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@@ -14,21 +14,14 @@ class IntervalSkipList
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   def expire(range, length_change)
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     expired_markers, first_node_after_range = overlapping(range)
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-    expired_markers.each do |marker|
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-      delete(marker)
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-    end
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-
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-    cur_node = first_node_after_range
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-    while cur_node do
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-      cur_node.key += length_change if cur_node.key >= range.last
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-      cur_node = cur_node.forward[0]
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-    end
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+    expired_markers.each { |marker| delete(marker) }
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+    first_node_after_range.propagate_length_change(length_change)    
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   end
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   def overlapping(range)
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     markers, first_node = containing_with_node(range.first)
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-    cur_node = first_node
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+    cur_node = first_node
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     begin
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       markers.concat(cur_node.forward_markers.flatten)
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       cur_node = cur_node.forward[0]

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@@ -23,6 +23,14 @@ class IntervalSkipList
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       demote_markers(path)
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     end
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+    def propagate_length_change(length_change)
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+      cur_node = self
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+      while cur_node do
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+        cur_node.key += length_change
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+        cur_node = cur_node.forward[0]
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+      end
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+    end
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+
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     protected
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     def update_forward_pointers(path)