php - 帮助提高这个youtube样式url生成器的效率

Question

经过一番搜索，我发现这个带加密的youtube样式url生成器隐藏了原始id ...但是我希望提高效率，因为它会被大量使用。到目前为止，我已经将它提高了20％......任何人都可以帮我改进它。

这是原作：

function alphaID($in, $to_num = false, $pad_up = false, $passKey = null)
{
    $index = "abcdefghijklmnopqrstuvwxyz0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";
    if ($passKey !== null) {
        // Although this function's purpose is to just make the
        // ID short - and not so much secure,
        // with this patch by Simon Franz (http://blog.snaky.org/)
        // you can optionally supply a password to make it harder
        // to calculate the corresponding numeric ID

        for ($n = 0; $n<strlen($index); $n++) {
            $i[] = substr( $index,$n ,1);
        }

        $passhash = hash('sha256',$passKey);
        $passhash = (strlen($passhash) < strlen($index))
            ? hash('sha512',$passKey)
            : $passhash;

        for ($n=0; $n < strlen($index); $n++) {
            $p[] = substr($passhash, $n ,1);
        }

        array_multisort($p, SORT_DESC, $i);
        $index = implode($i);
    }

    $base = strlen($index);

    if ($to_num) {
        // Digital number <<-- alphabet letter code
        $in = strrev($in);
        $out = 0;
        $len = strlen($in) - 1;
        for ($t = 0; $t <= $len; $t++) {
            $bcpow = bcpow($base, $len - $t);
            $out = $out + strpos($index, substr($in, $t, 1)) * $bcpow;
        }

        if (is_numeric($pad_up)) {
            $pad_up--;
            if ($pad_up > 0) {
                $out -= pow($base, $pad_up);
            }
        }
    } else {
        // Digital number -->> alphabet letter code
        if (is_numeric($pad_up)) {
            $pad_up--;
            if ($pad_up > 0) {
                $in += pow($base, $pad_up);
            }
        }

        $out = "";
        for ($t = floor(log10($in) / log10($base)); $t >= 0; $t--) {
            $a = floor($in / bcpow($base, $t));
            $out = $out . substr($index, $a, 1);
            $in = $in - ($a * bcpow($base, $t));
        }
        $out = strrev($out); // reverse
    }

    return $out;
}

到目前为止，这是我修改过的代码：

function alphaID($in, $to_num = false, $pad_up = false, $passKey = null)
{
    $index = 'abcdefghijklmnopqrstuvwxyz0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ';
    $i = array('a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z','0','1','2','3','4','5','6','7','8','9','A','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P','Q','R','S','T','U','V','W','X','Y','Z');
    if ($passKey !== null) {
        // Although this function's purpose is to just make the
        // ID short - and not so much secure,
        // with this patch by Simon Franz (http://blog.snaky.org/)
        // you can optionally supply a password to make it harder
        // to calculate the corresponding numeric ID
       $len = strlen($index); 


        $passhash = hash('sha256',$passKey);
        $passhash = (strlen($passhash) < $len)
            ? hash('sha512',$passKey)
            : $passhash;

        for ($n=0; $n < $len; $n++) {
            $p[] = substr($passhash, $n ,1);
        }

        array_multisort($p, SORT_DESC, $i);
        $index = implode($i);
    }

    $base = strlen($index);

    if ($to_num) {
        // Digital number <<-- alphabet letter code
        $in = strrev($in);
        $out = 0;
        $len = strlen($in) - 1;
        for ($t = 0; $t <= $len; $t++) {
            $bcpow = bcpow($base, $len - $t);
            $out = $out + strpos($index, substr($in, $t, 1)) * $bcpow;
        }

        if (is_numeric($pad_up)) {
            $pad_up--;
            if ($pad_up > 0) {
                $out -= pow($base, $pad_up);
            }
        }
    } else {
        // Digital number -->> alphabet letter code
        if (is_numeric($pad_up)) {
            $pad_up--;
            if ($pad_up > 0) {
                $in += pow($base, $pad_up);
            }
        }

        $out = "";
        for ($t = floor(log10($in) / log10($base)); $t >= 0; $t--) {
            $a = floor($in / bcpow($base, $t));
            $out = $out . substr($index, $a, 1);
            $in = $in - ($a * bcpow($base, $t));
        }
        $out = strrev($out); // reverse
    }

    return $out;
}

正如你看不出有什么重大区别，只有我从for循环中删除了strlen并将其存储在一个变量中并预先计算了索引的数组（有点笨拙......但是数组的生成是组成的大部分计算）。

信用到期：这是原始作者信息： * @author Kevin van Zonneveld * @author Simon Franz * @copyright 2008 Kevin van Zonneveld（kevin dot vanzonneveld dot net） * @license www dot opensource dot org / licenses / bsd-license dot php新BSD许可证 * @version SVN：发布：$ Id：alphaID.inc.php 344 2009-06-10 17：43：59Z kevin $ * @link kevin dot vanzonneveld dot net

我无法发布网址，因为我的声誉很低：S

Answer 1

我做了一些轻微的优化，以便在这里和那里删除一些额外的CPU周期。大多数事情，比如不必要的任务，额外的比较等。此外，字符串可以被视为数组，所以我也是这样做的：

function alphaID($in, $to_num = false, $pad_up = false, $passKey = null)
{
    static $passcache;
    if(empty($passcache))
        $passcache = array();

    $index = 'abcdefghijklmnopqrstuvwxyz0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ';
    $i = array('a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z','0','1','2','3','4','5','6','7','8','9','A','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P','Q','R','S','T','U','V','W','X','Y','Z');
    if (!empty($passKey)) {
        // Although this function's purpose is to just make the
        // ID short - and not so much secure,
        // with this patch by Simon Franz (http://blog.snaky.org/)
        // you can optionally supply a password to make it harder
        // to calculate the corresponding numeric ID

        if(isset($passcache[$passKey]))
            $index = $passcache[$passKey];
        else {
            if(strlen($passhash = hash('sha256',$passKey)) < strlen($index))
                $passhash = hash('sha512',$passKey);

            $p = str_split($passhash);

            array_multisort($p, SORT_DESC, $i);
            $index = implode($i);
            $passcache = $index;
        }
    }

    $base = strlen($index);

    if ($to_num) {
        // Digital number <<-- alphabet letter code
        $in = strrev($in);
        $out = 0;
        $len = strlen($in) - 1;
        for ($t = 0; $t <= $len; $t++) {
            $bcpow = bcpow($base, $len - $t);
            $out += strpos($index, $in[$t]) * $bcpow;
        }

        if (is_numeric($pad_up)) {
            $pad_up--;
            if ($pad_up > 0) {
                $out -= pow($base, $pad_up);
            }
        }
    } else {
        // Digital number -->> alphabet letter code
        if (is_numeric($pad_up)) {
            $pad_up--;
            if ($pad_up > 0) {
                $in += pow($base, $pad_up);
            }
        }

        $out = "";
        for ($t = floor(log10($in) / log10($base)); $t >= 0; $t--) {
            $bcp = bcpow($base, $t);
            $a = floor($in / $bcp);
            $out .= $index[$a];
            $in -= $a *  $bcp;
        }
        $out = strrev($out); // reverse
    }

    return $out;
}

编辑：我已更新为包含缓存。现在试试吧！

Answer 2

看起来你已经做好了摆脱冗余电话的工作。

看起来有几个调用bcpow（$ base，$ t）可以减少到一个......

$out = "";
for ($t = floor(log10($in) / log10($base)); $t >= 0; $t--) {
    $newbase = bcpow($base, $t);
    $a = floor($in / $newbase);
    $out = $out . substr($index, $a, 1);
    $in = $in - ($a * $newbase);
}
$out = strrev($out); // reverse

你可能不会注意到差异。

Answer 3

我认为你应该只生成一个索引并在网站上使用它。让我解释一下为什么......

散列和'$ base = strlen（$ index）;'以上的所有内容只是生成索引...你将不得不使用相同的$ passkey来解码一个网址。由于您无法知道使用了哪个密钥，因此您必须将其放在网站范围内。这意味着每次生成url的调用都将使用相同的密钥，从而生成相同的索引。

所以...我会剥离索引生成代码并生成一个唯一索引并将其存储在'$ index'变量中。