[23984] in Perl-Users-Digest
Perl-Users Digest, Issue: 6185 Volume: 10
daemon@ATHENA.MIT.EDU (Perl-Users Digest)
Wed Feb 25 14:06:00 2004
Date: Wed, 25 Feb 2004 11:05:02 -0800 (PST)
From: Perl-Users Digest <Perl-Users-Request@ruby.OCE.ORST.EDU>
To: Perl-Users@ruby.OCE.ORST.EDU (Perl-Users Digest)
Perl-Users Digest Wed, 25 Feb 2004 Volume: 10 Number: 6185
Today's topics:
ANNOUNCE: IO::Event version 0.502 ((null))
Digest Administrivia (Last modified: 6 Apr 01) (Perl-Users-Digest Admin)
----------------------------------------------------------------------
Date: Wed, 25 Feb 2004 02:36:34 GMT
From: muir@idiom.com ((null))
Subject: ANNOUNCE: IO::Event version 0.502
Message-Id: <HtnEzu.1Mo1@zorch.sf-bay.org>
You can find this in CPAN at
http://www.cpan.org/authors/id/MUIR/modules/IO-Event-0.502.tar.gz
or (until CPAN picks it up) at
ftp:://ftp.idiom.com/users/muir/CPAN/modules/IO-Event-0.502.tar.gz
I'm using IO::Event activly in development. I am not yet using
it in production. The code is getting stable and is good enough
for users other than myself.
-Dave
...CHANGELOG......................................................
Added can_read()
Bugfix: spurrious warning in unget()
Added ungets() to support FileHandle::Unget semantics
...POD............................................................
NAME
IO::Event - Tied Filehandles for Nonblocking IO with Object Callbacks
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 $filehandle 'stuff'".
CONSTRUCTORS
IO::Event->new($filehandle, $handler)
The basic "new" constructor takes a filehandle and returns a
psuedo-filehandle. Treat the IO::Event object as a filehandle. Do
not use the original filehandle without good reason (let us know if
you find a good reason so we can fix the problem).
The handler is the class or object where you provide callback
functions to handle IO events. It defaults to the package of the
calling context.
IO::Event::Socket::INET->new( [ARGS] )
This constructor uses IO::Socket::INET->new() to create a socket
using the ARGS provided. It returns an IO::Event object.
The handler defaults as above or can be set with an additional
pseudo-parameter for IO::Socket::UNIX->new(): "Handler". A
description for the socket can be provided with an additional
psuedo-parameter: "Description".
IO::Event::Socket::UNIX->new( [ARGS] )
This constructor uses IO::Socket::UNIX->new() to create a socket
using the ARGS provided. It returns an IO::Event object.
The handler defaults as above or can be set with an additional
pseudo-parameter for IO::Socket::UNIX->new(): "Handler". A
description for the socket can be provided with an additional
psuedo-parameter: "Description".
MANDATORY HANDLERS
These handler methods must be available in the handler object/class if
the situation in which they would be called arises.
ie_input($handler, $ieo, $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 $ieo filehandle, or by using a variety of
standard methods for getting data:
<$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
$ieo->ungets() like FileHandle::Unget
At end-of-file, ie_input will only be invoked once. There may or may
not be data in the input buffer.
ie_connection($handler, $ieo)
Invoked when a listen()ing socket is ready to accept(). It should
call accept:
sub ie_connection
{
my ($ieo) = @_;
my $newfh = $ieo->accept()
}
ie_read_ready($handler, $underlying_file_handle)
If autoreading is turned off then this will be invoked.
ie_werror($handler, $output_buffer_reference)
A write error has occured when trying to drain the write buffer.
Provide an empty subroutine if you don't care.
OPTIONAL HANDLERS
These handler methods will be called if they are defined but it is not
required that they be defined.
ie_eof($handler, $ieo, $input_buffer_reference)
This is invoked when the read-side of the filehandle has been closed
by its source.
ie_output
This is invoked when data has just been written to the underlying
filehandle.
ie_outputdone
This is invoked when all pending data has just been written to the
underlying filehandle.
ie_connected
This is invoked when a "connect()" completes.
ie_connect_timeout
This is invoked when a "connect()" attempt times out.
ie_died($handler, $ieo, $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, $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 $overflowing == 0) when there is no longer too much data in
the buffer.
METHODS
In addition to methods described in detail below, the following methods
behave like their "IO" (mostly "IO::Socket") counterparts (except for
being mostly non-blocking...):
connect
listen
open
close
read
sysread
syswrite
print
eof
Through AUTOLOAD (see the SUBSTITUTED METHODS section) methods are
passed to underlying "Event" objects:
loop
unloop
and many more...
Through AUTOLOAD (see the SUBSTITUTED METHODS section) methods are
passed to underlying "IO" objects:
fileno
stat
truncate
error
opened
untaint
and many more...
IO::Event defines its own methods too:
->accept($handler)
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.
->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.
->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.
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.
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
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?
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.
--
------------------------------
Date: 6 Apr 2001 21:33:47 GMT (Last modified)
From: Perl-Users-Request@ruby.oce.orst.edu (Perl-Users-Digest Admin)
Subject: Digest Administrivia (Last modified: 6 Apr 01)
Message-Id: <null>
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End of Perl-Users Digest V10 Issue 6185
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