近日，有同事说有个 5百万 的白名单处理， 到网上查找 相似案例， 说是有个bitmap的解法，

再次 google ，baidu 无相关 PHP 的解法， 于是自己写了一个：

?

<?php
/* 5百万 uid 白名单 之 PHP Bitmap 处理 
 * author: hushuilong
 * email: hushuilong at gmail dot com
 * */
class Bitmap 
{
	private $handler = NULL;
	private $max = 0;
	public function __construct($file) 
	{
		clearstatcache(true, $file);	
		if(file_exists($file))
			$this->handler = @fopen($file , 'r+') OR die('open bitmap file failed');
		else
			$this->handler = @fopen($file , 'w+') OR die('open bitmap file failed');

		$this->max = file_exists($file) ? (filesize($file) * 8 - 1) : 0;
	}
	public function __destruct() 
	{
		@fclose($this->handler);
	}
	
	private function binary_dump($binary_data)
	{
		return sprintf('%08d',decbin(hexdec(bin2hex($binary_data))));
	}
	
	private function num_check($num)
	{
		($num > -1) OR die('number must be greater than -1');
		($num < 4294967296) or die('number must be less than 4294967296'); // 2^32
		if ($this->max < $num) {
			fseek($this->handler, 0, SEEK_END);
			fwrite($this->handler , str_repeat("\x00",ceil(($num - $this->max)/8))); // fill with 0
			$this->max = ceil($num/8)*8 - 1;
		}		
	}
	
	public function set($num)
	{
		$this->num_check($num);
		fseek($this->handler, floor($num/8), SEEK_SET);
		$bin = fread($this->handler, 1) | pack('C',0x100 >> fmod($num,8)+1); // mark with 1
		
		fseek($this->handler, ftell($this->handler)-1, SEEK_SET); // write a new byte
		fwrite($this->handler, $bin); 
		fflush($this->handler);
	}
	
	public function del($num)
	{
		$this->num_check($num);
		fseek($this->handler, floor($num/8), SEEK_SET);
		$bin = fread($this->handler, 1) & ~pack('C',0x100 >> fmod($num,8)+1); // mark with 0
		
		fseek($this->handler, ftell($this->handler)-1, SEEK_SET); // write a new byte
		fwrite($this->handler, $bin); 
		fflush($this->handler);
	}	
	
	public function find($num)
	{
		if (fseek($this->handler, floor($num/8), SEEK_SET) == -1) return FALSE;
		$bin = fread($this->handler , 1);
		if ($bin === FALSE || strlen($bin) == 0) return FALSE;

		$bin = $bin & pack('C',0x100 >> fmod($num,8)+1);
		if($bin === "\x00") return FALSE;
		return TRUE;
	}
}

$b = new Bitmap('/dev/shm/bitmapdata');

// 设置白名单
$b->set(1); $b->set(3); $b->set(5);
$b->set(7); $b->set(9); $b->set(501);

$uid = 501;
var_dump($b->find($uid)); // 查找白名单

$b->del($uid); // 删除白名单
var_dump($b->find($uid)); // 查找白名单

?

其中 “$b = new Bitmap('/dev/shm/bitmapdata');”? 把文件，放在内存里，增加读写速度

执行结果如下：

hu@xunleiman-desktop:~/web/test/shm$ /bin/sh ./geany_run_script.sh
bool(true)
bool(false)

?

生成的bitmapdata文件 在附件里面：

?

?