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257 lines
9.4 KiB
Python
257 lines
9.4 KiB
Python
# Copyright 2004-2005 Elemental Security, Inc. All Rights Reserved.
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# Licensed to PSF under a Contributor Agreement.
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"""Convert graminit.[ch] spit out by pgen to Python code.
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Pgen is the Python parser generator. It is useful to quickly create a
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parser from a grammar file in Python's grammar notation. But I don't
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want my parsers to be written in C (yet), so I'm translating the
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parsing tables to Python data structures and writing a Python parse
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engine.
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Note that the token numbers are constants determined by the standard
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Python tokenizer. The standard token module defines these numbers and
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their names (the names are not used much). The token numbers are
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hardcoded into the Python tokenizer and into pgen. A Python
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implementation of the Python tokenizer is also available, in the
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standard tokenize module.
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On the other hand, symbol numbers (representing the grammar's
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non-terminals) are assigned by pgen based on the actual grammar
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input.
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Note: this module is pretty much obsolete; the pgen module generates
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equivalent grammar tables directly from the Grammar.txt input file
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without having to invoke the Python pgen C program.
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"""
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# Python imports
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import re
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# Local imports
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from pgen2 import grammar, token
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class Converter(grammar.Grammar):
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"""Grammar subclass that reads classic pgen output files.
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The run() method reads the tables as produced by the pgen parser
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generator, typically contained in two C files, graminit.h and
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graminit.c. The other methods are for internal use only.
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See the base class for more documentation.
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"""
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def run(self, graminit_h, graminit_c):
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"""Load the grammar tables from the text files written by pgen."""
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self.parse_graminit_h(graminit_h)
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self.parse_graminit_c(graminit_c)
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self.finish_off()
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def parse_graminit_h(self, filename):
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"""Parse the .h file written by pgen. (Internal)
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This file is a sequence of #define statements defining the
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nonterminals of the grammar as numbers. We build two tables
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mapping the numbers to names and back.
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"""
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try:
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f = open(filename)
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except OSError as err:
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print("Can't open %s: %s" % (filename, err))
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return False
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self.symbol2number = {}
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self.number2symbol = {}
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lineno = 0
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for line in f:
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lineno += 1
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mo = re.match(r"^#define\s+(\w+)\s+(\d+)$", line)
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if not mo and line.strip():
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print("%s(%s): can't parse %s" % (filename, lineno,
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line.strip()))
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else:
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symbol, number = mo.groups()
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number = int(number)
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assert symbol not in self.symbol2number
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assert number not in self.number2symbol
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self.symbol2number[symbol] = number
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self.number2symbol[number] = symbol
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return True
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def parse_graminit_c(self, filename):
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"""Parse the .c file written by pgen. (Internal)
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The file looks as follows. The first two lines are always this:
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#include "pgenheaders.h"
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#include "grammar.h"
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After that come four blocks:
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1) one or more state definitions
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2) a table defining dfas
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3) a table defining labels
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4) a struct defining the grammar
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A state definition has the following form:
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- one or more arc arrays, each of the form:
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static arc arcs_<n>_<m>[<k>] = {
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{<i>, <j>},
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...
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};
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- followed by a state array, of the form:
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static state states_<s>[<t>] = {
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{<k>, arcs_<n>_<m>},
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...
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};
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"""
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try:
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f = open(filename)
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except OSError as err:
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print("Can't open %s: %s" % (filename, err))
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return False
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# The code below essentially uses f's iterator-ness!
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lineno = 0
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# Expect the two #include lines
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lineno, line = lineno+1, next(f)
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assert line == '#include "pgenheaders.h"\n', (lineno, line)
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lineno, line = lineno+1, next(f)
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assert line == '#include "grammar.h"\n', (lineno, line)
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# Parse the state definitions
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lineno, line = lineno+1, next(f)
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allarcs = {}
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states = []
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while line.startswith("static arc "):
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while line.startswith("static arc "):
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mo = re.match(r"static arc arcs_(\d+)_(\d+)\[(\d+)\] = {$",
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line)
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assert mo, (lineno, line)
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n, m, k = list(map(int, mo.groups()))
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arcs = []
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for _ in range(k):
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lineno, line = lineno+1, next(f)
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mo = re.match(r"\s+{(\d+), (\d+)},$", line)
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assert mo, (lineno, line)
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i, j = list(map(int, mo.groups()))
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arcs.append((i, j))
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lineno, line = lineno+1, next(f)
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assert line == "};\n", (lineno, line)
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allarcs[(n, m)] = arcs
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lineno, line = lineno+1, next(f)
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mo = re.match(r"static state states_(\d+)\[(\d+)\] = {$", line)
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assert mo, (lineno, line)
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s, t = list(map(int, mo.groups()))
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assert s == len(states), (lineno, line)
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state = []
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for _ in range(t):
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lineno, line = lineno+1, next(f)
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mo = re.match(r"\s+{(\d+), arcs_(\d+)_(\d+)},$", line)
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assert mo, (lineno, line)
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k, n, m = list(map(int, mo.groups()))
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arcs = allarcs[n, m]
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assert k == len(arcs), (lineno, line)
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state.append(arcs)
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states.append(state)
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lineno, line = lineno+1, next(f)
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assert line == "};\n", (lineno, line)
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lineno, line = lineno+1, next(f)
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self.states = states
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# Parse the dfas
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dfas = {}
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mo = re.match(r"static dfa dfas\[(\d+)\] = {$", line)
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assert mo, (lineno, line)
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ndfas = int(mo.group(1))
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for i in range(ndfas):
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lineno, line = lineno+1, next(f)
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mo = re.match(r'\s+{(\d+), "(\w+)", (\d+), (\d+), states_(\d+),$',
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line)
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assert mo, (lineno, line)
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symbol = mo.group(2)
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number, x, y, z = list(map(int, mo.group(1, 3, 4, 5)))
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assert self.symbol2number[symbol] == number, (lineno, line)
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assert self.number2symbol[number] == symbol, (lineno, line)
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assert x == 0, (lineno, line)
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state = states[z]
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assert y == len(state), (lineno, line)
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lineno, line = lineno+1, next(f)
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mo = re.match(r'\s+("(?:\\\d\d\d)*")},$', line)
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assert mo, (lineno, line)
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first = {}
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rawbitset = eval(mo.group(1))
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for i, c in enumerate(rawbitset):
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byte = ord(c)
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for j in range(8):
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if byte & (1<<j):
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first[i*8 + j] = 1
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dfas[number] = (state, first)
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lineno, line = lineno+1, next(f)
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assert line == "};\n", (lineno, line)
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self.dfas = dfas
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# Parse the labels
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labels = []
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lineno, line = lineno+1, next(f)
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mo = re.match(r"static label labels\[(\d+)\] = {$", line)
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assert mo, (lineno, line)
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nlabels = int(mo.group(1))
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for i in range(nlabels):
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lineno, line = lineno+1, next(f)
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mo = re.match(r'\s+{(\d+), (0|"\w+")},$', line)
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assert mo, (lineno, line)
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x, y = mo.groups()
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x = int(x)
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if y == "0":
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y = None
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else:
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y = eval(y)
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labels.append((x, y))
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lineno, line = lineno+1, next(f)
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assert line == "};\n", (lineno, line)
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self.labels = labels
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# Parse the grammar struct
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lineno, line = lineno+1, next(f)
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assert line == "grammar _PyParser_Grammar = {\n", (lineno, line)
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lineno, line = lineno+1, next(f)
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mo = re.match(r"\s+(\d+),$", line)
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assert mo, (lineno, line)
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ndfas = int(mo.group(1))
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assert ndfas == len(self.dfas)
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lineno, line = lineno+1, next(f)
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assert line == "\tdfas,\n", (lineno, line)
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lineno, line = lineno+1, next(f)
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mo = re.match(r"\s+{(\d+), labels},$", line)
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assert mo, (lineno, line)
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nlabels = int(mo.group(1))
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assert nlabels == len(self.labels), (lineno, line)
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lineno, line = lineno+1, next(f)
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mo = re.match(r"\s+(\d+)$", line)
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assert mo, (lineno, line)
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start = int(mo.group(1))
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assert start in self.number2symbol, (lineno, line)
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self.start = start
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lineno, line = lineno+1, next(f)
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assert line == "};\n", (lineno, line)
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try:
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lineno, line = lineno+1, next(f)
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except StopIteration:
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pass
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else:
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assert 0, (lineno, line)
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def finish_off(self):
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"""Create additional useful structures. (Internal)."""
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self.keywords = {} # map from keyword strings to arc labels
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self.tokens = {} # map from numeric token values to arc labels
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for ilabel, (type, value) in enumerate(self.labels):
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if type == token.NAME and value is not None:
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self.keywords[value] = ilabel
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elif value is None:
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self.tokens[type] = ilabel
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