C语言编写的8位CRC校验

#define _CRT_SECURE_NO_WARNINGS #include <stdio.h> #include <Windows.h> #include <iostream> using namespace std; unsigned char crc8_chk_value(unsigned char *message, unsigned char len) { unsigned char crc; unsigned char i; crc = 0; while (len--) { crc ^= *message++; for (i = 0; i < 8; i++) { if (crc & 0x01) { crc = (crc >> 1) ^ 0x8c; } else crc >>= 1; } } return crc; } //计算一串数据的8位CRC校验码,并将CRC校验值插入到数据尾部 //参数1：数据 参数2：数据字节长度 参数3：除数(最高位与最低位必须为1) //(New,OK) char* crc(char* p_src_data,int data_len, unsigned char divisor) { char* p_new_data = nullptr; //新数据 if (data_len <= 0 || p_src_data == nullptr || (divisor & 0x81) != 0x81) goto err; //参数检查 p_new_data = new char[data_len + 2]; //为新数据分配内存,1字节为尾部插入的7位CRC校验码与0结尾字节 if (!p_new_data) goto err; ZeroMemory(p_new_data, data_len + 2); //用于计算的位数,当超出就是计算完毕了,剩下的就是CRC校验码,7为加入计算的尾部+7位, //-8代表第一次用于计算的8位 int max = ((data_len * 8) + 7) - 8; int index = 0; //用于控制当前处理的字节索引 unsigned char result = 0; //CRC校验码 //先计算一次 result = p_src_data[0] ^ divisor; result = (result << 1) | (p_src_data[((index / 8) + 1)] >> 7); index += 1; while (true) { if ((result >> 7) != 0) {//商为1 result = result ^ divisor; result = (result << 1) | ((p_src_data[(index / 8) + 1] >> (7 - index % 8)) & 0x01); index += 1; } else {//商为0 result = result ^ 0x00; result = (result << 1) | ((p_src_data[(index / 8) + 1] >> (7 - index % 8)) & 0x01); index += 1; } //结果 if (index >= max) { memcpy_s(p_new_data, data_len + 2, p_src_data, data_len); result = result ^ divisor; //插入 p_new_data[data_len] = (unsigned char)(result << 1); break; } } return p_new_data; err: if (p_new_data) { delete[]p_new_data; p_new_data = nullptr; } return nullptr; } //利用尾部的CRC校验码,验证数据完整性 //参数1：携带8位CRC校验码的数据 参数2：数据长度(包括CRC字节) 参数3：与crc函数除数一样 bool crc_integrity(char* p_data, int data_len, unsigned char divisor) { if (data_len <= 0 || p_data == nullptr || (divisor & 0x81) != 0x81) goto err; //参数检查 int max = (data_len * 8) - 1 - 8; int index = 0; //用于控制当前处理的字节索引 unsigned char result = 0; //CRC校验码 //先计算一次 result = p_data[0] ^ divisor; result = (result << 1) | (p_data[(index / 8) + 1] >> 7); index += 1; while (true) { if ((result >> 7) != 0) {//商为1 result = result ^ divisor; result = (result << 1) | ((p_data[(index / 8) + 1] >> (7 - index % 8)) & 0x01); index += 1; } else {//商为0 result = result ^ 0x00; result = (result << 1) | ((p_data[(index / 8) + 1] >> (7 - index % 8)) & 0x01); index += 1; } //结果 if (index >= max) { result = result ^ divisor; if ((result & (~0x80)) == 0) return true; else return false; } } return false; err: return false; } int main() { char value[100] = { "B1" }; char* data = crc(value, strlen(value), 0xD1); cout << endl; bool isok = crc_integrity(data, strlen(data), 0xD1); if (!isok) { DWORD err = 534; } delete[]data; return 0; //4e }