make raw_message faster with string += => <<

this method ain't used that much, but << is significantly
faster than += for Strings.

diff --git a/lib/sup/mbox/loader.rb b/lib/sup/mbox/loader.rb
index 086510ddf83b7841bbf331994a8d0b8770cd4de7..37d253ebf3cfb66902cd5a4b580cbb41aba1da9c 100644 (file)
--- a/lib/sup/mbox/loader.rb
+++ b/lib/sup/mbox/loader.rb
@@ -93,7 +93,7 @@ class Loader < Source
 
   def raw_message offset
     ret = ""
-    each_raw_message_line(offset) { |l| ret += l }
+    each_raw_message_line(offset) { |l| ret << l }
     ret
   end