refactored res.sendfile()

lib/response.js

@@ -143,9 +143,13 @@ res.status = function(code){
 };
 
 /**
- * Transfer the file at the given `path`. Automatically sets 
- * the _Content-Type_ response header field. `next()` is called
- * when `path` is a directory, or when an error occurs.
+ * Transfer the file at the given `path`.
+ * 
+ * Automatically sets the _Content-Type_ response header field.
+ * The callback `fn(err)` is invoked when the transfer is complete
+ * or when an error occurs. Be sure to check `res.headerSent`
+ * if you wish to attempt responding, as the header and some data
+ * may have already been transferred.
  *
  * Options:
  *
@@ -159,17 +163,25 @@ res.status = function(code){
  */
 
 res.sendfile = function(path, options, fn){
-  var next = this.req.next;
-  options = options || {};
+  var self = this
+    , next = this.req.next
+    , options = options || {};
 
   // support function as second arg
   if ('function' == typeof options) {
     fn = options;
     options = {};
   }
 
+  // callback
+  options.callback = function(err){
+    // TODO: remove when node adds this
+    self.headerSent = !! self._header;
+    fn && fn(err);
+  };
+
+  // transfer
   options.path = encodeURIComponent(path);
-  options.callback = fn;
   send(this.req, this, next, options);
 };