Rob*_*t K 152
TinyURL不会散列任何东西,它使用Base 36整数(甚至是62,使用小写和大写字母)来指示要访问的记录.
基数36到整数:
intval($str, 36);
基数为36的整数:
base_convert($val, 10, 36);
那么,而不是重定向到像/url/1234这样的路线/url/ax.这比散列更多地使用,因为不会发生冲突.通过这种方式,您可以轻松检查是否存在URL并在基础36中返回正确的现有ID,而无需用户知道它已在数据库中.
不要哈希,使用其他基础来做这种事情.(速度更快,可以防碰撞.)
Kev*_*sJr 78
我写了一个小lib来从整数生成混淆的哈希.
http://web.archive.org/web/20130727034425/http://blog.kevburnsjr.com/php-unique-hash
$ids = range(1,10);
foreach($ids as $id) {
echo PseudoCrypt::unhash($id) . "\n";
}m8z2p 8hy5e uqx83 gzwas 38vdh phug6 bqtiv xzslk k8ro9 6hqqy
2015年7月14日:添加下面的实际代码,因为它很难找到:
<?php
/**
* PseudoCrypt by KevBurns (http://blog.kevburnsjr.com/php-unique-hash)
* Reference/source: http://stackoverflow.com/a/1464155/933782
*
* I want a short alphanumeric hash that’s unique and who’s sequence is difficult to deduce.
* I could run it out to md5 and trim the first n chars but that’s not going to be very unique.
* Storing a truncated checksum in a unique field means that the frequency of collisions will increase
* geometrically as the number of unique keys for a base 62 encoded integer approaches 62^n.
* I’d rather do it right than code myself a timebomb. So I came up with this.
*
* Sample Code:
*
* echo "<pre>";
* foreach(range(1, 10) as $n) {
* echo $n." - ";
* $hash = PseudoCrypt::hash($n, 6);
* echo $hash." - ";
* echo PseudoCrypt::unhash($hash)."<br/>";
* }
*
* Sample Results:
* 1 - cJinsP - 1
* 2 - EdRbko - 2
* 3 - qxAPdD - 3
* 4 - TGtDVc - 4
* 5 - 5ac1O1 - 5
* 6 - huKpGQ - 6
* 7 - KE3d8p - 7
* 8 - wXmR1E - 8
* 9 - YrVEtd - 9
* 10 - BBE2m2 - 10
*/
class PseudoCrypt {
/* Key: Next prime greater than 62 ^ n / 1.618033988749894848 */
/* Value: modular multiplicative inverse */
private static $golden_primes = array(
'1' => '1',
'41' => '59',
'2377' => '1677',
'147299' => '187507',
'9132313' => '5952585',
'566201239' => '643566407',
'35104476161' => '22071637057',
'2176477521929' => '294289236153',
'134941606358731' => '88879354792675',
'8366379594239857' => '7275288500431249',
'518715534842869223' => '280042546585394647'
);
/* Ascii : 0 9, A Z, a z */
/* $chars = array_merge(range(48,57), range(65,90), range(97,122)) */
private static $chars62 = array(
0=>48,1=>49,2=>50,3=>51,4=>52,5=>53,6=>54,7=>55,8=>56,9=>57,10=>65,
11=>66,12=>67,13=>68,14=>69,15=>70,16=>71,17=>72,18=>73,19=>74,20=>75,
21=>76,22=>77,23=>78,24=>79,25=>80,26=>81,27=>82,28=>83,29=>84,30=>85,
31=>86,32=>87,33=>88,34=>89,35=>90,36=>97,37=>98,38=>99,39=>100,40=>101,
41=>102,42=>103,43=>104,44=>105,45=>106,46=>107,47=>108,48=>109,49=>110,
50=>111,51=>112,52=>113,53=>114,54=>115,55=>116,56=>117,57=>118,58=>119,
59=>120,60=>121,61=>122
);
public static function base62($int) {
$key = "";
while(bccomp($int, 0) > 0) {
$mod = bcmod($int, 62);
$key .= chr(self::$chars62[$mod]);
$int = bcdiv($int, 62);
}
return strrev($key);
}
public static function hash($num, $len = 5) {
$ceil = bcpow(62, $len);
$primes = array_keys(self::$golden_primes);
$prime = $primes[$len];
$dec = bcmod(bcmul($num, $prime), $ceil);
$hash = self::base62($dec);
return str_pad($hash, $len, "0", STR_PAD_LEFT);
}
public static function unbase62($key) {
$int = 0;
foreach(str_split(strrev($key)) as $i => $char) {
$dec = array_search(ord($char), self::$chars62);
$int = bcadd(bcmul($dec, bcpow(62, $i)), $int);
}
return $int;
}
public static function unhash($hash) {
$len = strlen($hash);
$ceil = bcpow(62, $len);
$mmiprimes = array_values(self::$golden_primes);
$mmi = $mmiprimes[$len];
$num = self::unbase62($hash);
$dec = bcmod(bcmul($num, $mmi), $ceil);
return $dec;
}
}
Gum*_*mbo 44
URL缩短服务而是使用自动递增的整数值(如补充数据库ID),并使用Base64或其他编码对其进行编码,以便每个字符具有更多信息(64而不是仅仅10个相似的数字).
Naz*_*riy 17
最短的哈希值是32个字符长度,你怎么能使用md5哈希的前8个字符
echo substr(md5('http://www.google.com'), 0, 8);
更新:这里有另一个类在这里写的特拉维尔帕金斯这需要记录号码并为它创建短哈希.14位数字产生8位数字符串.到达这个数字的那一天,你变得比tinyurl更受欢迎;)
class BaseIntEncoder {
//const $codeset = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
//readable character set excluded (0,O,1,l)
const codeset = "23456789abcdefghijkmnopqrstuvwxyzABCDEFGHIJKLMNPQRSTUVWXYZ";
static function encode($n){
$base = strlen(self::codeset);
$converted = '';
while ($n > 0) {
$converted = substr(self::codeset, bcmod($n,$base), 1) . $converted;
$n = self::bcFloor(bcdiv($n, $base));
}
return $converted ;
}
static function decode($code){
$base = strlen(self::codeset);
$c = '0';
for ($i = strlen($code); $i; $i--) {
$c = bcadd($c,bcmul(strpos(self::codeset, substr($code, (-1 * ( $i - strlen($code) )),1))
,bcpow($base,$i-1)));
}
return bcmul($c, 1, 0);
}
static private function bcFloor($x)
{
return bcmul($x, '1', 0);
}
static private function bcCeil($x)
{
$floor = bcFloor($x);
return bcadd($floor, ceil(bcsub($x, $floor)));
}
static private function bcRound($x)
{
$floor = bcFloor($x);
return bcadd($floor, round(bcsub($x, $floor)));
}
}
这是如何使用它的示例:
BaseIntEncoder::encode('1122344523');//result:3IcjVE
BaseIntEncoder::decode('3IcjVE');//result:1122344523
对于简短的哈希，url 友好，鉴于不允许可能的重复内容，我们可以使用hash()特别是CRC或Adler-32类型，因为它们正是为此而制作的：
循环冗余校验
循环冗余校验 (CRC) 是一种错误检测代码，常用于数字网络和存储设备中，用于检测原始数据的意外更改。根据其内容的多项式除法的余数，进入这些系统的数据块会附加一个简短的检查值。检索时，重复计算，如果检查值不匹配，可以采取纠正措施 https://en.wikipedia.org/wiki/Cyclic_redundancy_check
Adler-32是一种校验和算法（...），与相同长度的循环冗余校验相比，它以可靠性换取速度（更喜欢后者） https://en.wikipedia.org/wiki/Adler-32
echo hash("crc32", "Content of article...");
// Output fd3e7c6e
echo hash("adler32", "Content of article...");
// Output 55df075f