Refactor `Regexp#match` cache implementation (#7724)

* Refactor Regexp#match cache implementation

Improved variable and function names
Fixed [Bug 19537] (Maybe fixed in https://github.com/ruby/ruby/pull/7694)

* Add a comment of the glossary for "match cache"

* Skip to reset match cache when no cache point on null check

1 files changed, 11 insertions, 3 deletions

diff --git a/test/ruby/test_regexp.rb b/test/ruby/test_regexp.rb
index d50e481d2d..83dcb69530 100644
--- a/test/ruby/test_regexp.rb
+++ b/test/ruby/test_regexp.rb
@@ -1733,7 +1733,7 @@ class TestRegexp < Test::Unit::TestCase
     end;
   end
 
-  def test_cache_optimization_exponential
+  def test_match_cache_exponential
     assert_separately([], "#{<<-"begin;"}\n#{<<-'end;'}")
       timeout = #{ EnvUtil.apply_timeout_scale(10).inspect }
     begin;
@@ -1743,7 +1743,7 @@ class TestRegexp < Test::Unit::TestCase
     end;
   end
 
-  def test_cache_optimization_square
+  def test_match_cache_square
     assert_separately([], "#{<<-"begin;"}\n#{<<-'end;'}")
       timeout = #{ EnvUtil.apply_timeout_scale(10).inspect }
     begin;
@@ -1753,7 +1753,7 @@ class TestRegexp < Test::Unit::TestCase
     end;
   end
 
-  def test_cache_index_initialize
+  def test_cache_opcodes_initialize
     str = 'test1-test2-test3-test4-test_5'
     re = '^([0-9a-zA-Z\-/]*){1,256}$'
     100.times do
@@ -1781,6 +1781,14 @@ class TestRegexp < Test::Unit::TestCase
     assert_equal("123456789".match(/(?:x?\dx?){2,}/)[0], "123456789")
   end
 
+  def test_bug_19537
+    str = 'aac'
+    re = '^([ab]{1,3})(a?)*$'
+    100.times do
+      assert !Regexp.new(re).match?(str)
+    end    
+  end
+
   def test_linear_time_p
     assert_send [Regexp, :linear_time?, /a/]
     assert_send [Regexp, :linear_time?, 'a']