模擬實現strlen、strcpy、strncpy、strcat、strcmp

int my_strlen(const char* str)
{
     assert(str);

     int count = 0;
     while (*str++)
     {
          count++;
     }
     return count;
}


char* my_strspy(char* dst, const char* src)
{
     assert(dst);
     assert(src);

     char* ret = dst;
     while (*dst++ = *src++);

     return ret;
}


char* my_strncpy(char* dst, const char* src, int n)
{
     assert(dst);
     assert(src);

     char* ret = dst;
     while (n--)
     {
          *dst++ = *src++;
     }

     if (*(dst-1) != '\0')
     {
          *dst = '\0';
     }

     return ret;
}


int my_strcmp(char* str1, char* str2)
{
     assert(str1);
     assert(str2);

     while (*str1 == *str2)
     {
          if (*str1 == '\0' || *str2 == '\0')
          {
              return 0;
          }
          str1++;
          str2++;
     }
     return *str1 - *str2;
}

char* my_strcat(char* dst, const char* src)
{
     assert(dst);
     assert(src);
     char* ret = dst;
     while (*dst)
     {
          *dst++;
     }
     while (*dst++ = *src++);
     return ret;
}