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POE::Driver(3pm) User Contributed Perl Documentation POE::Driver(3pm)
NAME
POE::Driver - an abstract interface for buffered, non-blocking I/O
SYNOPSIS
This is a contrived example of how POE::Filter and POE::Driver objects may be used in a
stand-alone application.
my $driver = POE::Driver::SysRW->new();
my $filter = POE::Filter::Line->new();
my $list_of_octet_chunks = $filter->put("A line of text.");
$driver->put( $list_of_octet_chunks );
my $octets_remaining_in_buffer = $driver->flush($filehandle);
die "couldn't flush everything" if $octets_remaining_in_buffer;
while (1) {
my $octets_list = $driver->get($filehandle);
die $! unless defined $octets_list;
$filter->get_one_start($octets_list);
while (my $line = $filter->get_one()) {
print "Input: $line\n";
}
}
Most programs will use POE::Filter and POE::Driver objects as parameters to POE::Wheel
constructors. See the synopses for particular classes for details.
DESCRIPTION
POE::Driver is a common API for I/O drivers that can read from and write to various files,
sockets, pipes, and other devices.
POE "drivers" implement the specifics of reading and writing to devices. Drivers plug
into POE::Wheel objects so that wheels may support a large number of device types without
implementing a separate subclass for each.
As mentioned in the SYNOPSIS, POE::Driver objects may be used in stand-alone applications.
Public Driver Methods
These methods are the generic Driver interface, and every driver must implement them.
Specific drivers may have additional methods related to their particular tasks.
new
new() creates, initializes, and returns a new driver. Specific drivers may have different
constructor parameters. The default constructor parameters should configure the driver
for the most common use case.
get FILEHANDLE
get() immediately tries to read information from a FILEHANDLE. It returns an array
reference on success---even if nothing was read from the FILEHANDLE. get() returns undef
on error, and $! will be set to the reason why get() failed.
The returned arrayref will be empty if nothing was read from the FILEHANDLE.
In an EOF condition, get() returns undef with the numeric value of $! set to zero.
The arrayref returned by get() is suitable for passing to any POE::Filter's get() or
get_one_start() method. Wheels do exactly this internally.
put ARRAYREF
put() accepts an ARRAYREF of raw octet chunks. These octets are added to the driver's
internal output queue or buffer. put() returns the number of octets pending output
after the new octets are buffered.
Some drivers may flush data immediately from their put() methods.
flush FILEHANDLE
flush() attempts to write a driver's buffered data to a given FILEHANDLE. The driver
should flush as much data as possible in a single flush() call.
flush() returns the number of octets remaining in the driver's output queue or buffer
after the maximum amount of data has been written.
flush() denotes success or failure by the value of $! after it returns. $! will
always numerically equal zero on success. On failure, $! will contain the usual Errno
value. In either case, flush() will return the number of octets in the driver's
output queue.
get_out_messages_buffered
get_out_messages_buffered() returns the number of messages enqueued in the driver's
output queue, rounded up to the nearest whole message. Some applications require the
message count rather than the octet count.
Messages are raw octet chunks enqueued by put(). The following put() call enqueues
two messages for a total of six octets:
$filter->put( [ "one", "two" ] );
It is possible for a flush() call to write part of a message. A partial message still
counts as one message.
SEE ALSO
The SEE ALSO section in POE contains a table of contents covering the entire POE
distribution.
POE::Wheel - A base class for POE::Session mix-ins.
POE::Filter - A base class for data parsers and serializers.
POE::Driver::SysRW - A driver that encapsulates sysread() and buffered syswrite().
BUGS
There is no POE::Driver::SendRecv, but nobody has needed one so far. sysread() and
syswrite() manage to do almost everything people need.
In theory, drivers should be pretty much interchangeable. In practice, there seems to be
an impermeable barrier between the different SOCK_* types.
AUTHORS & COPYRIGHTS
Please see POE for more information about authors and contributors.
perl v5.30.0 2020-02-07 POE::Driver(3pm)
Generated by $Id: phpMan.php,v 4.55 2007/09/05 04:42:51 chedong Exp $ Author: Che Dong
On Apache
Under GNU General Public License
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