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LibVT: Implement new ANSI escape sequence parser

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This commit replaces the former, hand-written parser with a new one that
can be generated automatically according to a state change diagram.

The new `EscapeSequenceParser` class provides a more ergonomic interface
to dealing with escape sequences. This interface has been inspired by
Alacritty's [vte library](https://github.com/alacritty/vte/).

I tried to avoid changing the application logic inside the `Terminal`
class. While this code has not been thoroughly tested, I can't find
regressions in the basic command line utilities or `vttest`.

`Terminal` now displays nicer debug messages when it encounters an
unknown escape sequence. Defensive programming and bounds checks have
been added where we access parameters, and as a result, we can now
endure 4-5 seconds of `cat /dev/urandom`. :D

We generate EscapeSequenceStateMachine.h when building the in-kernel
LibVT, and we assume that the file is already in place when the userland
library is being built. This will probably cause problems later on, but
I can't find a way to do it nicely.
This commit is contained in:
Daniel Bertalan 2021-05-08 20:37:43 +02:00 • committed by Andreas Kling
parent 1b347298f1
commit be519022c3
11 changed files with 707 additions and 571 deletions
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2
Userland/Libraries/LibVT/StateMachine.txt
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@ -3,7 +3,7 @@
// The description of the state machine is taken from https://vt100.net/emu/dec_ansi_parser
// with added support for UTF-8 parsing
@name VTParserStateMachine
@name EscapeSequenceStateMachine
@namespace VT
@begin Ground