I wanted to check out this whole .NET Core business, so I downloaded it and started hacking. Oh, and I’m using Linux, so it’s all command line. Recipe for success, right? Let’s dive in!
Even more efficient UTF8 processing in C#
Last time, we took a text processing program and slashed its string allocations by a factor of one thousand, with execution time going from 1.02s to 0.07s. That’s not good enough. Let’s make it even faster.
Performant text processing in C#
I recently converted Subtex from D to C#. With the same amount of optimization, the C# version was thirty times slower. Let’s look at why.
Mirror, mirror on the wall — who’s the scrappiest scraper of all?
I implemented Silvermirror, a website mirroring tool. It’s got some interesting aspects that make it better than wget in some cases. Let’s dive in!
Read more “Mirror, mirror on the wall — who’s the scrappiest scraper of all?”
Implementing calendars
Calendars seem simple at first, but no system survives first context with reality. Let’s go through what types of calendars exist and how to support them all in one codebase. Our eventual focus will be on producing a calendar for games — but those more on the Dwarf Fortress end of the spectrum.
MUD life: time
We’ve been talking about procedural content generation for a MUD, but it would be rather sad to have a procedurally generated static MUD. A place where nothing ever changes.
If we want to talk about change over time, we need a notion of time.
MUD procedural generation: drawing the walls
This is the second post in a series on procedural generation for a MUD, which is a text-only MMO, or a multiplayer Zork. The eventual goal is to create a large, varied MUD containing multiple cities, towns, and wilderness biomes, and a wide array of NPCs and items, as the basis for more personalized and customized work.
Last time, we spoke about placing towers for the city walls. Let’s create the walls themselves.
MUD Procedural generation: outlining city walls
This starts a series on procedural generation for a MUD, which is a text-only MMO, or a multiplayer Zork. The eventual goal is to create a large, varied MUD containing multiple cities, towns, and wilderness biomes, and a wide array of NPCs and items, as the basis for more personalized and customized work.
Today we’re looking at generating the outline of a city: the city walls.
Subtex: doing a BBCode with LaTeX
I created Subtex, a LaTeX-inspired markup language for ebooks. Here, I’m going to talk about what caused me to create this language, what it does, and what’s interesting about it.
The Atlantis browser concept review
My reaction to this is a giant NO.
Extracting a browser kernel that runs services on top, that’s great. The rest, not so much. Right now, I have to trust Apple or the KDE devs or Google or Opera or Microsoft that my browser isn’t spying on me. Then I use RequestPolicy and Privacy Badger and sometimes NoScript to ensure the page itself isn’t doing bad things. But with Atlantis, I have to trust that every single website that contains anything I care about has done research on every component it depends on. And I already distrust these websites, by and large.
The examples didn’t have any security on them. They referenced compilers and stuff via unencrypted links. No checksums. No signing. So my bank does due diligence and determines that the parser and renderer and compiler it’s using are secure — but I get MITM’d and all my bank details are siphoned off to Russian hackers. Or the bank uses HTTPS and the server hosting the parser and renderer gets hacked and I get sad.
So instead my bank hosts everything itself. And there’s a bug in the RPC handler that allows arbitrary code execution. I know about it, upstream knows about it, there’s a fix released…but my bank is still using a three year old version and the Russian hackers are starting to feel sorry for me.
Fun, yes?
Security fixes
Fortunately, the security story is moderately straightforward. We have a central repository of trusted services. You can request specific versions of a service, but the browser doesn’t guarantee that it will honor your version request. For instance, if you request mshtml11.3.7, the browser might give you mshtml11.3.12. In point of fact, we’ll only support major.minor version requests; you always get the most recent patch version.
A service build is automatically retired after eighteen months to mitigate security risks. This is why the browser won’t always honor your version requests. You might have asked for mshtml4.0, but nobody’s been maintaining that for a decade and more, so the browser will give you the nearest equivalent.
Since we’re using a silo for trusted services, we can use a bunch of things like signed builds and certificate pinning to reduce your ability to muck about with my trusted resources.
Finally, Atlantis internally has an RPC mechanism defined. You can post arbitrary data to arbitrary pages. That’s a problem. You need a way to lock that down. Without a means of restricting it, I can construct a page that will fuzz your other open tabs. Perhaps you require a handle to a page in order to send RPCs, and the only way of getting a page ID is by opening it (or receiving the ID via an RPC). Perhaps there are named RPC channels that a page must enroll in, and the browser automatically drops RPCs that aren’t supported.
Privacy
One big thing that web devs tend to want is analytics. I’m not so keen on being tracked. It’s straightforward in Firefox to reduce tracking: suppress the HTTP referer header, add a pre-request hook that will disallow cross-origin requests contrary to a defined policy, and delete cookies on schedule. Maybe pass the Do Not Track header too.
How do I do that in Atlantis?
I have to trust Atlantis to pass the referer header, then I have to use a local proxy for everything it does. That works okay for HTTP, but it doesn’t work with HTTPS. With HTTPS, the referer header is encrypted and my proxy can’t see it. Or my proxy needs to have a certificate that the browser implicitly trusts for every site, and I have to disable certificate pinning in the browser.
This goes into the general realm of promoting user agency vs promoting developer agency.
Technical aspects
Atlantis uses abstract syntax trees as the basis of everything.
Abstract syntax trees let you abstract over different programming languages a little. Not much. You’re stuck with one set of semantics. It’s like trying to implement C on the JVM — you just can’t do it. You can do some of it, but you don’t get pointers and you don’t get structs, so you’ll end up writing a virtual machine on top of the JVM to support those.
So that’s a constraint that limits you a lot. The obvious alternative is LLVM bytecode. Google Chrome’s NaCL, if I recall correctly, uses LLVM, so it’s possible to sandbox it.
The other problem I have with the version presented is the rendering system. It builds a bitmap image and sends it off to the browser. I’m not sure how that will work for accessibility. I’m not sure how to highlight text and copy it that way. It’s good enough for research, not good enough for real life. And if you punt this to the service developer, 95% of them will ignore accessibility entirely, and 30% of them will forget about copy/paste.
What’s good?
If you split up a browser into multiple services running on a base, things get nicer on the technical side.
The core of the browser can just be a few process-oriented APIs, a series of drawing primitives, IO, etc. That’s simple enough to implement on its own.
Independent parties can develop services to implement, say, SVG or MathJAX. And with agreed-upon APIs, I can use the same service on IE and Firefox. This is good for web standards — they can be implemented more quickly, and it’s easier to track down the source of incompatibilities when you can insert the W3C version of MathJAX into Firefox, observe how it renders, and then swap out Trident for Gecko to see if there’s a bad interaction between Gecko and W3C:MathJAX that’s messing up the output.
Then I can implement browser addons as services that the user brings in. For special purposes, when the user allows, pages can do nonstandard things too, implementing their own services. For instance, the Elm programming language provides a moderately different layout system that tends to be pixel-based. (The relatively recent html package offers access to DOM, but the older stuff doesn’t.) That could be implemented as a new rendering service. Or if we find a way to provide sandboxed GPU access, we could get a Unity3D service. Or with DRM, a page could supply a service that converts encrypted audio to WAV.
There’s a lot of possibility here. And I’m sure that James Mickens has considered some of it. A one-hour talk isn’t the best for conveying the full depth of your vision. I’m excited to see his continuing work.