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1# Copyright 2004-2005 Elemental Security, Inc. All Rights Reserved.
2# Licensed to PSF under a Contributor Agreement.
3
4"""This module defines the data structures used to represent a grammar.
5
6These are a bit arcane because they are derived from the data
7structures used by Python's 'pgen' parser generator.
8
9There's also a table here mapping operators to their names in the
10token module; the Python tokenize module reports all operators as the
11fallback token code OP, but the parser needs the actual token code.
12
13"""
14
15# Python imports
16import os
17import pickle
18import tempfile
19from typing import Any, Dict, List, Optional, Tuple, TypeVar, Union
20
21# Local imports
22from . import token
23
24_P = TypeVar("_P", bound="Grammar")
25Label = Tuple[int, Optional[str]]
26DFA = List[List[Tuple[int, int]]]
27DFAS = Tuple[DFA, Dict[int, int]]
28Path = Union[str, "os.PathLike[str]"]
29
30
31class Grammar:
32 """Pgen parsing tables conversion class.
33
34 Once initialized, this class supplies the grammar tables for the
35 parsing engine implemented by parse.py. The parsing engine
36 accesses the instance variables directly. The class here does not
37 provide initialization of the tables; several subclasses exist to
38 do this (see the conv and pgen modules).
39
40 The load() method reads the tables from a pickle file, which is
41 much faster than the other ways offered by subclasses. The pickle
42 file is written by calling dump() (after loading the grammar
43 tables using a subclass). The report() method prints a readable
44 representation of the tables to stdout, for debugging.
45
46 The instance variables are as follows:
47
48 symbol2number -- a dict mapping symbol names to numbers. Symbol
49 numbers are always 256 or higher, to distinguish
50 them from token numbers, which are between 0 and
51 255 (inclusive).
52
53 number2symbol -- a dict mapping numbers to symbol names;
54 these two are each other's inverse.
55
56 states -- a list of DFAs, where each DFA is a list of
57 states, each state is a list of arcs, and each
58 arc is a (i, j) pair where i is a label and j is
59 a state number. The DFA number is the index into
60 this list. (This name is slightly confusing.)
61 Final states are represented by a special arc of
62 the form (0, j) where j is its own state number.
63
64 dfas -- a dict mapping symbol numbers to (DFA, first)
65 pairs, where DFA is an item from the states list
66 above, and first is a set of tokens that can
67 begin this grammar rule (represented by a dict
68 whose values are always 1).
69
70 labels -- a list of (x, y) pairs where x is either a token
71 number or a symbol number, and y is either None
72 or a string; the strings are keywords. The label
73 number is the index in this list; label numbers
74 are used to mark state transitions (arcs) in the
75 DFAs.
76
77 start -- the number of the grammar's start symbol.
78
79 keywords -- a dict mapping keyword strings to arc labels.
80
81 tokens -- a dict mapping token numbers to arc labels.
82
83 """
84
85 def __init__(self) -> None:
86 self.symbol2number: Dict[str, int] = {}
87 self.number2symbol: Dict[int, str] = {}
88 self.states: List[DFA] = []
89 self.dfas: Dict[int, DFAS] = {}
90 self.labels: List[Label] = [(0, "EMPTY")]
91 self.keywords: Dict[str, int] = {}
92 self.soft_keywords: Dict[str, int] = {}
93 self.tokens: Dict[int, int] = {}
94 self.symbol2label: Dict[str, int] = {}
95 self.version: Tuple[int, int] = (0, 0)
96 self.start = 256
97 # Python 3.7+ parses async as a keyword, not an identifier
98 self.async_keywords = False
99
100 def dump(self, filename: Path) -> None:
101 """Dump the grammar tables to a pickle file."""
102
103 # mypyc generates objects that don't have a __dict__, but they
104 # do have __getstate__ methods that will return an equivalent
105 # dictionary
106 if hasattr(self, "__dict__"):
107 d = self.__dict__
108 else:
109 d = self.__getstate__() # type: ignore
110
111 with tempfile.NamedTemporaryFile(
112 dir=os.path.dirname(filename), delete=False
113 ) as f:
114 pickle.dump(d, f, pickle.HIGHEST_PROTOCOL)
115 os.replace(f.name, filename)
116
117 def _update(self, attrs: Dict[str, Any]) -> None:
118 for k, v in attrs.items():
119 setattr(self, k, v)
120
121 def load(self, filename: Path) -> None:
122 """Load the grammar tables from a pickle file."""
123 with open(filename, "rb") as f:
124 d = pickle.load(f)
125 self._update(d)
126
127 def loads(self, pkl: bytes) -> None:
128 """Load the grammar tables from a pickle bytes object."""
129 self._update(pickle.loads(pkl))
130
131 def copy(self: _P) -> _P:
132 """
133 Copy the grammar.
134 """
135 new = self.__class__()
136 for dict_attr in (
137 "symbol2number",
138 "number2symbol",
139 "dfas",
140 "keywords",
141 "soft_keywords",
142 "tokens",
143 "symbol2label",
144 ):
145 setattr(new, dict_attr, getattr(self, dict_attr).copy())
146 new.labels = self.labels[:]
147 new.states = self.states[:]
148 new.start = self.start
149 new.version = self.version
150 new.async_keywords = self.async_keywords
151 return new
152
153 def report(self) -> None:
154 """Dump the grammar tables to standard output, for debugging."""
155 from pprint import pprint
156
157 print("s2n")
158 pprint(self.symbol2number)
159 print("n2s")
160 pprint(self.number2symbol)
161 print("states")
162 pprint(self.states)
163 print("dfas")
164 pprint(self.dfas)
165 print("labels")
166 pprint(self.labels)
167 print("start", self.start)
168
169
170# Map from operator to number (since tokenize doesn't do this)
171
172opmap_raw = """
173( LPAR
174) RPAR
175[ LSQB
176] RSQB
177: COLON
178, COMMA
179; SEMI
180+ PLUS
181- MINUS
182* STAR
183/ SLASH
184| VBAR
185& AMPER
186< LESS
187> GREATER
188= EQUAL
189. DOT
190% PERCENT
191` BACKQUOTE
192{ LBRACE
193} RBRACE
194@ AT
195@= ATEQUAL
196== EQEQUAL
197!= NOTEQUAL
198<> NOTEQUAL
199<= LESSEQUAL
200>= GREATEREQUAL
201~ TILDE
202^ CIRCUMFLEX
203<< LEFTSHIFT
204>> RIGHTSHIFT
205** DOUBLESTAR
206+= PLUSEQUAL
207-= MINEQUAL
208*= STAREQUAL
209/= SLASHEQUAL
210%= PERCENTEQUAL
211&= AMPEREQUAL
212|= VBAREQUAL
213^= CIRCUMFLEXEQUAL
214<<= LEFTSHIFTEQUAL
215>>= RIGHTSHIFTEQUAL
216**= DOUBLESTAREQUAL
217// DOUBLESLASH
218//= DOUBLESLASHEQUAL
219-> RARROW
220:= COLONEQUAL
221"""
222
223opmap = {}
224for line in opmap_raw.splitlines():
225 if line:
226 op, name = line.split()
227 opmap[op] = getattr(token, name)