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one_num = 8;
//默认32m*1
$this->space_group_num = $space_group_num;
$this->hash_space_assoc = array();
//分配空间
for($i=0; $ispace_group_num; $i++){
$this->hash_space_assoc[$i] = str_repeat($binary, $max_length);
}
$this->pow_array = array(
0 => 1,
1 => 2,
2 => 4,
3 => 8,
4 => 16,
5 => 32,
6 => 64,
7 => 128,
);
$this->chr_array = array();
$this->ord_array = array();
for($i=0; $i
$chr = chr($i);
$this->chr_array[$i] = $chr;
$this->ord_array[$chr] = $i;
}
$this->hash_func_pos = array(
0 => array(0, 7, 1),
1 => array(7, 7, 1),
2 => array(14, 7, 1),
3 => array(21, 7, 1),
4 => array(28, 7, 1),
5 => array(33, 7, 1),
6 => array(17, 7, 1),
);
$this->write_num = 0;
$this->ext_num = 0;
if(!$hash_func_num){
$this->hash_func_num = count($this->hash_func_pos);
}
else{
$this->hash_func_num = $hash_func_num;
}
}
function add($key) {
$hash_bit_set_num = 0;
// 离散key
$hash_basic = sha1($key);
// 截取前4位,然后十六进制转换为十进制
$hash_space = hexdec(substr($hash_basic, 0, 4));
// 取模
$hash_space = $hash_space % $this->space_group_num;
for($hash_i=0; $hash_ihash_func_num; $hash_i++){
$hash = hexdec(substr($hash_basic, $this->hash_func_pos[$hash_i][0], $this->hash_func_pos[$hash_i][1]));
$bit_pos = $hash >> 3;
$max = $this->ord_array[$this->hash_space_assoc[$hash_space][$bit_pos]];
$num = $hash - $bit_pos * $this->one_num;
$bit_pos_value = ($max >> $num) & 0x01;
if(!$bit_pos_value){
$max = $max | $this->pow_array[$num];
$this->hash_space_assoc[$hash_space][$bit_pos] = $this->chr_array[$max];
$this->write_num++;
}
else{
$hash_bit_set_num++;
}
}
if($hash_bit_set_num == $this->hash_func_num){
$this->ext_num++;
return true;
}
return false;
}
function get_stat() {
return array(
'ext_num' => $this->ext_num,
'write_num' => $this->write_num,
);
}
}
//test
//取6个哈希值，目前是最多7个
$hash_func_num = 6;
//分配1个存储空间，每个空间为32m，理论上是空间越大误判率越低，注意php.ini中可使用的内存限制
$space_group_num = 1;
$bf = new bloom_filter($hash_func_num, $space_group_num);
$list = array(
'http://test/1',
'http://test/2',
'http://test/3',
'http://test/4',
'http://test/5',
'http://test/6',
'http://test/1',
'http://test/2',
);
foreach($list as $k => $v){
if($bf->add($v)){
echo $v, \n;
}
}
http://www.bkjia.com/phpjc/976540.htmlwww.bkjia.comtruehttp://www.bkjia.com/phpjc/976540.htmltecharticlephp中实现bloom filter算法 这篇文章主要介绍了php中实现bloom filter算法,本文直接给出实现代码,代码中给出详细注释,bloom filter算法介绍等内容...