Improve Node#each_recursive performance

benchmark/each_recursive.yaml

@@ -0,0 +1,40 @@
+loop_count: 100
+contexts:
+  - gems:
+      rexml: 3.2.6
+    require: false
+    prelude: require 'rexml'
+  - name: master
+    prelude: |
+      $LOAD_PATH.unshift(File.expand_path("lib"))
+      require 'rexml'
+  - name: 3.2.6(YJIT)
+    gems:
+      rexml: 3.2.6
+    require: false
+    prelude: |
+      require 'rexml'
+      RubyVM::YJIT.enable
+  - name: master(YJIT)
+    prelude: |
+      $LOAD_PATH.unshift(File.expand_path("lib"))
+      require 'rexml'
+      RubyVM::YJIT.enable
+
+prelude: |
+  require 'rexml/document'
+
+  xml_source = +"<root>"
+  100.times do
+    x_node_source = ""
+    100.times do
+      x_node_source = "<x>#{x_node_source}</x>"
+    end
+    xml_source << x_node_source
+  end
+  xml_source << "</root>"
+
+  document = REXML::Document.new(xml_source)
+
+benchmark:
+  each_recursive: document.each_recursive { |_| }

lib/rexml/node.rb

@@ -52,10 +52,14 @@ def parent?
 
     # Visit all subnodes of +self+ recursively
     def each_recursive(&block) # :yields: node
-      self.elements.each {|node|
-        block.call(node)
-        node.each_recursive(&block)
-      }
+      stack = []
+      each { |child| stack.unshift child if child.node_type == :element }
+      until stack.empty?
+        child = stack.pop
+        yield child
+        n = stack.size
+        child.each { |grandchild| stack.insert n, grandchild if grandchild.node_type == :element }
+      end
     end
 
     # Find (and return) first subnode (recursively) for which the block

test/test_document.rb

@@ -417,6 +417,42 @@ def test_utf_16
           assert_equal(expected_xml, actual_xml)
         end
       end
+
+      class EachRecursiveTest < Test::Unit::TestCase
+        def test_each_recursive
+          xml_source = +'<?xml version="1.0" encoding="UTF-8" standalone="yes"?>'
+          xml_source << '<root name="root">'
+
+          expected_names = ["root"]
+
+          2.times do |x|
+            x_node_source = ''
+            inner_names = []
+            3.times do |y|
+              name = "#{x}_#{y}"
+              x_node_source = "<x name='#{name}'>#{x_node_source}</x>"
+              inner_names << name
+            end
+            expected_names.concat(inner_names.reverse)
+            xml_source << x_node_source
+          end
+
+          xml_source << '<!-- comment -->'
+          xml_source << '<![CDATA[ cdata ]]>'
+
+          xml_source << '</root>'
+
+          document = REXML::Document.new(xml_source)        
+
+          # Node#each_recursive iterates elements only.
+          # This does not iterate XML declerations, comments, attributes, CDATA sections, etc.
+          actual_names = []
+          document.each_recursive do |element|
+            actual_names << element.attributes["name"]
+          end
+          assert_equal(expected_names, actual_names)
+        end
+      end
     end
   end
 end