replace += with << in mbox reading

there's a tremendous speed difference between these two operators,
though neither of these points are bottlenecks.

diff --git a/lib/sup/mbox/loader.rb b/lib/sup/mbox/loader.rb
index 7fe912900e16d477fc7d690873d92e9c623f48c2..fbf31ae4fe96cfff269e9d0d373b58ffa6a06d90 100644 (file)
--- a/lib/sup/mbox/loader.rb
+++ b/lib/sup/mbox/loader.rb
@@ -86,7 +86,7 @@ class Loader < Source
     @mutex.synchronize do
       @f.seek offset
       until @f.eof? || (l = @f.gets) =~ /^\r*$/
-        ret += l
+        ret << l
       end
     end
     ret
@@ -94,7 +94,7 @@ 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