c語言實現CRC檢驗算法

今天抽空學習了下crc的使用，現將測試代碼貼至下方，整個代碼實現如下幾個功能

1. 代碼中提供創建crc_table的函數，並且也有做好的crc_table的函數
2. 首先打開一個文件，每讀取1024字節，對這1024個字節獲取crc校驗值，然後寫到一個新文件中，然後繼續讀取下一個1024個字節
3. 然後對新的文件進行星通的crc校驗，看和之前獲取到的校驗值是不是相同的

#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<stdint.h>

#define MAKE_TABLE

#ifdef MAKE_TABLE
uint32_t crc32_table[256];
int make_crc32_table()
{
	uint32_t c;
	int i = 0;
	int bit = 0;

	for(i = 0; i < 256; i++){
		c  = (uint32_t)i;

		for(bit = 0; bit < 8; bit++){
			if(c&1){
				c = (c >> 1)^(0xEDB88320);
			}else{
				c =  c >> 1;
			}

		}
		crc32_table[i] = c;
	}
}
#else
static const unsigned int crc32_table[] = {
 0x00000000L, 0x77073096L, 0xee0e612cL, 0x990951baL,
 0x076dc419L, 0x706af48fL, 0xe963a535L, 0x9e6495a3L,
 0x0edb8832L, 0x79dcb8a4L, 0xe0d5e91eL, 0x97d2d988L,
 0x09b64c2bL, 0x7eb17cbdL, 0xe7b82d07L, 0x90bf1d91L,
 0x1db71064L, 0x6ab020f2L, 0xf3b97148L, 0x84be41deL,
 0x1adad47dL, 0x6ddde4ebL, 0xf4d4b551L, 0x83d385c7L,
 0x136c9856L, 0x646ba8c0L, 0xfd62f97aL, 0x8a65c9ecL,
 0x14015c4fL, 0x63066cd9L, 0xfa0f3d63L, 0x8d080df5L,
 0x3b6e20c8L, 0x4c69105eL, 0xd56041e4L, 0xa2677172L,
 0x3c03e4d1L, 0x4b04d447L, 0xd20d85fdL, 0xa50ab56bL,
 0x35b5a8faL, 0x42b2986cL, 0xdbbbc9d6L, 0xacbcf940L,
 0x32d86ce3L, 0x45df5c75L, 0xdcd60dcfL, 0xabd13d59L,
 0x26d930acL, 0x51de003aL, 0xc8d75180L, 0xbfd06116L,
 0x21b4f4b5L, 0x56b3c423L, 0xcfba9599L, 0xb8bda50fL,
 0x2802b89eL, 0x5f058808L, 0xc60cd9b2L, 0xb10be924L,
 0x2f6f7c87L, 0x58684c11L, 0xc1611dabL, 0xb6662d3dL,
 0x76dc4190L, 0x01db7106L, 0x98d220bcL, 0xefd5102aL,
 0x71b18589L, 0x06b6b51fL, 0x9fbfe4a5L, 0xe8b8d433L,
 0x7807c9a2L, 0x0f00f934L, 0x9609a88eL, 0xe10e9818L,
 0x7f6a0dbbL, 0x086d3d2dL, 0x91646c97L, 0xe6635c01L,
 0x6b6b51f4L, 0x1c6c6162L, 0x856530d8L, 0xf262004eL,
 0x6c0695edL, 0x1b01a57bL, 0x8208f4c1L, 0xf50fc457L,
 0x65b0d9c6L, 0x12b7e950L, 0x8bbeb8eaL, 0xfcb9887cL,
 0x62dd1ddfL, 0x15da2d49L, 0x8cd37cf3L, 0xfbd44c65L,
 0x4db26158L, 0x3ab551ceL, 0xa3bc0074L, 0xd4bb30e2L,
 0x4adfa541L, 0x3dd895d7L, 0xa4d1c46dL, 0xd3d6f4fbL,
 0x4369e96aL, 0x346ed9fcL, 0xad678846L, 0xda60b8d0L,
 0x44042d73L, 0x33031de5L, 0xaa0a4c5fL, 0xdd0d7cc9L,
 0x5005713cL, 0x270241aaL, 0xbe0b1010L, 0xc90c2086L,
 0x5768b525L, 0x206f85b3L, 0xb966d409L, 0xce61e49fL,
 0x5edef90eL, 0x29d9c998L, 0xb0d09822L, 0xc7d7a8b4L,
 0x59b33d17L, 0x2eb40d81L, 0xb7bd5c3bL, 0xc0ba6cadL,
 0xedb88320L, 0x9abfb3b6L, 0x03b6e20cL, 0x74b1d29aL,
 0xead54739L, 0x9dd277afL, 0x04db2615L, 0x73dc1683L,
 0xe3630b12L, 0x94643b84L, 0x0d6d6a3eL, 0x7a6a5aa8L,
 0xe40ecf0bL, 0x9309ff9dL, 0x0a00ae27L, 0x7d079eb1L,
 0xf00f9344L, 0x8708a3d2L, 0x1e01f268L, 0x6906c2feL,
 0xf762575dL, 0x806567cbL, 0x196c3671L, 0x6e6b06e7L,
 0xfed41b76L, 0x89d32be0L, 0x10da7a5aL, 0x67dd4accL,
 0xf9b9df6fL, 0x8ebeeff9L, 0x17b7be43L, 0x60b08ed5L,
 0xd6d6a3e8L, 0xa1d1937eL, 0x38d8c2c4L, 0x4fdff252L,
 0xd1bb67f1L, 0xa6bc5767L, 0x3fb506ddL, 0x48b2364bL,
 0xd80d2bdaL, 0xaf0a1b4cL, 0x36034af6L, 0x41047a60L,
 0xdf60efc3L, 0xa867df55L, 0x316e8eefL, 0x4669be79L,
 0xcb61b38cL, 0xbc66831aL, 0x256fd2a0L, 0x5268e236L,
 0xcc0c7795L, 0xbb0b4703L, 0x220216b9L, 0x5505262fL,
 0xc5ba3bbeL, 0xb2bd0b28L, 0x2bb45a92L, 0x5cb36a04L,
 0xc2d7ffa7L, 0xb5d0cf31L, 0x2cd99e8bL, 0x5bdeae1dL,
 0x9b64c2b0L, 0xec63f226L, 0x756aa39cL, 0x026d930aL,
 0x9c0906a9L, 0xeb0e363fL, 0x72076785L, 0x05005713L,
 0x95bf4a82L, 0xe2b87a14L, 0x7bb12baeL, 0x0cb61b38L,
 0x92d28e9bL, 0xe5d5be0dL, 0x7cdcefb7L, 0x0bdbdf21L,
 0x86d3d2d4L, 0xf1d4e242L, 0x68ddb3f8L, 0x1fda836eL,
 0x81be16cdL, 0xf6b9265bL, 0x6fb077e1L, 0x18b74777L,
 0x88085ae6L, 0xff0f6a70L, 0x66063bcaL, 0x11010b5cL,
 0x8f659effL, 0xf862ae69L, 0x616bffd3L, 0x166ccf45L,
 0xa00ae278L, 0xd70dd2eeL, 0x4e048354L, 0x3903b3c2L,
 0xa7672661L, 0xd06016f7L, 0x4969474dL, 0x3e6e77dbL,
 0xaed16a4aL, 0xd9d65adcL, 0x40df0b66L, 0x37d83bf0L,
 0xa9bcae53L, 0xdebb9ec5L, 0x47b2cf7fL, 0x30b5ffe9L,
 0xbdbdf21cL, 0xcabac28aL, 0x53b39330L, 0x24b4a3a6L,
 0xbad03605L, 0xcdd70693L, 0x54de5729L, 0x23d967bfL,
 0xb3667a2eL, 0xc4614ab8L, 0x5d681b02L, 0x2a6f2b94L,
 0xb40bbe37L, 0xc30c8ea1L, 0x5a05df1bL, 0x2d02ef8dL
};
#endif

uint32_t make_crc(unsigned char *string, uint32_t size)
{
    unsigned int crc = 0xFFFFFFFF;
	while(size--)
		crc = (crc >> 8)^(crc32_table[(crc ^ *string++)&0xff]);

	return crc^0xffffffff;
}

void compare_crc(char *filename,int crc_num)
{
	FILE *sp = NULL;
	uint32_t count, i;
	uint32_t calcuCrc[crc_num];
	uint32_t srcCrc[crc_num];
	unsigned char buf[1024];

	if(filename == NULL){
		printf("filename is null\n");
		exit(1);
	}

	sp = fopen(filename, "rb");
	if(sp == NULL){
		printf("open file fail\n");
		return;
	}

    for(i=0;i<crc_num;i++){
    	fread(&srcCrc[i], 1, 4, sp);
    }

    i=0;
    if(sp){
        while(!feof(sp)){
            memset(buf, 0, sizeof(buf));
            count = fread(buf, 1, sizeof(buf), sp);
            calcuCrc[i++] = make_crc(buf, count);
        }
    }

    for(i=0;i<crc_num;i++){
        printf("%s %d 0x%x\n",__func__,__LINE__,calcuCrc[i]);
        printf("%s %d 0x%x\n",__func__,__LINE__,srcCrc[i]);
        if(calcuCrc[i] != srcCrc[i])
            printf("crc check error\n");
    }
    printf("crc check success\n");

	fclose(sp);
}


int main()
{
	int i, crc_num = 0;
	FILE *sp = NULL;
	FILE *dp = NULL;
	uint32_t count, crc = 0xFFFFFFFF;
	unsigned char buf[1024];

#ifdef MAKE_TABLE
	make_crc32_table();
#endif

	sp = fopen("/home/zhangtao/share/sec/test.txt", "rb");
	dp = fopen("/home/zhangtao/share/sec/testcrc.txt", "wb");
	if(!dp || !sp){
		printf("open file error\n");
		return -1;
	}

	while(!feof(sp)){
		memset(buf, 0, sizeof(buf));
		count = fread(buf, 1, sizeof(buf), sp);
		crc = make_crc(buf, count);
		crc_num++;
		fwrite(&crc, 1, 4, dp);//write the crc into the file testcrc.txt
	}

	fseek(sp, 0, SEEK_SET);
	while(!feof(sp)){
		memset(buf, 0, sizeof(buf));
        count = fread(buf, 1, sizeof(buf), sp);
		fwrite(buf, 1, count, dp);
	}

	fclose(sp);
	fclose(dp);

	/*compare crc*/
	compare_crc("/home/zhangtao/share/sec/testcrc.txt",crc_num);
	return 0;
}

結果如下所示：