134 lines
4.8 KiB
Python
134 lines
4.8 KiB
Python
#-----------------------------------------------------------------
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# plyparser.py
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#
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# PLYParser class and other utilities for simplifying programming
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# parsers with PLY
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#
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# Eli Bendersky [https://eli.thegreenplace.net/]
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# License: BSD
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#-----------------------------------------------------------------
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import warnings
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class Coord(object):
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""" Coordinates of a syntactic element. Consists of:
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- File name
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- Line number
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- (optional) column number, for the Lexer
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"""
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__slots__ = ('file', 'line', 'column', '__weakref__')
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def __init__(self, file, line, column=None):
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self.file = file
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self.line = line
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self.column = column
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def __str__(self):
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str = "%s:%s" % (self.file, self.line)
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if self.column: str += ":%s" % self.column
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return str
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class ParseError(Exception): pass
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class PLYParser(object):
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def _create_opt_rule(self, rulename):
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""" Given a rule name, creates an optional ply.yacc rule
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for it. The name of the optional rule is
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<rulename>_opt
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"""
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optname = rulename + '_opt'
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def optrule(self, p):
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p[0] = p[1]
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optrule.__doc__ = '%s : empty\n| %s' % (optname, rulename)
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optrule.__name__ = 'p_%s' % optname
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setattr(self.__class__, optrule.__name__, optrule)
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def _coord(self, lineno, column=None):
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return Coord(
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file=self.clex.filename,
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line=lineno,
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column=column)
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def _token_coord(self, p, token_idx):
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""" Returns the coordinates for the YaccProduction object 'p' indexed
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with 'token_idx'. The coordinate includes the 'lineno' and
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'column'. Both follow the lex semantic, starting from 1.
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"""
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last_cr = p.lexer.lexer.lexdata.rfind('\n', 0, p.lexpos(token_idx))
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if last_cr < 0:
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last_cr = -1
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column = (p.lexpos(token_idx) - (last_cr))
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return self._coord(p.lineno(token_idx), column)
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def _parse_error(self, msg, coord):
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raise ParseError("%s: %s" % (coord, msg))
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def parameterized(*params):
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""" Decorator to create parameterized rules.
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Parameterized rule methods must be named starting with 'p_' and contain
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'xxx', and their docstrings may contain 'xxx' and 'yyy'. These will be
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replaced by the given parameter tuples. For example, ``p_xxx_rule()`` with
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docstring 'xxx_rule : yyy' when decorated with
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``@parameterized(('id', 'ID'))`` produces ``p_id_rule()`` with the docstring
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'id_rule : ID'. Using multiple tuples produces multiple rules.
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"""
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def decorate(rule_func):
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rule_func._params = params
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return rule_func
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return decorate
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def template(cls):
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""" Class decorator to generate rules from parameterized rule templates.
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See `parameterized` for more information on parameterized rules.
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"""
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issued_nodoc_warning = False
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for attr_name in dir(cls):
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if attr_name.startswith('p_'):
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method = getattr(cls, attr_name)
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if hasattr(method, '_params'):
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# Remove the template method
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delattr(cls, attr_name)
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# Create parameterized rules from this method; only run this if
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# the method has a docstring. This is to address an issue when
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# pycparser's users are installed in -OO mode which strips
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# docstrings away.
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# See: https://github.com/eliben/pycparser/pull/198/ and
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# https://github.com/eliben/pycparser/issues/197
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# for discussion.
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if method.__doc__ is not None:
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_create_param_rules(cls, method)
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elif not issued_nodoc_warning:
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warnings.warn(
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'parsing methods must have __doc__ for pycparser to work properly',
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RuntimeWarning,
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stacklevel=2)
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issued_nodoc_warning = True
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return cls
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def _create_param_rules(cls, func):
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""" Create ply.yacc rules based on a parameterized rule function
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Generates new methods (one per each pair of parameters) based on the
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template rule function `func`, and attaches them to `cls`. The rule
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function's parameters must be accessible via its `_params` attribute.
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"""
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for xxx, yyy in func._params:
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# Use the template method's body for each new method
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def param_rule(self, p):
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func(self, p)
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# Substitute in the params for the grammar rule and function name
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param_rule.__doc__ = func.__doc__.replace('xxx', xxx).replace('yyy', yyy)
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param_rule.__name__ = func.__name__.replace('xxx', xxx)
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# Attach the new method to the class
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setattr(cls, param_rule.__name__, param_rule)
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