微博短链接算法php版本实现代码_php实例

思路： 1)将长网址md5生成32位签名串,分为4段, 每段8个字节; 2)对这四段循环处理, 取8个字节, 将他看成16进制串与0x3fffffff(30位1)与操作, 即超过30位的忽略处理; 3)这30位分成6段, 每5位的数字作为字母表的索引取得特定字符, 依次进行获得6位字符串; 4)总的md5串可以获得4个6位串; 取里面的任意一个就可作为这个长url的短url地址; 下面是PHP代码: 复制代码 代码如下: function shorturl($url='', $prefix='', $suffix='') { $base = array ( 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z', '0', '1', '2', '3', '4', '5'); $hex = md5($prefix.$url.$suffix); $hexLen = strlen($hex); $subHexLen = $hexLen / 8; $output = array(); for ($i = 0; $i $subHex = substr ($hex, $i * 8, 8); $int = 0x3FFFFFFF & (1 * ('0x'.$subHex)); $out = ''; for ($j = 0; $j $val = 0x0000001F & $int; $out .= $base[$val]; $int = $int >> 5; } $output[] = $out; } return $output; } $urls = shorturl('http://www.jb51.net/'); var_dump($urls); 结果 复制代码 代码如下: array(4) { [0]=> string(6) "alms1l" [1]=> string(6) "2ipmby" [2]=> string(6) "avo1hu" [3]=> string(6) "fdlban" } 另外一个版本： 复制代码 代码如下: function shorturl($url='', $prefix='', $suffix='') { $base = array( "a","b","c","d","e","f","g","h", "i","j","k","l","m","n","o","p", "q","r","s","t","u","v","w","x", "y","z","0","1","2","3","4","5", "6","7","8","9","A","B","C","D", "E","F","G","H","I","J","K","L", "M","N","O","P","Q","R","S","T", "U","V","W","X","Y","Z"); $hex = md5($prefix.$url.$suffix); $hexLen = strlen($hex); $subHexLen = $hexLen / 8; $output = array(); for ($i = 0; $i $subHex = substr ($hex, $i * 8, 8); $int = 0x3FFFFFFF & (1 * ('0x'.$subHex)); $out = ''; for ($j = 0; $j $val = 0x0000003D & $int; $out .= $base[$val]; $int = $int >> 5; } $output[] = $out; } return $output; } 结果： 复制代码 代码如下: array(4) { [0] => string(6) "6jmMVj" [1] => string(6) "2EnIby" [2] => string(6) "6vIVfu" [3] => string(6) "B7Fb6n" } 但是升级版本碰撞率反而更高了，不知道为什么。 测试碰撞的测试代码： 复制代码 代码如下: $result = array(); $repeats= array(); $loop = 20000; for($i=0;$i$url = 'http://www.jb51.net/?id='.$i; $shorta = shorturl($url); $short = $shorta[0]; if(in_array($short, $result)){ $repeats[] = $short; } $result[] = $short; } $result = array(); for($i=0;$i$url = 'http://www.jb51.net/?id='.$i; $shorta = shorturl($url); $short = $shorta[0]; if(in_array($short, $repeats)){ $result[$short][] = $url; } } var_dump($repeats); var_dump($result); 结果： 复制代码 代码如下: array(8) { [0] => string(6) "3eQBzq" [1] => string(6) "uQFnay" [2] => string(6) "qEZbIv" [3] => string(6) "fMneYf" [4] => string(6) "FJj6Fr" [5] => string(6) "3Eviym" [6] => string(6) "j2mmuy" [7] => string(6) "jyQfIv" } array(8) { 'jyQfIv' => array(2) { [0] => string(26) "http://www.jb51.net/?id=1640" [1] => string(27) "http://www.jb51.net/?id=18661" } 'fMneYf' => array(2) { [0] => string(26) "http://www.jb51.net/?id=2072" [1] => string(26) "http://www.jb51.net/?id=8480" } '3eQBzq' => array(2) { [0] => string(26) "http://www.jb51.net/?id=4145" [1] => string(26) "http://www.jb51.net/?id=4273" } 'j2mmuy' => array(2) { [0] => string(26) "http://www.jb51.net/?id=7131" [1] => string(27) "http://www.jb51.net/?id=17898" } 'qEZbIv' => array(2) { [0] => string(26) "http://www.jb51.net/?id=7320" [1] => string(26) "http://www.jb51.net/?id=8134" } 'uQFnay' => array(2) { [0] => string(26) "http://www.jb51.net/?id=7347" [1] => string(26) "http://www.jb51.net/?id=7962" } 'FJj6Fr' => array(2) { [0] => string(26) "http://www.jb51.net/?id=8628" [1] => string(26) "http://www.jb51.net/?id=9031" } '3Eviym' => array(2) { [0] => string(27) "http://www.jb51.net/?id=11175" [1] => string(27) "http://www.jb51.net/?id=14437" } }