throw if range header is already set

lib/uristream.js

@@ -65,6 +65,8 @@ function setupHttp(uri, options, dst) {
 
   var fetch = probe ? request.head : request.get;
   var headers = extend(defaults, options.headers);
+  if ('range' in headers)
+    throw new Error('range header is not allowed');
 
   // attach empty 'error' listener to keep dst from ever throwing
   dst.on('error', noop);
@@ -72,8 +74,6 @@ function setupHttp(uri, options, dst) {
   function fetchHttp(start) {
     if (start > 0)
       headers['range'] = 'bytes=' + start + '-';
-    else
-      delete headers['range'];
 
     var accum = 0, size = -1;
     var req = fetch({uri:uri, headers:headers, timeout:timeout});