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=head1 NAME
Prima::File - asynchronous stream I/O.
=head1 SYNOPSIS
use strict;
use Prima qw(Application);
# create pipe and autoflush the writer end
pipe(READ, WRITE) or die "pipe():$!\n";
select WRITE;
$|=1;
select STDOUT;
# create Prima listener on the reader end
my $read = Prima::File-> new(
file => \*READ,
mask => fe::Read,
onRead => sub {
$_ = <READ>;
print "read:$_\n";
},
);
print WRITE "line\n";
run Prima;
=head1 DESCRIPTION
Prima::File provides access to the I/O stream events,
that are called when a file handle becomes readable, writable
or if an exception occurred. Registering file handles to Prima::File
objects makes possible the stream operations coexist with the event loop.
=head1 USAGE
Prima::File is a descendant of Prima::Component.
Objects of Prima::File class must be binded to a valid file handle object,
before the associated events can occur:
my $f = Prima::File-> create();
$f-> file( *STDIN);
When a file handle, binded via the C<::file> property becomes readable,
writable or when an exception signaled, one of three correspondent
events called - C<Read>, C<Write> or C<Exception>. When a handle is
always readable, or always writable, or, some of these events are
desired to be blocked, the file event mask can be set via the C<::mask>
property:
$f-> mask( fe::Read | fe::Exception);
NB. Due to different system implementations, the only handles,
currently supported on all systems, are socket handle and disk file
handles. Pipes only work on unix platforms. The example file I<socket.pl>
elucidates the use of sockets together with Prima::File.
When a file handle is not needed anymore, it is expected to
be detached from an object explicitly:
$f-> file( undef);
However, if the system detects that a file handle is no longer valid,
it is automatically detached. It is possible to check, if a file handle
is still valid by calling the C<is_active()> method.
Prima::File events are basically the same I/O callbacks, provided by
a system C<select()> call. See documentation of your system's select()
for the implementation details.
=head1 API
=head2 Properties
=over
=item file HANDLE
Selects a file handle, that is to be monitored for stream I/O events.
If HANDLE is C<undef>, object is returned to a passive state, and
the previously binded file handle is de-selected.
=item mask EVENT_MASK
Selects a event mask, that is a combination of C<fe::XXX> integer constants,
each representing an event:
fe::Read
fe::Write
fe::Exception
The omitted events are effectively excluded from the system file event
multiplexing mechanism.
=back
=head2 Methods
=over
=item get_handle
Returns C<sprintf("0x%08x", fileno( file ))> string.
If C<::file> is C<undef>, -1 is used instead fileno() result.
=item is_active AUTODETACH = 0
Returns a boolean flag, indicating if a file handle is valid.
If AUTODETACH is 1, and the file handle is not valid,
C<file(undef)> is called.
=back
=head2 Events
=over
=item Read
Called when a file handle becomes readable. The callback procedure
is expected to call a non-blocking read() on the file handle.
=item Write
Called when a file handle becomes writable. The callback procedure
is expected to call a non-blocking write() on the file handle.
=item Exception
Called when an exception is signaled on a file handle.
The exceptions are specific to handle type and the operating system.
For example, a unix socket signals C<Exception> when a control status
data for a pseudo terminal or an out-of-band data arrives.
=back
=head1 AUTHOR
Dmitry Karasik, E<lt>dmitry@karasik.eu.orgE<gt>.
=head1 SEE ALSO
L<Prima>, L<Prima::Object>
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