cmk/utils/regex.py

   1 #!/usr/bin/python
   2 # -*- encoding: utf-8; py-indent-offset: 4 -*-
   3 # +------------------------------------------------------------------+
   4 # |             ____ _               _        __  __ _  __           |
   5 # |            / ___| |__   ___  ___| | __   |  \/  | |/ /           |
   6 # |           | |   | '_ \ / _ \/ __| |/ /   | |\/| | ' /            |
   7 # |           | |___| | | |  __/ (__|   <    | |  | | . \            |
   8 # |            \____|_| |_|\___|\___|_|\_\___|_|  |_|_|\_\           |
   9 # |                                                                  |
  10 # | Copyright Mathias Kettner 2016             mk@mathias-kettner.de |
  11 # +------------------------------------------------------------------+
  12 #
  13 # This file is part of Check_MK.
  14 # The official homepage is at http://mathias-kettner.de/check_mk.
  15 #
  16 # check_mk is free software;  you can redistribute it and/or modify it
  17 # under the  terms of the  GNU General Public License  as published by
  18 # the Free Software Foundation in version 2.  check_mk is  distributed
  19 # in the hope that it will be useful, but WITHOUT ANY WARRANTY;  with-
  20 # out even the implied warranty of  MERCHANTABILITY  or  FITNESS FOR A
  21 # PARTICULAR PURPOSE. See the  GNU General Public License for more de-
  22 # tails. You should have  received  a copy of the  GNU  General Public
  23 # License along with GNU Make; see the file  COPYING.  If  not,  write
  24 # to the Free Software Foundation, Inc., 51 Franklin St,  Fifth Floor,
  25 # Boston, MA 02110-1301 USA.
  26 """This module wraps some regex handling functions used by Check_MK"""
  27
  28 import re
  29 from typing import Dict, Pattern  # pylint:disable=unused-import
  30
  31 from cmk.utils.exceptions import MKGeneralException
  32 from cmk.utils.i18n import _
  33
  34 g_compiled_regexes = {}  # type: Dict[str, Pattern]
  35
  36
  37 def regex(pattern):
  38     """Compile regex or look it up in already compiled regexes.
  39     (compiling is a CPU consuming process. We cache compiled regexes)."""
  40     try:
  41         return g_compiled_regexes[pattern]
  42     except KeyError:
  43         pass
  44
  45     try:
  46         reg = re.compile(pattern)
  47     except Exception as e:
  48         raise MKGeneralException(_("Invalid regular expression '%s': %s") % (pattern, e))
  49
  50     g_compiled_regexes[pattern] = reg
  51     return reg
  52
  53
  54 # Checks if a string contains characters that make it neccessary
  55 # to use regular expression logic to handle it correctly
  56 def is_regex(pattern):
  57     for c in pattern:
  58         if c in '.?*+^$|[](){}\\':
  59             return True
  60     return False
  61
  62
  63 def escape_regex_chars(match):
  64     r = ""
  65     for c in match:
  66         if c in r"[]\().?{}|*^$+":
  67             r += "\\"
  68         r += c
  69     return r