将Hex Char转换为Int - 有更好的方法吗？

Question

我编写了一个函数来从Sirit IDentity MaX AVI读取器中获取数据并解析出设施代码和密钥卡号.我目前如何做到这一点,但有更好的方法吗？似乎有点hackish ...... buff&buf的大小是264

buf并且buff是char

从读者收到的数据:

2009/12/30 14:56:18 epc0 LN:001 C80507A0008A19FA 0000232F Xlat'd

char TAccessReader::HexCharToInt(char n)
{
    if (n >= '0' && n <= '9')
        return (n-'0');
    else

    if (n >= 'A' && n <= 'F')
        return (n-'A'+10);
    else
        return 0;
}

bool TAccessReader::CheckSirit(char *buf, long *key_num, unsigned char *fac) {

   unsigned short i, j, k;

   *key_num = 0; // Default is zero
   memset(buff, 0, sizeof(buff));

   i = sscanf(buf, "%s %s %s %s %s %s %s", &buff[0], &buff[20], &buff[40],
              &buff[60], &buff[80], &buff[140], &buff[160]);
   if (i == 7 && buff[147] && !buff[148]) {
       // UUGGNNNN UU=spare, GG=Facility Code, NNNN=Keycard Number (all HEX)

       // get facility code

       *fac = HexCharToInt(buff[142]) * 16 + HexCharToInt(buff[143]);
       *key_num = (unsigned short)HexCharToInt(buff[144]) * 4096 +
                  (unsigned short)HexCharToInt(buff[145]) * 256 +
                  (unsigned short)HexCharToInt(buff[146]) * 16 +
                  HexCharToInt(buff[147]);
   }
   // do some basic checks.. return true or false
}

Answer 1

只需使用std::stringstream:

#include <sstream>
#include <iostream>

using namespace std;

int main() {
    unsigned int x;   
    stringstream ss;
    ss << hex << "ff";
    ss >> x;
    // output it as a signed type
    cout << static_cast<int>(x) << endl;
}

您也可以strtol直接使用C:

#include <cstdlib>
#include <iostream>

using namespace std;

int main() {
    string s = "ff";
    char *p;
    long n = strtol(s.c_str(), &p, 16);
    if (*p != 0) {
        cout << "fail" << endl;
    }
    else {
        cout << n << endl;
    }
}