sanei_usb: Add function sanei_usb_get_endpoint, add range check in sanei_usb_set_endpoint

Since we now have the possibility to change the endpoint used for a particular USB communication type,
we also need a way to retrieve the current endpoint, so that one can e.g. reset the endpoint to the
old value after a single usb operation on a different endpoint.

include/sane/sanei_usb.h

@@ -267,6 +267,19 @@ extern SANE_Status sanei_usb_open (SANE_String_Const devname, SANE_Int * dn);
  */
 extern void sanei_usb_set_endpoint (SANE_Int dn, SANE_Int ep_type, SANE_Int ep);
 
+/** Retrieve the endpoint used for the USB communication
+ *
+ * Returns the endpoint used for the USB communication of the given type.
+ * This function can only be called after sanei_usb_open.
+ *
+ * @param dn device number
+ * @param ep_type type of endpoint to retrieve (bitwise or of USB_DIR_IN/OUT
+ *                and USB_ENDPOINT_TYPE_BULK/CONTROL/INTERRUPT/ISOCHRONOUS
+ * @return endpoint used for the given type
+ *
+ */
+extern SANE_Int sanei_usb_get_endpoint (SANE_Int dn, SANE_Int ep_type);
+
 /** Close a USB device.
  * 
  * @param dn device number

sanei/sanei_usb.c

@@ -1108,6 +1108,12 @@ sanei_usb_find_devices (SANE_Int vendor, SANE_Int product,
 void
 sanei_usb_set_endpoint (SANE_Int dn, SANE_Int ep_type, SANE_Int ep)
 {
+  if (dn >= device_number || dn < 0)
+    {
+      DBG (1, "sanei_usb_set_endpoint: dn >= device number || dn < 0\n");
+      return;
+    }
+
   DBG (5, "sanei_usb_set_endpoint: Setting endpoint of type 0x%02x to 0x%02x\n", ep_type, ep);
   switch (ep_type)
     {
@@ -1138,6 +1144,38 @@ sanei_usb_set_endpoint (SANE_Int dn, SANE_Int ep_type, SANE_Int ep)
     }
 }
 
+SANE_Int
+sanei_usb_get_endpoint (SANE_Int dn, SANE_Int ep_type)
+{
+  if (dn >= device_number || dn < 0)
+    {
+      DBG (1, "sanei_usb_get_endpoint: dn >= device number || dn < 0\n");
+      return 0;
+    }
+
+  switch (ep_type)
+    {
+      case USB_DIR_IN|USB_ENDPOINT_TYPE_BULK:
+	    return devices[dn].bulk_in_ep;
+      case USB_DIR_OUT|USB_ENDPOINT_TYPE_BULK:
+	    return devices[dn].bulk_out_ep;
+      case USB_DIR_IN|USB_ENDPOINT_TYPE_ISOCHRONOUS:
+	    return devices[dn].iso_in_ep;
+      case USB_DIR_OUT|USB_ENDPOINT_TYPE_ISOCHRONOUS:
+	    return devices[dn].iso_out_ep;
+      case USB_DIR_IN|USB_ENDPOINT_TYPE_INTERRUPT:
+	    return devices[dn].int_in_ep;
+      case USB_DIR_OUT|USB_ENDPOINT_TYPE_INTERRUPT:
+	    return devices[dn].int_out_ep;
+      case USB_DIR_IN|USB_ENDPOINT_TYPE_CONTROL:
+	    return devices[dn].control_in_ep;
+      case USB_DIR_OUT|USB_ENDPOINT_TYPE_CONTROL:
+	    return devices[dn].control_out_ep;
+      default:
+	    return 0;
+    }
+}
+
 SANE_Status
 sanei_usb_open (SANE_String_Const devname, SANE_Int * dn)
 {