AppPkg/Applications/Python/Python-2.7.2/Lib/lib2to3/pgen2/grammar.py

   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
   6 These are a bit arcane because they are derived from the data
   7 structures used by Python's 'pgen' parser generator.
   8
   9 There's also a table here mapping operators to their names in the
  10 token module; the Python tokenize module reports all operators as the
  11 fallback token code OP, but the parser needs the actual token code.
  12
  13 """
  14
  15 # Python imports
  16 import pickle
  17
  18 # Local imports
  19 from . import token, tokenize
  20
  21
  22 class Grammar(object):
  23     """Pgen parsing tables tables conversion class.
  24
  25     Once initialized, this class supplies the grammar tables for the
  26     parsing engine implemented by parse.py.  The parsing engine
  27     accesses the instance variables directly.  The class here does not
  28     provide initialization of the tables; several subclasses exist to
  29     do this (see the conv and pgen modules).
  30
  31     The load() method reads the tables from a pickle file, which is
  32     much faster than the other ways offered by subclasses.  The pickle
  33     file is written by calling dump() (after loading the grammar
  34     tables using a subclass).  The report() method prints a readable
  35     representation of the tables to stdout, for debugging.
  36
  37     The instance variables are as follows:
  38
  39     symbol2number -- a dict mapping symbol names to numbers.  Symbol
  40                      numbers are always 256 or higher, to distinguish
  41                      them from token numbers, which are between 0 and
  42                      255 (inclusive).
  43
  44     number2symbol -- a dict mapping numbers to symbol names;
  45                      these two are each other's inverse.
  46
  47     states        -- a list of DFAs, where each DFA is a list of
  48                      states, each state is is a list of arcs, and each
  49                      arc is a (i, j) pair where i is a label and j is
  50                      a state number.  The DFA number is the index into
  51                      this list.  (This name is slightly confusing.)
  52                      Final states are represented by a special arc of
  53                      the form (0, j) where j is its own state number.
  54
  55     dfas          -- a dict mapping symbol numbers to (DFA, first)
  56                      pairs, where DFA is an item from the states list
  57                      above, and first is a set of tokens that can
  58                      begin this grammar rule (represented by a dict
  59                      whose values are always 1).
  60
  61     labels        -- a list of (x, y) pairs where x is either a token
  62                      number or a symbol number, and y is either None
  63                      or a string; the strings are keywords.  The label
  64                      number is the index in this list; label numbers
  65                      are used to mark state transitions (arcs) in the
  66                      DFAs.
  67
  68     start         -- the number of the grammar's start symbol.
  69
  70     keywords      -- a dict mapping keyword strings to arc labels.
  71
  72     tokens        -- a dict mapping token numbers to arc labels.
  73
  74     """
  75
  76     def __init__(self):
  77         self.symbol2number = {}
  78         self.number2symbol = {}
  79         self.states = []
  80         self.dfas = {}
  81         self.labels = [(0, "EMPTY")]
  82         self.keywords = {}
  83         self.tokens = {}
  84         self.symbol2label = {}
  85         self.start = 256
  86
  87     def dump(self, filename):
  88         """Dump the grammar tables to a pickle file."""
  89         f = open(filename, "wb")
  90         pickle.dump(self.__dict__, f, 2)
  91         f.close()
  92
  93     def load(self, filename):
  94         """Load the grammar tables from a pickle file."""
  95         f = open(filename, "rb")
  96         d = pickle.load(f)
  97         f.close()
  98         self.__dict__.update(d)
  99
 100     def copy(self):
 101         """
 102         Copy the grammar.
 103         """
 104         new = self.__class__()
 105         for dict_attr in ("symbol2number", "number2symbol", "dfas", "keywords",
 106                           "tokens", "symbol2label"):
 107             setattr(new, dict_attr, getattr(self, dict_attr).copy())
 108         new.labels = self.labels[:]
 109         new.states = self.states[:]
 110         new.start = self.start
 111         return new
 112
 113     def report(self):
 114         """Dump the grammar tables to standard output, for debugging."""
 115         from pprint import pprint
 116         print "s2n"
 117         pprint(self.symbol2number)
 118         print "n2s"
 119         pprint(self.number2symbol)
 120         print "states"
 121         pprint(self.states)
 122         print "dfas"
 123         pprint(self.dfas)
 124         print "labels"
 125         pprint(self.labels)
 126         print "start", self.start
 127
 128
 129 # Map from operator to number (since tokenize doesn't do this)
 130
 131 opmap_raw = """
 132 ( LPAR
 133 ) RPAR
 134 [ LSQB
 135 ] RSQB
 136 : COLON
 137 , COMMA
 138 ; SEMI
 139 + PLUS
 140 - MINUS
 141 * STAR
 142 / SLASH
 143 | VBAR
 144 & AMPER
 145 < LESS
 146 > GREATER
 147 = EQUAL
 148 . DOT
 149 % PERCENT
 150 ` BACKQUOTE
 151 { LBRACE
 152 } RBRACE
 153 @ AT
 154 == EQEQUAL
 155 != NOTEQUAL
 156 <> NOTEQUAL
 157 <= LESSEQUAL
 158 >= GREATEREQUAL
 159 ~ TILDE
 160 ^ CIRCUMFLEX
 161 << LEFTSHIFT
 162 >> RIGHTSHIFT
 163 ** DOUBLESTAR
 164 += PLUSEQUAL
 165 -= MINEQUAL
 166 *= STAREQUAL
 167 /= SLASHEQUAL
 168 %= PERCENTEQUAL
 169 &= AMPEREQUAL
 170 |= VBAREQUAL
 171 ^= CIRCUMFLEXEQUAL
 172 <<= LEFTSHIFTEQUAL
 173 >>= RIGHTSHIFTEQUAL
 174 **= DOUBLESTAREQUAL
 175 // DOUBLESLASH
 176 //= DOUBLESLASHEQUAL
 177 -> RARROW
 178 """
 179
 180 opmap = {}
 181 for line in opmap_raw.splitlines():
 182     if line:
 183         op, name = line.split()
 184         opmap[op] = getattr(token, name)