将字符串转换成整数

/**********************************************************************
题目：写一个函数StrToInt,实现把字符串转换成整数的功能，类似atoi函数
**********************************************************************/
#include 
#include 

long long StrToIntCore(const char* str, bool minus);

enum Status {kValid = 0, kInvalid};
int g_nStatus = kValid;

int StrToInt(const char* str)
{
    g_nStatus = kInvalid;
    long long num = 0;

    if(str != NULL && *str != '\0') 
    {
        bool minus = false;
        if(*str == '+')	//处理+号
            str ++;
        else if(*str == '-') //处理-号
        {
            str ++;
            minus = true;
        }

        if(*str != '\0') //处理+-，之后的为'\0'的情形
        {
            num = StrToIntCore(str, minus);
        }
    }

    return (int)num;
}

long long StrToIntCore(const char* digit, bool minus)
{
    long long num = 0;

    while(*digit != '\0') 
    {
        if(*digit >= '0' && *digit <= '9') 
        {
            int flag = minus ? -1 : 1;
            num = num * 10 + flag * (*digit - '0');

            if((!minus && num > 0x7FFFFFFF) //处理溢出的情况
                || (minus && num < (signed int)0x80000000))
            {
                num = 0;
                break;
            }

            digit++;
        }
        else 
        {
            num = 0;
            break;
        }
    }

    if(*digit == '\0') 
    {
        g_nStatus = kValid;
    }

    return num;
}

// ====================测试代码====================
void Test(char* string)
{
    int result = StrToInt(string);
    if(result == 0 && g_nStatus == kInvalid)
        printf("the input %s is invalid.\n", string);
    else
        printf("number for %s is: %d.\n", string, result);
}

int main()
{
    Test(NULL);

    Test("");

    Test("123");

    Test("+123");
    
    Test("-123");

    Test("1a33");

    Test("+0");

    Test("-0");

    //有效的最大正整数, 0x7FFFFFFF
    Test("+2147483647");    

    Test("-2147483647");

    Test("+2147483648");

    //有效的最小负整数, 0x80000000
    Test("-2147483648");    

    Test("+2147483649");

    Test("-2147483649");

    Test("+");

    Test("-");

    return 0;
}

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