python/google/appengine/cron/groc.py

   1 #!/usr/bin/env python
   2 #
   3 # Copyright 2007 Google Inc.
   4 #
   5 # Licensed under the Apache License, Version 2.0 (the "License");
   6 # you may not use this file except in compliance with the License.
   7 # You may obtain a copy of the License at
   8 #
   9 #     http://www.apache.org/licenses/LICENSE-2.0
  10 #
  11 # Unless required by applicable law or agreed to in writing, software
  12 # distributed under the License is distributed on an "AS IS" BASIS,
  13 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  14 # See the License for the specific language governing permissions and
  15 # limitations under the License.
  16 #
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  25
  26 """A wrapper around the generated Groc parser and lexer."""
  27
  28
  29 import google
  30
  31 import antlr3
  32
  33 import GrocLexer
  34 import GrocParser
  35
  36
  37 class GrocException(Exception):
  38   """An error occurred while parsing the groc input string."""
  39
  40
  41 class GrocLexerWithErrors(GrocLexer.GrocLexer):
  42   """An overridden Lexer that raises exceptions."""
  43
  44   def emitErrorMessage(self, msg):
  45     """Raise an exception if the input fails to parse correctly.
  46
  47     Overriding the default, which normally just prints a message to
  48     stderr.
  49
  50     Arguments:
  51       msg: the error message
  52     Raises:
  53       GrocException: always.
  54     """
  55     raise GrocException(msg)
  56
  57
  58 class GrocParserWithErrors(GrocParser.GrocParser):
  59   """An overridden Parser that raises exceptions."""
  60
  61   def emitErrorMessage(self, msg):
  62     """Raise an exception if the input fails to parse correctly.
  63
  64     Overriding the default, which normally just prints a message to
  65     stderr.
  66
  67     Arguments:
  68       msg: the error message
  69     Raises:
  70       GrocException: always.
  71     """
  72     raise GrocException(msg)
  73
  74
  75 def CreateParser(parse_string):
  76   """Creates a Groc Parser."""
  77   input_string = antlr3.ANTLRStringStream(parse_string)
  78   lexer = GrocLexerWithErrors(input_string)
  79   tokens = antlr3.CommonTokenStream(lexer)
  80   parser = GrocParserWithErrors(tokens)
  81   return parser