[ViewVC] Diff of: cvs/AnyEvent/lib/AnyEvent.pm

Comparing AnyEvent/lib/AnyEvent.pm (file contents):
Revision 1.126 by root, Fri May 23 23:44:55 2008 UTC vs.
Revision 1.133 by root, Sun May 25 03:44:03 2008 UTC

 as those use one of the supported event loops. It is trivial to add new
 event loops to AnyEvent, too, so it is future-proof).
 In addition to being free of having to use I<the one and only true event
 model>, AnyEvent also is free of bloat and policy: with POE or similar
-modules, you get an enourmous amount of code and strict rules you have to
+modules, you get an enormous amount of code and strict rules you have to
 follow. AnyEvent, on the other hand, is lean and up to the point, by only
 offering the functionality that is necessary, in as thin as a wrapper as
 technically possible.
 Of course, if you want lots of policy (this can arguably be somewhat
 =head1 WATCHERS
 AnyEvent has the central concept of a I<watcher>, which is an object that
 stores relevant data for each kind of event you are waiting for, such as
-the callback to call, the filehandle to watch, etc.
+the callback to call, the file handle to watch, etc.
 These watchers are normal Perl objects with normal Perl lifetime. After
 creating a watcher it will immediately "watch" for events and invoke the
 callback when the event occurs (of course, only when the event model
 is in control).
 Although the callback might get passed parameters, their value and
 presence is undefined and you cannot rely on them. Portable AnyEvent
 callbacks cannot use arguments passed to signal watcher callbacks.
-Multiple signal occurances can be clumped together into one callback
+Multiple signal occurrences can be clumped together into one callback
-invocation, and callback invocation will be synchronous. synchronous means
+invocation, and callback invocation will be synchronous. Synchronous means
 that it might take a while until the signal gets handled by the process,
-but it is guarenteed not to interrupt any other callbacks.
+but it is guaranteed not to interrupt any other callbacks.
 The main advantage of using these watchers is that you can share a signal
 between multiple watchers.
 This watcher might use C<%SIG>, so programs overwriting those signals
 Condition variables can be created by calling the C<< AnyEvent->condvar
 >> method, usually without arguments. The only argument pair allowed is
 C<cb>, which specifies a callback to be called when the condition variable
 becomes true.
-After creation, the conditon variable is "false" until it becomes "true"
+After creation, the condition variable is "false" until it becomes "true"
-by calling the C<send> method.
+by calling the C<send> method (or calling the condition variable as if it
+were a callback).
 Condition variables are similar to callbacks, except that you can
 optionally wait for them. They can also be called merge points - points
-in time where multiple outstandign events have been processed. And yet
+in time where multiple outstanding events have been processed. And yet
-another way to call them is transations - each condition variable can be
+another way to call them is transactions - each condition variable can be
 used to represent a transaction, which finishes at some point and delivers
 a result.
 Condition variables are very useful to signal that something has finished,
 for example, if you write a module that does asynchronous http requests,
 you can block your main program until an event occurs - for example, you
 could C<< ->recv >> in your main program until the user clicks the Quit
 button of your app, which would C<< ->send >> the "quit" event.
 Note that condition variables recurse into the event loop - if you have
-two pieces of code that call C<< ->recv >> in a round-robbin fashion, you
+two pieces of code that call C<< ->recv >> in a round-robin fashion, you
 lose. Therefore, condition variables are good to export to your caller, but
 you should avoid making a blocking wait yourself, at least in callbacks,
 as this asks for trouble.
 Condition variables are represented by hash refs in perl, and the keys
 There are two "sides" to a condition variable - the "producer side" which
 eventually calls C<< -> send >>, and the "consumer side", which waits
 for the send to occur.
-Example:
+Example: wait for a timer.
    # wait till the result is ready
    my $result_ready = AnyEvent->condvar;
    # do something such as adding a timer
    # this "blocks" (while handling events) till the callback
    # calls send
    $result_ready->recv;
+Example: wait for a timer, but take advantage of the fact that
+condition variables are also code references.
+   my $done = AnyEvent->condvar;
+   my $delay = AnyEvent->timer (after => 5, cb => $done);
+   $done->recv;
 =head3 METHODS FOR PRODUCERS
 These methods should only be used by the producing side, i.e. the
 code/module that eventually sends the signal. Note that it is also
 the producer side which creates the condvar in most cases, but it isn't
 If a callback has been set on the condition variable, it is called
 immediately from within send.
 Any arguments passed to the C<send> call will be returned by all
 future C<< ->recv >> calls.
+Condition variables are overloaded so one can call them directly (as a
+code reference). Calling them directly is the same as calling C<send>.
 =item $cv->croak ($error)
 Similar to send, but causes all call's to C<< ->recv >> to invoke
 C<Carp::croak> with the given error message/object/scalar.
 doesn't execute once).
 This is the general pattern when you "fan out" into multiple subrequests:
 use an outer C<begin>/C<end> pair to set the callback and ensure C<end>
 is called at least once, and then, for each subrequest you start, call
-C<begin> and for eahc subrequest you finish, call C<end>.
+C<begin> and for each subrequest you finish, call C<end>.
 =back
 =head3 METHODS FOR CONSUMERS
 (programs might want to do that to stay interactive), so I<if you are
 using this from a module, never require a blocking wait>, but let the
 caller decide whether the call will block or not (for example, by coupling
 condition variables with some kind of request results and supporting
 callbacks so the caller knows that getting the result will not block,
-while still suppporting blocking waits if the caller so desires).
+while still supporting blocking waits if the caller so desires).
 Another reason I<never> to C<< ->recv >> in a module is that you cannot
 sensibly have two C<< ->recv >>'s in parallel, as that would require
 multiple interpreters or coroutines/threads, none of which C<AnyEvent>
 can supply.
 The callback will be called when the condition becomes "true", i.e. when
 C<send> or C<croak> are called. Calling C<recv> inside the callback
 or at any later time is guaranteed not to block.
 =back
+=head3 MAINLOOP EMULATION
+Sometimes (often for short test scripts, or even standalone programs
+who only want to use AnyEvent), you I<do> want your program to block
+indefinitely in some event loop.
+In that case, you cna use a condition variable like this:
+   AnyEvent->condvar->recv;
+This has the effect of entering the event loop and looping forever.
+Note that usually your program has some exit condition, in which case
+it is better to use the "traditional" approach of storing a condition
+variable, waiting for it, and sending it when the program should exit
+cleanly.
 =head1 GLOBAL VARIABLES AND FUNCTIONS
 =over 4
 no warnings;
 use strict;
 use Carp;
-our $VERSION = '3.6';
+our $VERSION = '4.03';
 our $MODEL;
 our $AUTOLOAD;
 our @ISA;
 our @ISA = AnyEvent::CondVar::Base::;
 package AnyEvent::CondVar::Base;
+use overload
+   '&{}'    => sub { my $self = shift; sub { $self->send (@_) } },
+   fallback => 1;
 sub _send {
    # nop
 }
 sub send {
 model it chooses.
 =item C<PERL_ANYEVENT_MODEL>
 This can be used to specify the event model to be used by AnyEvent, before
-autodetection and -probing kicks in. It must be a string consisting
+auto detection and -probing kicks in. It must be a string consisting
 entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
 and the resulting module name is loaded and if the load was successful,
 used as event model. If it fails to load AnyEvent will proceed with
-autodetection and -probing.
+auto detection and -probing.
 This functionality might change in future versions.
 For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
 could start your program like this:
 =item C<PERL_ANYEVENT_PROTOCOLS>
 Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
 for IPv4 or IPv6. The default is unspecified (and might change, or be the result
-of autoprobing).
+of auto probing).
 Must be set to a comma-separated list of protocols or address families,
 current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
 used, and preference will be given to protocols mentioned earlier in the
 list.
+This variable can effectively be used for denial-of-service attacks
+against local programs (e.g. when setuid), although the impact is likely
+small, as the program has to handle connection errors already-
 Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
 but support both and try to use both.  C<PERL_ANYEVENT_PROTOCOLS=ipv4>
 - only support IPv4, never try to resolve or contact IPv6
-addressses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
+addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
 IPv6, but prefer IPv6 over IPv4.
+=item C<PERL_ANYEVENT_EDNS0>
+Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension
+for DNS. This extension is generally useful to reduce DNS traffic, but
+some (broken) firewalls drop such DNS packets, which is why it is off by
+default.
+Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
+EDNS0 in its DNS requests.
 =back
 =head1 EXAMPLE PROGRAM
    syswrite $txn->{fh}, $txn->{request}
       or die "connection or write error";
    $txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });
 Again, C<fh_ready_r> waits till all data has arrived, and then stores the
-result and signals any possible waiters that the request ahs finished:
+result and signals any possible waiters that the request has finished:
    sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};
    if (end-of-file or data complete) {
      $txn->{result} = $txn->{buf};
    $txn->{finished}->recv;
    return $txn->{result};
 The actual code goes further and collects all errors (C<die>s, exceptions)
-that occured during request processing. The C<result> method detects
+that occurred during request processing. The C<result> method detects
 whether an exception as thrown (it is stored inside the $txn object)
 and just throws the exception, which means connection errors and other
 problems get reported tot he code that tries to use the result, not in a
 random callback.
 of various event loops I prepared some benchmarks.
 =head2 BENCHMARKING ANYEVENT OVERHEAD
 Here is a benchmark of various supported event models used natively and
-through anyevent. The benchmark creates a lot of timers (with a zero
+through AnyEvent. The benchmark creates a lot of timers (with a zero
 timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
 which it is), lets them fire exactly once and destroys them again.
 Source code for this benchmark is found as F<eg/bench> in the AnyEvent
 distribution.
 =back
 =head2 BENCHMARKING THE LARGE SERVER CASE
-This benchmark atcually benchmarks the event loop itself. It works by
+This benchmark actually benchmarks the event loop itself. It works by
-creating a number of "servers": each server consists of a socketpair, a
+creating a number of "servers": each server consists of a socket pair, a
 timeout watcher that gets reset on activity (but never fires), and an I/O
 watcher waiting for input on one side of the socket. Each time the socket
 watcher reads a byte it will write that byte to a random other "server".
 The effect is that there will be a lot of I/O watchers, only part of which
 are active at any one point (so there is a constant number of active
-fds for each loop iterstaion, but which fds these are is random). The
+fds for each loop iteration, but which fds these are is random). The
 timeout is reset each time something is read because that reflects how
 most timeouts work (and puts extra pressure on the event loops).
-In this benchmark, we use 10000 socketpairs (20000 sockets), of which 100
+In this benchmark, we use 10000 socket pairs (20000 sockets), of which 100
 (1%) are active. This mirrors the activity of large servers with many
 connections, most of which are idle at any one point in time.
 Source code for this benchmark is found as F<eg/bench2> in the AnyEvent
 distribution.
 =head3 Explanation of the columns
 I<sockets> is the number of sockets, and twice the number of "servers" (as
 each server has a read and write socket end).
-I<create> is the time it takes to create a socketpair (which is
+I<create> is the time it takes to create a socket pair (which is
 nontrivial) and two watchers: an I/O watcher and a timeout watcher.
 I<request>, the most important value, is the time it takes to handle a
 single "request", that is, reading the token from the pipe and forwarding
 it to another server. This includes deleting the old timeout and creating
 speed most when you have lots of watchers, not when you only have a few of
 them).
 EV is again fastest.
-Perl again comes second. It is noticably faster than the C-based event
+Perl again comes second. It is noticeably faster than the C-based event
 loops Event and Glib, although the difference is too small to really
 matter.
 POE also performs much better in this case, but is is still far behind the
 others.

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Comparing AnyEvent/lib/AnyEvent.pm (file contents): Revision 1.126 by root, Fri May 23 23:44:55 2008 UTC vs. Revision 1.133 by root, Sun May 25 03:44:03 2008 UTC

Diff Legend

Comparing AnyEvent/lib/AnyEvent.pm (file contents):
Revision 1.126 by root, Fri May 23 23:44:55 2008 UTC vs.
Revision 1.133 by root, Sun May 25 03:44:03 2008 UTC