C中字符串转整数

int htoi(char s[])  
{  
    int i;  
    int n = 0;  
    if (s[0] == '0' && (s[1]=='x' || s[1]=='X'))  
    {  
        i = 2;  
    }  
    else  
    {  
        i = 0;  
    }  
    for (; (s[i] >= '0' && s[i] <= '9') || (s[i] >= 'a' && s[i] <= 'z') || (s[i] >='A' && s[i] <= 'Z');++i)  
    {  
        if (tolower(s[i]) > '9')  
        {  
            n = 16 * n + (10 + tolower(s[i]) - 'a');  
        }  
        else  
        {  
            n = 16 * n + (tolower(s[i]) - '0');  
        }  
    }  
    return n;  
}


char a[]="01E0";

 int b=(htoi("01")<<8 | htoi("E0"));  

int c=  htoi("E0");   

b=(htoi("01")<<8) + (htoi("E0"));   

b=htoi("01E0");