1 ------------------------------------------------------------------------------
3 -- GNAT COMPILER COMPONENTS --
5 -- 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 --
9 -- Copyright (C) 2001-2007, AdaCore --
11 -- GNAT is free software; you can redistribute it and/or modify it under --
12 -- terms of the GNU General Public License as published by the Free Soft- --
13 -- ware Foundation; either version 2, or (at your option) any later ver- --
14 -- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
15 -- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
16 -- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License --
17 -- for more details. You should have received a copy of the GNU General --
18 -- Public License distributed with GNAT; see file COPYING. If not, write --
19 -- to the Free Software Foundation, 51 Franklin Street, Fifth Floor, --
20 -- Boston, MA 02110-1301, USA. --
22 -- As a special exception, if other files instantiate generics from this --
23 -- unit, or you link this unit with other files to produce an executable, --
24 -- this unit does not by itself cause the resulting executable to be --
25 -- covered by the GNU General Public License. This exception does not --
26 -- however invalidate any other reasons why the executable file might be --
27 -- covered by the GNU Public License. --
29 -- GNAT was originally developed by the GNAT team at New York University. --
30 -- Extensive contributions were provided by Ada Core Technologies Inc. --
32 ------------------------------------------------------------------------------
34 -- Portable sockets-based implementation of GNAT.Sockets.Thin.Signalling_Fds
35 -- used for platforms that do not support UNIX pipes.
37 -- Note: this code used to be in GNAT.Sockets, but has been moved to a
38 -- platform-specific file. It is now used only for non-UNIX platforms.
40 separate (GNAT.Sockets.Thin)
41 package body Signalling_Fds is
47 procedure Close (Sig : C.int) is
49 pragma Unreferenced (Res);
50 -- Res is assigned but never read, because we purposefully ignore
51 -- any error returned by the C_Close system call, as per the spec
61 function Create (Fds : not null access Fd_Pair) return C.int is
62 L_Sock, R_Sock, W_Sock : C.int := Failure;
63 -- Listening socket, read socket and write socket
65 Sin : aliased Sockaddr_In;
67 -- Address of listening socket
70 -- Return status of system calls
73 Fds.all := (Read_End | Write_End => Failure);
75 -- We open two signalling sockets. One of them is used to send data
76 -- to the other, which is included in a C_Select socket set. The
77 -- communication is used to force the call to C_Select to complete,
78 -- and the waiting task to resume its execution.
81 -- Retry loop, in case the C_Connect below fails
83 -- Create a listening socket
85 L_Sock := C_Socket (Constants.AF_INET, Constants.SOCK_STREAM, 0);
87 if L_Sock = Failure then
91 -- Bind the socket to an available port on localhost
94 Set_Length (Sin'Unchecked_Access, Len);
95 Sin.Sin_Family := Constants.AF_INET;
96 Sin.Sin_Addr.S_B1 := 127;
97 Sin.Sin_Addr.S_B2 := 0;
98 Sin.Sin_Addr.S_B3 := 0;
99 Sin.Sin_Addr.S_B4 := 1;
102 Res := C_Bind (L_Sock, Sin'Address, Len);
104 if Res = Failure then
110 Res := C_Getsockname (L_Sock, Sin'Address, Len'Access);
111 if Res = Failure then
115 -- Set socket to listen mode, with a backlog of 1 to guarantee that
116 -- exactly one call to connect(2) succeeds.
118 Res := C_Listen (L_Sock, 1);
120 if Res = Failure then
124 -- Create read end (client) socket
126 R_Sock := C_Socket (Constants.AF_INET, Constants.SOCK_STREAM, 0);
128 if R_Sock = Failure then
132 -- Connect listening socket
134 Res := C_Connect (R_Sock, Sin'Address, Len);
136 exit when Res /= Failure;
138 if Socket_Errno /= Constants.EADDRINUSE then
142 -- In rare cases, the above C_Bind chooses a port that is still
143 -- marked "in use", even though it has been closed (perhaps by some
144 -- other process that has already exited). This causes the above
145 -- C_Connect to fail with EADDRINUSE. In this case, we close the
146 -- ports, and loop back to try again. This mysterious windows
147 -- behavior is documented. See, for example:
148 -- http://msdn2.microsoft.com/en-us/library/ms737625.aspx
149 -- In an experiment with 2000 calls, 21 required exactly one retry, 7
150 -- required two, and none required three or more. Note that no delay
151 -- is needed between retries; retrying C_Bind will typically produce
154 pragma Assert (Res = Failure
156 Socket_Errno = Constants.EADDRINUSE);
157 pragma Warnings (Off); -- useless assignment to "Res"
158 Res := C_Close (W_Sock);
159 pragma Warnings (On);
161 Res := C_Close (R_Sock);
165 -- Since the call to connect(2) has suceeded and the backlog limit on
166 -- the listening socket is 1, we know that there is now exactly one
167 -- pending connection on L_Sock, which is the one from R_Sock.
169 W_Sock := C_Accept (L_Sock, Sin'Address, Len'Access);
171 if W_Sock = Failure then
175 -- Set TCP_NODELAY on W_Sock, since we always want to send the data out
179 (Socket => Socket_Type (W_Sock),
180 Level => IP_Protocol_For_TCP_Level,
181 Option => (Name => No_Delay, Enabled => True));
183 -- Close listening socket (ignore exit status)
185 Res := C_Close (L_Sock);
187 Fds.all := (Read_End => R_Sock, Write_End => W_Sock);
193 Saved_Errno : constant Integer := Socket_Errno;
196 if W_Sock /= Failure then
197 Res := C_Close (W_Sock);
200 if R_Sock /= Failure then
201 Res := C_Close (R_Sock);
204 if L_Sock /= Failure then
205 Res := C_Close (L_Sock);
208 Set_Socket_Errno (Saved_Errno);
218 function Read (Rsig : C.int) return C.int is
219 Buf : aliased Character;
221 return C_Recv (Rsig, Buf'Address, 1, Constants.MSG_Forced_Flags);
228 function Write (Wsig : C.int) return C.int is
229 Buf : aliased Character := ASCII.NUL;
231 return C_Send (Wsig, Buf'Address, 1, Constants.MSG_Forced_Flags);