NAME

       "IO::Async::OS" - operating system abstractions for "IO::Async"

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 "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.

       •   HAVE_POSIX_FORK

           True if the "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
           "IO_ASYNC_NO_FORK".

       •   HAVE_THREADS

           True if "ithreads" are available, meaning that the "threads" module can be used. This
           depends on whether perl was built with threading support.

           This may be overridable to be false by setting the environment variable
           "IO_ASYNC_NO_THREADS".

   getfamilybyname
          $family = IO::Async::OS->getfamilybyname( $name )

       Return a protocol family value based on the given name. If $name looks like a number it
       will be returned as-is. The string values "inet", "inet6" and "unix" will be converted to
       the appropriate "AF_*" constant.

   getsocktypebyname
          $socktype = IO::Async::OS->getsocktypebyname( $name )

       Return a socket type value based on the given name. If $name looks like a number it will
       be returned as-is. The string values "stream", "dgram" and "raw" will be converted to the
       appropriate "SOCK_*" constant.

   socketpair
          ( $S1, $S2 ) = IO::Async::OS->socketpair( $family, $socktype, $proto )

       An abstraction of the socketpair(2) syscall, where any argument may be missing (or given
       as "undef").

       If $family is not provided, a suitable value will be provided by the OS (likely "AF_UNIX"
       on POSIX-based platforms). If $socktype is not provided, then "SOCK_STREAM" will be used.

       Additionally, this method supports building connected "SOCK_STREAM" or "SOCK_DGRAM" pairs
       in the "AF_INET" family even if the underlying platform's socketpair(2) does not, by
       connecting two normal sockets together.

       $family and $socktype may also be given symbolically as defined by "getfamilybyname" and
       "getsocktypebyname".

   pipepair
          ( $rd, $wr ) = IO::Async::OS->pipepair

       An abstraction of the pipe(2) syscall, which returns the two new handles.

   pipequad
          ( $rdA, $wrA, $rdB, $wrB ) = IO::Async::OS->pipequad

       This method is intended for creating two pairs of filehandles that are linked together,
       suitable for passing as the STDIN/STDOUT pair to a child process.  After this function
       returns, $rdA and $wrA will be a linked pair, as will $rdB and $wrB.

       On platforms that support socketpair(2), this implementation will be preferred, in which
       case $rdA and $wrB will actually be the same filehandle, as will $rdB and $wrA. This saves
       a file descriptor in the parent process.

       When creating a IO::Async::Stream or subclass of it, the "read_handle" and "write_handle"
       parameters should always be used.

        my ( $childRd, $myWr, $myRd, $childWr ) = IO::Async::OS->pipequad;

        IO::Async::OS->open_child(
           stdin  => $childRd,
           stdout => $childWr,
           ...
        );

        my $str = IO::Async::Stream->new(
           read_handle  => $myRd,
           write_handle => $myWr,
           ...
        );
        IO::Async::OS->add( $str );

   signame2num
          $signum = IO::Async::OS->signame2num( $signame )

       This utility method converts a signal name (such as "TERM") into its system- specific
       signal number. This may be useful to pass to "POSIX::SigSet" or use in other places which
       use numbers instead of symbolic names.

   extract_addrinfo
          ( $family, $socktype, $protocol, $addr ) = IO::Async::OS->extract_addrinfo( $ai )

       Given an ARRAY or HASH reference value containing an addrinfo, returns a family, socktype
       and protocol argument suitable for a "socket" call and an address suitable for "connect"
       or "bind".

       If given an ARRAY it should be in the following form:

        [ $family, $socktype, $protocol, $addr ]

       If given a HASH it should contain the following keys:

        family socktype protocol addr

       Each field in the result will be initialised to 0 (or empty string for the address) if not
       defined in the $ai value.

       The family type may also be given as a symbolic string as defined by "getfamilybyname".

       The socktype may also be given as a symbolic string; "stream", "dgram" or "raw"; this will
       be converted to the appropriate "SOCK_*" constant.

       Note that the "addr" field, if provided, must be a packed socket address, such as returned
       by "pack_sockaddr_in" or "pack_sockaddr_un".

       If the HASH form is used, rather than passing a packed socket address in the "addr" field,
       certain other hash keys may be used instead for convenience on certain named families.

       family => 'inet'
           Will pack an IP address and port number from keys called "ip" and "port".  If "ip" is
           missing it will be set to "0.0.0.0". If "port" is missing it will be set to 0.

       family => 'inet6'
           Will pack an IP address and port number from keys called "ip" and "port".  If "ip" is
           missing it will be set to "::". If "port" is missing it will be set to 0. Optionally
           will also include values from "scopeid" and "flowinfo" keys if provided.

           This will only work if a "pack_sockaddr_in6" function can be found in "Socket"

       family => 'unix'
           Will pack a UNIX socket path from a key called "path".

LOOP IMPLEMENTATION METHODS

       The following methods are provided on "IO::Async::OS" because they are likely to require
       OS-specific implementations, but are used by IO::Async::Loop to implement its
       functionality. It can use the HASH reference "$loop->{os}" to store other data it
       requires.

   loop_watch_signal
   loop_unwatch_signal
          IO::Async::OS->loop_watch_signal( $loop, $signal, $code )

          IO::Async::OS->loop_unwatch_signal( $loop, $signal )

       Used to implement the "watch_signal" / "unwatch_signal" Loop pair.

   potentially_open_fds
          @fds = IO::Async::OS->potentially_open_fds

       Returns a list of filedescriptors which might need closing. By default this will return "0
       .. _SC_OPEN_MAX". OS-specific subclasses may have a better guess.

AUTHOR

       Paul Evans <leonerd@leonerd.org.uk>