微博短链接算法的php实现版本

发布时间:2020-03-06编辑:脚本学堂
分享下微博短链接算法用php实现的例子,有需要的朋友参考下。

微博短链接、短网址的实现思路:
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;

例子,PHP代码:
 

复制代码 代码示例:
<?php
//短链接,短网址,短url
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 < $subHexLen; $i++) {
        $subHex = substr ($hex, $i * 8, 8);
        $int = 0x3FFFFFFF & (1 * ('0x'.$subHex));
        $out = '';
        for ($j = 0; $j < 6; $j++) {
            $val = 0x0000001F & $int;
            $out .= $base[$val];
            $int = $int >> 5;
        }
        $output[] = $out;
    }
    return $output;
}
 
$urls = shorturl('http://www.jb200.com/');
var_dump($urls);
 

结果
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 代码示例:
<?php
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 < $subHexLen; $i++) {
        $subHex = substr ($hex, $i * 8, 8);
        $int = 0x3FFFFFFF & (1 * ('0x'.$subHex));
        $out = '';
        for ($j = 0; $j < 6; $j++) {
            $val = 0x0000003D & $int;
            $out .= $base[$val];
            $int = $int >> 5;
        }
        $output[] = $out;
    }
    return $output;
}
 

结果:
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,不知道为何?

测试碰撞的代码:
 

复制代码 代码示例:
<?php
$result = array();
$repeats= array();
$loop   = 20000;
 
for($i=0;$i<$loop;$i++){
    $url = 'http://www.jb200.com/?id='.$i;
    $shorta = shorturl($url);
    $short = $shorta[0];
    if(in_array($short, $result)){
        $repeats[] = $short;
    }
    $result[] = $short;
}
 
$result = array();
for($i=0;$i<$loop;$i++){
    $url = 'http://www.jb200.com/?id='.$i;
    $shorta = shorturl($url);
    $short = $shorta[0];
    if(in_array($short, $repeats)){
        $result[$short][] = $url;
    }
}
 
var_dump($repeats);
var_dump($result);
 

结果:
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.jb200.com/?id=1640"
    [1] =>
    string(27) "http://www.jb200.com/?id=18661"
  }
  'fMneYf' =>
  array(2) {
    [0] =>
    string(26) "http://www.jb200.com/?id=2072"
    [1] =>
    string(26) "http://www.jb200.com/?id=8480"
  }
  '3eQBzq' =>
  array(2) {
    [0] =>
    string(26) "http://www.jb200.com/?id=4145"
    [1] =>
    string(26) "http://www.jb200.com/?id=4273"
  }
  'j2mmuy' =>
  array(2) {
    [0] =>
    string(26) "http://www.jb200.com/?id=7131"
    [1] =>
    string(27) "http://www.jb200.com/?id=17898"
  }
  'qEZbIv' =>
  array(2) {
    [0] =>
    string(26) "http://www.jb200.com/?id=7320"
    [1] =>
    string(26) "http://www.jb200.com/?id=8134"
  }
  'uQFnay' =>
  array(2) {
    [0] =>
    string(26) "http://www.jb200.com/?id=7347"
    [1] =>
    string(26) "http://www.jb200.com/?id=7962"
  }
  'FJj6Fr' =>
  array(2) {
    [0] =>
    string(26) "http://www.jb200.com/?id=8628"
    [1] =>
    string(26) "http://www.jb200.com/?id=9031"
  }
  '3Eviym' =>
  array(2) {
    [0] =>
    string(27) "http://www.jb200.com/?id=11175"
    [1] =>
    string(27) "http://www.jb200.com/?id=14437"
  }
}