Wipforth

Wipforth is a Forth implementation that runs in the WebAssembly virtual machine. The system is bootstrapped from source on page load: the only non-text file is the favicon :)

I/O is done via memory-mapped peripherals, which are emulated in JavaScript.

• For the Forth kernel, see wipforth.ws
• For the emulator, see emu.js
• For the assembler, see asm.js
• For the prelude (Forth code loaded right after the kernel boots), see prelude.f
• For a description of the peripherals, see the Peripherals section below.

Building and Running Locally

There's a Guile script in the repo you can use for this:

guile server.scm

You should then be able to open http://localhost:8080 in a browser and use the system from there.

However, since everything is bootstrapped on the client, basically any HTTP server will do as long as it sets the appropriate response headers for SharedArrayBuffer use:

• Cross-Origin-Opener-Policy: same-origin
• Cross-Origin-Embedder-Policy: require-corp

So, if you don't have Guile on your system you can use something else like Python's http.server.

NOTE: You should definitely not use server.scm to serve the application on the open internet or anything like that; I just hacked it together for testing on localhost during development and it's probably hilariously insecure.

End-to-End Tests

There's a (fairly minimal at the moment) end-to-end test suite defined in tests.scm. To run it you'll need:

• Guile again (no substitute this time, sorry)
• guile-json
• Firefox

I'm also pretty sure it won't work on a non-POSIX system, though I haven't tried it.

Given that's all sorted, you should be able to run:

guile tests.scm

It will print a JUnit XML report to standard out. You can pretty-print it with xmllint if you have it installed:

guile tests.scm | xmllint --format -

Peripherals

Terminal

Name	Address	Size / B	Access
TXBUF	000h	32	write
RXBUF	080h	32	read
TXHEAD	100h	4	atomic read
TXTAIL	104h	4	atomic write
RXHEAD	108h	4	atomic write
RXTAIL	10Ch	4	atomic read

For both sending (TX) and receiving (RX), there are three registers: xBUF, xHEAD and xTAIL:

• xBUF registers are 128-byte FIFO ring buffers used for data
• The xHEAD and xTAIL registers specify the start and end of data in the ring buffer, xHEAD being the offset of the first byte of data, and xTAIL being the offset of the first byte after the data.

In order to be distinguishable from the empty state, the ring buffers must never be completely full -- there must always be at least one unoccupied byte between the tail and the head.

System status

Name	Address	Size / B	Access
SYSREADY	110h	4	atomic write
SYSINTER	114h	4	atomic read

The SYSREADY register is used to indicate when the system has booted up and is ready for user input. SYSINTER is set (and notified on) once the emulator has enabled user input and the system is interactive.