<img src="blob:https://example.com/b501e863-fe43-4b63-ae5d-dac14cac097e">

The web page that contains it renders the image fine, but when a fairly naïve user posts that link into a chat, it results in nothing: the blob referenced by <img> exists only in the memory of a specific browser instance, & the server will return 404 for any https://example.com/UUID.

Why do they do this? Every n years some people get scared of hotlinking (bastards keep stealing our traffic), AI luddites try to ruin business of evil corporations, & fans of toy-level DRM amuse themselves with a new scheme.

If you look at the fetch-requests of such a page, you'll see resources that look like images but actually aren't:

$ url='https://ia800206.us.archive.org/🙈.jpg'

$ curl -sI "$url" | grep -e type -e length -e obfuscate
content-type: image/jpeg
content-length: 267470
x-obfuscate: 1|uoEV6/PZOWtGhOZdVM898w==

$ curl -s "$url" | head -c25 | file -
/dev/stdin: data

Such a .jpg is encrypted. Part of the key is in the X-Obfuscate header, but neither a random AI scraper nor any social network knows about this. The cipher is also not disclosed, & every website may use any scheme it wants: following any recommendations would defeat the entire purpose of obfuscation.

The image-rendering algorithm then becomes:

1. download the encrypted file;

2. decrypt it using the key from the corresponding header & push the result into a blob;

3. create a link to the blob using URL.createObjectURL function;

4. inject into the DOM an img element whose src attribute is equal to the newly created link.

We can increase entropy further by writing our own custom element:

<img-blob alt="a fluffy cat" src="cat.bin"></img-blob>

that will do all of the above on its own. (I terser'ed the source code of the example for I absolutely don't want you to use it in anything serious: the entire approach is extremely user-hostile & anti-web.)

For efficiency, archive.org AES-CTR-encrypts only the first 1024 bytes of the image. Browsers know about AES but strictly require a secure context that can be annoying during testing; hence, for mickey mouse DRM we can simply use XOR-encryption.

The X-Obfuscate header itself can be obfuscated even more, e.g.:

x-obfuscate: rlW2MKWmnJ9hVwbtZFjtVzgyrFV6VPVkZwZ0AFW9Pt==

looks like a base64 string, but:

$ echo rlW2MKWmnJ9hVwbtZFjtVzgyrFV6VPVkZwZ0AFW9Pt== | base64 -d | xxd
base64: invalid input
00000000: ae55 b630 a5a6 9c9f 6157 06ed 6458 ed57  .U.0....aW..dX.W
00000010: 3832 ac55 7a54 f564 6706 7400 55bd 3e    82.UzT.dg.t.U.>

I checked if DeepSeek could figure it out: it spent 9 minutes & left 2 villages in Zhejiang province without water, was several times very close to the target, but ultimately failed.

The string had been post-processed with rot13:

$ alias rot13="tr 'A-Za-z' 'N-ZA-Mn-za-m'"
$ echo rlW2MKWmnJ9hVwbtZFjtVzgyrFV6VPVkZwZ0AFW9Pt== | rot13 | base64 -d
{"version": 1, "key": "12345"}

As homework, you can add an equivalent of loading="lazy" to the custom element using the Intersection Observer API.

At the same time, practically all browsers support MathML. Use it (pandoc's --mathml option), if you care only about the information superhighway: your formulas will look good on every modern device and scale delightfully. Otherwise, SVGs are the only truly portable option.

Now, how can we transform the html produced by

$ echo 'Ohm'\''s law: $I = \frac{V}{R}$.' |
  pandoc -s -f markdown --mathjax

into a fully standalone document where the formula gets converted into SVG nodes?

1. Use an html parser like Nokogiri, and replace each <span class="math"> node with an image. There are multiple ways to convert a TeX-looking string to an SVG: using MathJax itself (which provides a corresponding CLI example), or by doing it in a 'classical' fashion with pdflatex. (You can read more about this method in A practical guide to EPUB, chapters 3.4 and 4.6.)

2. Alternatively, load the page into a headless browser, inject MathJax scripts, and serialise the modified DOM back to html.

I tried the 2nd approach in 2016 with the now-defunct phantomjs. It worked, but debugging was far from enjoyable due to the strangest bugs in phantomjs. I can still run the old code, but it depends on an ancient version of the MathJax library that, for obvious reasons, isn't easily upgradable within the phantomjs pre-es6 environment.

Nowadays, Puppeteer would certainly do, but for this kind of task I prefer something more lightweight.

There's also jsdom. Back in 2016, I tried it as well, but it was much slower than running phantomjs. Recently, I gave jsdom another try and was pleasantly surprised. I'm not sure what exactly tipped the scales: computers, v8, or jsdom itself, but it no longer feels slow in combination with MathJax.

$ wc -l *js *conf.json
  24 loader.js
 105 mathjax-embed.js
  12 mathjax.conf.json
 141 total

Roughly 50% of the code is nodejs infrastructure junk (including CL parsing), the rest is a MathJax config and jsdom interactions:

let dom = new JSDOM(html, {
  url: `file://${base}/`,
  runScripts: /* very */ 'dangerously',
  resources: new MyResourceLoader(), // block ext. absolute urls
})

dom.window.my_exit = function() {
  cleanup(dom.window.document) // remove mathjax <script> tags
  console.log(dom.serialize())
}

dom.window.my_mathjax_conf = mathjax_conf // user-provided

let script = new Script(read(`${import.meta.dirname}/loader.js`))
let vmContext = dom.getInternalVMContext()
script.runInContext(vmContext)

The most annoying step here is setting url property that jsdom uses to resolve paths to relative resources. my_exit() function is called by MathJax when its job is supposedly finished. loader.js script is executed in the context of the loaded html:

window.MathJax = {
  output: { fontPath: '@mathjax/%%FONT%%-font' },
  startup: {
    ready() {
      MathJax.startup.defaultReady()
      MathJax.startup.promise.then(window.my_exit)
    }
  }
}

Object.assign(window.MathJax, window.my_mathjax_conf)

function main() {
  var script = document.createElement('script')
  script.src = 'mathjax/startup.js'
  document.head.appendChild(script)
}

document.addEventListener('DOMContentLoaded', main)

The full source is on Github.

Intended use is as follows:

$ echo 'Ohm'\''s law: $I = \frac{V}{R}$.' |
  pandoc -s -f markdown --mathjax |
  mathjax-embed > 1.html

The resulting html doesn't use JavaScript and doesn't fetch any external MathJax resources. mathjax-embed script itself always works offline.

For comparison, the size of SumatraPDF-3.5.2 installer is 8,246,744 bytes. It has no 'AI', no auto-updater (though it can check for new versions, which I find unnecessary, for anyone sane would install it via scoop anyway), and no ads for 'cloud storage'.

The following chart shows how the Adobe Reader installer has grown in size over the years. When possible, 64-bit versions of installers were used.

Next Day Update:

Best comment on Hacker News: "Looks like a chart crime scene."

Alright, here's your linear graph, along with the source from which both graphs were generated. All point labels are version numbers.

Weinberger described peculiarities of his netfs as

"If A mounted B's file system somewhere, and B mounted A's, then the directory tree was infinite. That's mathematics, not a bug."

His /usr/src/netfs/TODO contained an existential question:

'why does it get out of synch?'

The connection of this netfs and Sun's NFS is murky.

Steve Johnson:

"I remember Bill Joy visiting Bell Labs and getting a very complete demo of RFS and being very impressed. Within a year, Sun announced NFS."

Unix System V SVR3, released by AT&T in 1987, included a different version of netfs, which they officially began calling RFS. Appearing 18 months after Sun announced NFS, it briefly attempted to compete, but failed on 2 fronts simultaneously: ⓐ big vendors (Dec, IBM, HP) disliked its licensing terms, and ⓑ the protocol's brittleness discouraged ports to non-Unix systems. NFS won, becoming widely used--even by NeXTSTEP.

Lyndon Nerenberg:

'We ran RFS on a "cluster" of four 3B2s [AT&T microcomputers], and while it worked, to varying degrees, the statefulness of the protocol inevitably led to the whole thing locking up, requiring a reboot of all four machines to recover.'

Some time ago I heard about repurposing this particular model (Vontar X3) as a retro-gaming console, but anticipating battles similar to those with openwrt-on-outers--where 2 devices with the exact same name have slightly different hardware revisions (& as a result, nothing works as expected)--I've been putting off the adventure.

The easiest Linux gaming distro to deploy is a French one called Batocera.¹ Its wiki describes perfomance of a particular device in terms of console generation support:

(I've skipped the irrelevant generations.)

In my tests, while the modest S905X3 runs most psx & psp games acceptably, some titles have such a perceived frame drop (that do not occur on a desktop PC running the same emulator as Batocera) that it makes them unplayable. The prominent unsuccessful examples are CTR: Crash Team Racing (psx) and MotorStorm: Arctic Edge (psp).

The last Batocera version for the Vontar X3 is 35 (the OS images for this device haven't been updated since '22). I dd'ed batocera-s905gen3-tvbox-gen3-35-20220910.img onto a 32GB SD card, inserted the card into the TV box, pressed its reset button with a toothpick, plugged in the power cable, & saw this:

The TV's info popups indicated that the resolution of this shaky image was 1080i (interlaced?) instead of the expected 1080p. I then tried 2 completely different (albeit much newer) TVs, as well as a capture card--none of them had any problems negotiating a proper resolution with Batocera.

After pointlessly suffering with various kernel parameters, I ended up with the following kludge to disable the interlaced mode:

1. Connect the device to your LAN via the ethernet port. Batocera runs Avahi, hence we can just say

    $ ssh root@batocera.local
   

   (The password is 'linux'.)

2. Run

    # batocera-resolution listModes | head -10
    max-1920x1080:maximum 1920x1080
    max-640x480:maximum 640x480
    0.0.1920x1080.60:HDMIA 1920x1080 60Hz (1920x1080i)
    0.1.1920x1080.60:HDMIA 1920x1080 60Hz (1920x1080)
    0.2.1920x1080.60:HDMIA 1920x1080 60Hz (1920x1080)
    0.3.1920x1080.60:HDMIA 1920x1080 60Hz (1920x1080i)
    0.4.1920x1080.50:HDMIA 1920x1080 50Hz (1920x1080)
    0.5.1920x1080.50:HDMIA 1920x1080 50Hz (1920x1080i)
    0.6.1920x1080.24:HDMIA 1920x1080 24Hz (1920x1080)
    0.7.1920x1080.24:HDMIA 1920x1080 24Hz (1920x1080)
   

   inside Batocera. Take a note of a mode you'd like to see.

3. Turn the device off. Extract the SD card out of it & insert it into a PC. The card has 2 partition: the 1st one is fat32 that has batocera-boot.conf file. Add a line to it:

    es.resolution=0.1.1920x1080.60
   

The picture will still incessantly jerk from left to right, but only during the boot phase:

# batocera-info
Disk format: ext4
Temperature: 66°C
Architecture: tvbox-gen3
Model: Shenzhen Haochuangyi Technology Co., Ltd H96 Max
System: Linux 5.10.134
Available memory: 624/932 MB
Cpu model: ARMv8 Processor rev 0 (v8l)
Cpu number: 4
Cpu max frequency: 1908 MHz

There is little to add here. You copy your .nes/.sfc/.chd/.iso files to /userdata/roms/{nes,snes,psx,psp} either directly onto the 2nd partition of the SD card, or via ssh, or even smb, for Batocera runs Samba.

1. I couldn't find any guidance on how to pronouce it: there is a type of beetles called /bə'tosərə/, but some youtubers say it as /bαto'sɛrα/.

'[1852] In the regiment there was a Lieutenant Slaughter who was very liable to sea-sickness. It almost made him sick to see the wave of a table-cloth when the servants were spreading it.

'Soon after his graduation, Slaughter was ordered to California and took passage by a sailing vessel going around Cape Horn. The vessel was seven months making the voyage, and Slaughter was sick every moment of the time, never more so than while lying at anchor after reaching his place of destination.

'On landing in California he found orders which had come by the Isthmus, notifying him of a mistake in his assignment; he should have been ordered to the northern lakes. He started back by the Isthmus route and was sick all the way. But when he arrived at the East he was again ordered to California, this time definitely, and at this date was making his third trip. He was as sick as ever, and had been so for more than a month while lying at anchor in the bay.

'I remember him well, seated with his elbows on the table in front of him, his chin between his hands, and looking the picture of despair. At last he broke out, "I wish I had taken my father's advice; he wanted me to go into the navy; if I had done so, I should not have had to go to sea so much." Poor Slaughter! it was his last sea voyage. He was killed by Indians in Oregon.'

(From Personal Memoirs of U.S. Grant, Ch. XIV by Ulysses S. Grant.)

$ touch `printf "\033[1;33m\033[44mhello"`
$ ls
''$'\033''[1;33m'$'\033''[44mhello'
$ tar cf 1.tar *hello
$ busybox tar tf 1.tar
hello
$ rpm -q busybox
busybox-1.36.1-8.fc41.x86_64
$  

Oopsie-daisy.

A simple ls|cat or ls|less -r produces the same effect.

This won't work with gnu tar & bsdtar, for they both properly escape escape sequences.

Date: Wed, 3 Jul 2024 17:29:26 -0600
From: Marc Rochkind <mrochkind@gmail.com>
Newsgroups: gmane.org.unix-heritage.general
Subject: Re: Anyone ever heard of teaching a case study of Initial Unix?
Message-ID: <CAOkr1zXSefHKOqTCaGE7Zb_T09HD-s2pM9QfTW8PuMkLGioDGg@mail.gmail.com>

On Wed, Jul 3, 2024 at 9:27 AM Vincenzo Nicosia wrote:
> The programmers considered as "fungible workforce" by mainstream
> software engineering and project management theories are *paid* to
> to their programming job, and they mostly have to carry that job
> over working on prescribed objectives and timelines which have been
> decided by somebody else, managers who know nothing at all about
> software development. Personal interest in the project, passion,
> motivation, curiosity, creative power, sense of beauty, the joy of
> belonging to a community of likeminded people, are never part of the
> equation, at any point.

What a cynical take on software development! The logical error is to
assume that if something is sometimes true (e.g., "managers who know
nothing at all about software development") then it is always true.

My experience over many decades is quite different. Most often,
managers know software quite well. Where they fail is in their very
poor understanding of how to manage people.

The bias that operates in software development, and perhaps all
organizations, is that when there is a disagreement between management
and non-management (e.g., programmers), the non-managers usually
assume that they are always right and the managers are wrong.

I have never met a programmer or group of programmers who were always
right. Most often, they are ignorant of financing, regulatory
constraints, product schedules, commitments, staffing issues, and
everything else that isn't coding. (There are exceptions, but they are
uncommon.) Management, by definition, is the art and science of using
resources to reach an objective. Programmers generally are concerned
only with themselves as a resource and with their own personal
programming objective. It is unusual to find a programmer who
understands management.