# Copyright 2004-2005 Elemental Security, Inc. All Rights Reserved.

# Licensed to PSF under a Contributor Agreement.

"""Convert graminit.[ch] spit out by pgen to Python code.

Pgen is the Python parser generator.  It is useful to quickly create a

parser from a grammar file in Python's grammar notation.  But I don't

want my parsers to be written in C (yet), so I'm translating the

parsing tables to Python data structures and writing a Python parse

engine.

Note that the token numbers are constants determined by the standard

Python tokenizer.  The standard token module defines these numbers and

their names (the names are not used much).  The token numbers are

hardcoded into the Python tokenizer and into pgen.  A Python

implementation of the Python tokenizer is also available, in the

standard tokenize module.

On the other hand, symbol numbers (representing the grammar's

non-terminals) are assigned by pgen based on the actual grammar

input.

Note: this module is pretty much obsolete; the pgen module generates

equivalent grammar tables directly from the Grammar.txt input file

without having to invoke the Python pgen C program.

"""

# Python imports

import re

# Local imports

from pgen2 import grammar, token

class Converter(grammar.Grammar):

    """Grammar subclass that reads classic pgen output files.

    The run() method reads the tables as produced by the pgen parser

    generator, typically contained in two C files, graminit.h and

    graminit.c.  The other methods are for internal use only.

    See the base class for more documentation.

    """

    def run(self, graminit_h, graminit_c):

        """Load the grammar tables from the text files written by pgen."""

        self.parse_graminit_h(graminit_h)

        self.parse_graminit_c(graminit_c)

        self.finish_off()

    def parse_graminit_h(self, filename):

        """Parse the .h file writen by pgen.  (Internal)

        This file is a sequence of #define statements defining the

        nonterminals of the grammar as numbers.  We build two tables

        mapping the numbers to names and back.

        """

        try:

            f = open(filename)

        except IOError, err:

            print "Can't open %s: %s" % (filename, err)

            return False

        self.symbol2number = {}

        self.number2symbol = {}

        lineno = 0

        for line in f:

            lineno += 1

            mo = re.match(r"^#define\s+(\w+)\s+(\d+)$", line)

            if not mo and line.strip():

                print "%s(%s): can't parse %s" % (filename, lineno,

                                                  line.strip())

            else:

                symbol, number = mo.groups()

                number = int(number)

                assert symbol not in self.symbol2number

                assert number not in self.number2symbol

                self.symbol2number[symbol] = number

                self.number2symbol[number] = symbol

        return True

    def parse_graminit_c(self, filename):

        """Parse the .c file writen by pgen.  (Internal)

        The file looks as follows.  The first two lines are always this:

        #include "pgenheaders.h"

        #include "grammar.h"

        After that come four blocks:

        1) one or more state definitions

        2) a table defining dfas

        3) a table defining labels

        4) a struct defining the grammar

        A state definition has the following form:

        - one or more arc arrays, each of the form:

          static arc arcs_<n>_<m>[<k>] = {

                  {<i>, <j>},

                  ...

          };

        - followed by a state array, of the form:

          static state states_<s>[<t>] = {

                  {<k>, arcs_<n>_<m>},

                  ...

          };

        """

        try:

            f = open(filename)

        except IOError, err:

            print "Can't open %s: %s" % (filename, err)

            return False

        # The code below essentially uses f's iterator-ness!

        lineno = 0

        # Expect the two #include lines

        lineno, line = lineno+1, f.next()

        assert line == '#include "pgenheaders.h"\n', (lineno, line)

        lineno, line = lineno+1, f.next()

        assert line == '#include "grammar.h"\n', (lineno, line)

        # Parse the state definitions

        lineno, line = lineno+1, f.next()

        allarcs = {}

        states = []

        while line.startswith("static arc "):

            while line.startswith("static arc "):

                mo = re.match(r"static arc arcs_(\d+)_(\d+)\[(\d+)\] = {$",

                              line)

                assert mo, (lineno, line)

                n, m, k = map(int, mo.groups())

                arcs = []

                for _ in range(k):

                    lineno, line = lineno+1, f.next()

                    mo = re.match(r"\s+{(\d+), (\d+)},$", line)

                    assert mo, (lineno, line)

                    i, j = map(int, mo.groups())

                    arcs.append((i, j))

                lineno, line = lineno+1, f.next()

                assert line == "};\n", (lineno, line)

                allarcs[(n, m)] = arcs

                lineno, line = lineno+1, f.next()

            mo = re.match(r"static state states_(\d+)\[(\d+)\] = {$", line)

            assert mo, (lineno, line)

            s, t = map(int, mo.groups())

            assert s == len(states), (lineno, line)

            state = []

            for _ in range(t):

                lineno, line = lineno+1, f.next()

                mo = re.match(r"\s+{(\d+), arcs_(\d+)_(\d+)},$", line)

                assert mo, (lineno, line)

                k, n, m = map(int, mo.groups())

                arcs = allarcs[n, m]

                assert k == len(arcs), (lineno, line)

                state.append(arcs)

            states.append(state)

            lineno, line = lineno+1, f.next()

            assert line == "};\n", (lineno, line)

            lineno, line = lineno+1, f.next()

        self.states = states

        # Parse the dfas

        dfas = {}

        mo = re.match(r"static dfa dfas\[(\d+)\] = {$", line)

        assert mo, (lineno, line)

        ndfas = int(mo.group(1))

        for i in range(ndfas):

            lineno, line = lineno+1, f.next()

            mo = re.match(r'\s+{(\d+), "(\w+)", (\d+), (\d+), states_(\d+),$',

                          line)

            assert mo, (lineno, line)

            symbol = mo.group(2)

            number, x, y, z = map(int, mo.group(1, 3, 4, 5))

            assert self.symbol2number[symbol] == number, (lineno, line)

            assert self.number2symbol[number] == symbol, (lineno, line)

            assert x == 0, (lineno, line)

            state = states[z]

            assert y == len(state), (lineno, line)

            lineno, line = lineno+1, f.next()

            mo = re.match(r'\s+("(?:\\\d\d\d)*")},$', line)

            assert mo, (lineno, line)

            first = {}

            rawbitset = eval(mo.group(1))

            for i, c in enumerate(rawbitset):

                byte = ord(c)

                for j in range(8):

                    if byte & (1<<j):

                        first[i*8 + j] = 1

            dfas[number] = (state, first)

        lineno, line = lineno+1, f.next()

        assert line == "};\n", (lineno, line)

        self.dfas = dfas

        # Parse the labels

        labels = []

        lineno, line = lineno+1, f.next()

        mo = re.match(r"static label labels\[(\d+)\] = {$", line)

        assert mo, (lineno, line)

        nlabels = int(mo.group(1))

        for i in range(nlabels):

            lineno, line = lineno+1, f.next()

            mo = re.match(r'\s+{(\d+), (0|"\w+")},$', line)

            assert mo, (lineno, line)

            x, y = mo.groups()

            x = int(x)

            if y == "0":

                y = None

            else:

                y = eval(y)

            labels.append((x, y))

        lineno, line = lineno+1, f.next()

        assert line == "};\n", (lineno, line)

        self.labels = labels

        # Parse the grammar struct

        lineno, line = lineno+1, f.next()

        assert line == "grammar _PyParser_Grammar = {\n", (lineno, line)

        lineno, line = lineno+1, f.next()

        mo = re.match(r"\s+(\d+),$", line)

        assert mo, (lineno, line)

        ndfas = int(mo.group(1))

        assert ndfas == len(self.dfas)

        lineno, line = lineno+1, f.next()

        assert line == "\tdfas,\n", (lineno, line)

        lineno, line = lineno+1, f.next()

        mo = re.match(r"\s+{(\d+), labels},$", line)

        assert mo, (lineno, line)

        nlabels = int(mo.group(1))

        assert nlabels == len(self.labels), (lineno, line)

        lineno, line = lineno+1, f.next()

        mo = re.match(r"\s+(\d+)$", line)

        assert mo, (lineno, line)

        start = int(mo.group(1))

        assert start in self.number2symbol, (lineno, line)

        self.start = start

        lineno, line = lineno+1, f.next()

        assert line == "};\n", (lineno, line)

        try:

            lineno, line = lineno+1, f.next()

        except StopIteration:

            pass

        else:

            assert 0, (lineno, line)

    def finish_off(self):

        """Create additional useful structures.  (Internal)."""

        self.keywords = {} # map from keyword strings to arc labels

        self.tokens = {}   # map from numeric token values to arc labels

        for ilabel, (type, value) in enumerate(self.labels):

            if type == token.NAME and value is not None:

                self.keywords[value] = ilabel

            elif value is None:

                self.tokens[type] = ilabel