src/crc16.c

   1 #include "redis.h"
   2
   3 /*
   4  * Copyright 2001-2010 Georges Menie (www.menie.org)
   5  * Copyright 2010 Salvatore Sanfilippo (adapted to Redis coding style)
   6  * All rights reserved.
   7  * Redistribution and use in source and binary forms, with or without
   8  * modification, are permitted provided that the following conditions are met:
   9  *
  10  *     * Redistributions of source code must retain the above copyright
  11  *       notice, this list of conditions and the following disclaimer.
  12  *     * Redistributions in binary form must reproduce the above copyright
  13  *       notice, this list of conditions and the following disclaimer in the
  14  *       documentation and/or other materials provided with the distribution.
  15  *     * Neither the name of the University of California, Berkeley nor the
  16  *       names of its contributors may be used to endorse or promote products
  17  *       derived from this software without specific prior written permission.
  18  *
  19  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND ANY
  20  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
  21  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
  22  * DISCLAIMED. IN NO EVENT SHALL THE REGENTS AND CONTRIBUTORS BE LIABLE FOR ANY
  23  * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
  24  * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  25  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
  26  * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  27  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
  28  * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  29  */
  30
  31 /* CRC16 implementation acording to CCITT standards.
  32  *
  33  * Note by @antirez: this is actually the XMODEM CRC 16 algorithm, using the
  34  * following parameters:
  35  *
  36  * Name                       : "XMODEM", also known as "ZMODEM", "CRC-16/ACORN"
  37  * Width                      : 16 bit
  38  * Poly                       : 1021 (That is actually x^16 + x^12 + x^5 + 1)
  39  * Initialization             : 0000
  40  * Reflect Input byte         : False
  41  * Reflect Output CRC         : False
  42  * Xor constant to output CRC : 0000
  43  * Output for "123456789"     : 31C3
  44  */
  45
  46 static const uint16_t crc16tab[256]= {
  47     0x0000,0x1021,0x2042,0x3063,0x4084,0x50a5,0x60c6,0x70e7,
  48     0x8108,0x9129,0xa14a,0xb16b,0xc18c,0xd1ad,0xe1ce,0xf1ef,
  49     0x1231,0x0210,0x3273,0x2252,0x52b5,0x4294,0x72f7,0x62d6,
  50     0x9339,0x8318,0xb37b,0xa35a,0xd3bd,0xc39c,0xf3ff,0xe3de,
  51     0x2462,0x3443,0x0420,0x1401,0x64e6,0x74c7,0x44a4,0x5485,
  52     0xa56a,0xb54b,0x8528,0x9509,0xe5ee,0xf5cf,0xc5ac,0xd58d,
  53     0x3653,0x2672,0x1611,0x0630,0x76d7,0x66f6,0x5695,0x46b4,
  54     0xb75b,0xa77a,0x9719,0x8738,0xf7df,0xe7fe,0xd79d,0xc7bc,
  55     0x48c4,0x58e5,0x6886,0x78a7,0x0840,0x1861,0x2802,0x3823,
  56     0xc9cc,0xd9ed,0xe98e,0xf9af,0x8948,0x9969,0xa90a,0xb92b,
  57     0x5af5,0x4ad4,0x7ab7,0x6a96,0x1a71,0x0a50,0x3a33,0x2a12,
  58     0xdbfd,0xcbdc,0xfbbf,0xeb9e,0x9b79,0x8b58,0xbb3b,0xab1a,
  59     0x6ca6,0x7c87,0x4ce4,0x5cc5,0x2c22,0x3c03,0x0c60,0x1c41,
  60     0xedae,0xfd8f,0xcdec,0xddcd,0xad2a,0xbd0b,0x8d68,0x9d49,
  61     0x7e97,0x6eb6,0x5ed5,0x4ef4,0x3e13,0x2e32,0x1e51,0x0e70,
  62     0xff9f,0xefbe,0xdfdd,0xcffc,0xbf1b,0xaf3a,0x9f59,0x8f78,
  63     0x9188,0x81a9,0xb1ca,0xa1eb,0xd10c,0xc12d,0xf14e,0xe16f,
  64     0x1080,0x00a1,0x30c2,0x20e3,0x5004,0x4025,0x7046,0x6067,
  65     0x83b9,0x9398,0xa3fb,0xb3da,0xc33d,0xd31c,0xe37f,0xf35e,
  66     0x02b1,0x1290,0x22f3,0x32d2,0x4235,0x5214,0x6277,0x7256,
  67     0xb5ea,0xa5cb,0x95a8,0x8589,0xf56e,0xe54f,0xd52c,0xc50d,
  68     0x34e2,0x24c3,0x14a0,0x0481,0x7466,0x6447,0x5424,0x4405,
  69     0xa7db,0xb7fa,0x8799,0x97b8,0xe75f,0xf77e,0xc71d,0xd73c,
  70     0x26d3,0x36f2,0x0691,0x16b0,0x6657,0x7676,0x4615,0x5634,
  71     0xd94c,0xc96d,0xf90e,0xe92f,0x99c8,0x89e9,0xb98a,0xa9ab,
  72     0x5844,0x4865,0x7806,0x6827,0x18c0,0x08e1,0x3882,0x28a3,
  73     0xcb7d,0xdb5c,0xeb3f,0xfb1e,0x8bf9,0x9bd8,0xabbb,0xbb9a,
  74     0x4a75,0x5a54,0x6a37,0x7a16,0x0af1,0x1ad0,0x2ab3,0x3a92,
  75     0xfd2e,0xed0f,0xdd6c,0xcd4d,0xbdaa,0xad8b,0x9de8,0x8dc9,
  76     0x7c26,0x6c07,0x5c64,0x4c45,0x3ca2,0x2c83,0x1ce0,0x0cc1,
  77     0xef1f,0xff3e,0xcf5d,0xdf7c,0xaf9b,0xbfba,0x8fd9,0x9ff8,
  78     0x6e17,0x7e36,0x4e55,0x5e74,0x2e93,0x3eb2,0x0ed1,0x1ef0
  79 };
  80
  81 uint16_t crc16(const char *buf, int len) {
  82     int counter;
  83     uint16_t crc = 0;
  84     for (counter = 0; counter < len; counter++)
  85             crc = (crc<<8) ^ crc16tab[((crc>>8) ^ *buf++)&0x00FF];
  86     return crc;
  87 }