CRC16 CCITT / 16位CRC检验算法的C语言实现

crc16-ccitt

CRC16 CCITT / 16位CRC检验算法的C语言实现

crc16_sansi.c

#include "crc16_sansi.h"

uint16_t gen_crc16_ref(const uint8_t *buffer, long buffer_length) {
  unsigned char c = 0;
  unsigned char treat = 0;
  unsigned char bcrc = 0;
  uint16_t wcrc = 0;

  for (int i = 0; i < buffer_length; i++) {
    c = buffer[i];

    for (int j = 0; j < 8; j++) {
      treat = c & 0x80;
      c <<= 1;
      bcrc = (wcrc >> 8) & 0x80;
      wcrc <<= 1;
      if (treat != bcrc)
        wcrc ^= 0x1021;
    }
  }

  return wcrc;
}

// https://github.com/antirez/redis/blob/3.2.6/src/crc16.c

/*
 * Copyright 2001-2010 Georges Menie (www.menie.org)
 * Copyright 2010-2012 Salvatore Sanfilippo (adapted to Redis coding style)
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 *     * Redistributions of source code must retain the above copyright
 *       notice, this list of conditions and the following disclaimer.
 *     * Redistributions in binary form must reproduce the above copyright
 *       notice, this list of conditions and the following disclaimer in the
 *       documentation and/or other materials provided with the distribution.
 *     * Neither the name of the University of California, Berkeley nor the
 *       names of its contributors may be used to endorse or promote products
 *       derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND ANY
 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL THE REGENTS AND CONTRIBUTORS BE LIABLE FOR ANY
 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

/* CRC16 implementation according to CCITT standards.
 *
 * Note by @antirez: this is actually the XMODEM CRC 16 algorithm, using the
 * following parameters:
 *
 * Name                       : "XMODEM", also known as "ZMODEM", "CRC-16/ACORN"
 * Width                      : 16 bit
 * Poly                       : 1021 (That is actually x^16 + x^12 + x^5 + 1)
 * Initialization             : 0000
 * Reflect Input byte         : False
 * Reflect Output CRC         : False
 * Xor constant to output CRC : 0000
 * Output for "123456789"     : 31C3
 */

static const uint16_t crc16tab[256] = {
    0x0000, 0x1021, 0x2042, 0x3063, 0x4084, 0x50a5, 0x60c6, 0x70e7, 0x8108,
    0x9129, 0xa14a, 0xb16b, 0xc18c, 0xd1ad, 0xe1ce, 0xf1ef, 0x1231, 0x0210,
    0x3273, 0x2252, 0x52b5, 0x4294, 0x72f7, 0x62d6, 0x9339, 0x8318, 0xb37b,
    0xa35a, 0xd3bd, 0xc39c, 0xf3ff, 0xe3de, 0x2462, 0x3443, 0x0420, 0x1401,
    0x64e6, 0x74c7, 0x44a4, 0x5485, 0xa56a, 0xb54b, 0x8528, 0x9509, 0xe5ee,
    0xf5cf, 0xc5ac, 0xd58d, 0x3653, 0x2672, 0x1611, 0x0630, 0x76d7, 0x66f6,
    0x5695, 0x46b4, 0xb75b, 0xa77a, 0x9719, 0x8738, 0xf7df, 0xe7fe, 0xd79d,
    0xc7bc, 0x48c4, 0x58e5, 0x6886, 0x78a7, 0x0840, 0x1861, 0x2802, 0x3823,
    0xc9cc, 0xd9ed, 0xe98e, 0xf9af, 0x8948, 0x9969, 0xa90a, 0xb92b, 0x5af5,
    0x4ad4, 0x7ab7, 0x6a96, 0x1a71, 0x0a50, 0x3a33, 0x2a12, 0xdbfd, 0xcbdc,
    0xfbbf, 0xeb9e, 0x9b79, 0x8b58, 0xbb3b, 0xab1a, 0x6ca6, 0x7c87, 0x4ce4,
    0x5cc5, 0x2c22, 0x3c03, 0x0c60, 0x1c41, 0xedae, 0xfd8f, 0xcdec, 0xddcd,
    0xad2a, 0xbd0b, 0x8d68, 0x9d49, 0x7e97, 0x6eb6, 0x5ed5, 0x4ef4, 0x3e13,
    0x2e32, 0x1e51, 0x0e70, 0xff9f, 0xefbe, 0xdfdd, 0xcffc, 0xbf1b, 0xaf3a,
    0x9f59, 0x8f78, 0x9188, 0x81a9, 0xb1ca, 0xa1eb, 0xd10c, 0xc12d, 0xf14e,
    0xe16f, 0x1080, 0x00a1, 0x30c2, 0x20e3, 0x5004, 0x4025, 0x7046, 0x6067,
    0x83b9, 0x9398, 0xa3fb, 0xb3da, 0xc33d, 0xd31c, 0xe37f, 0xf35e, 0x02b1,
    0x1290, 0x22f3, 0x32d2, 0x4235, 0x5214, 0x6277, 0x7256, 0xb5ea, 0xa5cb,
    0x95a8, 0x8589, 0xf56e, 0xe54f, 0xd52c, 0xc50d, 0x34e2, 0x24c3, 0x14a0,
    0x0481, 0x7466, 0x6447, 0x5424, 0x4405, 0xa7db, 0xb7fa, 0x8799, 0x97b8,
    0xe75f, 0xf77e, 0xc71d, 0xd73c, 0x26d3, 0x36f2, 0x0691, 0x16b0, 0x6657,
    0x7676, 0x4615, 0x5634, 0xd94c, 0xc96d, 0xf90e, 0xe92f, 0x99c8, 0x89e9,
    0xb98a, 0xa9ab, 0x5844, 0x4865, 0x7806, 0x6827, 0x18c0, 0x08e1, 0x3882,
    0x28a3, 0xcb7d, 0xdb5c, 0xeb3f, 0xfb1e, 0x8bf9, 0x9bd8, 0xabbb, 0xbb9a,
    0x4a75, 0x5a54, 0x6a37, 0x7a16, 0x0af1, 0x1ad0, 0x2ab3, 0x3a92, 0xfd2e,
    0xed0f, 0xdd6c, 0xcd4d, 0xbdaa, 0xad8b, 0x9de8, 0x8dc9, 0x7c26, 0x6c07,
    0x5c64, 0x4c45, 0x3ca2, 0x2c83, 0x1ce0, 0x0cc1, 0xef1f, 0xff3e, 0xcf5d,
    0xdf7c, 0xaf9b, 0xbfba, 0x8fd9, 0x9ff8, 0x6e17, 0x7e36, 0x4e55, 0x5e74,
    0x2e93, 0x3eb2, 0x0ed1, 0x1ef0};

uint16_t gen_crc16_redis(const uint8_t *buffer, long buffer_length) {
  int counter;
  uint16_t crc = 0;
  for (counter = 0; counter < buffer_length; counter++)
    crc = (crc << 8) ^ crc16tab[((crc >> 8) ^ *buffer++) & 0x00FF];
  return crc;
}

crc16_sansi.h

#ifndef CRC16_SANSI_H
#define CRC16_SANSI_H

#include <stdint.h>

// At Sansi, we use CRC-16-CCITT for 2-byte checksums.
// Here are some implementations that have identical outputs.

// Found in previous protocol documentation.
// Readable but slow. Use this as a reference.
uint16_t gen_crc16_ref(const uint8_t *buffer, long buffer_length);

// Implementation used in Redis. Much faster than reference.
uint16_t gen_crc16_redis(const uint8_t *buffer, long buffer_length);

#endif /* CRC16_SANSI_H */

main.c

//
//  main.c
//  crc16
//
//  Created by qingpei on 29/12/2016.
//  Copyright © 2016 sansi. All rights reserved.
//

#include "crc16_sansi.h"
#include <stdio.h>
#include <stdlib.h>
#include <time.h>

int main(int argc, const char *argv[]) {
  if (argc < 2) {
    printf("Usage: crc16 filename");
  } else {
    FILE *fp;
    long lSize;
    unsigned char *buffer;

    fp = fopen(argv[1], "rb");
    if (!fp)
      perror(argv[1]), exit(1);

    fseek(fp, 0L, SEEK_END);
    lSize = ftell(fp);
    rewind(fp);

    /* allocate memory for entire content */
    buffer = calloc(1, lSize + 1);
    if (!buffer)
      fclose(fp), fputs("memory alloc fails", stderr), exit(1);

    /* copy the file into the buffer */
    if (1 != fread(buffer, lSize, 1, fp))
      fclose(fp), free(buffer), fputs("entire read fails", stderr), exit(1);

    /* do your work here, buffer is a string contains the whole text */

    clock_t start, diff;
    uint16_t crc16 = 0;
    unsigned long msec = 0;

    start = clock();

    crc16 = gen_crc16_redis(buffer, lSize);

    diff = clock() - start;

    msec = diff * 1000 / CLOCKS_PER_SEC;
    printf("%-*s:\t", 20, "gen_crc16_redis");
    printf("crc16=%hx\t", crc16);

    printf("time=%ld.%03lds\n", msec / 1000, msec % 1000);

    start = clock();

    crc16 = gen_crc16_ref(buffer, lSize);

    diff = clock() - start;

    msec = diff * 1000 / CLOCKS_PER_SEC;
    printf("%-*s:\t", 20, "gen_crc16_ref");
    printf("crc16=%hx\t", crc16);

    printf("time=%ld.%03lds\n", msec / 1000, msec % 1000);

    fclose(fp);
    free(buffer);
  }
  return 0;
}

Makefile

CC=gcc
CFLAGS=-I. -g -Wall -O3
DEPS = crc16_sansi.h
OBJ = crc16_sansi.o main.o

TARGET = crc16
TESTFILE = testfile

%.o: %.c $(DEPS)
	$(CC) -c -o $@ $< $(CFLAGS)

$(TARGET): $(OBJ)
	gcc -o $@ $^ $(CFLAGS)
	
clean:
	rm -f *.o *~ $(TARGET) $(TESTFILE)
	
test:
	# Creating a 100 MB test file with random content
	dd if=/dev/random of=$(TESTFILE) bs=1000000 count=100 &> /dev/null
	# generate crc16 for the test file
	$(TARGET) $(TESTFILE)