SimpleSkiplist: added specs for :reverse and some bugfixes

lib/strokedb/data_structures/simple_skiplist.rb

@@ -45,7 +45,6 @@ def empty?
     end
 
     # Complicated search algorithm
-    # TODO: add reverse support
     # 
     def search(start_key, end_key, limit, offset, reverse, with_keys)
       offset ||= 0
@@ -59,22 +58,28 @@ def search(start_key, end_key, limit, offset, reverse, with_keys)
       collect_values(start_node, end_key, limit, reverse, with_keys)
     end
 
-    # 
+    # TODO: add C routins for this to optimize performance
     #
     def find_by_prefix(start_key, reverse)
-      # TODO: add reverse support
       dir = dir_for_reverse(reverse)
-      x = anchor(reverse) # head [FIXME: change method name]
+      x = anchor(reverse)
       # if no prefix given, just return a first node
       !start_key and return node_next(x, 0, dir)
 
       level = node_level(x)
       while level > 0
         level -= 1
         xnext = node_next(x, level, dir)
-        while node_compare(xnext, start_key) < 0
-          x = xnext
-          xnext = node_next(x, level, dir)
+        if reverse
+          while node_compare(xnext, start_key) > 0
+            x = xnext
+            xnext = node_next(x, level, dir)
+          end
+        else
+          while node_compare(xnext, start_key) < 0
+            x = xnext
+            xnext = node_next(x, level, dir)
+          end
         end
       end
       xnext == anchor(!reverse) and return nil
@@ -86,7 +91,7 @@ def find_by_prefix(start_key, reverse)
     # 
     def skip_nodes(node, offset, reverse)
       dir = dir_for_reverse(reverse)
-      tail = @tail
+      tail = anchor(!reverse)
       while offset > 0 && node != tail
         node = node_next(node, 0, dir)
         offset -= 1
@@ -105,7 +110,11 @@ def collect_values(x, end_prefix, limit, reverse, with_keys)
       end_prefix ||= ""
       pfx_size = end_prefix.size
       while x != tail
-        node_key(x)[0, pfx_size] > end_prefix and return values
+        if reverse
+          node_key(x)[0, pfx_size] < end_prefix and return values
+        else
+          node_key(x)[0, pfx_size] > end_prefix and return values
+        end
         values.size >= limit and return values
         values << meth.call(x).freeze
         x = node_next(x, 0, dir)
@@ -400,11 +409,6 @@ def new_node(level, key, value)
       ]
     end
 
-    # TODO: drop this after serialization routines updated
-    def new_anchor
-      new_node(@maxlevel, nil, nil)
-    end
-
     def new_anchors(level)
       h = new_node(level, nil, nil)
       t = new_node(level, nil, nil)

spec/lib/strokedb/data_structures/simple_skiplist_spec.rb

@@ -260,6 +260,11 @@
       r = search_with_options(@list, :reverse => true, :with_keys => true)
       r.should == @key_values.reverse
     end
+
+    it "should find a value in a reversed order" do
+      r = search_with_options(@list, :start_key => "ab", :end_key => "aa", :reverse => true)
+      r.should == %w[ab\ value aa\ value]
+    end
 
     def search_should_yield(results, os = {})
       # TODO: added reverse cases

spec/lib/strokedb/views/view_spec.rb

@@ -69,6 +69,12 @@ def view.map(uuid, doc)
     @view.find(:key => @article2).should == [@comment21, @comment22]
     @view.find(:key => @article3).should == [ ]
   end
+
+  it "should find all the article's comments in a reverse order" do
+    @view.find(:key => @article1, :reverse => true).should == [@comment13, @comment12, @comment11]
+    @view.find(:key => @article2, :reverse => true).should == [@comment22, @comment21]
+    @view.find(:key => @article3, :reverse => true).should == [ ]
+  end
 
   it "should find all the article's comments with limit" do
     @view.find(:key => @article1, :limit => 2).should == [@comment11, @comment12]