don't partition if the key includes '/'.

lib/ykk.rb

@@ -59,7 +59,7 @@ def file_of(key)
   end
 
   def partition(key)
-    return [key] unless self.partition_size > 0
+    return [key] if /\// =~ key || self.partition_size <= 0
     key.scan(/.{1,#{partition_size}}/)
   end
 

spec/ykk_spec.rb

@@ -19,6 +19,8 @@
     it 'generates file path' do
       YKK.file_of('foo').should == @tmpdir + '/fo/o'
       YKK.file_of('fooooo').should == @tmpdir + '/fo/oo/oo'
+      YKK.file_of('/fooooo').should == @tmpdir + '/fooooo' # 先頭に / を付けると fooooo というキーを使いつつディレクトリを分割しないという裏技が可能に！
+      YKK.file_of('foo/bar').should == @tmpdir + '/foo/bar' # / を使うと任意の箇所でディレクトリ階層を分けることが可能に！
     end
   end
 
@@ -36,6 +38,13 @@
     File.exists?(YKK.file_of('a/b')).should be_true
   end
 
+  it 'should raise error when bump　filename and dirname' do
+    YKK['foo'] = 'foo'
+    lambda {
+      YKK['foo/bar'] = 'foo bar'
+    }.should raise_error(Errno::ENOTDIR)
+  end
+
   it 'should store data with "<<"' do
     key = YKK << {:a => 'b', :c => 'd'}
     YKK[key].should == {:a => 'b', :c => 'd'}