iOS进制转换

//tmpid 要转化的进制数  //length 要转化的进制长度- (void)systemTmpid:(NSInteger)tmpid withLength:(int)length {    NSString *a = @"";    while (tmpid)    {        a = [[NSString stringWithFormat:@"%ld",tmpid%2] stringByAppendingString:a];        if (tmpid/2 < 1)        {            break;        }        tmpid = tmpid/2 ;    }    if (a.length <= length)    {        NSMutableString *b = [[NSMutableString alloc]init];;        for (int i = 0; i < length - a.length; i++)        {            [b appendString:@"0"];        }        a = [b stringByAppendingString:a];    }    NSLog(@"---%@",a);}