tokenize.py

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#!/usr/bin/env python
#
# Copyright 2007 Neal Norwitz
# Portions Copyright 2007 Google Inc.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#      http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

"""Tokenize C++ source code."""

__author__ = 'nnorwitz@google.com (Neal Norwitz)'


try:
    # Python 3.x
    import builtins
except ImportError:
    # Python 2.x
    import __builtin__ as builtins


import sys

from cpp import utils


if not hasattr(builtins, 'set'):
    # Nominal support for Python 2.3.
    from sets import Set as set


# Add $ as a valid identifier char since so much code uses it.
_letters = 'abcdefghijklmnopqrstuvwxyz'
VALID_IDENTIFIER_CHARS = set(_letters + _letters.upper() + '_0123456789$')
HEX_DIGITS = set('0123456789abcdefABCDEF')
INT_OR_FLOAT_DIGITS = set('01234567890eE-+')


# C++0x string preffixes.
_STR_PREFIXES = set(('R', 'u8', 'u8R', 'u', 'uR', 'U', 'UR', 'L', 'LR'))


# Token types.
UNKNOWN = 'UNKNOWN'
SYNTAX = 'SYNTAX'
CONSTANT = 'CONSTANT'
NAME = 'NAME'
PREPROCESSOR = 'PREPROCESSOR'

# Where the token originated from.  This can be used for backtracking.
# It is always set to WHENCE_STREAM in this code.
WHENCE_STREAM, WHENCE_QUEUE = range(2)


class Token(object):
    """Data container to represent a C++ token.

    Tokens can be identifiers, syntax char(s), constants, or
    pre-processor directives.

    start contains the index of the first char of the token in the source
    end contains the index of the last char of the token in the source
    """

    def __init__(self, token_type, name, start, end):
        self.token_type = token_type
        self.name = name
        self.start = start
        self.end = end
        self.whence = WHENCE_STREAM

    def __str__(self):
        if not utils.DEBUG:
            return 'Token(%r)' % self.name
        return 'Token(%r, %s, %s)' % (self.name, self.start, self.end)

    __repr__ = __str__


def _GetString(source, start, i):
    i = source.find('"', i+1)
    while source[i-1] == '\\':
        # Count the trailing backslashes.
        backslash_count = 1
        j = i - 2
        while source[j] == '\\':
            backslash_count += 1
            j -= 1
        # When trailing backslashes are even, they escape each other.
        if (backslash_count % 2) == 0:
            break
        i = source.find('"', i+1)
    return i + 1


def _GetChar(source, start, i):
    # NOTE(nnorwitz): may not be quite correct, should be good enough.
    i = source.find("'", i+1)
    while source[i-1] == '\\':
        # Need to special case '\\'.
        if (i - 2) > start and source[i-2] == '\\':
            break
        i = source.find("'", i+1)
    # Try to handle unterminated single quotes (in a #if 0 block).
    if i < 0:
        i = start
    return i + 1


def GetTokens(source):
    """Returns a sequence of Tokens.

    Args:
      source: string of C++ source code.

    Yields:
      Token that represents the next token in the source.
    """
    # Cache various valid character sets for speed.
    valid_identifier_chars = VALID_IDENTIFIER_CHARS
    hex_digits = HEX_DIGITS
    int_or_float_digits = INT_OR_FLOAT_DIGITS
    int_or_float_digits2 = int_or_float_digits | set('.')

    # Only ignore errors while in a #if 0 block.
    ignore_errors = False
    count_ifs = 0

    i = 0
    end = len(source)
    while i < end:
        # Skip whitespace.
        while i < end and source[i].isspace():
            i += 1
        if i >= end:
            return

        token_type = UNKNOWN
        start = i
        c = source[i]
        if c.isalpha() or c == '_':              # Find a string token.
            token_type = NAME
            while source[i] in valid_identifier_chars:
                i += 1
            # String and character constants can look like a name if
            # they are something like L"".
            if (source[i] == "'" and (i - start) == 1 and
                source[start:i] in 'uUL'):
                # u, U, and L are valid C++0x character preffixes.
                token_type = CONSTANT
                i = _GetChar(source, start, i)
            elif source[i] == "'" and source[start:i] in _STR_PREFIXES:
                token_type = CONSTANT
                i = _GetString(source, start, i)
        elif c == '/' and source[i+1] == '/':    # Find // comments.
            i = source.find('\n', i)
            if i == -1:  # Handle EOF.
                i = end
            continue
        elif c == '/' and source[i+1] == '*':    # Find /* comments. */
            i = source.find('*/', i) + 2
            continue
        elif c in ':+-<>&|*=':                   # : or :: (plus other chars).
            token_type = SYNTAX
            i += 1
            new_ch = source[i]
            if new_ch == c:
                i += 1
            elif c == '-' and new_ch == '>':
                i += 1
            elif new_ch == '=':
                i += 1
        elif c in '()[]{}~!?^%;/.,':             # Handle single char tokens.
            token_type = SYNTAX
            i += 1
            if c == '.' and source[i].isdigit():
                token_type = CONSTANT
                i += 1
                while source[i] in int_or_float_digits:
                    i += 1
                # Handle float suffixes.
                for suffix in ('l', 'f'):
                    if suffix == source[i:i+1].lower():
                        i += 1
                        break
        elif c.isdigit():                        # Find integer.
            token_type = CONSTANT
            if c == '0' and source[i+1] in 'xX':
                # Handle hex digits.
                i += 2
                while source[i] in hex_digits:
                    i += 1
            else:
                while source[i] in int_or_float_digits2:
                    i += 1
            # Handle integer (and float) suffixes.
            for suffix in ('ull', 'll', 'ul', 'l', 'f', 'u'):
                size = len(suffix)
                if suffix == source[i:i+size].lower():
                    i += size
                    break
        elif c == '"':                           # Find string.
            token_type = CONSTANT
            i = _GetString(source, start, i)
        elif c == "'":                           # Find char.
            token_type = CONSTANT
            i = _GetChar(source, start, i)
        elif c == '#':                           # Find pre-processor command.
            token_type = PREPROCESSOR
            got_if = source[i:i+3] == '#if' and source[i+3:i+4].isspace()
            if got_if:
                count_ifs += 1
            elif source[i:i+6] == '#endif':
                count_ifs -= 1
                if count_ifs == 0:
                    ignore_errors = False

            # TODO(nnorwitz): handle preprocessor statements (\ continuations).
            while 1:
                i1 = source.find('\n', i)
                i2 = source.find('//', i)
                i3 = source.find('/*', i)
                i4 = source.find('"', i)
                # NOTE(nnorwitz): doesn't handle comments in #define macros.
                # Get the first important symbol (newline, comment, EOF/end).
                i = min([x for x in (i1, i2, i3, i4, end) if x != -1])

                # Handle #include "dir//foo.h" properly.
                if source[i] == '"':
                    i = source.find('"', i+1) + 1
                    assert i > 0
                    continue
                # Keep going if end of the line and the line ends with \.
                if not (i == i1 and source[i-1] == '\\'):
                    if got_if:
                        condition = source[start+4:i].lstrip()
                        if (condition.startswith('0') or
                            condition.startswith('(0)')):
                            ignore_errors = True
                    break
                i += 1
        elif c == '\\':                          # Handle \ in code.
            # This is different from the pre-processor \ handling.
            i += 1
            continue
        elif ignore_errors:
            # The tokenizer seems to be in pretty good shape.  This
            # raise is conditionally disabled so that bogus code
            # in an #if 0 block can be handled.  Since we will ignore
            # it anyways, this is probably fine.  So disable the
            # exception and  return the bogus char.
            i += 1
        else:
            sys.stderr.write('Got invalid token in %s @ %d token:%s: %r\n' %
                             ('?', i, c, source[i-10:i+10]))
            raise RuntimeError('unexpected token')

        if i <= 0:
            print('Invalid index, exiting now.')
            return
        yield Token(token_type, source[start:i], start, i)


if __name__ == '__main__':
    def main(argv):
        """Driver mostly for testing purposes."""
        for filename in argv[1:]:
            source = utils.ReadFile(filename)
            if source is None:
                continue

            for token in GetTokens(source):
                print('%-12s: %s' % (token.token_type, token.name))
                # print('\r%6.2f%%' % (100.0 * index / token.end),)
            sys.stdout.write('\n')


    main(sys.argv)