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#  You may distribute under the terms of either the GNU General Public License
#  or the Artistic License (the same terms as Perl itself)
#
#  (C) Paul Evans, 2012-2015 -- leonerd@leonerd.org.uk

package IO::Async::OS;

use strict;
use warnings;

our $VERSION = '0.70';

our @ISA = qw( IO::Async::OS::_Base );

if( eval { require "IO/Async/OS/$^O.pm" } ) {
   @ISA = "IO::Async::OS::$^O";
}

package # hide from CPAN
   IO::Async::OS::_Base;

use Carp;

use Socket 1.95 qw(
   AF_INET AF_INET6 AF_UNIX INADDR_LOOPBACK SOCK_DGRAM SOCK_RAW SOCK_STREAM
   pack_sockaddr_in inet_aton
   pack_sockaddr_in6 inet_pton
   pack_sockaddr_un
);

use IO::Socket (); # empty import

use POSIX qw( sysconf _SC_OPEN_MAX );

# Win32 [and maybe other places] don't have an _SC_OPEN_MAX. About the best we
# can do really is just make up some largeish number and hope for the best.
use constant OPEN_MAX_FD => eval { sysconf(_SC_OPEN_MAX) } || 1024;

# Some constants that define features of the OS

use constant HAVE_SOCKADDR_IN6 => defined eval { pack_sockaddr_in6 0, inet_pton( AF_INET6, "2001::1" ) };
use constant HAVE_SOCKADDR_UN  => defined eval { pack_sockaddr_un "/foo" };

# Do we have to fake S_ISREG() files read/write-ready in select()?
use constant HAVE_FAKE_ISREG_READY => 0;

# Do we have to select() for for evec to get connect() failures
use constant HAVE_SELECT_CONNECT_EVEC => 0;
# Ditto; do we have to poll() for POLLPRI to get connect() failures
use constant HAVE_POLL_CONNECT_POLLPRI => 0;

# Does connect() yield EWOULDBLOCK for nonblocking in progress?
use constant HAVE_CONNECT_EWOULDBLOCK => 0;

# Can we rename() files that are open?
use constant HAVE_RENAME_OPEN_FILES => 1;

# Do we have IO::Socket::IP available?
use constant HAVE_IO_SOCKET_IP => defined eval { require IO::Socket::IP };

# Can we reliably watch for POSIX signals, including SIGCHLD to reliably
# inform us that a fork()ed child has exit()ed?
use constant HAVE_SIGNALS => 1;

# Do we support POSIX-style true fork()ed processes at all?
use constant HAVE_POSIX_FORK => !$ENV{IO_ASYNC_NO_FORK};
# Can we potentially support threads? (would still need to 'require threads')
use constant HAVE_THREADS => !$ENV{IO_ASYNC_NO_THREADS} &&
   eval { require Config && $Config::Config{useithreads} };

# Preferred trial order for built-in Loop classes
use constant LOOP_BUILTIN_CLASSES => qw( Poll Select );

# Should there be any other Loop classes we try before the builtin ones?
use constant LOOP_PREFER_CLASSES => ();

# Do we have Sereal available?
use constant HAVE_SEREAL => defined eval { require Sereal::Encoder; require Sereal::Decoder; };

=head1 NAME

C<IO::Async::OS> - operating system abstractions for C<IO::Async>

=head1 DESCRIPTION

This module acts as a class to provide a number of utility methods whose exact
behaviour may depend on the type of OS it is running on. It is provided as a
class so that specific kinds of operating system can override methods in it.

As well as these support functions it also provides a number of constants, all
with names beginning C<HAVE_> which describe various features that may or may
not be available on the OS or perl build. Most of these are either hard-coded
per OS, or detected at runtime.

The following constants may be overridden by environment variables.

=over 4

=item * HAVE_POSIX_FORK

True if the C<fork()> call has full POSIX semantics (full process separation).
This is true on most OSes but false on MSWin32.

This may be overridden to be false by setting the environment variable
C<IO_ASYNC_NO_FORK>.

=item * HAVE_THREADS