Define Pathname#sub in C on CRuby for efficiency

* The eval to set $~ is inneficient, so only do it when necessary (when running without the C extension).

Author: eregon

ext/pathname/pathname.c

@@ -2,6 +2,7 @@
 
 static VALUE rb_cPathname;
 static ID id_at_path;
+static ID id_sub;
 
 static VALUE
 get_strpath(VALUE obj)
@@ -61,6 +62,27 @@ path_cmp(VALUE self, VALUE other)
     return INT2FIX(0);
 }
 
+/*
+ * Return a pathname which is substituted by String#sub.
+ *
+ *	path1 = Pathname.new('/usr/bin/perl')
+ *	path1.sub('perl', 'ruby')
+ *	    #=> #<Pathname:/usr/bin/ruby>
+ */
+static VALUE
+path_sub(int argc, VALUE *argv, VALUE self)
+{
+    VALUE str = get_strpath(self);
+
+    if (rb_block_given_p()) {
+        str = rb_block_call(str, id_sub, argc, argv, 0, 0);
+    }
+    else {
+        str = rb_funcallv(str, id_sub, argc, argv);
+    }
+    return rb_class_new_instance(1, &str, rb_obj_class(self));
+}
+
 static void init_ids(void);
 
 void
@@ -79,11 +101,13 @@ InitVM_pathname(void)
 {
     rb_cPathname = rb_define_class("Pathname", rb_cObject);
     rb_define_method(rb_cPathname, "<=>", path_cmp, 1);
+    rb_define_method(rb_cPathname, "sub", path_sub, -1);
 }
 
 void
 init_ids(void)
 {
 #undef rb_intern
     id_at_path = rb_intern("@path");
+    id_sub = rb_intern("sub");
 }

lib/pathname.rb

@@ -288,23 +288,25 @@ def inspect # :nodoc:
     "#<#{self.class}:#{@path}>"
   end
 
-  # Return a pathname which is substituted by String#sub.
-  def sub(pattern, *args, **kwargs, &block)
-    if block
-      path = @path.sub(pattern, *args, **kwargs) {|*sub_args|
-        begin
-          old = Thread.current[:pathname_sub_matchdata]
-          Thread.current[:pathname_sub_matchdata] = $~
-          eval("$~ = Thread.current[:pathname_sub_matchdata]", block.binding)
-        ensure
-          Thread.current[:pathname_sub_matchdata] = old
-        end
-        yield(*sub_args)
-      }
-    else
-      path = @path.sub(pattern, *args, **kwargs)
+  unless method_defined?(:sub, false)
+    # Return a pathname which is substituted by String#sub.
+    def sub(pattern, *args, **kwargs, &block)
+      if block
+        path = @path.sub(pattern, *args, **kwargs) {|*sub_args|
+          begin
+            old = Thread.current[:pathname_sub_matchdata]
+            Thread.current[:pathname_sub_matchdata] = $~
+            eval("$~ = Thread.current[:pathname_sub_matchdata]", block.binding)
+          ensure
+            Thread.current[:pathname_sub_matchdata] = old
+          end
+          yield(*sub_args)
+        }
+      else
+        path = @path.sub(pattern, *args, **kwargs)
+      end
+      self.class.new(path)
     end
-    self.class.new(path)
   end
 
   # Return a pathname with +repl+ added as a suffix to the basename.