Storage responds to length

Now the storage will return the current length.
And not the set length anymore. But if there are datasets in the storge it
will be as long as the setted length.
It also can return the length of its datasets.

lib/rubella/storage.rb

@@ -8,7 +8,7 @@ module Rubella
   #
   class Storage
     attr_reader :data
-    attr_reader :length
+    # :length
 
     def initialize data, length = 0
       @data       = data
@@ -31,14 +31,14 @@ module Rubella
       @length = length
 
       # Use length only, if length is valid
-      if @length != 0 and @data.length != 0
+      if @length != 0 and self.length != 0
         # Drop entries, if more than new length
-        while @data.length > @length
+        while self.length > @length
           @data.pop
         end
         # Prefill with empty content, if less than new length
-        dummy_data = Array.new(@data[0].length, 0)
-        while @data.length < @length
+        dummy_data = Array.new(self.dataset_length, 0)
+        while self.length < @length
           @data.unshift dummy_data
         end
       end
@@ -46,6 +46,26 @@ module Rubella
       @length
     end
 
+    # Returns the current length of the storage.
+    # (How many datasets it holds.)
+    #
+    # @return Integer length
+    #
+    def length
+      @data.length
+    end
+
+    # Returns the length of a dataset.
+    # Will return 0, if no datasets in storage.
+    #
+    # @return Integer length of one dataset
+    #
+    def dataset_length
+      return 0 if self.length == 0
+
+      @data[0].length
+    end
+
     # Adds the data from the given storage to the own data and return this as a
     # new Storage. Does not modify one of the storages. 
     #