wsutil/crc6.c

   1 /*
   2  *  crc6.c
   3  *
   4  * Wireshark - Network traffic analyzer
   5  * By Gerald Combs <gerald@wireshark.org>
   6  * Copyright 1998 Gerald Combs
   7  *
   8  * SPDX-License-Identifier: GPL-2.0-or-later
   9  */
  10
  11 /*
  12    Patch by Ross Jacobs <rossbjacobs@gmail.com>:
  13       Fixed CRC6 0x6F lookup table + function per Wireshark bug 14875
  14 */
  15
  16 #include "config.h"
  17
  18 #include "crc6.h"
  19
  20 /**
  21  * Functions and types for CRC checks.
  22  *
  23  * Generated on Wed Jan 2 2019,
  24  * by pycrc v0.9.1, http://www.tty1.net/pycrc/
  25  * using the configuration:
  26  *    Width        = 6
  27  *    Poly         = 0x6f
  28  *    XorIn        = 0
  29  *    ReflectIn    = False
  30  *    XorOut       = 0
  31  *    ReflectOut   = False
  32  */
  33 static const uint8_t crc6_table[256] = {
  34         0x00, 0x2f, 0x31, 0x1e, 0x0d, 0x22, 0x3c, 0x13, 0x1a, 0x35, 0x2b, 0x04, 0x17, 0x38, 0x26, 0x09,
  35         0x34, 0x1b, 0x05, 0x2a, 0x39, 0x16, 0x08, 0x27, 0x2e, 0x01, 0x1f, 0x30, 0x23, 0x0c, 0x12, 0x3d,
  36         0x07, 0x28, 0x36, 0x19, 0x0a, 0x25, 0x3b, 0x14, 0x1d, 0x32, 0x2c, 0x03, 0x10, 0x3f, 0x21, 0x0e,
  37         0x33, 0x1c, 0x02, 0x2d, 0x3e, 0x11, 0x0f, 0x20, 0x29, 0x06, 0x18, 0x37, 0x24, 0x0b, 0x15, 0x3a,
  38         0x0e, 0x21, 0x3f, 0x10, 0x03, 0x2c, 0x32, 0x1d, 0x14, 0x3b, 0x25, 0x0a, 0x19, 0x36, 0x28, 0x07,
  39         0x3a, 0x15, 0x0b, 0x24, 0x37, 0x18, 0x06, 0x29, 0x20, 0x0f, 0x11, 0x3e, 0x2d, 0x02, 0x1c, 0x33,
  40         0x09, 0x26, 0x38, 0x17, 0x04, 0x2b, 0x35, 0x1a, 0x13, 0x3c, 0x22, 0x0d, 0x1e, 0x31, 0x2f, 0x00,
  41         0x3d, 0x12, 0x0c, 0x23, 0x30, 0x1f, 0x01, 0x2e, 0x27, 0x08, 0x16, 0x39, 0x2a, 0x05, 0x1b, 0x34,
  42         0x1c, 0x33, 0x2d, 0x02, 0x11, 0x3e, 0x20, 0x0f, 0x06, 0x29, 0x37, 0x18, 0x0b, 0x24, 0x3a, 0x15,
  43         0x28, 0x07, 0x19, 0x36, 0x25, 0x0a, 0x14, 0x3b, 0x32, 0x1d, 0x03, 0x2c, 0x3f, 0x10, 0x0e, 0x21,
  44         0x1b, 0x34, 0x2a, 0x05, 0x16, 0x39, 0x27, 0x08, 0x01, 0x2e, 0x30, 0x1f, 0x0c, 0x23, 0x3d, 0x12,
  45         0x2f, 0x00, 0x1e, 0x31, 0x22, 0x0d, 0x13, 0x3c, 0x35, 0x1a, 0x04, 0x2b, 0x38, 0x17, 0x09, 0x26,
  46         0x12, 0x3d, 0x23, 0x0c, 0x1f, 0x30, 0x2e, 0x01, 0x08, 0x27, 0x39, 0x16, 0x05, 0x2a, 0x34, 0x1b,
  47         0x26, 0x09, 0x17, 0x38, 0x2b, 0x04, 0x1a, 0x35, 0x3c, 0x13, 0x0d, 0x22, 0x31, 0x1e, 0x00, 0x2f,
  48         0x15, 0x3a, 0x24, 0x0b, 0x18, 0x37, 0x29, 0x06, 0x0f, 0x20, 0x3e, 0x11, 0x02, 0x2d, 0x33, 0x1c,
  49         0x21, 0x0e, 0x10, 0x3f, 0x2c, 0x03, 0x1d, 0x32, 0x3b, 0x14, 0x0a, 0x25, 0x36, 0x19, 0x07, 0x28
  50 };
  51
  52 /**
  53  * CRC6 is used by 3GPP (TS 25.415, TS 25.446) for header CRCs
  54  * Poly: D^6 + D^5 + D^3 + D^2 + D^1 + 1
  55  *
  56  * TS 25.415 docs: https://www.etsi.org/deliver/etsi_ts/125400_125499/125415/04.06.00_60/ts_125415v040600p.pdf
  57  * TS 25.446 docs: https://www.etsi.org/deliver/etsi_ts/125400_125499/125446/10.01.00_60/ts_125446v100100p.pdf
  58 */
  59 uint16_t crc6_0X6F(uint16_t crc, const uint8_t *data, int data_len)
  60 {
  61     uint8_t tbl_idx;
  62
  63     while (data_len--) {
  64         tbl_idx = (crc << 2) ^ *data;
  65         crc = crc6_table[tbl_idx] & 0x3f;
  66         data++;
  67     }
  68     return crc & 0x3f;
  69 }
  70
  71 /*
  72  * Editor modelines  -  https://www.wireshark.org/tools/modelines.html
  73  *
  74  * Local variables:
  75  * c-basic-offset: 4
  76  * tab-width: 8
  77  * indent-tabs-mode: nil
  78  * End:
  79  *
  80  * vi: set shiftwidth=4 tabstop=8 expandtab:
  81  * :indentSize=4:tabSize=8:noTabs=true:
  82  */