diff --git a/cmake/FileIterator.cmake b/cmake/FileIterator.cmake
index c20011f5..98b56c56 100644
--- a/cmake/FileIterator.cmake
+++ b/cmake/FileIterator.cmake
@@ -1,10 +1,31 @@
 # Interface for iterating over a text file by line.
+#
+# Example usage:
+#
+# fi_open_file(${some_file})
+#
+# while(NOT fi_done)
+#     fi_get_next_line()
+#
+#     message(STATUS "read line: ${fi_line}")
+# endwhile()
+
+macro(fi_check_done)
+    string(LENGTH "${fi_file_contents}" len)
+
+    set(fi_done FALSE PARENT_SCOPE)
+
+    if(len EQUAL 0)
+        set(fi_done TRUE PARENT_SCOPE)
+    endif()
+endmacro()
 
 function(fi_open_file file)
     file(READ "${file}" fi_file_contents)
 
     set(fi_file_contents "${fi_file_contents}" PARENT_SCOPE)
-    set(fi_done          FALSE                 PARENT_SCOPE)
+
+    fi_check_done()
 endfunction()
 
 function(fi_get_next_line)
@@ -16,13 +37,7 @@ function(fi_get_next_line)
 
     string(SUBSTRING "${fi_file_contents}" ${pos} -1 fi_file_contents)
 
-    string(LENGTH "${fi_file_contents}" len)
-
-    set(fi_done FALSE PARENT_SCOPE)
-
-    if(len EQUAL 0)
-        set(fi_done TRUE PARENT_SCOPE)
-    endif()
+    fi_check_done()
 
     set(fi_line          "${fi_line}"          PARENT_SCOPE)
     set(fi_file_contents "${fi_file_contents}" PARENT_SCOPE)