*** empty log message ***

[software/libev.git] / ev.pod

diff --git a/ev.pod b/ev.pod
index 075d6727ca64754bbf0657c97dd052ff5a7efac0..45c9c6068f23e5b70e18ac61cba0841b31f60f8d 100644 (file)
--- a/ev.pod
+++ b/ev.pod
@@ -10,7 +10,7 @@ libev - a high performance full-featured event loop written in C
 
 Libev is an event loop: you register interest in certain events (such as a
 file descriptor being readable or a timeout occuring), and it will manage
 
 Libev is an event loop: you register interest in certain events (such as a
 file descriptor being readable or a timeout occuring), and it will manage

-these event sources and provide your program events.
+these event sources and provide your program with events.

 
 To do this, it must take more or less complete control over your process
 (or thread) by executing the I<event loop> handler, and will then
 
 To do this, it must take more or less complete control over your process
 (or thread) by executing the I<event loop> handler, and will then


@@ -27,13 +27,15 @@ Libev supports select, poll, the linux-specific epoll and the bsd-specific
 kqueue mechanisms for file descriptor events, relative timers, absolute
 timers with customised rescheduling, signal events, process status change
 events (related to SIGCHLD), and event watchers dealing with the event
 kqueue mechanisms for file descriptor events, relative timers, absolute
 timers with customised rescheduling, signal events, process status change
 events (related to SIGCHLD), and event watchers dealing with the event

-loop mechanism itself (idle, prepare and check watchers).
+loop mechanism itself (idle, prepare and check watchers). It also is quite
+fast (see this L<benchmark|http://libev.schmorp.de/bench.html> comparing
+it to libevent for example).

 
 =head1 CONVENTIONS
 
 Libev is very configurable. In this manual the default configuration
 will be described, which supports multiple event loops. For more info
 
 =head1 CONVENTIONS
 
 Libev is very configurable. In this manual the default configuration
 will be described, which supports multiple event loops. For more info

-about various configuraiton options please have a look at the file
+about various configuration options please have a look at the file

 F<README.embed> in the libev distribution. If libev was configured without
 support for multiple event loops, then all functions taking an initial
 argument of name C<loop> (which is always of type C<struct ev_loop *>)
 F<README.embed> in the libev distribution. If libev was configured without
 support for multiple event loops, then all functions taking an initial
 argument of name C<loop> (which is always of type C<struct ev_loop *>)


@@ -71,10 +73,10 @@ not a problem.
 =item ev_set_allocator (void *(*cb)(void *ptr, long size))
 
 Sets the allocation function to use (the prototype is similar to the
 =item ev_set_allocator (void *(*cb)(void *ptr, long size))
 
 Sets the allocation function to use (the prototype is similar to the

-realloc function). It is used to allocate and free memory (no surprises
-here). If it returns zero when memory needs to be allocated, the library
-might abort or take some potentially destructive action. The default is
-your system realloc function.
+realloc C function, the semantics are identical). It is used to allocate
+and free memory (no surprises here). If it returns zero when memory
+needs to be allocated, the library might abort or take some potentially
+destructive action. The default is your system realloc function.

 
 You could override this function in high-availability programs to, say,
 free some memory if it cannot allocate memory, to use a special allocator,
 
 You could override this function in high-availability programs to, say,
 free some memory if it cannot allocate memory, to use a special allocator,


@@ -86,7 +88,7 @@ Set the callback function to call on a retryable syscall error (such
 as failed select, poll, epoll_wait). The message is a printable string
 indicating the system call or subsystem causing the problem. If this
 callback is set, then libev will expect it to remedy the sitution, no
 as failed select, poll, epoll_wait). The message is a printable string
 indicating the system call or subsystem causing the problem. If this
 callback is set, then libev will expect it to remedy the sitution, no

-matter what, when it returns. That is, libev will geenrally retry the
+matter what, when it returns. That is, libev will generally retry the

 requested operation, or, if the condition doesn't go away, do bad stuff
 (such as abort).
 
 requested operation, or, if the condition doesn't go away, do bad stuff
 (such as abort).
 


@@ -100,9 +102,10 @@ events, and dynamically created loops which do not.
 
 If you use threads, a common model is to run the default event loop
 in your main thread (or in a separate thrad) and for each thread you
 
 If you use threads, a common model is to run the default event loop
 in your main thread (or in a separate thrad) and for each thread you

-create, you also create another event loop. Libev itself does no lockign
-whatsoever, so if you mix calls to different event loops, make sure you
-lock (this is usually a bad idea, though, even if done right).
+create, you also create another event loop. Libev itself does no locking
+whatsoever, so if you mix calls to the same event loop in different
+threads, make sure you lock (this is usually a bad idea, though, even if
+done correctly, because its hideous and inefficient).

 
 =over 4
 
 
 =over 4
 


@@ -117,7 +120,7 @@ If you don't know what event loop to use, use the one returned from this
 function.
 
 The flags argument can be used to specify special behaviour or specific
 function.
 
 The flags argument can be used to specify special behaviour or specific

-backends to use, and is usually specified as 0 (or EVFLAG_AUTO)
+backends to use, and is usually specified as 0 (or EVFLAG_AUTO).

 
 It supports the following flags:
 
 
 It supports the following flags:
 


@@ -130,11 +133,12 @@ thing, believe me).
 
 =item EVFLAG_NOENV
 
 
 =item EVFLAG_NOENV
 

-If this flag bit is ored into the flag value then libev will I<not> look
-at the environment variable C<LIBEV_FLAGS>. Otherwise (the default), this
-environment variable will override the flags completely. This is useful
-to try out specific backends to tets their performance, or to work around
-bugs.
+If this flag bit is ored into the flag value (or the program runs setuid
+or setgid) then libev will I<not> look at the environment variable
+C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
+override the flags completely if it is found in the environment. This is
+useful to try out specific backends to test their performance, or to work
+around bugs.

 
 =item EVMETHOD_SELECT  portable select backend
 
 
 =item EVMETHOD_SELECT  portable select backend
 


@@ -295,8 +299,8 @@ As long as your watcher is active (has been started but not stopped) you
 must not touch the values stored in it. Most specifically you must never
 reinitialise it or call its set method.
 
 must not touch the values stored in it. Most specifically you must never
 reinitialise it or call its set method.
 

-You cna check wether an event is active by calling the C<ev_is_active
-(watcher *)> macro. To see wether an event is outstanding (but the
+You cna check whether an event is active by calling the C<ev_is_active
+(watcher *)> macro. To see whether an event is outstanding (but the

 callback for it has not been called yet) you cna use the C<ev_is_pending
 (watcher *)> macro.
 
 callback for it has not been called yet) you cna use the C<ev_is_pending
 (watcher *)> macro.
 


@@ -402,12 +406,26 @@ information given in the last section.
 
 =head2 struct ev_io - is my file descriptor readable or writable
 
 
 =head2 struct ev_io - is my file descriptor readable or writable
 

-I/O watchers check wether a file descriptor is readable or writable
+I/O watchers check whether a file descriptor is readable or writable

 in each iteration of the event loop (This behaviour is called
 level-triggering because you keep receiving events as long as the
 condition persists. Remember you cna stop the watcher if you don't want to
 act on the event and neither want to receive future events).
 
 in each iteration of the event loop (This behaviour is called
 level-triggering because you keep receiving events as long as the
 condition persists. Remember you cna stop the watcher if you don't want to
 act on the event and neither want to receive future events).
 

+In general you can register as many read and/or write event watchers oer
+fd as you want (as long as you don't confuse yourself). Setting all file
+descriptors to non-blocking mode is also usually a good idea (but not
+required if you know what you are doing).
+
+You have to be careful with dup'ed file descriptors, though. Some backends
+(the linux epoll backend is a notable example) cannot handle dup'ed file
+descriptors correctly if you register interest in two or more fds pointing
+to the same file/socket etc. description.
+
+If you must do this, then force the use of a known-to-be-good backend
+(at the time of this writing, this includes only EVMETHOD_SELECT and
+EVMETHOD_POLL).
+

 =over 4
 
 =item ev_io_init (ev_io *, callback, int fd, int events)
 =over 4
 
 =item ev_io_init (ev_io *, callback, int fd, int events)