rm2k-wasm

WebAssembly bindings for rm2k-lib, which reads and writes the RPG Maker 2000/2003 LCF binary formats, generated via wasm-bindgen.

The domain model (Database, Map, Save, TreeMap and everything nested under them) is close to a hundred structs, so it is not individually wrapped. Instead, loaded values cross the JS boundary as plain JavaScript values via serde-wasm-bindgen, reusing rm2k-lib's own serde feature. value is therefore untyped (any) on the TypeScript side by design - treat it as the same object shape you'd get from rm2k's own serde_json output, documented in the root crate's README.

Install

npm install rm2k-wasm

API

class LoadResult {
    value: any;
    header: Uint8Array;
    // Diagnostic[]-shaped: { offset: number, chunkId: number, structName: string, kind: string }
    diagnostics: any;
}

enum Engine { R2K, R2K3 }

function loadDatabase(bytes: Uint8Array): LoadResult;
function saveDatabase(value: any, engine: Engine, preserveHeader: boolean, header: Uint8Array): Uint8Array;

function loadMap(bytes: Uint8Array): LoadResult;
function saveMap(value: any, engine: Engine, preserveHeader: boolean, header: Uint8Array): Uint8Array;

function loadSave(bytes: Uint8Array): LoadResult;
function saveSave(value: any, engine: Engine, preserveHeader: boolean, header: Uint8Array): Uint8Array;

function loadTreeMap(bytes: Uint8Array): LoadResult;
function saveTreeMap(value: any, engine: Engine, preserveHeader: boolean, header: Uint8Array): Uint8Array;

Every loadX call always collects recoverable parse diagnostics (see the root crate's "Leniency" docs) rather than silently discarding them - diagnostics is usually an empty array. header is the file's original magic bytes; pass it back into saveX with preserveHeader: true to keep a non-canonical header byte-exact. Engine picks which RPG Maker's field layout to write, since R2K and R2K3 diverge on a handful of structs.

Usage

import init, { loadDatabase, saveDatabase, Engine } from "rm2k-wasm";

await init(); // browsers & Deno: no-arg init() works out of the box

const bytes = new Uint8Array(await Deno.readFile("./RPG_RT.ldb"));
const { value, header, diagnostics } = loadDatabase(bytes);
if (diagnostics.length > 0) console.warn(diagnostics);

value.system.system_name = "..."; // edit the loosely-typed value in place
const out = saveDatabase(value, Engine.R2K, true, header);

Under Node/Bun, init()'s default fetch()-based loading doesn't apply - pass the .wasm bytes explicitly instead:

import { readFile } from "node:fs/promises";
import init, { loadDatabase } from "rm2k-wasm";

await init(
  await readFile(new URL("./rm2k_wasm_bg.wasm", import.meta.resolve("rm2k-wasm"))),
);

Building

wasm-pack build --release --target web

Requires the wasm32-unknown-unknown rustup target (rustup target add wasm32-unknown-unknown) and wasm-pack (cargo binstall wasm-pack). Output goes to pkg/ (gitignored): the compiled .wasm, a JS glue module, a .d.ts, and the package.json this crate publishes to npm from.

Testing

wasm-pack test --node

Exercises the serde-wasm-bindgen conversion boundary against synthetic, guaranteed-valid values (Setup::defaults) rather than a real game file - see tests/smoke.rs.