handle_{got,sent}data: separate length and error params.

Now we pass an error code in a separate dedicated parameter, instead
of overloading the length parameter so that a negative value means an
error code. This enables length to become unsigned without causing
trouble.

windows/winhandl.c

@@ -664,9 +664,9 @@ void handle_got_event(HANDLE event)
 	     * EOF, or (nearly equivalently) read error.
 	     */
 	    h->u.i.defunct = true;
-	    h->u.i.gotdata(h, NULL, -h->u.i.readerr);
+	    h->u.i.gotdata(h, NULL, 0, h->u.i.readerr);
 	} else {
-	    backlog = h->u.i.gotdata(h, h->u.i.buffer, h->u.i.len);
+	    backlog = h->u.i.gotdata(h, h->u.i.buffer, h->u.i.len, 0);
 	    handle_throttle(&h->u.i, backlog);
 	}
         break;
@@ -686,11 +686,11 @@ void handle_got_event(HANDLE event)
 	     * thread is terminating by now).
 	     */
 	    h->u.o.defunct = true;
-	    h->u.o.sentdata(h, -h->u.o.writeerr);
+	    h->u.o.sentdata(h, 0, h->u.o.writeerr);
 	} else {
 	    bufchain_consume(&h->u.o.queued_data, h->u.o.lenwritten);
             noise_ultralight(NOISE_SOURCE_IOLEN, h->u.o.lenwritten);
-	    h->u.o.sentdata(h, bufchain_size(&h->u.o.queued_data));
+	    h->u.o.sentdata(h, bufchain_size(&h->u.o.queued_data), 0);
 	    handle_try_output(&h->u.o);
 	}
         break;

windows/winhsock.c

@@ -45,11 +45,11 @@ typedef struct HandleSocket {
     Socket sock;
 } HandleSocket;
 
-static int handle_gotdata(struct handle *h, const void *data, int len)
+static int handle_gotdata(struct handle *h, const void *data, int len, int err)
 {
     HandleSocket *hs = (HandleSocket *)handle_get_privdata(h);
 
-    if (len < 0) {
+    if (err) {
 	plug_closing(hs->plug, "Read error from handle", 0, 0);
 	return 0;
     } else if (len == 0) {
@@ -79,25 +79,22 @@ static int handle_gotdata(struct handle *h, const void *data, int len)
     }
 }
 
-static int handle_stderr(struct handle *h, const void *data, int len)
+static int handle_stderr(struct handle *h, const void *data, int len, int err)
 {
     HandleSocket *hs = (HandleSocket *)handle_get_privdata(h);
 
-    if (len > 0)
+    if (!err && len > 0)
         log_proxy_stderr(hs->plug, &hs->stderrdata, data, len);
 
     return 0;
 }
 
-static void handle_sentdata(struct handle *h, int new_backlog)
+static void handle_sentdata(struct handle *h, int new_backlog, int err)
 {
     HandleSocket *hs = (HandleSocket *)handle_get_privdata(h);
 
-    if (new_backlog < 0) {
-        /* Special case: this is actually reporting an error writing
-         * to the underlying handle, and our input value is the error
-         * code itself, negated. */
-        plug_closing(hs->plug, win_strerror(-new_backlog), -new_backlog, 0);
+    if (err) {
+        plug_closing(hs->plug, win_strerror(err), err, 0);
         return;
     }
 

windows/winplink.c

@@ -205,14 +205,11 @@ char *do_select(SOCKET skt, bool startup)
     return NULL;
 }
 
-int stdin_gotdata(struct handle *h, const void *data, int len)
+int stdin_gotdata(struct handle *h, const void *data, int len, int err)
 {
-    if (len < 0) {
-	/*
-	 * Special case: report read error.
-	 */
+    if (err) {
 	char buf[4096];
-	FormatMessage(FORMAT_MESSAGE_FROM_SYSTEM, NULL, -len, 0,
+	FormatMessage(FORMAT_MESSAGE_FROM_SYSTEM, NULL, err, 0,
 		      buf, lenof(buf), NULL);
 	buf[lenof(buf)-1] = '\0';
 	if (buf[strlen(buf)-1] == '\n')
@@ -232,14 +229,11 @@ int stdin_gotdata(struct handle *h, const void *data, int len)
 	return 0;
 }
 
-void stdouterr_sent(struct handle *h, int new_backlog)
+void stdouterr_sent(struct handle *h, int new_backlog, int err)
 {
-    if (new_backlog < 0) {
-	/*
-	 * Special case: report write error.
-	 */
+    if (err) {
 	char buf[4096];
-	FormatMessage(FORMAT_MESSAGE_FROM_SYSTEM, NULL, -new_backlog, 0,
+	FormatMessage(FORMAT_MESSAGE_FROM_SYSTEM, NULL, err, 0,
 		      buf, lenof(buf), NULL);
 	buf[lenof(buf)-1] = '\0';
 	if (buf[strlen(buf)-1] == '\n')
@@ -248,6 +242,7 @@ void stdouterr_sent(struct handle *h, int new_backlog)
 		(h == stdout_handle ? "output" : "error"), buf);
 	cleanup_exit(0);
     }
+
     if (backend_connected(backend)) {
         backend_unthrottle(backend, (handle_backlog(stdout_handle) +
                                      handle_backlog(stderr_handle)));

windows/winser.c

@@ -40,10 +40,11 @@ static void serial_terminate(Serial *serial)
     }
 }
 
-static int serial_gotdata(struct handle *h, const void *data, int len)
+static int serial_gotdata(
+    struct handle *h, const void *data, int len, int err)
 {
     Serial *serial = (Serial *)handle_get_privdata(h);
-    if (len <= 0) {
+    if (err || len == 0) {
 	const char *error_msg;
 
 	/*
@@ -53,7 +54,7 @@ static int serial_gotdata(struct handle *h, const void *data, int len)
 	 * pipes or some other non-serial device, in which case EOF
 	 * may become meaningful here.
 	 */
-	if (len == 0)
+        if (!err)
 	    error_msg = "End of file reading from serial device";
 	else
 	    error_msg = "Error reading from serial device";
@@ -66,16 +67,16 @@ static int serial_gotdata(struct handle *h, const void *data, int len)
 
 	seat_connection_fatal(serial->seat, "%s", error_msg);
 
-	return 0;		       /* placate optimiser */
+	return 0;
     } else {
 	return seat_stdout(serial->seat, data, len);
     }
 }
 
-static void serial_sentdata(struct handle *h, int new_backlog)
+static void serial_sentdata(struct handle *h, int new_backlog, int err)
 {
     Serial *serial = (Serial *)handle_get_privdata(h);
-    if (new_backlog < 0) {
+    if (err) {
 	const char *error_msg = "Error writing to serial device";
 
 	serial_terminate(serial);

windows/winstuff.h

@@ -603,8 +603,10 @@ void init_ucs(Conf *, struct unicode_data *);
 #define HANDLE_FLAG_IGNOREEOF 2
 #define HANDLE_FLAG_UNITBUFFER 4
 struct handle;
-typedef int (*handle_inputfn_t)(struct handle *h, const void *data, int len);
-typedef void (*handle_outputfn_t)(struct handle *h, int new_backlog);
+typedef int (*handle_inputfn_t)(
+    struct handle *h, const void *data, int len, int err);
+typedef void (*handle_outputfn_t)(
+    struct handle *h, int new_backlog, int err);
 struct handle *handle_input_new(HANDLE handle, handle_inputfn_t gotdata,
 				void *privdata, int flags);
 struct handle *handle_output_new(HANDLE handle, handle_outputfn_t sentdata,