十六进制字符串转uint

uint32_t HexStr2Int(CString str)
{
    uint32_t nRet = 0;
    int nStart = 0;

    if (str.Left(2).CompareNoCase("0x") == 0)
        nStart = 2;

    for (int i = nStart; i < str.GetLength(); i++)
    {
        if (str[i] >= '0' && str[i] <= '9')
            nRet = nRet * 16 + str[i] - '0';
        else if (str[i] >= 'A' && str[i] <= 'F')
            nRet = nRet * 16 + str[i] - 'A' + 10;
        else if (str[i] >= 'a' && str[i] <= 'f')
            nRet = nRet * 16 + str[i] - 'a' + 10;
        else
        {
            AfxMessageBox("Invalid Hexadecimal Format!", MB_OK);
            return -1;
        }
    }
    return nRet;