字符串转换成整形值

字符串转换成整形值，能够考虑的异常因素有很多。编写代码之前设计测试用例很有帮助。

enum STATUS{STRNULL=0, STREMPTY, STRINVALID, STROVERFLOW, STRVALID};
enum SIGN{NEGATIVE=0, POSITIVE};
enum STATUS status = STRVALID;
enum SIGN sign = POSITIVE;
int str2int(const char *str)
{
    long long num = 0;

    if (str == NULL)
    {
        status = STRNULL;

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

    if (*str == '-' || *str == '+')
    {    
        if (*str == '-')
        {
            sign = NEGATIVE;
        }
        if ( *(str+1) == '')
        {
            status = STREMPTY;

            return 0; 
        }

        str++;
    }
    else if (*str == '')
    {
        status = STREMPTY;

        return 0; 
    }
    else
    {
        while(*str != '')
        {
            if (*str >= '0' && *str <= '9')
            {
                num = num * 10 + *str - '0';

                if (num > 0x80000000)
                {
                    status = STROVERFLOW;

                    return 0; 
                }
            }
            else
            {
                status = STRINVALID;

                return 0; 
            }

            str++;
        }

    }
    
    if (sign == NEGATIVE)
    {
        num = -num;
    }

    return (int)num;

}

int main(int argc, char** argv)
{
        char *pString = "   -2147483648";
    
        int num = str2int(pString);

    switch (status)
    {
    case STRVALID:
        {
            cout << num << endl;
        }
        break;
    case STREMPTY:
        {
            cout << "Empty str" << endl;
        }
        break;
    case STRNULL:
        {
            cout << "NULL str" << endl;
        }
        break;
    case STROVERFLOW:
        {
            cout << "Overflow str" << endl;
        }
        break;
    default:
        {
            cout << "NONE digit str" << endl;
        }
    }
    
    system("pause");

    return 0;
}