Name: Will YouTube Ever Run Out Of Video IDs?
Uploaded: 2018-05-25T07:53:52.000Z
Duration: 5 min 10 s

每一部 YouTube 的影片都有自己的代號。

It's up in the URL: a string of eleven characters

就在網址裡面：一列共11位的字元，

情態副詞

that uniquely identifies which video you want.

Now, YouTube has millions and millions of
videos.

時至今日，YouTube 上有數以百萬計的影片。

The last stats that they released said they
have

400 hours of video being uploaded every minute.

每分鐘有超過400小時的影片被上傳

So: are they ever going to run out of those
IDs?

那麼問題來了：「代碼會有用盡的一天嗎？」

Well, to find out, let's talk about counting
systems.

嗯，要想知道著個答案，我們先來談談記數系統

我們人類數數以 10 為底，從 0 到 9。

關於這點，希望你不會感到陌生

電腦 (計算機) 則是以 2 為底的 2 進位，

但那對我們人類閱讀上來說有困難

it gets too long to write really, really quickly,

因為要在短時間內寫下來實在是太長了

so often computers will display it in base
16, hexadecimal.

所以來說一般在電腦 (計算機) 上是以 16為底的 16 進位

你會從 0 算到 9 再來是 A 到 F (10 ~ 15)，

and then you start adding to the next column.

對於 16 進位人類無法一看就懂，

but it's efficient if we have to type it in
somewhere,

但若是要記下來的話還是可以的，

and 16 - 2 to the power of 4 - is also easy
for computers to deal with.

再說16，也就是 2 的 4 次方，對電腦 (計算機) 來說也是很容易處理的。

That'd be a ridiculous counting system, right?
Except.

你想說那是個很愚蠢的記數方式，是吧？然而，

64 is another one of those easy numbers for
computers,

64 對電腦 (計算機) 來說只不過是另一個簡單的數字罷了

then small letters a to z, and two other characters.

再加上小寫的 a 到 z，最後再加兩個其他符號。

大部分的時候是用 / 和 + (斜線和加號)

所以 YouTube 改用 - 和 _ (連字號和底線)

我們說的 YouTube 的網址，那串獨一無二的代碼

is really just a random number in base 64.

就只是一串以 64 為底的亂碼罷了。

They could have have picked base 10 or base
16,

他們 (YouTube) 大可選用以 10 為底或是以 16 為底，

但他們 (YouTube) 沒有：他們選擇以 64 為底，

because it will let you cram a huge number
into a small space

如此一來便可將一個巨大的數字壓縮成短短的幾位數

and still make it vaguely human readable.

並且讓人類在某種程度上是可閱讀的

Author and programmer Sam Hughes, by the way,

順帶一提，身為作家和工程師的 Sam hughes

pushed this to the limit, and invented Base
65,536,

將此一方法發揮到了極致，創造了 65536 進位，

which includes basically every character from
every language.

這種進位法也囊括了幾乎所有語言的所有字符。

but when has that ever stopped programmers?

但工程師們從來就是對此一行為樂此不疲。

So why didn't YouTube just start counting
at 1 and work up?

那麼為什麼 YouTube 不從 1 開始然後往上加就好了呢？

Well, first, they would have to synchronise
their counting

這麼說吧，若是如此他們首先必須要

between all the servers handling the video
uploads,

先將負責上傳影片的伺服器同步，或是

or they'd have to assign each server a block
of numbers.

他們必須要先劃分清楚每一台伺服器負責的數字區間。

Either way, there's a lot of tracking to do,

但無論以上哪種方法，都要不斷的檢查、

a lot of making sure that it's never duplicated.

重複確認影片的編號絕對不會重複。

Instead, they just generate a random number
for each video,

相反地，現在他們只要為每一部影片產出一組亂數，

see if it's already taken, and if not, use
it.

並確認該組亂數沒有被使用就夠了。

And secondly, it is a really, really bad idea

1, 2, 3 等等的數字絕對不是一個好主意。

Incremental counters, as they're called, can
be a big security flaw:

使用遞增記數的話，會產生非常嚴重的安全漏洞：

if you see video 283 up there, then you might
wonder:

如果你看見了一個編號 283 的影片，你一定會想：

編號 284 的影片是什麼？那 282 呢？

這種編排法是很容易被類推的，

YouTube Unlisted videos, the ones that don't
appear publicly

用遞增記數的話就做不到影片非公開了（YouTube 上的非公開影片，

but that you can send the link to people,
those wouldn't work.

雖說是非公開，但你仍然可以把網址發給你的朋友。）

And by the way? Lots of badly designed sites
do use incremental counters.

喔對了，有不少設計不良的網站就是用這種遞增記數的

It might tell your competitors exactly how
many customers you have,

這就好像在告訴你的競爭對手說你有多少使用者，

他們只要稍微數一下就知道了。

It might let people download all your records
easily,

也很容易讓有心人下載你所有的記錄，

And in one site that someone in Florida emailed
me about this week,

有個在佛羅里達州的人跟我說他知道有個網站，

it lets you look at other people's personal
details.

甚至讓你有辦法查看其他人的個人資料。

Don't use incremental counters if you're building
a web site. Use a random number.

如果你要架設網站的話請記住要用『亂數』，
『不、要、用、遞、增、記、數』

just how big are the numbers that YouTube
uses?

One character of base 64 lets you have 64
ID numbers.

64 進位的一位數可以有 64 個不同的 ID

Two characters? That's 64 by 64, or 4,096.

Three characters? 64 times 64 times 64 -- or
64 to the power of 3.

三位？64 x 64 x64 或是 64 的三次方。

That is already more than a quarter of a million.

And if we go to four? Well, now we're above
16 million.

四位數呢？那就是大於 1600 萬了

If you use Base 64, then you can assign an
ID number

如果用 64 進位的話，就可以生產出足以

to everyone who lives in London down there
twice over,

超出倫敦居住人口數兩倍的影片代碼了，

而這，僅僅只用了四、位、數。

This gets big fast. We can keep on doing this,

這數字成長的飛快。若我們繼續下去的話

and by seven characters we're already at four
quadrillion.

當我們用了七位數的時候就會得到超過 四兆 組的代碼。

Now, I assume that YouTube checks through
a dictionary,

呃...在這邊我希望 YouTube 有先檢查過，

and doesn't allow any actual words to appear
up there --

確保上面那串代碼不會有「單字」的出現

But that is going to be a tiny minority of
the URLs,

當然那只佔了眾多網址中一小部分罷了，

so for our purposes, we can pretty much just
ignore that.

所以在這邊我們可以暫時先忽略那些

At YouTube's 11 characters, we are at 73 quintillion
786 quadrillion

而 YouTube 用 11 位數產生的代碼可供
7378 京 (京：10^16)

That's enough for every single human on planet
Earth

而這足以讓這顆星球上的 每、一、個、人

to upload a video every minute for around
18,000 years.

以每分鐘上傳一部影片的速度，持續大約18000年

Can they run out of URLs? Technically, yes.

他們的網址會有用完的一天嗎？
理論上來說，會。

實際上呢？並不會。
但如果真的用完的話呢？

他們只需要再進一位就好啦（11--->12）

[Translating these subtitles? Add your name here!]

哈！一鏡到底！一鏡到底啦！YES！