Experimental parser: better escaping

tools/lexer_generator/regex_lexer.py

 # Copyright 2013 the V8 project authors. All rights reserved.
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 import ply.lex as lex
 
+def build_escape_map(chars):
+  def add_escape(d, char):
+    d['\\' + char] = char
+    return d
+  return reduce(add_escape, chars,
+    {'\\t' : '\t', '\\r' : '\r', '\\n' : '\n', '\\v' : '\v', '\\f' : '\f'})
+
 class RegexLexer:
 
   tokens = (
 
     'GROUP_BEGIN',
     'GROUP_END',
 
     'CLASS_BEGIN',
     'CLASS_END',
 
@@ skipping 15 matching lines @@
     'CLASS_LITERAL',
     'CLASS_LITERAL_AS_OCTAL',
     'CHARACTER_CLASS',
   )
 
   states = (
     ('class','exclusive'),
     ('repeat','exclusive'),
   )
 
+  __escaped_literals = build_escape_map("(){}[]?+.*|\\")
+
   def t_ESCAPED_LITERAL(self, t):
-    r'\\\(|\\\)|\\\[|\\\]|\\\||\\\+|\\\*|\\\?|\\\.|\\\\|\\\{|\\\}'
+    r'\\.'
     t.type = 'LITERAL'
-    t.value = t.value[1:]
+    t.value = RegexLexer.__escaped_literals[t.value]
     return t
 
   t_GROUP_BEGIN = r'\('
   t_GROUP_END = r'\)'
 
   t_OR = r'\|'
   t_ONE_OR_MORE = r'\+'
   t_ZERO_OR_MORE = r'\*'
   t_ZERO_OR_ONE = r'\?'
 
@@ skipping 12 matching lines @@
     return t
 
   t_class_RANGE = '-'
   t_class_NOT = '\^'
   t_class_CHARACTER_CLASS = r':\w+:'
 
   def t_class_CLASS_LITERAL_AS_OCTAL(self, t):
     r'\\\d+'
     return t
 
-  escaped_class_literals = {
-    '\\t' : '\t', '\\r' : '\r', '\\n' : '\n', '\\v' : '\v', '\\f' : '\f',
-    '\\^' : '^', '\\[' : '[', '\\]' : ']', '\\-' : '-', '\\:' : ':',
-  }
+  __escaped_class_literals = build_escape_map("^[]-:")
 
   def t_class_ESCAPED_CLASS_LITERAL(self, t):
-    r'\\\^|\\-|\\\[|\\\]|\\\:|\\\w'
+    r'\\.'
     t.type = 'CLASS_LITERAL'
-    t.value = RegexLexer.escaped_class_literals[t.value]
+    t.value = RegexLexer.__escaped_class_literals[t.value]
     return t
 
   t_class_CLASS_LITERAL = r'[\w $_+]'
 
   def t_REPEAT_BEGIN(self, t):
     r'\{'
     self.lexer.push_state('repeat')
     return t
 
   def t_repeat_REPEAT_END(self, t):
     r'\}'
     self.lexer.pop_state()
     return t
 
   t_repeat_NUMBER = r'[0-9]+'
   t_repeat_COMMA = r','
 
   t_ANY_ignore  = '\n'
 
   def t_ANY_error(self, t):
     raise Exception("Illegal character '%s'" % t.value[0])
 
   def build(self, **kwargs):
     self.lexer = lex.lex(module=self, **kwargs)