socket closing --> OS.SysErr

There is a semantic ambiguity that the Standard ML Basis
Definition that needs clearing up--According to the documentation at
http://www.standardml.org/Basis/socket.html, recvVec and recvVec' are
defined as follows:

> recvVec (sock, n)
> recvVec'(sock, n, {peek,oob})
>    These functions receive up to n bytes from the active stream socket
>    sock. The size of the resulting vector is the number of bytes that 
>    were successfully received, which may be less than n. If the 
>    connection has been closed at the other end (or if n is 0), then 
>    the empty vector will be returned.
>
>    In the second version, if peek is true, the data is received but 
>    not discarded from the connection. If oob is true, the data is 
>    received out-of-band, that is, before any other incoming data that 
>    may have been buffered.
>
>    These functions raise SysErr if the socket sock has been closed and 
>    they raise Size if n < 0 or n > Word8Vector.maxLen.

Now, when a socket closes, does recvVec return 0 bytes, or raise SysErr?

The current implementation returns 0 bytes.  If this is the intent, please
change the documentation.  If however, OS.SysErr should be raised, please 
apply the patch below.  Also, John, you can then change this section of 
eXene ;-) 

smlnj/src/eXene/lib/protocol/xio.sml:
>                  | read (n, vl) = let
>                      val v = Socket.recvVec(sock, n)
>                      in
>                        case (W8V.length v)
>(**** NOTE: we need a more graceful way to signal that the socket has closed!! ***)
>                         of 0 => raise Fail "Socket closed"
>                          | len => read (n - len, v::vl)
>                        (* end case *)


-David


--- smlnj/src/system/Basis/Implementation/Sockets/socket.sml.old	2004-11-06 15:33:32.182113600 -0500
+++ smlnj/src/system/Basis/Implementation/Sockets/socket.sml	2004-11-06 17:39:50.005109400 -0500
@@ -357,7 +357,10 @@
       fun recvV _ (_, 0, _, _) = W8V.fromList[]
 	| recvV getfd (sock, nbytes, peek, oob) =
 	    if nbytes < 0 then raise Size
-	    else recvV' (getfd sock, nbytes, peek, oob)
+	    else let val data = recvV' (getfd sock, nbytes, peek, oob)
+		 in if W8V.length(data) = 0 then raise OS.SysErr("Socket Closed", NONE)
+		    else data
+		 end
       val recvA : (int * w8array * int * int * bool * bool) -> int
 	    = sockFn "recvBuf"
     in


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