VT100 Parser in C3

This project provides a robust, UTF-8 aware VT100 escape/control sequence parser written in C3. It is built on the comprehensive state machine design described in DEC’s ANSI-compatible video terminal parser, mirroring the behavior of classic DEC VT100/VT220/VT500 terminals while transparently handling UTF-8 encoded streams.

Features

• State-machine accurate: Implements the complete, correct state diagram from the DEC reference.

• UTF-8 safe: Correctly decodes UTF-8 sequences outside escape/control handling, and decodes multi-byte characters as appropriate.

• Full ANSI/DEC compatibility: Covers all C0 controls, ESC sequences, CSI (Control Sequence Introducer), OSC (Operating System Command), DCS (Device Control String), and others.

• Composability: Designed for integration into terminal emulators, logging tools, or any VT100-aware I/O pipeline.

Note: This parser is intended as a reusable library and does not perform rendering or host-dependent output; it emits structured actions for downstream handling. For full terminal emulation, connect the parser output to a stateful terminal model and rendering loop.

Example

import vt100;
import std::io;

fn void parser_callback(VTParser *parser, Actions action, Char32 c) => @pool()
{
	char[4] out;
	switch (action)
	{
		case ACTION_EXECUTE:
		case ACTION_PRINT:
			if (c > 0xFF)
			{
				if (try len = conv::char32_to_utf8(c, out[..]))
				{
					io::printf("%s", (String)out[:len]);
				}
			}
			else
			{
				io::printf("%c", (char)c);
			}
		default:
			break;
	}
}

fn void main() => @assert_leak(true)
{
	VTParser parser;
	parser.init(&parser_callback);
	parser.parse(io::stdin());
}

References

• DEC ANSI parser state machine
• Parser implementation in c
• ANSI X3.64-1979 specification (summary)

License

MIT License