Move caching into font builder

font-src/gen/caching/index.js

@@ -0,0 +1,66 @@
+"use strict";
+
+const fs = require("fs-extra");
+const zlib = require("zlib");
+const { encode, decode } = require("@msgpack/msgpack");
+
+const Edition = 3;
+const MAX_AGE = 5;
+
+class GfEntry {
+	constructor(age, value) {
+		this.age = age;
+		this.value = value;
+	}
+}
+
+class Cache {
+	constructor() {
+		this.gf = new Map();
+	}
+	loadRep(version, rep) {
+		if (!rep || rep.version !== version + "@" + Edition) return;
+		for (const [k, e] of Object.entries(rep.gf)) {
+			this.gf.set(k, new GfEntry((e.age || 0) + 1, e.value));
+		}
+	}
+	toRep(version) {
+		let gfRep = {};
+		for (const [k, e] of this.gf) {
+			if (e.age < MAX_AGE) gfRep[k] = { age: e.age, value: e.value };
+		}
+		return { version: version + "@" + Edition, gf: gfRep };
+	}
+
+	// Geometry flattening conversion cache
+	getGF(k) {
+		const entry = this.gf.get(k);
+		if (!entry) return undefined;
+		else return entry.value;
+	}
+	refreshGF(k) {
+		const entry = this.gf.get(k);
+		if (!entry) return;
+		entry.age = 0;
+	}
+	saveGF(k, v) {
+		this.gf.set(k, new GfEntry(0, v));
+	}
+}
+
+exports.load = async function (argv) {
+	let cache = new Cache();
+	if (argv.oCache && fs.existsSync(argv.oCache)) {
+		const buf = zlib.gunzipSync(await fs.readFile(argv.oCache));
+		cache.loadRep(argv.menu.version, decode(buf));
+	}
+	return cache;
+};
+
+exports.save = async function savePTCache(argv, cache) {
+	if (argv.oCache) {
+		const buf = encode(cache.toRep(argv.menu.version));
+		const bufZip = zlib.gzipSync(Buffer.from(buf.buffer, buf.byteOffset, buf.byteLength));
+		await fs.writeFile(argv.oCache, bufZip);
+	}
+};