IO::Async::OS(3pm)

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;

   $loop->open_process(
      stdin  => $childRd,
      stdout => $childWr,
      ...
   );

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

  signum2name
   $signame = IO::Async::OS->signum2name( $signum );

The inverse of signame2num; this method convers signal numbers into readable 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".

  make_addr_for_peer
   $connectaddr = IO::Async::OS->make_addr_for_peer( $family, $listenaddr );

Given the "sockdomain" and "sockname" of a listening socket. creates an address suitable to connect() to it.

This method will handle specially any "AF_INET" address bound to "INADDR_ANY" or any "AF_INET6" address bound to "IN6ADDR_ANY", as some OSes do not allow connect(2)ing to those and would instead insist on receiving "INADDR_LOOPBACK" or "IN6ADDR_LOOPBACK" respectively.

This method is used by the "->connect( peer => $sock )" parameter of handle and loop connect methods.

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>