=head1 NAME

AnyEvent::Util - various utility functions.

=head1 SYNOPSIS

   use AnyEvent::Util;

=head1 DESCRIPTION

This module implements various utility functions, mostly replacing
well-known functions by event-ised counterparts.

All functions documented without C<AnyEvent::Util::> prefix are exported
by default.

=over 4

=cut

package AnyEvent::Util;

no warnings;
use strict;

use Carp ();
use Errno ();
use Socket ();

use AnyEvent ();

use base 'Exporter';

our @EXPORT = qw(fh_nonblocking guard fork_call portable_pipe);
our @EXPORT_OK = qw(AF_INET6 WSAEWOULDBLOCK WSAEINPROGRESS WSAEINVAL WSAWOULDBLOCK);

our $VERSION = 4.151;

BEGIN {
   my $posix = 1 * eval { local $SIG{__DIE__}; require POSIX };
   eval "sub POSIX() { $posix }";
}

BEGIN {
   # TODO remove this once not used anymore
   *socket_inet_aton = \&Socket::inet_aton; # take a copy, in case Coro::LWP overrides it
}

BEGIN {
   my $af_inet6 = eval { local $SIG{__DIE__}; &Socket::AF_INET6 };

   # uhoh
   $af_inet6 ||= 10 if $^O =~ /linux/;
   $af_inet6 ||= 23 if $^O =~ /cygwin/i;
   $af_inet6 ||= 23 if AnyEvent::WIN32;
   $af_inet6 ||= 24 if $^O =~ /openbsd|netbsd/;
   $af_inet6 ||= 28 if $^O =~ /freebsd/;

   $af_inet6 && socket my $ipv6_socket, $af_inet6, &Socket::SOCK_STREAM, 0 # check if they can be created
      or $af_inet6 = 0;

   eval "sub AF_INET6() { $af_inet6 }"; die if $@;

   delete $AnyEvent::PROTOCOL{ipv6} unless $af_inet6;
}

BEGIN {
   # broken windows perls use undocumented error codes...
   if (AnyEvent::WIN32) {
      eval "sub WSAEINVAL()      { 10022 }";
      eval "sub WSAEWOULDBLOCK() { 10035 }";
      eval "sub WSAWOULDBLOCK() { 10035 }"; # TODO remove here ands from @export_ok
      eval "sub WSAEINPROGRESS() { 10036 }";
   } else {
      # these should never match any errno value
      eval "sub WSAEINVAL()      { -1e99 }";
      eval "sub WSAEWOULDBLOCK() { -1e99 }";
      eval "sub WSAWOULDBLOCK() { -1e99 }"; # TODO
      eval "sub WSAEINPROGRESS() { -1e99 }";
   }
}

=item ($r, $w) = portable_pipe

Calling C<pipe> in Perl is portable - except it doesn't really work on
sucky windows platforms (at least not with most perls - cygwin's perl
notably works fine).

On that platform, you actually get two file handles you cannot use select
on.

This function gives you a pipe that actually works even on the broken
Windows platform (by creating a pair of TCP sockets, so do not expect any
speed from that).

Returns the empty list on any errors.

=cut

sub portable_pipe() {