README
E
Fault
- ::cancel_restoreMachine::cancel_restore
- ::finish_saveMachine::finish_save
- ::is_haltedMachine::is_halted
- ::newMachine::new
- ::positionMachine::position
- ::restore_dataMachine::restore_data
- ::runMachine::run
- ::save_dataMachine::save_data
- ::send_charMachine::send_char
- ::send_lineMachine::send_line
- ::take_outputMachine::take_output
- ::upper_windowMachine::upper_window

moon-zvm

A resumable Z-machine v3/v5 interpreter with Quetzal saves

z-machine

interpreter

interactive-fiction

Download zip

Author

aa-11aa

Version

0.1.0

License

Apache-2.0

Repository

github.com/aa-11aa/moon-zvm

Last updated

1 hour ago

Downloads

No dependencies

#moon-zvm

A Z-machine v3/v5 interpreter written in MoonBit. The interpreter core has no FFI or external package dependencies. Terminal file access is a small Node.js host; the browser host runs the same core as Wasm GC.

#Try an adventure

Install MoonBit (moonc 0.10.16 or newer) and Node.js 22.3 or newer. From this directory:

moon run cmd/main --target js -- examples/lantern.z5

The included original adventure, The Last Lantern, takes a few commands to finish:

north
take
south
south
quit

look, inventory, save, and restore also work. Save and restore prompt for a local Quetzal filename. A .z3 build is included as well. The command-line host is a plain transcript interface; it does not emulate terminal cursor positioning. It exits with a nonzero status on execution errors.

To play a raw story file you own, replace the example path with its .z3 or .z5 path. Games are not fetched or bundled automatically.

#Browser

node tools/build-web.mjs
python -m http.server 8000 --directory dist

Open http://localhost:8000 and choose Play The Last Lantern, or load your own story. The browser needs Wasm GC and JS string builtins. It provides a fixed-width upper window, a lower transcript, local story loading, save downloads and save restoration. Files stay on the device.

#Embed the core

Import the root package aa-11aa/moon-zvm with an alias such as @zvm. A registry release is not yet available; use this checkout to run the examples and tests.

let machine = @zvm.Machine::new(story_bytes)
let state = machine.run(budget=20000)
let text = machine.take_output()

run returns "budget", "line", "char", "save", "restore", or "halted". A host drains take_output(), displays upper_window(), and responds to requests:

State	Host action
budget	Schedule another slice; allow cancellation between slices
line	send_line(command)
char	send_char(zscii_code)
save	Persist save_data(), then call finish_save(success)
restore	restore_data(bytes), or cancel_restore()
halted	Stop execution

Invalid stories, unsupported instructions and execution faults raise Invalid(String). position() gives the current PC; runtime error messages include the instruction address. A rejected save leaves the pending restore intact so the host can retry or cancel. The interpreter enforces instruction, call-stack, evaluation-stack, abbreviation-depth and buffered-output limits.

#Implemented

Raw v3/v5 headers, big-endian dynamic/static memory, 16-bit arithmetic.
Long, short, variable and extended instruction encodings; routine calls, arguments, locals, globals and evaluation stacks.
Comparisons, branches, signed arithmetic, indirect variables, object trees, attributes and variable-size properties.
Z-encoded strings, abbreviation tables, custom alphabets and ZSCII output.
ASCII line input, dictionary encoding, lexical analysis, character input and memory output streams (including nesting).
Fixed 80×25 split window, upper-window cursor positioning and erasure, lower transcript output.
Sixteen levels of undo; Quetzal IFZS files with IFhd, UMem and Stks output, and CMem/UMem input.
Restart, checksum verification, table operations and catch/throw.

#Boundaries

This project does not claim full Standard 1.1 conformance. The header deliberately reports standard revision 0.0. Czech and Praxix check many execution details, but do not establish complete screen or game compatibility.

Supported story versions: 3 and 5 only. No Blorb extraction, v6 graphics or sound.
Line input is printable ASCII. ZSCII output supports the standard accented-character table and v5 Unicode translation tables. Timed input is unavailable.
The hosts offer plain text. Colour, bold/italic styles, font 3, pictures, mouse, external transcripts, command recording and auxiliary files are not advertised. Font 1 and fixed font 4 are available; unsupported fonts return 0.
v3 reports that it cannot display the automatic status line. The upper-window API is for explicit split-window output.
Random numbers use a 16-bit PRNG with rejection sampling for bounded ranges. The CLI/browser supply fresh host seeds on load, restart and @random 0; explicit negative seeds remain reproducible. Embedded callers can pass seed_source to Machine::new; omitting it gives deterministic seeds for tests. The PRNG is not cryptographic.
Quetzal exchange has been tested in both directions with Dumb Frotz 2.44 using the original v3/v5 adventure. This does not establish compatibility with every interpreter or every save file.
The core is intended for JS, Wasm GC, Wasm and native. The CLI is Node.js only. Native tests run in Linux CI; Windows needs MSVC Build Tools and the Windows SDK.

#Verify

moon check --target all --deny-warn
moon test --target js
moon test --target wasm-gc
moon test --target wasm
moon test --target native
moon info
moon fmt --check
python tools/conformance.py
python tools/conformance.py --praxix
node tools/build-web.mjs
node tools/verify-wasm.mjs
node tools/verify-player.mjs
# Optional independent interpreter, installed separately:
python tools/interop.py --dfrotz /path/to/dfrotz

The story runner checks Czech v3: 349 passed / 0 failed and v5: 406 passed / 0 failed. Each additionally prints 19 visual checks, which are not counted as automated passes. The optional Praxix runner downloads a hash-pinned story from its author's repository (with archive mirrors as fallbacks), feeds all / quit, and checks its automatic summary; Standard 1.1 colour and Standard 1.2 capability groups are skipped. Transcripts are saved under ignored test-results/.

The original adventure is tested in both v3 and v5 with navigation, inventory and a save/restore round trip. verify-wasm.mjs repeats an adventure through the actual browser Wasm exports. MoonBit tests additionally exercise malformed headers, every first-byte opcode, truncated saves, arithmetic, stack semantics and input suspension.

verify-player.mjs tests the browser host's asynchronous request ordering with mocks: stopped restores cannot restart a game, older downloads cannot replace a newer story, oversized files are rejected before reading, and rejected commands remain available for correction. These controller checks supplement the interpreter tests; they are not a substitute for browser UI testing.

#References and licensing

The runtime was implemented from The Z-Machine Standards Document 1.1 and Quetzal 1.4. No Frotz or other interpreter source was used or ported.

Runtime and original examples: Apache-2.0 (see LICENSE). Third-party test stories retain their own license notices; see fixtures/SOURCES.md. Inform 6 compiles the original demonstration story and the v3 Czech test; Inform is not a runtime dependency. Frotz (GPL-2.0) is used only as an optional external behavior/save-format reference; neither its executable nor its source is included in the module. Proprietary game files, including Zork, are not distributed here.

Fault

source

pub(all) suberror Fault {
  Invalid(String)
}

Errors in story data or execution are reported rather than indexing unchecked memory.

Machine

source

type Machine

A resumable interpreter. File and terminal I/O belong to the embedding host.

Machine::cancel_restore

source

fn Machine::cancel_restore(self : Machine) -> Unit raise Fault

Cancel an unavailable or declined restore operation.

Machine::finish_save

source

fn Machine::finish_save(self : Machine, success : Bool) -> Unit raise Fault

Tell the interpreter whether its host persisted the pending save.

Machine::is_halted

source

fn Machine::is_halted(self : Machine) -> Bool

True after @quit.

Machine::new

source

fn Machine::new(story : Bytes, seed_source? : () -> Int) -> Machine raise Fault

Load a raw v3 or v5 story. Blorb containers must be extracted by the host. Hosts can provide fresh seeds for normal play and @random 0. The default seed source is deterministic for reproducible embedding and tests.

Machine::position

source

fn Machine::position(self : Machine) -> Int

Inspect execution position for diagnostics.

Machine::restore_data

source

fn Machine::restore_data(self : Machine, data : Bytes) -> Unit raise Fault

Restore Quetzal CMem or UMem. The complete file is validated before changing state. A rejected file leaves the pending restore available for cancellation or retry.

Machine::run

source

fn Machine::run(self : Machine, budget? : Int) -> String raise Fault

Run up to budget instructions. Returns "halted", "line", "char", or "budget". A budget prevents a hostile or looping story from monopolising its host.

Machine::save_data

source

fn Machine::save_data(self : Machine) -> Bytes raise Fault

Produce an interoperable Quetzal IFZS save while run() reports "save". Uses UMem (uncompressed dynamic memory) and standard Stks call frames.

Machine::send_char

source

fn Machine::send_char(self : Machine, code : Int) -> Unit raise Fault

Supply a ZSCII character when run returns "char".

Machine::send_line

source

fn Machine::send_line(self : Machine, line : String) -> Unit raise Fault

Supply one complete ASCII command when run returns "line". Input is lowercased, clipped to the story's buffer, and tokenised.

Machine::take_output

source

fn Machine::take_output(self : Machine) -> String

Take buffered text without advancing the interpreter.

Machine::upper_window

source

fn Machine::upper_window(self : Machine) -> String

Current upper window as fixed-width text. Lower-window output uses take_output().

Source Files

Install

Download zip

A resumable Z-machine v3/v5 interpreter with Quetzal saves

z-machineinterpreterinteractive-fiction

aa-11aa

Apache-2.0

github.com/aa-11aa/moon-zvm

Updated 1 hour ago

2 downloads

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moon-zvm

#moon-zvm

#Try an adventure

#Browser

#Embed the core

#Implemented

#Boundaries

#Verify

#References and licensing

#Fault

#Machine

#Machine::cancel_restore

#Machine::finish_save

#Machine::is_halted

#Machine::new

#Machine::position

#Machine::restore_data

#Machine::run

#Machine::save_data

#Machine::send_char

#Machine::send_line

#Machine::take_output

#Machine::upper_window

Source Files

Fault

Machine

Machine::cancel_restore

Machine::finish_save

Machine::is_halted

Machine::new

Machine::position

Machine::restore_data

Machine::run

Machine::save_data

Machine::send_char

Machine::send_line

Machine::take_output

Machine::upper_window