Base10到base64网址缩短 [英] Base10 to base64 url shortening

问题描述

我正在为要学习php的项目编写一个url缩短功能，下面是代码(顺便说一句，我想global这不是一件好事:P):

I'm coding an url shortener function for a project in which I'm learning php, here is the code (btw I suppose that global here is not a good thing to do :P):

$alphabet = array(1 => "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",
                "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","_","-");

function shorten($id){
    global $alphabet;
    $shortenedId = "";
    while($id>0){
        $remainder = $id % 64;
        $id = $id / 64;     
        $shortenedId = $alphabet[$remainder].$shortenedId;
    }
    return $shortenedId;
}

该代码摘自这篇Wikipedia文章，并适用于php.我的问题是，当我将64的倍数传递给函数时，我得到了一个错误的结果(出于我的目的)，例如128返回不正确的b，应该是aaa，但是对于3位数字来说太长了数字.

The code is taken from this Wikipedia article and adapted to php. My problem is that when I pass a multiple of 64 to the function I get a wrong (for my purpose) result, for instance 128 returns b which is not correct, it should have been aaa, but that's too long for a 3-digit number.

我也开始认为这段代码有问题，如果我以$id的形式传递1'000'000'000'000，我会得到nItOq ...我觉得这是错误的，因为类似url缩短的服务如果我使用bit.ly，则会返回6个数字的ID，我认为这种算法并不比他们的算法更好.

Also I'm starting to think that there's something wrong in this code, if I pass 1'000'000'000'000 as $id I get nItOq... I feel it's wrong because a url shortening service like bit.ly returns a 6 number id if I use it, and I don't think that this algorithm is better than theirs.

因此，有两个问题:

• 您在上面的代码中发现任何错误了吗?
• 如何管理64多个ID?我是否必须忽略它们并传递给下一个?

推荐答案

仅需进行一些细微调整，主要的两个是使字母表的索引为零而不是单索引，并从id中减去余数.划分之前

Just a couple of little tweaks needed, the main two were to make the the alphabet zero indexed rather than one-indexed, and to subtract the remainder from the id before dividing

function shorten($id)
{
    $alphabet = 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789_-';
    $shortenedId = '';
    while($id>0) {
        $remainder = $id % 64;
        $id = ($id-$remainder) / 64;     
        $shortenedId = $alphabet{$remainder} . $shortenedId;
    };
    return $shortenedId;
}

这是进一步的修改版本，...我很喜欢

and here's a further modified version which... well I just like

function shorten($id, $alphabet='0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ_-')
{
    $base = strlen($alphabet);
    $short = '';
    while($id) {
        $id = ($id-($r=$id%$base))/$base;     
        $short = $alphabet{$r} . $short;
    };
    return $short;
}

编辑:将串联排序为与OP相同

sorted concatenation to be the same as the OPs

这篇关于Base10到base64网址缩短的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！