re2c
firejail
re2c | firejail | |
---|---|---|
12 | 139 | |
1,026 | 5,464 | |
- | - | |
6.8 | 9.7 | |
19 days ago | 3 days ago | |
C | C | |
GNU General Public License v3.0 or later | GNU General Public License v3.0 only |
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re2c
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Ask HN: What are some unpopular technologies you wish people knew more about?
(1) Zulip Chat - https://zulip.com/ - seems to be reasonably popular, but more people should know about it
I’ve been using it for over 5 years now [1], and it’s as good as ever. It’s way faster than any other chat app I’ve used. It has a good UI and conversation model. It has a simple and functional API that lets me curl threads and write blog posts based on them.
(only problem is that I Ctrl-+ in my browser to make the font bigger – I think it’s too dense for most people)
(2) re2c regex to state machine compiler - https://re2c.org
A gem from the 90’s, which people have done a great job maintaining and improving (getting Go and Rust target support in the last few years). I started using it in 2016, and used for a new program a few months ago. I came to the conclusion that it should have been built into C, because C has shitty string processing – and Ken Thompson both invented C AND brought regular languages to computing !!
In comparison, treesitter lexers are very low level, fiddly, and error prone. I recently saw dozens of ad hoc fixes to the tree-sitter-bash lexer, which is unsurprising if you look at the structure of the code (manually crawling through backslashes and braces in C).
https://github.com/tree-sitter/tree-sitter-bash/blob/master/...
These fixes are definitely appreciated, but I think it indicates a problem with the model itself.
(based on https://lobste.rs/s/endspx/software_you_are_thankful_for#c_y...)
[1] https://www.oilshell.org/blog/2018/04/26.html
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Irregular Expressions
The "Papers" section on re2c's web site continues Laurikari's work: http://re2c.org/
... but I haven't found them particularly accessible. And it's not clear it's a viable strategy in a general purpose regex engine. Namely, I'm not sure how much bigger it makes the DFA.
Also, AFAIK, these are DFAs. They are different theoretical structures with explicitly more power.
> and then an NDFA is used to match a third time, to extract the capture groups.
That's the PikeVM. It's an NFA simulation. Although it uses additional storage and is otherwise more computationally powerful than just a plain NFA.
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My experience crafting an interpreter with Rust (2021)
> What do you gain by using it?
Performance, although this possibly depends on your compiler, whether you use PGO, and similar finicky issues.
Example: https://eli.thegreenplace.net/2012/07/12/computed-goto-for-e...
Some prior HN discussion: https://news.ycombinator.com/item?id=18678920
Another example where goto is relevant is implementing finite automata. A (very short) paper from 1988 that discusses three different ways of implementing a finite state machine is "How (Not) to Code a Finite State Machine". The documentation of RE2C may be even more interesting: https://re2c.org
RE2C is a program that compiles finite automata into C, Go, or Rust code. It provides many implementation strategies: it can make use of computed or labelled gotos when the language provides them.
Implementing pushdown automata comes with similar issues.
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How to compile DPDK-22.11.1
wget https://github.com/skvadrik/re2c/releases/download/1.0.3/re2c-1.0.3.tar.gz tar -zxvf re2c-1.0.3.tar.gz cd re2c-1.0.3/ ./configure make make install
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Best approach for writing a lexer
In Rust I use https://docs.rs/logos/latest/logos/. I think another similar is http://re2c.org
- re2c is a free and open-source lexer generator for C/C++, Go and Rust
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File parsing with PHP, Bison and re2c
re2c is an open-source lexer generator. It uses regular expressions to recognize tokens.
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Best option for Rust Parser and Lexer Generators?
Those suggested crates are still more or less the popular options. There was also recently added support for Rust in re2c.
- How Does One Develop the Grammar for their New Language
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Javascript Date String Parsing
First, the implementation of strtotime is a textbook study in why other people's C code is not where you want to spend time. You can see the guts of the implementation logic here. This isn't stock C code -- it's code for a system called re2c. This system allows you to write regular expressions in a custom DSL (domain specific language), and then transform/compile those regular expressions down to C programs (also C++ and Go) that will execute those regular expressions. Something in PHP's make file uses this parse_date.re file to generate parse_date.c. If you don't realize parse_date.c is a generated file, this can be extremely rough going. If you've not familiar with re2c is can be regular rough going. We leave further exploration as an exercise for the reader -- an exercise we haven't taken ourself.
firejail
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Sandboxing All the Things with Flatpak and BubbleBox
bubblewrap is designed as a low-level too. There is nothing quick and dirty about it. It disallows everything by default and you have to be explicit about what you want to share with the host. If your application needs complex permissions/resources, then you will need to have a complex bubblewrap command line.
Once you have figured out which permissions/resources you need for a given program, you can wrap the command line invocation in a shell script.
If you want other people to do the work of defining permissions/resources, then have a look at firejail: https://github.com/netblue30/firejail
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Ask HN: What are some unpopular technologies you wish people knew more about?
Firejail is cool: https://github.com/netblue30/firejail
Linux namespaces/cgroups but nowhere near as heavy as Docker.
I use it when I want to limit the memory of a Python script:
```
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Toolship: A (More) Secure Workstation
Firejail can also be a useful option, though no good if you're on Mac https://firejail.wordpress.com/
Uses the same Linux primitives as docker etc, but can be a bit more ergonomic for this use case
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Firejail: Light, featureful and zero-dependency security sandbox for Linux
Firejail, Flatpak (which uses Bubblewrap under the hood), and Snap (which uses AppArmor) all use the same underlying technology: Linux namespaces.
This question comes up a lot, and has been answered here: https://github.com/netblue30/firejail/wiki/Frequently-Asked-...
TL;DR: Firejail has much more comprehensive features than Flatpak (Bubblewrap). Firejail also has more comprehensive network support, support for AppArmor and SELinux, and easier seccomp filtering.
Compared to Snap (which uses AppArmor), Firejail is compatible with AppArmor and again goes above and beyond with a lot of additional features.
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Bubblewrap – Low-level unprivileged sandboxing tool used by Flatpak
Wonderful little tool, too bad you must chain various exec calling tools to get cgroups (a bit akin to `ionice ... nice ... cmd`) and Linux users namespaces can't allow UNIX sockets while preventing network access (I think?).
Migrated from Firejail when its complexity annoyed me too much and I hit https://github.com/netblue30/firejail/issues/3001 (Firejail doesn't like parens or brackets in --put/--get parameters) to a badly NIH version using bwrap and bash to have "profiles":
- Firejail: Light featureful and zero-dependency security sandbox for Linux
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Do, or do not. There is no try
Firejail does this. The profile database is the two "profile" directories in https://github.com/netblue30/firejail/tree/master/etc
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Strange times make for strange friends...
What do you mean by a Firefox container? Do you mean FireJail?
What are some alternatives?
parser-demo - Good source layout with Flex and Bison
bubblewrap - Low-level unprivileged sandboxing tool used by Flatpak and similar projects
Luxon - ⏱ A library for working with dates and times in JS
flatpak - Linux application sandboxing and distribution framework
cmark - CommonMark parsing and rendering library and program in C
bubblejail - Bubblewrap based sandboxing for desktop applications
lowdown - simple markdown translator
Flatseal - Manage Flatpak permissions
moment - Parse, validate, manipulate, and display dates in javascript.
yabai - A tiling window manager for macOS based on binary space partitioning
plex - a parser and lexer generator as a Rust procedural macro
podman - Podman: A tool for managing OCI containers and pods.