar; |
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75 | |
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76 | my $io_watcher = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub { |
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77 | warn "io event <$_[0]>\n"; # will always output <r> |
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78 | chomp (my $input = <STDIN>); # read a line |
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79 | warn "read: $input\n"; # output what has been read |
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80 | $cv->broadcast if $input =~ /^q/i; # quit program if /^q/i |
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81 | }); |
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82 | |
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83 | my $time_watcher; # can only be used once |
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84 | |
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85 | sub new_timer { |
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86 | $timer = AnyEvent->timer (after => 1, cb => sub { |
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87 | warn "timeout\n"; # print 'timeout' about every second |
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88 | &new_timer; # and restart the time |
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89 | }); |
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90 | } |
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91 | |
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92 | new_timer; # create first timer |
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93 | |
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94 | $cv->wait; # wait until user enters /^q/i |
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95 | |
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96 | REAL-WORLD EXAMPLE |
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97 | Consider the Net::FCP module. It features (among others) the following |
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98 | API calls, which are to freenet what HTTP GET requests are to http: |
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99 | |
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100 | my $data = $fcp->client_get ($url); # blocks |
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101 | |
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102 | my $transaction = $fcp->txn_client_get ($url); # does not block |
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103 | $transaction->cb ( sub { ... } ); # set optional result callback |
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104 | my $data = $transaction->result; # possibly blocks |
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105 | |
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106 | The "client_get" method works like "LWP::Simple::get": it requests the |
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107 | given URL and waits till the data has arrived. It is defined to be: |
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108 | |
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109 | sub client_get { $_[0]->txn_client_get ($_[1])->result } |
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110 | |
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111 | And in fact is automatically generated. This is the blocking API of |
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112 | Net::FCP, and it works as simple as in any other, similar, module. |
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113 | |
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114 | More complicated is "txn_client_get": It only creates a transaction |
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115 | (completion, result, ...) object and initiates the transaction. |
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116 | |
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117 | my $txn = bless { }, Net::FCP::Txn::; |
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118 | |
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119 | It also creates a condition variable that is used to signal the |
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120 | completion of the request: |
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121 | |
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122 | $txn->{finished} = AnyAvent->condvar; |
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123 | |
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124 | It then creates a socket in non-blocking mode. |
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125 | |
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126 | socket $txn->{fh}, ...; |
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127 | fcntl $txn->{fh}, F_SETFL, O_NONBLOCK; |
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128 | connect $txn->{fh}, ... |
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129 | and !$!{EWOULDBLOCK} |
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130 | and !$!{EINPROGRESS} |
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131 | and Carp::croak "unable to connect: $!\n"; |
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132 | |
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133 | Then it creates a write-watcher which gets called whenever an error |
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134 | occurs or the connection succeeds: |
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135 | |
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136 | $txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'w', cb => sub { $txn->fh_ready_w }); |
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137 | |
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138 | And returns this transaction object. The "fh_ready_w" callback gets |
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139 | called as soon as the event loop detects that the socket is ready for |
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140 | writing. |
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141 | |
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142 | The "fh_ready_w" method makes the socket blocking again, writes the |
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143 | request data and replaces the watcher by a read watcher (waiting for |
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144 | reply data). The actual code is more complicated, but that doesn't |
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145 | matter for this example: |
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146 | |
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147 | fcntl $txn->{fh}, F_SETFL, 0; |
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148 | syswrite $txn->{fh}, $txn->{request} |
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149 | or die "connection or write error"; |
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150 | $txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r }); |
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151 | |
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152 | Again, "fh_ready_r" waits till all data has arrived, and then stores the |
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153 | result and signals any possible waiters that the request ahs finished: |
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154 | |
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155 | sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf}; |
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156 | |
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157 | if (end-of-file or data complete) { |
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158 | $txn->{result} = $txn->{buf}; |
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159 | $txn->{finished}->broadcast; |
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160 | $txb->{cb}->($txn) of $txn->{cb}; # also call callback |
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161 | } |
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162 | |
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163 | The "result" method, finally, just waits for the finished signal (if the |
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164 | request was already finished, it doesn't wait, of course, and returns |
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165 | the data: |
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166 | |
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167 | $txn->{finished}->wait; |
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168 | return $txn->{result}; |
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169 | |
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170 | The actual code goes further and collects all errors ("die"s, |
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171 | exceptions) that occured during request processing. The "result" method |
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172 | detects wether an exception as thrown (it is stored inside the $txn |
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173 | object) and just throws the exception, which means connection errors and |
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174 | other problems get reported tot he code that tries to use the result, |
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175 | not in a random callback. |
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176 | |
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177 | All of this enables the following usage styles: |
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178 | |
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179 | 1. Blocking: |
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180 | |
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181 | my $data = $fcp->client_get ($url); |
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182 | |
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183 | 2. Blocking, but parallelizing: |
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184 | |
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185 | my @datas = map $_->result, |
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186 | map $fcp->txn_client_get ($_), |
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187 | @urls; |
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188 | |
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189 | Both blocking examples work without the module user having to know |
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190 | anything about events. |
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191 | |
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192 | 3a. Event-based in a main program, using any support Event module: |
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193 | |
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194 | use Event; |
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195 | |
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196 | $fcp->txn_client_get ($url)->cb (sub { |
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197 | my $txn = shift; |
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198 | my $data = $txn->result; |
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199 | ... |
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200 | }); |
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201 | |
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202 | Event::loop; |
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203 | |
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204 | 3b. The module user could use AnyEvent, too: |
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205 | |
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206 | use AnyEvent; |
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207 | |
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208 | my $quit = AnyEvent->condvar; |
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209 | |
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210 | $fcp->txn_client_get ($url)->cb (sub { |
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211 | ... |
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212 | $quit->broadcast; |
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213 | }); |
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214 | |
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215 | $quit->wait; |
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216 | |
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217 | SEE ALSO |
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218 | Event modules: Coro::Event, Coro, Event, Glib::Event, Glib. |
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219 | |
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220 | Implementations: AnyEvent::Impl::Coro, AnyEvent::Impl::Event, |
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221 | AnyEvent::Impl::Glib, AnyEvent::Impl::Tk. |
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222 | |
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223 | Nontrivial usage example: Net::FCP. |
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224 | |
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225 | |