Speed up for Backend::Simple#interpolate

lib/i18n/backend/simple.rb

@@ -3,6 +3,9 @@
 module I18n
   module Backend
     class Simple
+      INTERPOLATION_RESERVED_KEYS = %w(scope default)
+      MATCH = /(\\\\)?\{\{([^\}]+)\}\}/
+
       # Accepts a list of paths to translation files. Loads translations from 
       # plain Ruby (*.rb) or YAML files (*.yml). See #load_rb and #load_yml
       # for details.
@@ -114,29 +117,29 @@ def pluralize(locale, entry, count)
         # the <tt>{{...}}</tt> key in a string (once for the string and once for the
         # interpolation).
         def interpolate(locale, string, values = {})
-          return string if !string.is_a?(String)
+          return string unless string.is_a?(String)
 
           string = string.gsub(/%d/, '{{count}}').gsub(/%s/, '{{value}}')
+
           if string.respond_to?(:force_encoding)
-             original_encoding = string.encoding
-             string.force_encoding(Encoding::BINARY)
-           end
-          s = StringScanner.new(string)
-
-          while s.skip_until(/\{\{/)
-            s.string[s.pos - 3, 1] = '' and next if s.pre_match[-1, 1] == '\\'            
-            start_pos = s.pos - 2
-            key = s.scan_until(/\}\}/)[0..-3]
-            end_pos = s.pos - 1            
+            original_encoding = string.encoding
+            string.force_encoding(Encoding::BINARY)
+          end
 
-            raise ReservedInterpolationKey.new(key, string) if %w(scope default).include?(key)
-            raise MissingInterpolationArgument.new(key, string) unless values.has_key? key.to_sym
+          result = string.gsub(MATCH) do
+            escaped, pattern, key = $1, $2, $2.to_sym
 
-            s.string[start_pos..end_pos] = values[key.to_sym].to_s
-            s.unscan
+            if escaped
+              pattern
+            elsif INTERPOLATION_RESERVED_KEYS.include?(pattern)
+              raise ReservedInterpolationKey.new(pattern, string)
+            elsif !values.include?(key)
+              raise MissingInterpolationArgument.new(pattern, string)
+            else
+              values[key].to_s
+            end
           end
-
-          result = s.string
+
           result.force_encoding(original_encoding) if original_encoding
           result
         end