Optimize SAX2Parser#get_namespace (#207)

``` RUBYLIB= BUNDLER_ORIG_RUBYLIB= /Users/naitoh/.rbenv/versions/3.3.4/bin/ruby -v -S benchmark-driver /Users/naitoh/ghq/github.com/naitoh/rexml/benchmark/parse.yaml ruby 3.3.4 (2024-07-09 revision be1089c8ec) [arm64-darwin22] Calculating ------------------------------------- before after before(YJIT) after(YJIT) dom 18.085 17.677 33.086 32.778 i/s - 100.000 times in 5.529372s 5.657097s 3.022471s 3.050832s sax 25.450 26.182 44.797 47.916 i/s - 100.000 times in 3.929249s 3.819475s 2.232309s 2.086982s pull 29.160 29.089 55.407 53.531 i/s - 100.000 times in 3.429304s 3.437757s 1.804825s 1.868072s stream 29.137 29.055 52.780 51.368 i/s - 100.000 times in 3.432007s 3.441754s 1.894649s 1.946724s Comparison: dom before(YJIT): 33.1 i/s after(YJIT): 32.8 i/s - 1.01x slower before: 18.1 i/s - 1.83x slower after: 17.7 i/s - 1.87x slower sax after(YJIT): 47.9 i/s before(YJIT): 44.8 i/s - 1.07x slower after: 26.2 i/s - 1.83x slower before: 25.5 i/s - 1.88x slower pull before(YJIT): 55.4 i/s after(YJIT): 53.5 i/s - 1.04x slower before: 29.2 i/s - 1.90x slower after: 29.1 i/s - 1.90x slower stream before(YJIT): 52.8 i/s after(YJIT): 51.4 i/s - 1.03x slower before: 29.1 i/s - 1.81x slower after: 29.1 i/s - 1.82x slower ``` - sax - YJIT=ON : 1.07x faster - YJIT=OFF : 1.03x faster

Author: naitoh

lib/rexml/parsers/sax2parser.rb

@@ -259,6 +259,8 @@ def add( pair )
  end
 
  def get_namespace( prefix )
+ return nil if @namespace_stack.empty?
+
  uris = (@namespace_stack.find_all { |ns| not ns[prefix].nil? }) ||
  (@namespace_stack.find { |ns| not ns[nil].nil? })
  uris[-1][prefix] unless uris.nil? or 0 == uris.size

test/test_sax.rb

@@ -99,6 +99,52 @@ def test_sax2
  end
  end
 
+ def test_without_namespace
+ xml = <<-XML
+<root >
+ <a att1='1' att2='2' att3='&lt;'>
+ <b />
+ </a>
+</root>
+ XML
+
+ parser = REXML::Parsers::SAX2Parser.new(xml)
+ elements = []
+ parser.listen(:start_element) do |uri, localname, qname, attrs|
+ elements << [uri, localname, qname, attrs]
+ end
+ parser.parse
+ assert_equal([
+ [nil, "root", "root", {}],
+ [nil, "a", "a", {"att1"=>"1", "att2"=>"2", "att3"=>"&lt;"}],
+ [nil, "b", "b", {}]
+ ], elements)
+ end
+
+ def test_with_namespace
+ xml = <<-XML
+<root xmlns="http://example.org/default"
+ xmlns:foo="http://example.org/foo"
+ xmlns:bar="http://example.org/bar">
+ <a foo:att='1' bar:att='2' att='&lt;'>
+ <bar:b />
+ </a>
+</root>
+ XML
+
+ parser = REXML::Parsers::SAX2Parser.new(xml)
+ elements = []
+ parser.listen(:start_element) do |uri, localname, qname, attrs|
+ elements << [uri, localname, qname, attrs]
+ end
+ parser.parse
+ assert_equal([
+ ["http://example.org/default", "root", "root", {"xmlns"=>"http://example.org/default", "xmlns:bar"=>"http://example.org/bar", "xmlns:foo"=>"http://example.org/foo"}],
+ ["http://example.org/default", "a", "a", {"att"=>"&lt;", "bar:att"=>"2", "foo:att"=>"1"}],
+ ["http://example.org/bar", "b", "bar:b", {}]
+ ], elements)
+ end
+
  class EntityExpansionLimitTest < Test::Unit::TestCase
  class GeneralEntityTest < self
  def test_have_value