NAME IO::Event - Tied Filehandles for Nonblocking IO with Object Callbacks SYNOPSIS use IO::Event; use IO::Event 'emulate_Event'; my $ioe = IO::Event->new($filehandle); my $ioe = IO::Event::Socket::INET->new( [ARGS] ) my $ioe = IO::Event::Socket::UNIX->new( [ARGS] ) my $timer = IO::Event->timer(interval => $seconds); IO::Event::loop(); IO::Event::unloop_all(); DESCRIPTION IO::Event provides a object-based callback system for handling nonblocking IO. The design goal is to provide a system that just does the right thing w/o the user needing to think about it much. All APIs are kept as simple as possible yet at the same time, all functionality is accesible if needed. Simple things are easy. Hard things are possible. Most of the time file handling syntax will work fine: "<$filehandle>" and "print $filehandle 'stuff'". After initial setup, call "IO::Event::loop()". IO::Event was originally written to use Event. It turns out that Event has bugs and now IO::Event can provide it's own select loop instead of using the one from Event. CONSTRUCTORS IO::Event->new($filehandle, [ $handler, [ $options ]]) The basic "new" constructor takes a filehandle and returns a psuedo-filehandle. Treat the IO::Event object as a filehandle. Do not use the original filehandle without good reason (let us know if you find a good reason so we can fix the problem). The handler is the class or object where you provide callback functions to handle IO events. It defaults to the package of the calling context. If present, $options is a hash reference with the following possible keys: description A text description of this filehandle. Used for debugging and error messages. read_only Set to true if this is a read-only filehandle. Do not accept output. write_only Set to true if this is a write-only filehandle. Do not attept to read. autoread Set to 0 if this should not be an auto-read filehandle. IO::Event::Socket::INET->new( [ARGS] ) This constructor uses IO::Socket::INET->new() to create a socket using the ARGS provided. It returns an IO::Event object. The handler defaults as above or can be set with an additional pseudo-parameter for IO::Socket::UNIX->new(): "Handler". A description for the socket can be provided with an additional psuedo-parameter: "Description". IO::Event::Socket::UNIX->new( [ARGS] ) This constructor uses IO::Socket::UNIX->new() to create a socket using the ARGS provided. It returns an IO::Event object. The handler defaults as above or can be set with an additional pseudo-parameter for IO::Socket::UNIX->new(): "Handler". A description for the socket can be provided with an additional psuedo-parameter: "Description". MANDATORY HANDLERS These handler methods must be available in the handler object/class if the situation in which they would be called arises. ie_input($handler, $ioe, $input_buffer_reference) Invoked when there is fresh data in the input buffer. The input can be retreived via directly reading it from $$input_buffer_reference or via "read()" from the $ioe filehandle, or by using a variety of standard methods for getting data: <$ioe> like IO::Handle $ioe->get() like Data::LineBuffer $ioe->read() like IO::Handle $ioe->sysread() like IO::Handle $ioe->getline() like IO::Handle $ioe->getlines() like IO::Handle $ioe->getsome() see below $ioe->ungets() like FileHandle::Unget At end-of-file, ie_input will only be invoked once. There may or may not be data in the input buffer. ie_connection($handler, $ioe) Invoked when a listen()ing socket is ready to accept(). It should call accept: sub ie_connection { my ($pkg, $ioe) = @_; my $newfh = $ioe->accept() } ie_read_ready($handler, $ioe, $underlying_file_handle) If autoreading is turned off then this will be invoked. ie_werror($handler, $ioe, $output_buffer_reference) A write error has occured when trying to drain the write buffer. Provide an empty subroutine if you don't care. OPTIONAL HANDLERS These handler methods will be called if they are defined but it is not required that they be defined. ie_eof($handler, $ioe, $input_buffer_reference) This is invoked when the read-side of the filehandle has been closed by its source. ie_output This is invoked when data has just been written to the underlying filehandle. ie_outputdone This is invoked when all pending data has just been written to the underlying filehandle. ie_connected This is invoked when a "connect()" completes. ie_connect_failed($handler, $ioe, $error_code) This is invoked when a "connect()" fails. For a timeout, the error code will be ETIMEOUT. ie_died($handler, $ioe, $method, $@) If another handler calls "die" then ie_died will be called with the IO::Event object, the name of the method just invoked, and the die string. If no ie_died() callback exists then execution will terminate. ie_timer This is invoked for timer events. These will only arise if set using thing underlying Event object. ie_exception Invoked when an exceptional condition arises on the underlying filehandle ie_outputoverflow($handler, $ioe, $overflowing, $output_buffer_reference) Invoked when there is too much output data and the output buffers are overflowing. You can take some action to generate less output. This will be invoked exactly once (with $overflowing == 1) when there is too much data in the buffer and then exactly once again (with $overflowing == 0) when there is no longer too much data in the buffer. METHODS In addition to methods described in detail below, the following methods behave like their "IO" (mostly "IO::Socket") counterparts (except for being mostly non-blocking...): connect listen open read sysread syswrite print eof shutdown Through AUTOLOAD (see the SUBSTITUTED METHODS section) methods are passed to underlying "Event" objects: loop unloop and many more... Through AUTOLOAD (see the SUBSTITUTED METHODS section) methods are passed to underlying "IO" objects: fileno stat truncate error opened untaint and many more... IO::Event defines its own methods too: ->accept($handler, %options) accept() is nearly identical to the normal IO::Socket::accept() method except that instead of optionally passing a class specifier for the new socket, you optionally pass a handler object or class. The returned filehandle is an IO::Event object. Supported options: description Sets the description for the new socket autoread Set to 0 if you do not want auto-read ->can_read($amount) Returns true if $amount bytes worth of input is available for reading. Note: this does not return true at EOF so be careful not to hang forever at EOF. ->getsome($amount) Returns $amount bytes worth of input or undef if the request can't be filled. Returns what it can at EOF. ->get() get() is like getline() except that it pre-chomp()s the results and assumes the input_record_separator is "\n". This is like get() from Data::LineBuffer. ->unget() Push chomp()ed lines back into the input buffer. This is like unget() from Data::LineBuffer. ->ungetline(), ->xungetc(), ->ungets() This is what ungetc() should be: it pushes a string back into the input buffer. This is unlike IO::Handle->ungetc which takes an ordinal and pushes one character back into the the input buffer. ->handler($new_handler) Sets the handler object/class if $new_handler is provided. Returns the old handler. ->filehandle() Returns the underlying "IO::Handle". ->event() Returns the underling "Event". ->listener($listening) Used to note that a filehandle is being used to listen for connections (instead of receiving data). A passed parameter of 0 does the opposite. Returns the old value. This is mostly used internally in IO::Event. ->input_record_separator($new_sep) IO::Handle doesn't allow input_record_separator's on a per filehandle basis. IO::Event does. If you don't ever set a filehandle's input record separator, then it contineously defaults to the current value of $/. If you set it, then it will use your value and never look at $/ again. ->readevents($readevents) Get/set listening for read-ready events on the underlying filehandle. This could be used by ie_outputoverflow to control input flows. ->output_bufsize($output_bufsize) Get/set the size of the output buffer. ->autoread($autoread) Get/set automatic reading if data when data can be read. Without autoread turned on, the input buffer ins't filled and none of the read methods will work. The point of this is for working with non-data filehandles. This is an experts-only method that kinda defeats the purpose of this module. This would be necessary using recv() to get data. ->drain() Used to start looking for write-ready events on the underlying filehandle. In normal operation this is handled automatically. Deprecated: use writeevents(1) instead. ->reentrant($reentrant) Get/set reentrant callbacks. By default, IO::Event avoids making reentrant callbacks. This is good because your code is less likely to break. This is bad because you won't learn about things right away. For example, you will not learn the the output buffer is overflowing during print(). You'll have to wait for the output buffer to begin draining to find out. This could be a problem. ->close() If there is output buffered, close will be delayed until the output buffer drains. ->forceclose Close close immediately, even if there is output buffered. SUBSTITUED METHODS Any method invocations that fail because the method isn't defined in IO::Event will by tried twice more: once using trying for a method on the inner (hidden) filehandle and once more trying for a method on the Event object that's used to create the select loop for this module. EXAMPLE SERVER # This is a tcp line echo server my $listener = IO::Event::Socket::INET->new( Listen => 10, Proto => 'tcp', LocalPort => 2821, ); Event::loop(); sub ie_connection { my ($pkg, $lstnr) = @_; my $client = $lstnr->accept(); printf "accepted connection from %s:%s\n", $client->peerhost, $client->peerport; } sub ie_input { my ($pkg, $client, $ibufref) = @_; print $client <$client>; } SYSREAD and EOF sysread() is incompatable with eof() because eof() uses getc(). Most of the time this isn't a problem. In other words, some of the time this is a problem: lines go missing. For this reason, IO::Event never uses sysread(). In fact, if you ask it to do a sysread() it does a read() for you instead. On the other hand, at the current time no problems with syswrite have come to light and IO::Event uses syswrite and never any other form of write/print etc. AVOIDING Event.pm If you find that your IO::Event program works fine for a while and then slows down or fails to receive all the events you expect, the problem may be in Event. IO::Event can optionally use it's own select loop instead of Event. To use IO::Event's select loop, import "emulate_Event". use IO::Event 'emulate_Event'; IO::Event does not provide a complete emulation of everything that Event does. It provides the full timer API: my $timer = IO::Event::timer( [ARGS] ) instead of my $timer = Event::timer( [ARGS] ) However it does not provide timer events on filehandles, nor does it provide events for signals, or variable accesses. Use "IO::Event::loop()" instead of "Event::loop()". Use "IO::Event::unloop_all()" instead of "Event::unloop_all()". It does not provide any other methods or functions from Event. If you need them, please send a patch. IO::Event's definition for "loop()", "timer()", and "unloop_all()" defaults to the Event version unless "emulate_Event" has been imported. This allows you to easily switch back and forth between Event's dispatcher and IO::Event's version. IO::Event's version is generally lower performance but it seems to be more reliable. DATA STRUCTURE The filehandle object itself is a funny kind of hash reference. If you want to use it to store your own data, you can. Please don't use hash keys that begin "ie_" or "io_" as those are the prefixes used by "IO::Event" and "IO::Socket". The syntax is kinda funny: ${*$filehandle}{'your_hash_key'} SEE ALSO The following perl modules do something that is kinda similar to what is being done here: IO::Multiplex IO::NonBlocking IO::Select Event POE POE::Component::Server::TCP Net::Socket::NonBlock Net::Server::Multiplex NetServer::Generic The API borrows most heavily from IO::Multiplex. IO::Event uses Event.pm and thus can be used in programs that are already using Event or POE. BUGS The test suite only covers 40% of the code. The module is used by its author and seems solid. LICENSE Copyright (C) 2002-2009 David Muir Sharnoff . This module may be used/copied/etc on the same terms as Perl itself.