iOS 对两个相等长度的字符串进行异或运算

+ (NSString *)pinxCreator:(NSString *)pan withPinv:(NSString *)pinv
{
    if (pan.length != pinv.length)
    {
        return nil;
    }
    
    const char *panchar = [pan UTF8String];
    const char *pinvchar = [pinv UTF8String];
    
    
    NSString *temp = [[NSString alloc] init];

    for (int i = 0; i < pan.length; i++)
    {
        int panValue = [self charToint:panchar[i]];
        int pinvValue = [self charToint:pinvchar[i]];
        
        temp = [temp stringByAppendingString:[NSString stringWithFormat:@"%X",panValue^pinvValue]];
    }
    return temp;
    
}

+ (int)charToint:(char)tempChar
{
    if (tempChar >= ‘0‘ && tempChar <=‘9‘)
    {
        return tempChar - ‘0‘;
    }
    else if (tempChar >= ‘A‘ && tempChar <= ‘F‘)
    {
        return tempChar - ‘A‘ + 10;
    }
    
    return 0;
}