NAME¶
"IO::Async::Channel" - pass values into or out from an
IO::Async::Routine
DESCRIPTION¶
A "IO::Async::Channel" object allows Perl values to be passed into or
out of an IO::Async::Routine. It is intended to be used primarily with a
Routine object rather than independently. For more detail and examples on how
to use this object see also the documentation for IO::Async::Routine.
A Channel object is shared between the main process of the program and the
process running within the Routine. In the main process it will be used in
asynchronous mode, and in the Routine process it will be used in synchronous
mode. In asynchronous mode all methods return immediately and use
"IO::Async"-style futures or callback functions. In synchronous
within the Routine process the methods block until they are ready and may be
used for flow-control within the routine. Alternatively, a Channel may be
shared between two different Routine objects, and not used directly by the
controlling program.
The channel itself represents a FIFO of Perl reference values. New values may be
put into the channel by the "send" method in either mode. Values may
be retrieved from it by the "recv" method. Values inserted into the
Channel are snapshot by the "send" method. Any changes to referred
variables will not be observed by the other end of the Channel after the
"send" method returns.
Since the channel uses Storable to serialise values to write over the
communication filehandle only reference values may be passed. To pass a single
scalar value, "send" a SCALAR reference to it, and dereference the
result of "recv".
CONSTRUCTOR¶
$channel = IO::Async::Channel->new¶
Returns a new "IO::Async::Channel" object. This object reference
itself should be shared by both sides of a "fork()"ed process. After
"fork()" the two "setup_*" methods may be used to
configure the object for operation on either end.
While this object does in fact inherit from IO::Async::Notifier for
implementation reasons it is not intended that this object be used as a
Notifier. It should not be added to a Loop object directly; event management
will be handled by its containing "IO::Async::Routine" object.
METHODS¶
The following methods documented with a trailing call to "->get"
return Future instances.
Similar to the standard "configure" method on
"IO::Async::Notifier", this is used to change details of the
Channel's operation.
- on_recv => CODE
- May only be set on an async mode channel. If present, will be invoked
whenever a new value is received, rather than using the "recv"
method.
$on_recv->( $channel, $data )
- on_eof => CODE
- May only be set on an async mode channel. If present, will be invoked when
the channel gets closed by the peer.
$on_eof->( $channel )
$channel->send( $data )¶
Pushes the data stored in the given Perl reference into the FIFO of the Channel,
where it can be received by the other end. When called on a synchronous mode
Channel this method may block if a "write()" call on the underlying
filehandle blocks. When called on an asynchronous mode channel this method
will not block.
$channel->send_frozen( $record )¶
A variant of the "send" method; this method pushes the byte record
given. This should be the result of a call to "Storable::freeze()".
$data = $channel->recv¶
When called on a synchronous mode Channel this method will block until a Perl
reference value is available from the other end and then return it. If the
Channel is closed this method will return "undef". Since only
references may be passed and all Perl references are true the truth of the
result of this method can be used to detect that the channel is still open and
has not yet been closed.
$data = $channel->recv->get¶
When called on an asynchronous mode Channel this method returns a future which
will eventually yield the next Perl reference value that becomes available
from the other end. If the Channel is closed, the future will fail with an
"eof" failure.
$channel->recv( %args )¶
When not returning a future, takes the following named arguments:
- on_recv => CODE
- Called when a new Perl reference value is available. Will be passed the
Channel object and the reference data.
$on_recv->( $channel, $data )
- on_eof => CODE
- Called if the Channel was closed before a new value was ready. Will be
passed the Channel object.
$on_eof->( $channel )
$channel->close¶
Closes the channel. Causes a pending "recv" on the other end to return
undef or the queued "on_eof" callbacks to be invoked.
AUTHOR¶
Paul Evans <leonerd@leonerd.org.uk>