From 079eb39eb0ebe5ea54cab54d90fbbe4e446bb8b6 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Mika=C3=ABl=20Ates?= Date: Fri, 24 May 2013 17:03:34 +0200 Subject: [PATCH] Some helper functions (crc16 module dependency). --- utils.py | 50 ++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 50 insertions(+) create mode 100644 utils.py diff --git a/utils.py b/utils.py new file mode 100644 index 0000000..3fd0ca1 --- /dev/null +++ b/utils.py @@ -0,0 +1,50 @@ +# -*- coding: utf-8 -*- +''' + librfid - RFID EPC Class 1 Gen2 / ISO/IEC 18000-6C compliant library + + Copyright (C) 2013 Entr'ouvert + + This program is free software: you can redistribute it and/or modify + it under the terms of the GNU Affero General Public License as + published by the Free Software Foundation, either version 3 of the + License, or (at your option) any later version. + + This program is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + GNU Affero General Public License for more details. + + You should have received a copy of the GNU Affero General Public License + along with this program. If not, see . + + + Helper functions +''' + + +import crc16 +from binascii import unhexlify + +from _exceptions import OverheadException + + +def get_length_on_2_bytes(string): + length = len(string) + fmt = '%%0%dx' % (16 // 4) + return unhexlify(fmt % length) + +def get_integer_on_two_bytes(integer): + if integer > 65535: + raise OverheadException('Integer to big to be converted in a string ' + 'of two bytes') + fmt = '%%0%dx' % (16 // 4) + return unhexlify(fmt % integer) + +def get_crc_16_CCITT(string): + # Polynome x16 + x12 + x5 + 1, 0x1021 + crc = crc16.crc16xmodem(string, 0xffff) + fmt = '%%0%dx' % (16 // 4) + return unhexlify(fmt % crc) + +def switch_big_to_little_indian(string): + return string[::-1]