Experimental lexer generator: Don't go BACK();

tools/lexer_generator/code_generator.py

 # Copyright 2013 the V8 project authors. All rights reserved.
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are
 # met:
 #
 #     * Redistributions of source code must retain the above copyright
 #       notice, this list of conditions and the following disclaimer.
 #     * Redistributions in binary form must reproduce the above
 #       copyright notice, this list of conditions and the following
 #       disclaimer in the documentation and/or other materials provided
@@ skipping 59 matching lines @@
     action = state.action()
     if action:
       if action.type() == 'terminate':
         code += 'PUSH_TOKEN(Token::EOS); return 0;'
         return code
       elif action.type() == 'terminate_illegal':
         code += 'PUSH_TOKEN(Token::ILLEGAL); return 1;'
         return code
 
     code += '''
-    yych = *(++cursor_);
     //fprintf(stderr, "char at hand is %c (%d)\\n", yych, yych);\n'''
 
     for key, s in state.transitions().items():
       code += CodeGenerator.key_to_code(key)
       code += ''' {
+        FORWARD();
         goto code_%s;
     }
 ''' % s.node_number()
 
     if action:
       if action.type() == 'code':
-        code += '%s\nBACK();\ngoto code_%s;\n' % (action.data(),
-                                                  start_node_number)
+        code += '%s\n\ngoto code_%s;\n' % (action.data(),
+                                           start_node_number)
       elif action.type() == 'push_token':
         content = 'PUSH_TOKEN(Token::%s);' % action.data()
-        code += '%s\nBACK();\ngoto code_%s;\n' % (content,
-                                                  start_node_number)
+        code += '%s\ngoto code_%s;\n' % (content,
+                                         start_node_number)
       else:
         raise Exception("unknown type %s" % action.type())
     else:
       code += 'goto default_action;'
     return code
 
   @staticmethod
   def rule_processor_to_code(rule_processor, use_mdfa):
     if use_mdfa:
       dfa = rule_processor.default_automata().minimal_dfa()
@@ skipping 13 matching lines @@
       code += CodeGenerator.dfa_state_to_code(state, start_node_number)
       return code
     code = dfa.visit_all_states(f, code)
 
     default_action_code = ''
     if rule_processor.default_action:
       if rule_processor.default_action.type() == 'push_token':
         default_action_code = '''
 default_action:
   //fprintf(stderr, "default action\\n");
-  PUSH_TOKEN(Token::%s)
+  PUSH_TOKEN(Token::%s);
+  FORWARD();
   goto code_%s;''' % (rule_processor.default_action.data(), start_node_number)
       else:
         raise Exception("Default action type %s not supported" % action.type())
 
     code += '''
   CHECK(false);
 %s
   return 0;
 }
 
 }
 }
 ''' % default_action_code
     return code