Added CSS/XPath Parser.parse_with_cache

This method parses and caches ASTs using Oga::LRU. Currently the default
of 1024 keys is used.

See #71 for more information.

benchmark/css/parser/parser_bench.rb

@@ -3,7 +3,13 @@ require_relative '../../benchmark_helper'
 css = 'foo bar bar.some_class element#with_id[title="Foo"]'
 
 Benchmark.ips do |bench|
-  bench.report 'CSS' do
+  bench.report 'without cache' do
     Oga::CSS::Parser.new(css).parse
   end
+
+  bench.report 'with cache' do
+    Oga::CSS::Parser.parse_with_cache(css)
+  end
+
+  bench.compare!
 end

benchmark/xpath/parser/parser_bench.rb

@@ -3,7 +3,13 @@ require_relative '../../benchmark_helper'
 xpath = '/wikimedia/projects/project[@name="Wikipedia"]/editions/edition/text()'
 
 Benchmark.ips do |bench|
-  bench.report 'Wikipedia example' do
+  bench.report 'without cache' do
     Oga::XPath::Parser.new(xpath).parse
   end
+
+  bench.report 'with cache' do
+    Oga::XPath::Parser.parse_with_cache(xpath)
+  end
+
+  bench.compare!
 end

lib/oga/css/parser.rll

@@ -310,6 +310,19 @@ even
 
 %inner
 {
+  ##
+  # @return [Oga::LRU]
+  #
+  CACHE = LRU.new
+
+  ##
+  # @param [String] data
+  # @return [AST::Node]
+  #
+  def self.parse_with_cache(data)
+    return CACHE.get_or_set(data) { new(data).parse }
+  end
+
   ##
   # @param [String] data The input to parse.
   #

lib/oga/xpath/parser.rll

@@ -223,6 +223,19 @@ variable
 
 %inner
 {
+  ##
+  # @return [Oga::LRU]
+  #
+  CACHE = LRU.new
+
+  ##
+  # @param [String] data
+  # @return [AST::Node]
+  #
+  def self.parse_with_cache(data)
+    return CACHE.get_or_set(data) { new(data).parse }
+  end
+
   ##
   # @param [String] data The input to parse.
   #

spec/oga/css/parser/cache_spec.rb

@@ -0,0 +1,27 @@
+require 'spec_helper'
+
+describe Oga::CSS::Parser do
+  describe 'parse_with_cache' do
+    after do
+      described_class::CACHE.clear
+    end
+
+    it 'parses an expression' do
+      described_class.parse_with_cache('foo')
+        .should == s(:axis, 'descendant', s(:test, nil, 'foo'))
+    end
+
+    it 'caches an expression after parsing it' do
+      described_class.any_instance
+        .should_receive(:parse)
+        .once
+        .and_call_original
+
+      described_class.parse_with_cache('foo')
+        .should == s(:axis, 'descendant', s(:test, nil, 'foo'))
+
+      described_class.parse_with_cache('foo')
+        .should == s(:axis, 'descendant', s(:test, nil, 'foo'))
+    end
+  end
+end

spec/oga/xpath/parser/cache_spec.rb

@@ -0,0 +1,27 @@
+require 'spec_helper'
+
+describe Oga::XPath::Parser do
+  describe 'parse_with_cache' do
+    after do
+      described_class::CACHE.clear
+    end
+
+    it 'parses an expression' do
+      described_class.parse_with_cache('foo')
+        .should == s(:axis, 'child', s(:test, nil, 'foo'))
+    end
+
+    it 'caches an expression after parsing it' do
+      described_class.any_instance
+        .should_receive(:parse)
+        .once
+        .and_call_original
+
+      described_class.parse_with_cache('foo')
+        .should == s(:axis, 'child', s(:test, nil, 'foo'))
+
+      described_class.parse_with_cache('foo')
+        .should == s(:axis, 'child', s(:test, nil, 'foo'))
+    end
+  end
+end