stricter test for end of string

cores/esp8266/FS.cpp

@@ -123,13 +123,12 @@ const char* File::name() const {
 
 String File::readString()
 {
-    size_t sz = size() - position() - 1;
+    size_t sz = size() - position() + 1;
     String str;
-    if (sz<1)
+    if (sz < 1)
         return str;
     str.reserve(sz);
-    size_t pos=0;
-    while (pos++ < sz)
+    while (available())
     {
         str += (char)read();
     }