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Diffstat (limited to 'python/helpers/pydev/third_party/pep8/lib2to3/lib2to3/pgen2/parse.py')
| -rw-r--r-- | python/helpers/pydev/third_party/pep8/lib2to3/lib2to3/pgen2/parse.py | 201 |
1 files changed, 201 insertions, 0 deletions
diff --git a/python/helpers/pydev/third_party/pep8/lib2to3/lib2to3/pgen2/parse.py b/python/helpers/pydev/third_party/pep8/lib2to3/lib2to3/pgen2/parse.py new file mode 100644 index 000000000000..6bebdbba7e52 --- /dev/null +++ b/python/helpers/pydev/third_party/pep8/lib2to3/lib2to3/pgen2/parse.py @@ -0,0 +1,201 @@ +# Copyright 2004-2005 Elemental Security, Inc. All Rights Reserved. +# Licensed to PSF under a Contributor Agreement. + +"""Parser engine for the grammar tables generated by pgen. + +The grammar table must be loaded first. + +See Parser/parser.c in the Python distribution for additional info on +how this parsing engine works. + +""" + +# Local imports +from . import token + +class ParseError(Exception): + """Exception to signal the parser is stuck.""" + + def __init__(self, msg, type, value, context): + Exception.__init__(self, "%s: type=%r, value=%r, context=%r" % + (msg, type, value, context)) + self.msg = msg + self.type = type + self.value = value + self.context = context + +class Parser(object): + """Parser engine. + + The proper usage sequence is: + + p = Parser(grammar, [converter]) # create instance + p.setup([start]) # prepare for parsing + <for each input token>: + if p.addtoken(...): # parse a token; may raise ParseError + break + root = p.rootnode # root of abstract syntax tree + + A Parser instance may be reused by calling setup() repeatedly. + + A Parser instance contains state pertaining to the current token + sequence, and should not be used concurrently by different threads + to parse separate token sequences. + + See driver.py for how to get input tokens by tokenizing a file or + string. + + Parsing is complete when addtoken() returns True; the root of the + abstract syntax tree can then be retrieved from the rootnode + instance variable. When a syntax error occurs, addtoken() raises + the ParseError exception. There is no error recovery; the parser + cannot be used after a syntax error was reported (but it can be + reinitialized by calling setup()). + + """ + + def __init__(self, grammar, convert=None): + """Constructor. + + The grammar argument is a grammar.Grammar instance; see the + grammar module for more information. + + The parser is not ready yet for parsing; you must call the + setup() method to get it started. + + The optional convert argument is a function mapping concrete + syntax tree nodes to abstract syntax tree nodes. If not + given, no conversion is done and the syntax tree produced is + the concrete syntax tree. If given, it must be a function of + two arguments, the first being the grammar (a grammar.Grammar + instance), and the second being the concrete syntax tree node + to be converted. The syntax tree is converted from the bottom + up. + + A concrete syntax tree node is a (type, value, context, nodes) + tuple, where type is the node type (a token or symbol number), + value is None for symbols and a string for tokens, context is + None or an opaque value used for error reporting (typically a + (lineno, offset) pair), and nodes is a list of children for + symbols, and None for tokens. + + An abstract syntax tree node may be anything; this is entirely + up to the converter function. + + """ + self.grammar = grammar + self.convert = convert or (lambda grammar, node: node) + + def setup(self, start=None): + """Prepare for parsing. + + This *must* be called before starting to parse. + + The optional argument is an alternative start symbol; it + defaults to the grammar's start symbol. + + You can use a Parser instance to parse any number of programs; + each time you call setup() the parser is reset to an initial + state determined by the (implicit or explicit) start symbol. + + """ + if start is None: + start = self.grammar.start + # Each stack entry is a tuple: (dfa, state, node). + # A node is a tuple: (type, value, context, children), + # where children is a list of nodes or None, and context may be None. + newnode = (start, None, None, []) + stackentry = (self.grammar.dfas[start], 0, newnode) + self.stack = [stackentry] + self.rootnode = None + self.used_names = set() # Aliased to self.rootnode.used_names in pop() + + def addtoken(self, type, value, context): + """Add a token; return True iff this is the end of the program.""" + # Map from token to label + ilabel = self.classify(type, value, context) + # Loop until the token is shifted; may raise exceptions + while True: + dfa, state, node = self.stack[-1] + states, first = dfa + arcs = states[state] + # Look for a state with this label + for i, newstate in arcs: + t, v = self.grammar.labels[i] + if ilabel == i: + # Look it up in the list of labels + assert t < 256 + # Shift a token; we're done with it + self.shift(type, value, newstate, context) + # Pop while we are in an accept-only state + state = newstate + while states[state] == [(0, state)]: + self.pop() + if not self.stack: + # Done parsing! + return True + dfa, state, node = self.stack[-1] + states, first = dfa + # Done with this token + return False + elif t >= 256: + # See if it's a symbol and if we're in its first set + itsdfa = self.grammar.dfas[t] + itsstates, itsfirst = itsdfa + if ilabel in itsfirst: + # Push a symbol + self.push(t, self.grammar.dfas[t], newstate, context) + break # To continue the outer while loop + else: + if (0, state) in arcs: + # An accepting state, pop it and try something else + self.pop() + if not self.stack: + # Done parsing, but another token is input + raise ParseError("too much input", + type, value, context) + else: + # No success finding a transition + raise ParseError("bad input", type, value, context) + + def classify(self, type, value, context): + """Turn a token into a label. (Internal)""" + if type == token.NAME: + # Keep a listing of all used names + self.used_names.add(value) + # Check for reserved words + ilabel = self.grammar.keywords.get(value) + if ilabel is not None: + return ilabel + ilabel = self.grammar.tokens.get(type) + if ilabel is None: + raise ParseError("bad token", type, value, context) + return ilabel + + def shift(self, type, value, newstate, context): + """Shift a token. (Internal)""" + dfa, state, node = self.stack[-1] + newnode = (type, value, context, None) + newnode = self.convert(self.grammar, newnode) + if newnode is not None: + node[-1].append(newnode) + self.stack[-1] = (dfa, newstate, node) + + def push(self, type, newdfa, newstate, context): + """Push a nonterminal. (Internal)""" + dfa, state, node = self.stack[-1] + newnode = (type, None, context, []) + self.stack[-1] = (dfa, newstate, node) + self.stack.append((newdfa, 0, newnode)) + + def pop(self): + """Pop a nonterminal. (Internal)""" + popdfa, popstate, popnode = self.stack.pop() + newnode = self.convert(self.grammar, popnode) + if newnode is not None: + if self.stack: + dfa, state, node = self.stack[-1] + node[-1].append(newnode) + else: + self.rootnode = newnode + self.rootnode.used_names = self.used_names |