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------------------------------------------------------------------------------
-- --
-- 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) 2001-2018, 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 3, 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. --
-- --
-- As a special exception under Section 7 of GPL version 3, you are granted --
-- additional permissions described in the GCC Runtime Library Exception, --
-- version 3.1, as published by the Free Software Foundation. --
-- --
-- You should have received a copy of the GNU General Public License and --
-- a copy of the GCC Runtime Library Exception along with this program; --
-- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see --
-- <http://www.gnu.org/licenses/>. --
-- --
-- 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;
<<Fail>>
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 => System.Null_Address,
Tolen => 0);
end Write;
end Signalling_Fds;
|
