Use a faster and simpler #accept for TCPServer and UNIXServer

* The Addrinfo and extra native calls are not needed for those.
* This is also less prone to races related to a concurrent Socket#close
  as it is a single native call instead of multiple.

Author: eregon

lib/truffle/socket/tcp_server.rb

@@ -63,16 +63,12 @@ def listen(backlog)
   end
 
   def accept
-    socket, _ = Truffle::Socket.accept_and_addrinfo(self, TCPSocket, true)
-
-    socket
+    Truffle::Socket.accept(self, TCPSocket, true)
   end
 
   private def __accept_nonblock(exception)
     self.nonblock = true
-    socket, _ = Truffle::Socket.accept_and_addrinfo(self, TCPSocket, exception)
-
-    socket
+    Truffle::Socket.accept(self, TCPSocket, exception)
   end
 
   def sysaccept

lib/truffle/socket/truffle.rb

@@ -124,6 +124,21 @@ def self.accept_and_addrinfo(source, new_class, exception)
       end
     end
 
+    def self.accept(source, new_class, exception)
+      raise IOError, 'socket has been closed' if source.closed?
+
+      fd = Truffle::Socket::Foreign.accept(source.fileno, ::FFI::Pointer::NULL, ::FFI::Pointer::NULL)
+      if fd < 0
+        if !exception and Errno.errno == Truffle::POSIX::EAGAIN_ERRNO
+          return :wait_readable
+        else
+          Error.read_error('accept(2)', source)
+        end
+      end
+
+      new_class.for_fd(fd)
+    end
+
     def self.listen(source, backlog)
       backlog = Primitive.rb_to_int(backlog)
       err     = Foreign.listen(source.fileno, backlog)

lib/truffle/socket/unix_server.rb

@@ -51,16 +51,12 @@ def listen(backlog)
   end
 
   def accept
-    socket, _ = Truffle::Socket.accept_and_addrinfo(self, UNIXSocket, true)
-
-    socket
+    Truffle::Socket.accept(self, UNIXSocket, true)
   end
 
   private def __accept_nonblock(exception)
     self.nonblock = true
-    socket, _ = Truffle::Socket.accept_and_addrinfo(self, UNIXSocket, exception)
-
-    socket
+    Truffle::Socket.accept(self, UNIXSocket, exception)
   end
 
   def sysaccept