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Ben Murdoch7757ec22013-07-23 11:17:36 +01001# Copyright (C) 2013 Google Inc. All rights reserved.
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28
29"""Lexer for Blink IDL.
30
31The lexer uses the PLY (Python Lex-Yacc) library to build a tokenizer which
32understands the Blink dialect of Web IDL and produces a token stream suitable
33for the Blink IDL parser.
34
35Blink IDL is identical to Web IDL at the token level, but the base lexer
36does not discard comments. We need to override (and not include comments in
37the token stream), as otherwise comments must be explicitly included in the
38phrase grammar of the parser.
39
40FIXME: Change base lexer to discard comments, and simply used the base
41lexer, eliminating this separate lexer.
42
43Web IDL:
44 http://www.w3.org/TR/WebIDL/
45Web IDL Grammar:
46 http://www.w3.org/TR/WebIDL/#idl-grammar
47PLY:
48 http://www.dabeaz.com/ply/
49"""
50
51# Disable attribute validation, as lint can't import parent class to check
52# pylint: disable=E1101
53
54import os.path
55import sys
56
57# Base lexer is in Chromium src/tools/idl_parser
58module_path, module_name = os.path.split(__file__)
59tools_dir = os.path.join(module_path, os.pardir, os.pardir, os.pardir, os.pardir, os.pardir, 'tools')
60sys.path.append(tools_dir)
61
62from idl_parser.idl_lexer import IDLLexer
63
64REMOVE_TOKENS = ['COMMENT']
65
66
67class BlinkIDLLexer(IDLLexer):
68 # ignore comments
69 def t_COMMENT(self, t):
70 r'(/\*(.|\n)*?\*/)|(//.*(\n[ \t]*//.*)*)'
71 self.AddLines(t.value.count('\n'))
72
73 # Analogs to _AddToken/_AddTokens in base lexer
74 # Needed to remove COMMENT token, since comments ignored
75 def _RemoveToken(self, token):
76 try:
77 self.tokens.remove(token)
78 except ValueError:
79 raise RuntimeError('Token "%s" not present, so cannot be removed ' % token)
80
81 def _RemoveTokens(self, tokens):
82 for token in tokens:
83 self._RemoveToken(token)
84
85 def __init__(self):
86 IDLLexer.__init__(self)
87 self._RemoveTokens(REMOVE_TOKENS)
88
89
90# If run by itself, attempt to build the lexer
91if __name__ == '__main__':
92 lexer = BlinkIDLLexer()