RDoc::Parser::C: Integrate do_classes and do_modules by one regexp match

The full scan of the C source code (`@content.scan`) is very slow.
The old code invokes the scan six times in `do_classes` and
`do_modules`.

This change integrates the six scans into one by merging the regexps.
The integrated regexp is a bit hard to maintain, but the speed up is
significant: approx. 30 sec -> 20 sec in Ruby's `make rdoc`.

In addition, this change omits `do_boot_defclass` unless the file name
is `class.c`.  `boot_defclass` is too specific to Ruby's source code, so
RDoc should handle it as a special case.

Before this change:

     TOTAL    (pct)     SAMPLES    (pct)     FRAME
       858  (13.6%)         858  (13.6%)     (garbage collection)
       292   (4.6%)         264   (4.2%)     RDoc::Parser::C#do_define_class
       263   (4.2%)         250   (3.9%)     RDoc::Parser::C#do_define_module
       275   (4.3%)         241   (3.8%)     RDoc::Parser::C#do_define_class_under
       248   (3.9%)         237   (3.7%)     RDoc::Parser::C#do_define_module_under
       234   (3.7%)         234   (3.7%)     RDoc::Parser::C#gen_body_table
       219   (3.5%)         219   (3.5%)     Ripper::Lexer#state_obj
       217   (3.4%)         216   (3.4%)     RDoc::Parser::C#do_struct_define_without_accessor
       205   (3.2%)         205   (3.2%)     RDoc::Parser::C#do_boot_defclass
       205   (3.2%)         205   (3.2%)     RDoc::Parser::C#do_singleton_class

The six methods take approx. 22.2%.
`do_define_class` (4.2%) + `do_define_class_under` (3.8%) +
`do_define_module` (3,9$) + `do_define_module_under` (3.7%) +
`do_struct_define_without_accessor` (3.4%) + `do_singleton_class` (3.2%)

After this change, the methods are integrated to `do_classes_and_modules`
which takes only 5.8%.

     TOTAL    (pct)     SAMPLES    (pct)     FRAME
       812  (16.7%)         812  (16.7%)     (garbage collection)
       355   (7.3%)         284   (5.8%)     RDoc::Parser::C#do_classes_and_modules
       225   (4.6%)         225   (4.6%)     RDoc::Parser::C#gen_body_table
       429   (8.8%)         210   (4.3%)     RDoc::Parser::RubyTools#get_tk
       208   (4.3%)         208   (4.3%)     RDoc::TokenStream#add_tokens

2 files changed, 98 insertions, 134 deletions

diff --git a/lib/rdoc/parser/c.rb b/lib/rdoc/parser/c.rb
index 5cc009e499..8265712370 100644
--- a/lib/rdoc/parser/c.rb
+++ b/lib/rdoc/parser/c.rb
@@ -324,12 +324,100 @@ class RDoc::Parser::C < RDoc::Parser
   # Scans #content for rb_define_class, boot_defclass, rb_define_class_under
   # and rb_singleton_class
 
-  def do_classes
-    do_boot_defclass
-    do_define_class
-    do_define_class_under
-    do_singleton_class
-    do_struct_define_without_accessor
+  def do_classes_and_modules
+    do_boot_defclass if @file_name == "class.c"
+
+    @content.scan(
+      %r(
+        (?<var_name>[\w\.]+)\s* =
+        \s*rb_(?:
+          define_(?:
+            class(?: # rb_define_class(class_name_1, parent_name_1)
+              \s*\(
+                \s*"(?<class_name_1>\w+)",
+                \s*(?<parent_name_1>\w+)\s*
+              \)
+            |
+              _under\s*\( # rb_define_class_under(class_under, class_name2, parent_name2...)
+                \s* (?<class_under>\w+),
+                \s* "(?<class_name_2>\w+)",
+                \s*
+                (?:
+                  (?<parent_name_2>[\w\*\s\(\)\.\->]+) |
+                  rb_path2class\("(?<path>[\w:]+)"\)
+                )
+              \s*\)
+            )
+          |
+            module(?: # rb_define_module(module_name_1)
+              \s*\(
+                \s*"(?<module_name_1>\w+)"\s*
+              \)
+            |
+              _under\s*\( # rb_define_module_under(module_under, module_name_1)
+                \s*(?<module_under>\w+),
+                \s*"(?<module_name_2>\w+)"
+              \s*\)
+            )
+          )
+      |
+        struct_define_without_accessor\s*\( # rb_struct_define_without_accessor(class_name_3, parent_name_3, ...)
+          \s*"(?<class_name_3>\w+)",
+          \s*(?<parent_name_3>\w+),
+          \s*\w+,        # Allocation function
+          (?:\s*"\w+",)* # Attributes
+          \s*NULL
+        \)
+      |
+        singleton_class\s*\( # rb_singleton_class(target_class_name)
+          \s*(?<target_class_name>\w+)
+        \)
+        )
+      )mx
+    ) do
+      class_name = $~[:class_name_1]
+      type = :class
+      if class_name
+        # rb_define_class(class_name_1, parent_name_1)
+        parent_name = $~[:parent_name_1]
+        #under = nil
+      else
+        class_name = $~[:class_name_2]
+        if class_name
+          # rb_define_class_under(class_under, class_name2, parent_name2...)
+          parent_name = $~[:parent_name_2] || $~[:path]
+          under = $~[:class_under]
+        else
+          class_name = $~[:class_name_3]
+          if class_name
+            # rb_struct_define_without_accessor(class_name_3, parent_name_3, ...)
+            parent_name = $~[:parent_name_3]
+            #under = nil
+          else
+            type = :module
+            class_name = $~[:module_name_1]
+            #parent_name = nil
+            if class_name
+              # rb_define_module(module_name_1)
+              #under = nil
+            else
+              class_name = $~[:module_name_2]
+              if class_name
+                # rb_define_module_under(module_under, module_name_1)
+                under = $~[:module_under]
+              else
+                # rb_singleton_class(target_class_name)
+                target_class_name = $~[:target_class_name]
+                handle_singleton $~[:var_name], target_class_name
+                next
+              end
+            end
+          end
+        end
+      end
+
+      handle_class_module($~[:var_name], type, class_name, parent_name, under)
+    end
   end
 
   ##
@@ -378,65 +466,6 @@ class RDoc::Parser::C < RDoc::Parser
     end
   end
 
-  ##
-  # Scans #content for rb_define_class
-
-  def do_define_class
-    # The '.' lets us handle SWIG-generated files
-    @content.scan(/([\w\.]+)\s* = \s*rb_define_class\s*
-              \(
-                 \s*"(\w+)",
-                 \s*(\w+)\s*
-              \)/mx) do |var_name, class_name, parent|
-      handle_class_module(var_name, :class, class_name, parent, nil)
-    end
-  end
-
-  ##
-  # Scans #content for rb_define_class_under
-
-  def do_define_class_under
-    @content.scan(/([\w\.]+)\s* =                  # var_name
-                   \s*rb_define_class_under\s*
-                   \(
-                     \s* (\w+),                    # under
-                     \s* "(\w+)",                  # class_name
-                     \s*
-                     (?:
-                       ([\w\*\s\(\)\.\->]+) |      # parent_name
-                       rb_path2class\("([\w:]+)"\) # path
-                     )
-                     \s*
-                   \)
-                  /mx) do |var_name, under, class_name, parent_name, path|
-      parent = path || parent_name
-
-      handle_class_module var_name, :class, class_name, parent, under
-    end
-  end
-
-  ##
-  # Scans #content for rb_define_module
-
-  def do_define_module
-    @content.scan(/(\w+)\s* = \s*rb_define_module\s*\(\s*"(\w+)"\s*\)/mx) do
-      |var_name, class_name|
-      handle_class_module(var_name, :module, class_name, nil, nil)
-    end
-  end
-
-  ##
-  # Scans #content for rb_define_module_under
-
-  def do_define_module_under
-    @content.scan(/(\w+)\s* = \s*rb_define_module_under\s*
-              \(
-                 \s*(\w+),
-                 \s*"(\w+)"
-              \s*\)/mx) do |var_name, in_module, class_name|
-      handle_class_module(var_name, :module, class_name, nil, in_module)
-    end
-  end
 
   ##
   # Scans #content for rb_include_module
@@ -519,42 +548,6 @@ class RDoc::Parser::C < RDoc::Parser
   end
 
   ##
-  # Scans #content for rb_define_module and rb_define_module_under
-
-  def do_modules
-    do_define_module
-    do_define_module_under
-  end
-
-  ##
-  # Scans #content for rb_singleton_class
-
-  def do_singleton_class
-    @content.scan(/([\w\.]+)\s* = \s*rb_singleton_class\s*
-                  \(
-                    \s*(\w+)
-                  \s*\)/mx) do |sclass_var, class_var|
-      handle_singleton sclass_var, class_var
-    end
-  end
-
-  ##
-  # Scans #content for struct_define_without_accessor
-
-  def do_struct_define_without_accessor
-    @content.scan(/([\w\.]+)\s* = \s*rb_struct_define_without_accessor\s*
-              \(
-                 \s*"(\w+)",  # Class name
-                 \s*(\w+),    # Parent class
-                 \s*\w+,      # Allocation function
-                 (\s*"\w+",)* # Attributes
-                 \s*NULL
-              \)/mx) do |var_name, class_name, parent|
-      handle_class_module(var_name, :class, class_name, parent, nil)
-    end
-  end
-
-  ##
   # Finds the comment for an alias on +class_name+ from +new_name+ to
   # +old_name+
 
@@ -1247,8 +1240,7 @@ class RDoc::Parser::C < RDoc::Parser
   def scan
     remove_commented_out_lines
 
-    do_modules
-    do_classes
+    do_classes_and_modules
     do_missing
 
     do_constants
diff --git a/test/rdoc/test_rdoc_parser_c.rb b/test/rdoc/test_rdoc_parser_c.rb
index 81727ad759..6601d28f60 100644
--- a/test/rdoc/test_rdoc_parser_c.rb
+++ b/test/rdoc/test_rdoc_parser_c.rb
@@ -304,32 +304,6 @@ void Init_Blah(void) {
     assert_equal 'This should show up as an alias', methods.last.comment.text
   end
 
-  def test_do_classes_boot_class
-    content = <<-EOF
-/* Document-class: Foo
- * this is the Foo boot class
- */
-VALUE cFoo = boot_defclass("Foo", rb_cObject);
-    EOF
-
-    klass = util_get_class content, 'cFoo'
-    assert_equal "this is the Foo boot class", klass.comment.text
-    assert_equal 'Object', klass.superclass
-  end
-
-  def test_do_classes_boot_class_nil
-    content = <<-EOF
-/* Document-class: Foo
- * this is the Foo boot class
- */
-VALUE cFoo = boot_defclass("Foo", 0);
-    EOF
-
-    klass = util_get_class content, 'cFoo'
-    assert_equal "this is the Foo boot class", klass.comment.text
-    assert_nil klass.superclass
-  end
-
   def test_do_aliases_missing_class
     content = <<-EOF
 void Init_Blah(void) {
@@ -511,7 +485,7 @@ void Init_foo(){
 
     @parser = util_parser content
 
-    @parser.do_classes
+    @parser.do_classes_and_modules
     @parser.do_constants
 
     klass = @parser.classes['cFoo']
@@ -581,8 +555,7 @@ void Init_curses(){
 
     @parser = util_parser content
 
-    @parser.do_modules
-    @parser.do_classes
+    @parser.do_classes_and_modules
     @parser.do_constants
 
     klass = @parser.classes['mCurses']
@@ -608,8 +581,7 @@ void Init_File(void) {
 
     @parser = util_parser content
 
-    @parser.do_modules
-    @parser.do_classes
+    @parser.do_classes_and_modules
     @parser.do_constants
 
     klass = @parser.classes['rb_mFConst']