------------------------------------------------------------------------------ -- -- -- GNAT COMPILER COMPONENTS -- -- -- -- G N A T . S O C K E T S . T H I N . S I G N A L L I N G _ F D S -- -- -- -- B o d y -- -- -- -- Copyright (C) 2001-2008, AdaCore -- -- -- -- GNAT is free software; you can redistribute it and/or modify it under -- -- terms of the GNU General Public License as published by the Free Soft- -- -- ware Foundation; either version 2, or (at your option) any later ver- -- -- sion. GNAT is distributed in the hope that it will be useful, but WITH- -- -- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY -- -- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License -- -- for more details. You should have received a copy of the GNU General -- -- Public License distributed with GNAT; see file COPYING. If not, write -- -- to the Free Software Foundation, 51 Franklin Street, Fifth Floor, -- -- Boston, MA 02110-1301, USA. -- -- -- -- As a special exception, if other files instantiate generics from this -- -- unit, or you link this unit with other files to produce an executable, -- -- this unit does not by itself cause the resulting executable to be -- -- covered by the GNU General Public License. This exception does not -- -- however invalidate any other reasons why the executable file might be -- -- covered by the GNU Public License. -- -- -- -- GNAT was originally developed by the GNAT team at New York University. -- -- Extensive contributions were provided by Ada Core Technologies Inc. -- -- -- ------------------------------------------------------------------------------ -- Portable sockets-based implementation of GNAT.Sockets.Thin.Signalling_Fds -- used for platforms that do not support UNIX pipes. -- Note: this code used to be in GNAT.Sockets, but has been moved to a -- platform-specific file. It is now used only for non-UNIX platforms. separate (GNAT.Sockets.Thin) package body Signalling_Fds is ----------- -- Close -- ----------- procedure Close (Sig : C.int) is Res : C.int; pragma Unreferenced (Res); -- Res is assigned but never read, because we purposefully ignore -- any error returned by the C_Close system call, as per the spec -- of this procedure. begin Res := C_Close (Sig); end Close; ------------ -- Create -- ------------ function Create (Fds : not null access Fd_Pair) return C.int is L_Sock, R_Sock, W_Sock : C.int := Failure; -- Listening socket, read socket and write socket Sin : aliased Sockaddr_In; Len : aliased C.int; -- Address of listening socket Res : C.int; pragma Warnings (Off, Res); -- Return status of system calls (usually ignored, hence warnings off) begin Fds.all := (Read_End | Write_End => Failure); -- We open two signalling sockets. One of them is used to send data -- to the other, which is included in a C_Select socket set. The -- communication is used to force the call to C_Select to complete, -- and the waiting task to resume its execution. loop -- Retry loop, in case the C_Connect below fails -- Create a listening socket L_Sock := C_Socket (SOSC.AF_INET, SOSC.SOCK_STREAM, 0); if L_Sock = Failure then goto Fail; end if; -- Bind the socket to an available port on localhost Set_Family (Sin.Sin_Family, Family_Inet); Sin.Sin_Addr.S_B1 := 127; Sin.Sin_Addr.S_B2 := 0; Sin.Sin_Addr.S_B3 := 0; Sin.Sin_Addr.S_B4 := 1; Sin.Sin_Port := 0; Len := C.int (Lengths (Family_Inet)); Res := C_Bind (L_Sock, Sin'Address, Len); if Res = Failure then goto Fail; end if; -- Get assigned port Res := C_Getsockname (L_Sock, Sin'Address, Len'Access); if Res = Failure then goto Fail; end if; -- Set socket to listen mode, with a backlog of 1 to guarantee that -- exactly one call to connect(2) succeeds. Res := C_Listen (L_Sock, 1); if Res = Failure then goto Fail; end if; -- Create read end (client) socket R_Sock := C_Socket (SOSC.AF_INET, SOSC.SOCK_STREAM, 0); if R_Sock = Failure then goto Fail; end if; -- Connect listening socket Res := C_Connect (R_Sock, Sin'Address, Len); exit when Res /= Failure; if Socket_Errno /= SOSC.EADDRINUSE then goto Fail; end if; -- In rare cases, the above C_Bind chooses a port that is still -- marked "in use", even though it has been closed (perhaps by some -- other process that has already exited). This causes the above -- C_Connect to fail with EADDRINUSE. In this case, we close the -- ports, and loop back to try again. This mysterious Windows -- behavior is documented. See, for example: -- http://msdn2.microsoft.com/en-us/library/ms737625.aspx -- In an experiment with 2000 calls, 21 required exactly one retry, 7 -- required two, and none required three or more. Note that no delay -- is needed between retries; retrying C_Bind will typically produce -- a different port. pragma Assert (Res = Failure and then Socket_Errno = SOSC.EADDRINUSE); Res := C_Close (W_Sock); W_Sock := Failure; Res := C_Close (R_Sock); R_Sock := Failure; end loop; -- Since the call to connect(2) has succeeded and the backlog limit on -- the listening socket is 1, we know that there is now exactly one -- pending connection on L_Sock, which is the one from R_Sock. W_Sock := C_Accept (L_Sock, Sin'Address, Len'Access); if W_Sock = Failure then goto Fail; end if; -- Set TCP_NODELAY on W_Sock, since we always want to send the data out -- immediately. Set_Socket_Option (Socket => Socket_Type (W_Sock), Level => IP_Protocol_For_TCP_Level, Option => (Name => No_Delay, Enabled => True)); -- Close listening socket (ignore exit status) Res := C_Close (L_Sock); Fds.all := (Read_End => R_Sock, Write_End => W_Sock); return Thin_Common.Success; <> declare Saved_Errno : constant Integer := Socket_Errno; begin if W_Sock /= Failure then Res := C_Close (W_Sock); end if; if R_Sock /= Failure then Res := C_Close (R_Sock); end if; if L_Sock /= Failure then Res := C_Close (L_Sock); end if; Set_Socket_Errno (Saved_Errno); end; return Failure; end Create; ---------- -- Read -- ---------- function Read (Rsig : C.int) return C.int is Buf : aliased Character; begin return C_Recv (Rsig, Buf'Address, 1, SOSC.MSG_Forced_Flags); end Read; ----------- -- Write -- ----------- function Write (Wsig : C.int) return C.int is Buf : aliased Character := ASCII.NUL; begin return C_Sendto (Wsig, Buf'Address, 1, Flags => SOSC.MSG_Forced_Flags, To => null, Tolen => 0); end Write; end Signalling_Fds;