
=head1 NAME

IO::Event - Tied Filehandles for Nonblocking IO with Object Callbacks

=head1 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: C<< <$filehandle> >>
and C<print $filehandle 'stuff'>.

=head1 CONSTRUCTORS

=over 4

=item IO::Event->new($filehandle, $handler)

The basic C<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. 

=item 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(): 
C<Handler>.  A description for the socket can be provided
with an additional psuedo-parameter: C<Description>.

=item 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(): 
C<Handler>.  A description for the socket can be provided
with an additional psuedo-parameter: C<Description>.

=back

=head1 MANDATORY HANDLERS

These handler methods must be available in the handler
object/class if the situation in which they would be
called arises.

=over 4

=item ie_input($handler, $ieo, $input_buffer_reference)

Invoked when there is fresh data in the input buffer.  The 
input can be retreived via directly reading it from
C<$$input_buffer_reference> or via C<read()> from the
$ieo filehandle, or by using a variety of standard
methods for getting data: 
	
	<$ieo>			like IO::Handle
	$ieo->get()		like Data::LineBuffer
	$ieo->read()		like IO::Handle
	$ieo->sysread()		like IO::Handle
	$ieo->getline()		like IO::Handle
	$ieo->getlines()	like IO::Handle
	$ieo->getsome()		see below
	$ieo->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.  

=item ie_connection($handler, $ieo)

Invoked when a listen()ing socket is ready to accept().
It should call accept:

	sub ie_connection
	{
		my ($ieo) = @_;
		my $newfh = $ieo->accept()
	}

=item ie_read_ready($handler, $underlying_file_handle)

If autoreading is turned off then this will be invoked.

=item ie_werror($handler, $output_buffer_reference)

A write error has occured when trying to drain the write
buffer.  Provide an empty subroutine if you don't care.

=back

=head1 OPTIONAL HANDLERS

These handler methods will be called if they are defined
but it is not required that they be defined.

=over 4

=item ie_eof($handler, $ieo, $input_buffer_reference)

This is invoked when the read-side of the filehandle has
been closed by its source.

=item ie_output

This is invoked when data has just been written to the 
underlying filehandle.

=item ie_outputdone

This is invoked when all pending data has just been written
to the underlying filehandle.

=item ie_connected

This is invoked when a C<connect()> completes.

=item ie_connect_timeout

This is invoked when a C<connect()> attempt times out.

=item ie_died($handler, $ieo, $method, $@)

If another handler calls C<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.

=item ie_timer

This is invoked for timer events.  These will only arise
if set using thing underlying Event object.

=item ie_exception

Invoked when an exceptional condition arises on the 
underlying filehandle

=item ie_outputoverflow($handler, $ieo, $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.

=back

=head1 METHODS

In addition to methods described in detail below, the following
methods behave like their C<IO> (mostly C<IO::Socket>) counterparts
(except for being mostly non-blocking...):

	connect
	listen
	open
	close
	read
	sysread
	syswrite
	print
	eof

Through AUTOLOAD (see the SUBSTITUTED METHODS section) methods 
are passed to underlying C<Event> objects:

	loop
	unloop
	and many more...

Through AUTOLOAD (see the SUBSTITUTED METHODS section) methods 
are passed to underlying C<IO> objects:

	fileno
	stat
	truncate
	error
	opened
	untaint
	and many more...

IO::Event defines its own methods too:

=over 4

=item ->accept($handler)

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/class.   The returned filehandle is an
IO::Event object.

=item ->can_read($amount)

Returns true if C<$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.

=item ->getsome($amount)

Returns C<$amount> bytes worth of input or undef if the request
can't be filled.  Returns what it can at EOF.

=item ->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.

=item ->unget()

Push chomp()ed lines back into the input buffer.
This is like unget() from Data::LineBuffer.

=item ->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.

=item ->handler($new_handler)

Sets the handler object/class if $new_handler is provided.
Returns the old handler.

=item ->filehandle()

Returns the underlying C<IO::Handle>.

=item ->event()

Returns the underling C<Event>.

=item ->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.

=item ->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 C<$/>.  If you set it, then it will use your value and never
look at C<$/> again.

=item ->readevents($readevents)

Get/set listening for read-ready events on the underlying
filehandle.  This could be used by ie_outputoverflow to
control input flows.  

=item ->output_bufsize($output_bufsize)

Get/set the size of the output buffer.

=item ->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.

=item ->drain()

Used to start looking for write-ready events on the underlying
filehandle.  In normal operation this is handled automatically.

=item ->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.

=back

=head1 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.

=head1 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>;
	}

=head1 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.

=head1 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 C<ie_> or C<io_> as those are the
prefixes used by C<IO::Event> and C<IO::Socket>.  

The syntax is kinda funny:

	${*$filehandle}{'your_hash_key'}  

=head1 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.

=head1 BUGS

This code is still greenish.   The test suite only covers 40% 
of the code.

Nothing sane is done with excptional conditions.  What causes
them anyway?

=head1 LICENSE

Copyright (C) 2002-2003 David Muir Sharnoff <muir@idiom.com>.
This module may be used/copied/etc on the same terms as Perl 
itself.

