1 | NAME |
1 | NAME |
2 | EV - perl interface to libevent, monkey.org/~provos/libevent/ |
2 | EV - perl interface to libev, a high performance full-featured event |
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3 | loop |
3 | |
4 | |
4 | SYNOPSIS |
5 | SYNOPSIS |
5 | use EV; |
6 | use EV; |
6 | |
7 | |
7 | # TIMER |
8 | # TIMERS |
8 | |
9 | |
9 | my $w = EV::timer 2, 0, sub { |
10 | my $w = EV::timer 2, 0, sub { |
10 | warn "is called after 2s"; |
11 | warn "is called after 2s"; |
11 | }; |
12 | }; |
12 | |
13 | |
13 | my $w = EV::timer 2, 1, sub { |
14 | my $w = EV::timer 2, 2, sub { |
14 | warn "is called roughly every 2s (repeat = 1)"; |
15 | warn "is called roughly every 2s (repeat = 2)"; |
15 | }; |
16 | }; |
16 | |
17 | |
17 | undef $w; # destroy event watcher again |
18 | undef $w; # destroy event watcher again |
18 | |
19 | |
19 | # IO |
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20 | |
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21 | my $w = EV::timer_abs 0, 60, sub { |
20 | my $w = EV::periodic 0, 60, 0, sub { |
22 | warn "is called every minute, on the minute, exactly"; |
21 | warn "is called every minute, on the minute, exactly"; |
23 | }; |
22 | }; |
24 | |
23 | |
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24 | # IO |
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25 | |
25 | my $w = EV::io \*STDIN, EV::READ | EV::PERSIST, sub { |
26 | my $w = EV::io *STDIN, EV::READ, sub { |
26 | my ($w, $events) = @_; # all callbacks get the watcher object and event mask |
27 | my ($w, $revents) = @_; # all callbacks receive the watcher and event mask |
27 | if ($events & EV::TIMEOUT) { |
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28 | warn "nothign received on stdin for 10 seconds, retrying"; |
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29 | } else { |
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30 | warn "stdin is readable, you entered: ", <STDIN>; |
28 | warn "stdin is readable, you entered: ", <STDIN>; |
31 | } |
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32 | }; |
29 | }; |
33 | $w->timeout (10); |
30 | |
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31 | # SIGNALS |
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32 | |
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33 | my $w = EV::signal 'QUIT', sub { |
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34 | warn "sigquit received\n"; |
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35 | }; |
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36 | |
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37 | # CHILD/PID STATUS CHANGES |
34 | |
38 | |
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39 | my $w = EV::child 666, sub { |
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40 | my ($w, $revents) = @_; |
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41 | my $status = $w->rstatus; |
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42 | }; |
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43 | |
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44 | # STAT CHANGES |
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45 | my $w = EV::stat "/etc/passwd", 10, sub { |
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46 | my ($w, $revents) = @_; |
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47 | warn $w->path, " has changed somehow.\n"; |
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48 | }; |
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49 | |
35 | # MAINLOOP |
50 | # MAINLOOP |
36 | EV::dispatch; # loop as long as watchers are active |
51 | EV::loop; # loop until EV::unloop is called or all watchers stop |
37 | EV::loop; # the same thing |
52 | EV::loop EV::LOOP_ONESHOT; # block until at least one event could be handled |
38 | EV::loop EV::LOOP_ONCE; |
53 | EV::loop EV::LOOP_NONBLOCK; # try to handle same events, but do not block |
39 | EV::loop EV::LOOP_ONSHOT; |
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40 | |
54 | |
41 | DESCRIPTION |
55 | DESCRIPTION |
42 | This module provides an interface to libevent |
56 | This module provides an interface to libev |
43 | (<http://monkey.org/~provos/libevent/>). You probably should acquaint |
57 | (<http://software.schmorp.de/pkg/libev.html>). While the documentation |
44 | yourself with its documentation and source code to be able to use this |
58 | below is comprehensive, one might also consult the documentation of |
45 | module fully. |
59 | libev itself (<http://cvs.schmorp.de/libev/ev.html>) for more subtle |
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60 | details on watcher semantics or some discussion on the available |
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61 | backends, or how to force a specific backend with "LIBEV_FLAGS", or just |
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62 | about in any case because it has much more detailed information. |
46 | |
63 | |
47 | Please note thta this module disables the libevent EPOLL method by |
64 | BASIC INTERFACE |
48 | default, see BUGS, below, if you need to enable it. |
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49 | |
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50 | FUNCTIONAL INTERFACE |
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51 | $EV::NPRI |
65 | $EV::DIED |
52 | How many priority levels are available. |
66 | Must contain a reference to a function that is called when a |
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67 | callback throws an exception (with $@ containing thr error). The |
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68 | default prints an informative message and continues. |
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69 | |
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70 | If this callback throws an exception it will be silently ignored. |
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71 | |
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72 | $time = EV::time |
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73 | Returns the current time in (fractional) seconds since the epoch. |
53 | |
74 | |
54 | $time = EV::now |
75 | $time = EV::now |
55 | Returns the time in (fractional) seconds since the epoch. |
76 | Returns the time the last event loop iteration has been started. |
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77 | This is the time that (relative) timers are based on, and refering |
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78 | to it is usually faster then calling EV::time. |
56 | |
79 | |
57 | $version = EV::version |
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58 | $method = EV::method |
80 | $method = EV::method |
59 | Return version string and event polling method used. |
81 | Returns an integer describing the backend used by libev |
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82 | (EV::METHOD_SELECT or EV::METHOD_EPOLL). |
60 | |
83 | |
61 | EV::loop $flags # EV::LOOP_ONCE, EV::LOOP_ONESHOT |
84 | EV::loop [$flags] |
62 | EV::loopexit $after |
85 | Begin checking for events and calling callbacks. It returns when a |
63 | Exit any active loop or dispatch after $after seconds or immediately |
86 | callback calls EV::unloop. |
64 | if $after is missing or zero. |
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65 | |
87 | |
66 | EV::dispatch |
88 | The $flags argument can be one of the following: |
67 | Same as "EV::loop 0". |
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68 | |
89 | |
69 | EV::event $callback |
90 | 0 as above |
70 | Creates a new event watcher waiting for nothing, calling the given |
91 | EV::LOOP_ONESHOT block at most once (wait, but do not loop) |
71 | callback. |
92 | EV::LOOP_NONBLOCK do not block at all (fetch/handle events but do not wait) |
72 | |
93 | |
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94 | EV::unloop [$how] |
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95 | When called with no arguments or an argument of EV::UNLOOP_ONE, |
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96 | makes the innermost call to EV::loop return. |
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97 | |
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98 | When called with an argument of EV::UNLOOP_ALL, all calls to |
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99 | EV::loop will return as fast as possible. |
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100 | |
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101 | $count = EV::loop_count |
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102 | Return the number of times the event loop has polled for new events. |
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103 | Sometiems useful as a generation counter. |
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104 | |
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105 | EV::once $fh_or_undef, $events, $timeout, $cb->($revents) |
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106 | This function rolls together an I/O and a timer watcher for a single |
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107 | one-shot event without the need for managing a watcher object. |
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108 | |
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109 | If $fh_or_undef is a filehandle or file descriptor, then $events |
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110 | must be a bitset containing either "EV::READ", "EV::WRITE" or |
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111 | "EV::READ | EV::WRITE", indicating the type of I/O event you want to |
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112 | wait for. If you do not want to wait for some I/O event, specify |
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113 | "undef" for $fh_or_undef and 0 for $events). |
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114 | |
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115 | If timeout is "undef" or negative, then there will be no timeout. |
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116 | Otherwise a EV::timer with this value will be started. |
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117 | |
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118 | When an error occurs or either the timeout or I/O watcher triggers, |
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119 | then the callback will be called with the received event set (in |
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120 | general you can expect it to be a combination of "EV:ERROR", |
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121 | "EV::READ", "EV::WRITE" and "EV::TIMEOUT"). |
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122 | |
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123 | EV::once doesn't return anything: the watchers stay active till |
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124 | either of them triggers, then they will be stopped and freed, and |
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125 | the callback invoked. |
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126 | |
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127 | WATCHER OBJECTS |
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128 | A watcher is an object that gets created to record your interest in some |
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129 | event. For instance, if you want to wait for STDIN to become readable, |
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130 | you would create an EV::io watcher for that: |
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131 | |
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132 | my $watcher = EV::io *STDIN, EV::READ, sub { |
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133 | my ($watcher, $revents) = @_; |
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134 | warn "yeah, STDIN should not be readable without blocking!\n" |
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135 | }; |
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136 | |
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137 | All watchers can be active (waiting for events) or inactive (paused). |
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138 | Only active watchers will have their callbacks invoked. All callbacks |
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139 | will be called with at least two arguments: the watcher and a bitmask of |
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140 | received events. |
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141 | |
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142 | Each watcher type has its associated bit in revents, so you can use the |
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143 | same callback for multiple watchers. The event mask is named after the |
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144 | type, i..e. EV::child sets EV::CHILD, EV::prepare sets EV::PREPARE, |
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145 | EV::periodic sets EV::PERIODIC and so on, with the exception of I/O |
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146 | events (which can set both EV::READ and EV::WRITE bits), and EV::timer |
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147 | (which uses EV::TIMEOUT). |
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148 | |
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149 | In the rare case where one wants to create a watcher but not start it at |
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150 | the same time, each constructor has a variant with a trailing "_ns" in |
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151 | its name, e.g. EV::io has a non-starting variant EV::io_ns and so on. |
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152 | |
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153 | Please note that a watcher will automatically be stopped when the |
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154 | watcher object is destroyed, so you *need* to keep the watcher objects |
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155 | returned by the constructors. |
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156 | |
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157 | Also, all methods changing some aspect of a watcher (->set, ->priority, |
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158 | ->fh and so on) automatically stop and start it again if it is active, |
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159 | which means pending events get lost. |
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160 | |
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161 | COMMON WATCHER METHODS |
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162 | This section lists methods common to all watchers. |
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163 | |
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164 | $w->start |
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165 | Starts a watcher if it isn't active already. Does nothing to an |
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166 | already active watcher. By default, all watchers start out in the |
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167 | active state (see the description of the "_ns" variants if you need |
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168 | stopped watchers). |
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169 | |
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170 | $w->stop |
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171 | Stop a watcher if it is active. Also clear any pending events |
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172 | (events that have been received but that didn't yet result in a |
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173 | callback invocation), regardless of whether the watcher was active |
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174 | or not. |
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175 | |
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176 | $bool = $w->is_active |
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177 | Returns true if the watcher is active, false otherwise. |
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178 | |
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179 | $current_data = $w->data |
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180 | $old_data = $w->data ($new_data) |
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181 | Queries a freely usable data scalar on the watcher and optionally |
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182 | changes it. This is a way to associate custom data with a watcher: |
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183 | |
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184 | my $w = EV::timer 60, 0, sub { |
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185 | warn $_[0]->data; |
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186 | }; |
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187 | $w->data ("print me!"); |
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188 | |
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189 | $current_cb = $w->cb |
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190 | $old_cb = $w->cb ($new_cb) |
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191 | Queries the callback on the watcher and optionally changes it. You |
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192 | can do this at any time without the watcher restarting. |
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193 | |
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194 | $current_priority = $w->priority |
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195 | $old_priority = $w->priority ($new_priority) |
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196 | Queries the priority on the watcher and optionally changes it. |
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197 | Pending watchers with higher priority will be invoked first. The |
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198 | valid range of priorities lies between EV::MAXPRI (default 2) and |
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199 | EV::MINPRI (default -2). If the priority is outside this range it |
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200 | will automatically be normalised to the nearest valid priority. |
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201 | |
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202 | The default priority of any newly-created watcher is 0. |
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203 | |
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204 | Note that the priority semantics have not yet been fleshed out and |
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205 | are subject to almost certain change. |
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206 | |
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207 | $w->trigger ($revents) |
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208 | Call the callback *now* with the given event mask. |
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209 | |
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210 | $previous_state = $w->keepalive ($bool) |
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211 | Normally, "EV::loop" will return when there are no active watchers |
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212 | (which is a "deadlock" because no progress can be made anymore). |
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213 | This is convinient because it allows you to start your watchers (and |
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214 | your jobs), call "EV::loop" once and when it returns you know that |
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215 | all your jobs are finished (or they forgot to register some watchers |
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216 | for their task :). |
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217 | |
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218 | Sometimes, however, this gets in your way, for example when you the |
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219 | module that calls "EV::loop" (usually the main program) is not the |
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220 | same module as a long-living watcher (for example a DNS client |
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221 | module written by somebody else even). Then you might want any |
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222 | outstanding requests to be handled, but you would not want to keep |
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223 | "EV::loop" from returning just because you happen to have this |
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224 | long-running UDP port watcher. |
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225 | |
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226 | In this case you can clear the keepalive status, which means that |
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227 | even though your watcher is active, it won't keep "EV::loop" from |
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228 | returning. |
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229 | |
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230 | The initial value for keepalive is true (enabled), and you cna |
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231 | change it any time. |
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232 | |
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233 | Example: Register an I/O watcher for some UDP socket but do not keep |
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234 | the event loop from running just because of that watcher. |
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235 | |
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236 | my $udp_socket = ... |
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237 | my $udp_watcher = EV::io $udp_socket, EV::READ, sub { ... }; |
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238 | $udp_watcher->keepalive (0); |
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239 | |
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240 | WATCHER TYPES |
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241 | Each of the following subsections describes a single watcher type. |
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242 | |
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243 | I/O WATCHERS - is this file descriptor readable or writable? |
73 | my $w = EV::io $fileno_or_fh, $eventmask, $callback |
244 | $w = EV::io $fileno_or_fh, $eventmask, $callback |
74 | my $w = EV::io_ns $fileno_or_fh, $eventmask, $callback |
245 | $w = EV::io_ns $fileno_or_fh, $eventmask, $callback |
75 | As long as the returned watcher object is alive, call the $callback |
246 | As long as the returned watcher object is alive, call the $callback |
76 | when the events specified in $eventmask happen. Initially, the |
247 | when at least one of events specified in $eventmask occurs. |
77 | timeout is disabled. |
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78 | |
248 | |
79 | Youc an additionall set a timeout to occur on the watcher, but note |
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80 | that this timeout will not be reset when you get an I/O event in the |
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81 | EV::PERSIST case, and reaching a timeout will always stop the |
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82 | watcher even in the EV::PERSIST case. |
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83 | |
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84 | If you want a timeout to occur only after a specific time of |
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85 | inactivity, set a repeating timeout and do NOT use EV::PERSIST. |
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86 | |
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87 | Eventmask can be one or more of these constants ORed together: |
249 | The $eventmask can be one or more of these constants ORed together: |
88 | |
250 | |
89 | EV::READ wait until read() wouldn't block anymore |
251 | EV::READ wait until read() wouldn't block anymore |
90 | EV::WRITE wait until write() wouldn't block anymore |
252 | EV::WRITE wait until write() wouldn't block anymore |
91 | EV::PERSIST stay active after a (non-timeout) event occured |
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92 | |
253 | |
93 | The "io_ns" variant doesn't add/start the newly created watcher. |
254 | The "io_ns" variant doesn't start (activate) the newly created |
94 | |
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95 | my $w = EV::timer $after, $repeat, $callback |
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96 | my $w = EV::timer_ns $after, $repeat, $callback |
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97 | Calls the callback after $after seconds. If $repeat is true, the |
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98 | timer will be restarted after the callback returns. This means that |
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99 | the callback would be called roughly every $after seconds, prolonged |
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100 | by the time the callback takes. |
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101 | |
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102 | The "timer_ns" variant doesn't add/start the newly created watcher. |
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103 | |
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104 | my $w = EV::timer_abs $at, $interval, $callback |
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105 | my $w = EV::timer_abs_ns $at, $interval, $callback |
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106 | Similar to EV::timer, but the time is given as an absolute point in |
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107 | time ($at), plus an optional $interval. |
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108 | |
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109 | If the $interval is zero, then the callback will be called at the |
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110 | time $at if that is in the future, or as soon as possible if its in |
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111 | the past. It will not automatically repeat. |
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112 | |
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113 | If the $interval is nonzero, then the watcher will always be |
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114 | scheduled to time out at the next "$at + integer * $interval" time. |
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115 | |
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116 | This can be used to schedule a callback to run at very regular |
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117 | intervals, as long as the processing time is less then the interval |
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118 | (otherwise obviously events will be skipped). |
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119 | |
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120 | Another way to think about it (for the mathematically inclined) is |
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121 | that "timer_abs" will try to tun the callback at the next possible |
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122 | time where "$time = $at (mod $interval)", regardless of any time |
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123 | jumps. |
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124 | |
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125 | The "timer_abs_ns" variant doesn't add/start the newly created |
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126 | watcher. |
255 | watcher. |
127 | |
256 | |
128 | my $w = EV::signal $signum, $callback |
257 | $w->set ($fileno_or_fh, $eventmask) |
129 | my $w = EV::signal_ns $signum, $callback |
258 | Reconfigures the watcher, see the constructor above for details. Can |
130 | Call the callback when signal $signum is received. |
259 | be called at any time. |
131 | |
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132 | The "signal_ns" variant doesn't add/start the newly created watcher. |
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133 | |
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134 | THE EV::Event CLASS |
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135 | All EV functions creating an event watcher (designated by "my $w =" |
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136 | above) support the following methods on the returned watcher object: |
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137 | |
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138 | $w->add ($timeout) |
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139 | Stops and (re-)starts the event watcher, setting the optional |
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140 | timeout to the given value, or clearing the timeout if none is |
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141 | given. |
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142 | |
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143 | $w->start |
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144 | Stops and (re-)starts the event watcher without touching the |
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145 | timeout. |
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146 | |
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147 | $w->del |
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148 | $w->stop |
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149 | Stop the event watcher if it was started. |
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150 | |
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151 | $current_callback = $w->cb |
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152 | $old_callback = $w->cb ($new_callback) |
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153 | Return the previously set callback and optionally set a new one. |
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154 | |
260 | |
155 | $current_fh = $w->fh |
261 | $current_fh = $w->fh |
156 | $old_fh = $w->fh ($new_fh) |
262 | $old_fh = $w->fh ($new_fh) |
157 | Returns the previously set filehandle and optionally set a new one. |
263 | Returns the previously set filehandle and optionally set a new one. |
158 | |
264 | |
159 | $current_eventmask = $w->events |
265 | $current_eventmask = $w->events |
160 | $old_eventmask = $w->events ($new_eventmask) |
266 | $old_eventmask = $w->events ($new_eventmask) |
161 | Returns the previously set event mask and optionally set a new one. |
267 | Returns the previously set event mask and optionally set a new one. |
162 | |
268 | |
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269 | TIMER WATCHERS - relative and optionally repeating timeouts |
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270 | $w = EV::timer $after, $repeat, $callback |
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271 | $w = EV::timer_ns $after, $repeat, $callback |
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272 | Calls the callback after $after seconds (which may be fractional). |
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273 | If $repeat is non-zero, the timer will be restarted (with the |
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274 | $repeat value as $after) after the callback returns. |
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275 | |
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276 | This means that the callback would be called roughly after $after |
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277 | seconds, and then every $repeat seconds. The timer does his best not |
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278 | to drift, but it will not invoke the timer more often then once per |
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279 | event loop iteration, and might drift in other cases. If that isn't |
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280 | acceptable, look at EV::periodic, which can provide long-term stable |
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281 | timers. |
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282 | |
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283 | The timer is based on a monotonic clock, that is, if somebody is |
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284 | sitting in front of the machine while the timer is running and |
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285 | changes the system clock, the timer will nevertheless run (roughly) |
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286 | the same time. |
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287 | |
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288 | The "timer_ns" variant doesn't start (activate) the newly created |
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289 | watcher. |
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290 | |
163 | $w->timeout ($after, $repeat) |
291 | $w->set ($after, $repeat) |
164 | Resets the timeout (see "EV::timer" for details). |
292 | Reconfigures the watcher, see the constructor above for details. Can |
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293 | be called at any time. |
165 | |
294 | |
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295 | $w->again |
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296 | Similar to the "start" method, but has special semantics for |
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297 | repeating timers: |
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298 | |
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299 | If the timer is active and non-repeating, it will be stopped. |
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300 | |
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301 | If the timer is active and repeating, reset the timeout to occur |
|
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302 | $repeat seconds after now. |
|
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303 | |
|
|
304 | If the timer is inactive and repeating, start it using the repeat |
|
|
305 | value. |
|
|
306 | |
|
|
307 | Otherwise do nothing. |
|
|
308 | |
|
|
309 | This behaviour is useful when you have a timeout for some IO |
|
|
310 | operation. You create a timer object with the same value for $after |
|
|
311 | and $repeat, and then, in the read/write watcher, run the "again" |
|
|
312 | method on the timeout. |
|
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313 | |
|
|
314 | PERIODIC WATCHERS - to cron or not to cron? |
|
|
315 | $w = EV::periodic $at, $interval, $reschedule_cb, $callback |
|
|
316 | $w = EV::periodic_ns $at, $interval, $reschedule_cb, $callback |
|
|
317 | Similar to EV::timer, but is not based on relative timeouts but on |
|
|
318 | absolute times. Apart from creating "simple" timers that trigger |
|
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319 | "at" the specified time, it can also be used for non-drifting |
|
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320 | absolute timers and more complex, cron-like, setups that are not |
|
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321 | adversely affected by time jumps (i.e. when the system clock is |
|
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322 | changed by explicit date -s or other means such as ntpd). It is also |
|
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323 | the most complex watcher type in EV. |
|
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324 | |
|
|
325 | It has three distinct "modes": |
|
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326 | |
|
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327 | * absolute timer ($interval = $reschedule_cb = 0) |
|
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328 | This time simply fires at the wallclock time $at and doesn't |
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329 | repeat. It will not adjust when a time jump occurs, that is, if |
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330 | it is to be run at January 1st 2011 then it will run when the |
|
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331 | system time reaches or surpasses this time. |
|
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332 | |
|
|
333 | * non-repeating interval timer ($interval > 0, $reschedule_cb = 0) |
|
|
334 | In this mode the watcher will always be scheduled to time out at |
|
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335 | the next "$at + N * $interval" time (for some integer N) and |
|
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336 | then repeat, regardless of any time jumps. |
|
|
337 | |
|
|
338 | This can be used to create timers that do not drift with respect |
|
|
339 | to system time: |
|
|
340 | |
|
|
341 | my $hourly = EV::periodic 0, 3600, 0, sub { print "once/hour\n" }; |
|
|
342 | |
|
|
343 | That doesn't mean there will always be 3600 seconds in between |
|
|
344 | triggers, but only that the the clalback will be called when the |
|
|
345 | system time shows a full hour (UTC). |
|
|
346 | |
|
|
347 | Another way to think about it (for the mathematically inclined) |
|
|
348 | is that EV::periodic will try to run the callback in this mode |
|
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349 | at the next possible time where "$time = $at (mod $interval)", |
|
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350 | regardless of any time jumps. |
|
|
351 | |
|
|
352 | * manual reschedule mode ($reschedule_cb = coderef) |
|
|
353 | In this mode $interval and $at are both being ignored. Instead, |
|
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354 | each time the periodic watcher gets scheduled, the reschedule |
|
|
355 | callback ($reschedule_cb) will be called with the watcher as |
|
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356 | first, and the current time as second argument. |
|
|
357 | |
|
|
358 | *This callback MUST NOT stop or destroy this or any other |
|
|
359 | periodic watcher, ever*. If you need to stop it, return 1e30 and |
|
|
360 | stop it afterwards. |
|
|
361 | |
|
|
362 | It must return the next time to trigger, based on the passed |
|
|
363 | time value (that is, the lowest time value larger than to the |
|
|
364 | second argument). It will usually be called just before the |
|
|
365 | callback will be triggered, but might be called at other times, |
|
|
366 | too. |
|
|
367 | |
|
|
368 | This can be used to create very complex timers, such as a timer |
|
|
369 | that triggers on each midnight, local time (actually 24 hours |
|
|
370 | after the last midnight, to keep the example simple. If you know |
|
|
371 | a way to do it correctly in about the same space (without |
|
|
372 | requiring elaborate modules), drop me a note :): |
|
|
373 | |
|
|
374 | my $daily = EV::periodic 0, 0, sub { |
|
|
375 | my ($w, $now) = @_; |
|
|
376 | |
|
|
377 | use Time::Local (); |
|
|
378 | my (undef, undef, undef, $d, $m, $y) = localtime $now; |
|
|
379 | 86400 + Time::Local::timelocal 0, 0, 0, $d, $m, $y |
|
|
380 | }, sub { |
|
|
381 | print "it's midnight or likely shortly after, now\n"; |
|
|
382 | }; |
|
|
383 | |
|
|
384 | The "periodic_ns" variant doesn't start (activate) the newly created |
|
|
385 | watcher. |
|
|
386 | |
|
|
387 | $w->set ($at, $interval, $reschedule_cb) |
|
|
388 | Reconfigures the watcher, see the constructor above for details. Can |
|
|
389 | be called at any time. |
|
|
390 | |
|
|
391 | $w->again |
|
|
392 | Simply stops and starts the watcher again. |
|
|
393 | |
|
|
394 | SIGNAL WATCHERS - signal me when a signal gets signalled! |
|
|
395 | $w = EV::signal $signal, $callback |
|
|
396 | $w = EV::signal_ns $signal, $callback |
|
|
397 | Call the callback when $signal is received (the signal can be |
|
|
398 | specified by number or by name, just as with "kill" or %SIG). |
|
|
399 | |
|
|
400 | EV will grab the signal for the process (the kernel only allows one |
|
|
401 | component to receive a signal at a time) when you start a signal |
|
|
402 | watcher, and removes it again when you stop it. Perl does the same |
|
|
403 | when you add/remove callbacks to %SIG, so watch out. |
|
|
404 | |
|
|
405 | You can have as many signal watchers per signal as you want. |
|
|
406 | |
|
|
407 | The "signal_ns" variant doesn't start (activate) the newly created |
|
|
408 | watcher. |
|
|
409 | |
|
|
410 | $w->set ($signal) |
|
|
411 | Reconfigures the watcher, see the constructor above for details. Can |
|
|
412 | be called at any time. |
|
|
413 | |
|
|
414 | $current_signum = $w->signal |
|
|
415 | $old_signum = $w->signal ($new_signal) |
|
|
416 | Returns the previously set signal (always as a number not name) and |
|
|
417 | optionally set a new one. |
|
|
418 | |
|
|
419 | CHILD WATCHERS - watch out for process status changes |
|
|
420 | $w = EV::child $pid, $callback |
|
|
421 | $w = EV::child_ns $pid, $callback |
|
|
422 | Call the callback when a status change for pid $pid (or any pid if |
|
|
423 | $pid is 0) has been received. More precisely: when the process |
|
|
424 | receives a "SIGCHLD", EV will fetch the outstanding exit/wait status |
|
|
425 | for all changed/zombie children and call the callback. |
|
|
426 | |
|
|
427 | It is valid (and fully supported) to install a child watcher after a |
|
|
428 | child has exited but before the event loop has started its next |
|
|
429 | iteration (for example, first you "fork", then the new child process |
|
|
430 | might exit, and only then do you install a child watcher in the |
|
|
431 | parent for the new pid). |
|
|
432 | |
|
|
433 | You can access both exit (or tracing) status and pid by using the |
|
|
434 | "rstatus" and "rpid" methods on the watcher object. |
|
|
435 | |
|
|
436 | You can have as many pid watchers per pid as you want, they will all |
|
|
437 | be called. |
|
|
438 | |
|
|
439 | The "child_ns" variant doesn't start (activate) the newly created |
|
|
440 | watcher. |
|
|
441 | |
|
|
442 | $w->set ($pid) |
|
|
443 | Reconfigures the watcher, see the constructor above for details. Can |
|
|
444 | be called at any time. |
|
|
445 | |
|
|
446 | $current_pid = $w->pid |
|
|
447 | $old_pid = $w->pid ($new_pid) |
|
|
448 | Returns the previously set process id and optionally set a new one. |
|
|
449 | |
|
|
450 | $exit_status = $w->rstatus |
|
|
451 | Return the exit/wait status (as returned by waitpid, see the waitpid |
|
|
452 | entry in perlfunc). |
|
|
453 | |
|
|
454 | $pid = $w->rpid |
|
|
455 | Return the pid of the awaited child (useful when you have installed |
|
|
456 | a watcher for all pids). |
|
|
457 | |
|
|
458 | STAT WATCHERS - did the file attributes just change? |
|
|
459 | $w = EV::stat $path, $interval, $callback |
|
|
460 | $w = EV::stat_ns $path, $interval, $callback |
|
|
461 | Call the callback when a file status change has been detected on |
|
|
462 | $path. The $path does not need to exist, changing from "path exists" |
|
|
463 | to "path does not exist" is a status change like any other. |
|
|
464 | |
|
|
465 | The $interval is a recommended polling interval for systems where |
|
|
466 | OS-supported change notifications don't exist or are not supported. |
|
|
467 | If you use 0 then an unspecified default is used (which is highly |
|
|
468 | recommended!), which is to be expected to be around five seconds |
|
|
469 | usually. |
|
|
470 | |
|
|
471 | This watcher type is not meant for massive numbers of stat watchers, |
|
|
472 | as even with OS-supported change notifications, this can be |
|
|
473 | resource-intensive. |
|
|
474 | |
|
|
475 | The "stat_ns" variant doesn't start (activate) the newly created |
|
|
476 | watcher. |
|
|
477 | |
|
|
478 | ... = $w->stat |
|
|
479 | This call is very similar to the perl "stat" built-in: It stats |
|
|
480 | (using "lstat") the path specified in the watcher and sets perls |
|
|
481 | stat cache (as well as EV's idea of the current stat values) to the |
|
|
482 | values found. |
|
|
483 | |
|
|
484 | In scalar context, a boolean is return indicating success or failure |
|
|
485 | of the stat. In list context, the same 13-value list as with stat is |
|
|
486 | returned (except that the blksize and blocks fields are not |
|
|
487 | reliable). |
|
|
488 | |
|
|
489 | In the case of an error, errno is set to "ENOENT" (regardless of the |
|
|
490 | actual error value) and the "nlink" value is forced to zero (if the |
|
|
491 | stat was successful then nlink is guaranteed to be non-zero). |
|
|
492 | |
|
|
493 | See also the next two entries for more info. |
|
|
494 | |
|
|
495 | ... = $w->attr |
|
|
496 | Just like "$w->stat", but without the initial stat'ing: this returns |
|
|
497 | the values most recently detected by EV. See the next entry for more |
|
|
498 | info. |
|
|
499 | |
|
|
500 | ... = $w->prev |
|
|
501 | Just like "$w->stat", but without the initial stat'ing: this returns |
|
|
502 | the previous set of values, before the change. |
|
|
503 | |
|
|
504 | That is, when the watcher callback is invoked, "$w->prev" will be |
|
|
505 | set to the values found *before* a change was detected, while |
|
|
506 | "$w->attr" returns the values found leading to the change detection. |
|
|
507 | The difference (if any) between "prev" and "attr" is what triggered |
|
|
508 | the callback. |
|
|
509 | |
|
|
510 | If you did something to the filesystem object and do not want to |
|
|
511 | trigger yet another change, you can call "stat" to update EV's idea |
|
|
512 | of what the current attributes are. |
|
|
513 | |
166 | $w->timeout_abs ($at, $interval) |
514 | $w->set ($path, $interval) |
167 | Resets the timeout (see "EV::timer_abs" for details). |
515 | Reconfigures the watcher, see the constructor above for details. Can |
|
|
516 | be called at any time. |
168 | |
517 | |
169 | $w->priority_set ($priority) |
518 | $current_path = $w->path |
170 | Set the priority of the watcher to $priority (0 <= $priority < |
519 | $old_path = $w->path ($new_path) |
171 | $EV::NPRI). |
520 | Returns the previously set path and optionally set a new one. |
172 | |
521 | |
173 | BUGS |
522 | $current_interval = $w->interval |
174 | Lots. Libevent itself isn't well tested and rather buggy, and this |
523 | $old_interval = $w->interval ($new_interval) |
175 | module is quite new at the moment. |
524 | Returns the previously set interval and optionally set a new one. |
|
|
525 | Can be used to query the actual interval used. |
176 | |
526 | |
177 | Please note that the epoll method is not, in general, reliable in |
527 | IDLE WATCHERS - when you've got nothing better to do... |
178 | programs that use fork (even if no libveent calls are being made in the |
528 | $w = EV::idle $callback |
179 | forked process). If your program behaves erratically, try setting the |
529 | $w = EV::idle_ns $callback |
180 | environment variable "EVENT_NOEPOLL" first when running the program. |
530 | Call the callback when there are no other pending watchers of the |
|
|
531 | same or higher priority (excluding check, prepare and other idle |
|
|
532 | watchers of the same or lower priority, of course). They are called |
|
|
533 | idle watchers because when the watcher is the highest priority |
|
|
534 | pending event in the process, the process is considered to be idle |
|
|
535 | at that priority. |
181 | |
536 | |
182 | In general, if you fork, then you can only use the EV module in one of |
537 | If you want a watcher that is only ever called when *no* other |
183 | the children. |
538 | events are outstanding you have to set the priority to "EV::MINPRI". |
|
|
539 | |
|
|
540 | The process will not block as long as any idle watchers are active, |
|
|
541 | and they will be called repeatedly until stopped. |
|
|
542 | |
|
|
543 | For example, if you have idle watchers at priority 0 and 1, and an |
|
|
544 | I/O watcher at priority 0, then the idle watcher at priority 1 and |
|
|
545 | the I/O watcher will always run when ready. Only when the idle |
|
|
546 | watcher at priority 1 is stopped and the I/O watcher at priority 0 |
|
|
547 | is not pending with the 0-priority idle watcher be invoked. |
|
|
548 | |
|
|
549 | The "idle_ns" variant doesn't start (activate) the newly created |
|
|
550 | watcher. |
|
|
551 | |
|
|
552 | PREPARE WATCHERS - customise your event loop! |
|
|
553 | $w = EV::prepare $callback |
|
|
554 | $w = EV::prepare_ns $callback |
|
|
555 | Call the callback just before the process would block. You can still |
|
|
556 | create/modify any watchers at this point. |
|
|
557 | |
|
|
558 | See the EV::check watcher, below, for explanations and an example. |
|
|
559 | |
|
|
560 | The "prepare_ns" variant doesn't start (activate) the newly created |
|
|
561 | watcher. |
|
|
562 | |
|
|
563 | CHECK WATCHERS - customise your event loop even more! |
|
|
564 | $w = EV::check $callback |
|
|
565 | $w = EV::check_ns $callback |
|
|
566 | Call the callback just after the process wakes up again (after it |
|
|
567 | has gathered events), but before any other callbacks have been |
|
|
568 | invoked. |
|
|
569 | |
|
|
570 | This is used to integrate other event-based software into the EV |
|
|
571 | mainloop: You register a prepare callback and in there, you create |
|
|
572 | io and timer watchers as required by the other software. Here is a |
|
|
573 | real-world example of integrating Net::SNMP (with some details left |
|
|
574 | out): |
|
|
575 | |
|
|
576 | our @snmp_watcher; |
|
|
577 | |
|
|
578 | our $snmp_prepare = EV::prepare sub { |
|
|
579 | # do nothing unless active |
|
|
580 | $dispatcher->{_event_queue_h} |
|
|
581 | or return; |
|
|
582 | |
|
|
583 | # make the dispatcher handle any outstanding stuff |
|
|
584 | ... not shown |
|
|
585 | |
|
|
586 | # create an I/O watcher for each and every socket |
|
|
587 | @snmp_watcher = ( |
|
|
588 | (map { EV::io $_, EV::READ, sub { } } |
|
|
589 | keys %{ $dispatcher->{_descriptors} }), |
|
|
590 | |
|
|
591 | EV::timer +($event->[Net::SNMP::Dispatcher::_ACTIVE] |
|
|
592 | ? $event->[Net::SNMP::Dispatcher::_TIME] - EV::now : 0), |
|
|
593 | 0, sub { }, |
|
|
594 | ); |
|
|
595 | }; |
|
|
596 | |
|
|
597 | The callbacks are irrelevant (and are not even being called), the |
|
|
598 | only purpose of those watchers is to wake up the process as soon as |
|
|
599 | one of those events occurs (socket readable, or timer timed out). |
|
|
600 | The corresponding EV::check watcher will then clean up: |
|
|
601 | |
|
|
602 | our $snmp_check = EV::check sub { |
|
|
603 | # destroy all watchers |
|
|
604 | @snmp_watcher = (); |
|
|
605 | |
|
|
606 | # make the dispatcher handle any new stuff |
|
|
607 | ... not shown |
|
|
608 | }; |
|
|
609 | |
|
|
610 | The callbacks of the created watchers will not be called as the |
|
|
611 | watchers are destroyed before this cna happen (remember EV::check |
|
|
612 | gets called first). |
|
|
613 | |
|
|
614 | The "check_ns" variant doesn't start (activate) the newly created |
|
|
615 | watcher. |
|
|
616 | |
|
|
617 | FORK WATCHERS - the audacity to resume the event loop after a fork |
|
|
618 | Fork watchers are called when a "fork ()" was detected. The invocation |
|
|
619 | is done before the event loop blocks next and before "check" watchers |
|
|
620 | are being called, and only in the child after the fork. |
|
|
621 | |
|
|
622 | $w = EV::fork $callback |
|
|
623 | $w = EV::fork_ns $callback |
|
|
624 | Call the callback before the event loop is resumed in the child |
|
|
625 | process after a fork. |
|
|
626 | |
|
|
627 | The "fork_ns" variant doesn't start (activate) the newly created |
|
|
628 | watcher. |
|
|
629 | |
|
|
630 | PERL SIGNALS |
|
|
631 | While Perl signal handling (%SIG) is not affected by EV, the behaviour |
|
|
632 | with EV is as the same as any other C library: Perl-signals will only be |
|
|
633 | handled when Perl runs, which means your signal handler might be invoked |
|
|
634 | only the next time an event callback is invoked. |
|
|
635 | |
|
|
636 | The solution is to use EV signal watchers (see "EV::signal"), which will |
|
|
637 | ensure proper operations with regards to other event watchers. |
|
|
638 | |
|
|
639 | If you cannot do this for whatever reason, you can also force a watcher |
|
|
640 | to be called on every event loop iteration by installing a "EV::check" |
|
|
641 | watcher: |
|
|
642 | |
|
|
643 | my $async_check = EV::check sub { }; |
|
|
644 | |
|
|
645 | This ensures that perl shortly gets into control for a short time, and |
|
|
646 | also ensures slower overall operation. |
|
|
647 | |
|
|
648 | THREADS |
|
|
649 | Threads are not supported by this module in any way. Perl pseudo-threads |
|
|
650 | is evil stuff and must die. As soon as Perl gains real threads I will |
|
|
651 | work on thread support for it. |
|
|
652 | |
|
|
653 | FORK |
|
|
654 | Most of the "improved" event delivering mechanisms of modern operating |
|
|
655 | systems have quite a few problems with fork(2) (to put it bluntly: it is |
|
|
656 | not supported and usually destructive). Libev makes it possible to work |
|
|
657 | around this by having a function that recreates the kernel state after |
|
|
658 | fork in the child. |
|
|
659 | |
|
|
660 | On non-win32 platforms, this module requires the pthread_atfork |
|
|
661 | functionality to do this automatically for you. This function is quite |
|
|
662 | buggy on most BSDs, though, so YMMV. The overhead for this is quite |
|
|
663 | negligible, because everything the function currently does is set a flag |
|
|
664 | that is checked only when the event loop gets used the next time, so |
|
|
665 | when you do fork but not use EV, the overhead is minimal. |
|
|
666 | |
|
|
667 | On win32, there is no notion of fork so all this doesn't apply, of |
|
|
668 | course. |
184 | |
669 | |
185 | SEE ALSO |
670 | SEE ALSO |
186 | L<EV::DNS>, L<event(3)>, L<event.h>, L<evdns.h>. |
671 | EV::ADNS (asynchronous dns), Glib::EV (makes Glib/Gtk2 use EV as event |
187 | L<EV::AnyEvent>. |
672 | loop), Coro::EV (efficient coroutines with EV). |
188 | |
673 | |
189 | AUTHOR |
674 | AUTHOR |
190 | Marc Lehmann <schmorp@schmorp.de> |
675 | Marc Lehmann <schmorp@schmorp.de> |
191 | http://home.schmorp.de/ |
676 | http://home.schmorp.de/ |
192 | |
677 | |