c - 计算C中某些字符的CRC16错误

我正在尝试使用此代码来计算CRC16旁路。对于常规字符，它可以工作，但是对于像0xA0 0x00 0x01 0x01这样的十六进制序列，它会失败，并且不会返回正确的值。对我好一点，通常我不编写C代码。

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

unsigned short CalculateCRC(unsigned char* a_szBuffuer, short a_sBufferLen){
    unsigned short usCRC = 0;
    for (short j = 0; j < a_sBufferLen; j++)
    {
    unsigned char* pucPtr = (unsigned char *)&usCRC;
    *(pucPtr + 1) = *(pucPtr + 1) ^ *a_szBuffuer++;
    for (short i = 0; i <= 7; i++)
    {
    if (usCRC & ((unsigned short) 0x8000))
    {
    usCRC = usCRC << 1;
    usCRC = usCRC ^ ((unsigned short) 0x8005);
    }
    else
    usCRC = usCRC << 1;
    }
    }
    return (usCRC);
}

void append(char* s, char c)
{
        int len = strlen(s);
        s[len] = c;
        s[len+1] = '\0';
}

int main() {

   char d = (char)0xA0;
   char d1 = (char)0x00;
   char d2 = (char)0x01;
   char d3 = (char)0x01;
   char sss[256]="";

   append(sss, d);
   append(sss, d1);
   append(sss, d2);
   append(sss, d3);
   unsigned char* uCB1 = (unsigned char*)sss;
   unsigned short CRC= CalculateCRC(uCB1,4);

   printf("CRC = %i\n", CRC);
   printf("%s\n", sss);
   printf("%x\n", CRC);
}

最佳答案

strlen(s);用于查找字符串的长度，而不是查找所使用的字符数组的长度，尤其是如果它可能包含'\0'时。 @Eugene Sh.

代码需要跟踪与另一个变量一起使用的数组大小。

// void append(char* s, char c) {
void append(char* s, size_t *sz, char c) {
  s[*sz] = c;
  (*sz)++;
}

...
size_t size = 0;
append(sss, &size, d);
append(sss, &size, d1);
append(sss, &size, d2);
append(sss, &size, d3);
unsigned char* uCB1 = (unsigned char*)sss;
unsigned short CRC= CalculateCRC(uCB1, size);

// printf("%s\n", sss);
write a loop to print each `sss[]`.

关于c - 计算C中某些字符的CRC16错误，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/48266708/