整数左移一位相当于将该数乘以2。编写一个函数

unsigned power2( unsigned number, unsigned pow )
{
    unsigned c=1;
    unsigned bitmask = 1<<31;    
    while(c<31)        //溢出判断
    {
        if( number&bitmask ) break;        //查找最高位的1
        c++;
        bitmask>>=1;
    }
    if(pow<c)
        return number<<pow;
    else
    {
        cout<<"overflow!\n";
        return 0;
    }
}