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