Added an XML backend (#8)

src/xml.ts

@@ -0,0 +1,174 @@
+import type { Backend, File, StatsLike } from '@zenfs/core';
+import { decodeRaw, encodeRaw, Errno, ErrnoError, FileSystem, PreloadFile, Stats, Sync } from '@zenfs/core';
+import { S_IFDIR, S_IFREG } from '@zenfs/core/emulation/constants.js';
+
+export interface XMLOptions {
+	parent?: Node;
+}
+
+const statsLikeKeys = ['size', 'mode', 'atimeMs', 'mtimeMs', 'ctimeMs', 'birthtimeMs', 'uid', 'gid', 'ino', 'nlink'] as const;
+
+function get_stats(node: Element): Stats {
+	const stats: Partial<StatsLike<number>> = {};
+	for (const key of statsLikeKeys) {
+		const value = node.getAttribute(key);
+		stats[key] = value != null ? parseInt(value, 16) : undefined;
+	}
+	return new Stats(stats);
+}
+
+function set_stats(node: Element, stats: Partial<StatsLike<number>>): void {
+	for (const key of statsLikeKeys) {
+		if (stats[key] != undefined) {
+			node.setAttribute(key, stats[key].toString(16));
+		}
+	}
+}
+
+function get_paths(node: Element): string[] {
+	let paths: string[];
+	try {
+		paths = JSON.parse(node.getAttribute('paths')!) as string[];
+	} catch {
+		paths = [];
+	}
+	return paths;
+}
+
+function add_path(node: Element, path: string): void {
+	const paths = get_paths(node);
+	paths.push(path);
+	node.setAttribute('paths', JSON.stringify(paths));
+}
+
+function remove_path(node: Element, path: string): void {
+	const paths = get_paths(node);
+
+	const i = paths.indexOf(path);
+	if (i == -1) return;
+	paths.splice(i, 1);
+
+	if (!paths.length) {
+		node.remove();
+	} else {
+		node.setAttribute('paths', JSON.stringify(paths));
+	}
+}
+
+export class XMLFS extends Sync(FileSystem) {
+	protected document = new DOMParser().parseFromString('<fs></fs>', 'application/xml');
+
+	public constructor(public readonly parent?: Node) {
+		super();
+
+		try {
+			this.create('[[init]]', '/', { mode: 0o777 | S_IFDIR });
+		} catch (e: any) {
+			const error = e as ErrnoError;
+			if (error.code != 'EEXIST') throw error;
+		}
+
+		if (parent) parent.appendChild(this.document.documentElement);
+	}
+
+	public renameSync(oldPath: string, newPath: string): void {
+		const node = this.get('rename', oldPath);
+		remove_path(node, oldPath);
+		add_path(node, newPath);
+	}
+
+	public statSync(path: string): Stats {
+		return get_stats(this.get(path, 'stat'));
+	}
+
+	public openFileSync(path: string, flag: string): File {
+		const node = this.get('openFile', path);
+		return new PreloadFile(this, path, flag, get_stats(node), encodeRaw(node.textContent!));
+	}
+
+	public createFileSync(path: string, flag: string, mode: number): File {
+		const stats = new Stats({ mode: mode | S_IFREG });
+		this.create('createFile', path, stats);
+		return new PreloadFile(this, path, flag, stats);
+	}
+
+	public unlinkSync(path: string): void {
+		const node = this.get('unlink', path);
+		if (get_stats(node).isDirectory()) throw ErrnoError.With('EISDIR', path, 'unlink');
+		remove_path(node, path);
+	}
+
+	public rmdirSync(path: string): void {
+		const node = this.get('rmdir', path);
+		if (node.textContent?.length) throw ErrnoError.With('ENOTEMPTY', path, 'rmdir');
+		if (!get_stats(node).isDirectory()) throw ErrnoError.With('ENOTDIR', path, 'rmdir');
+		remove_path(node, path);
+	}
+
+	public mkdirSync(path: string, mode: number): void {
+		this.create('mkdir', path, { mode: mode | S_IFDIR });
+	}
+
+	public readdirSync(path: string): string[] {
+		const node = this.get('readdir', path);
+		if (!get_stats(node).isDirectory()) throw ErrnoError.With('ENOTDIR', path, 'rmdir');
+		try {
+			return JSON.parse(node.textContent!) as string[];
+		} catch (e) {
+			throw new ErrnoError(Errno.EIO, 'Invalid directory listing: ' + e, path, 'readdir');
+		}
+	}
+
+	public linkSync(target: string, link: string): void {
+		const node = this.get('link', target);
+		add_path(node, link);
+	}
+
+	public syncSync(path: string, data: Uint8Array, stats: Readonly<Stats>): void {
+		const node = this.get('sync', path);
+		node.textContent = decodeRaw(data);
+		set_stats(node, stats);
+	}
+
+	public toString(): string {
+		return new XMLSerializer().serializeToString(this.document);
+	}
+
+	protected get(syscall: string, path: string): Element {
+		const { children } = this.document.documentElement;
+		for (let i = 0; i < children.length; i++) {
+			if (get_paths(children[i]).includes(path)) return children[i];
+		}
+		throw ErrnoError.With('ENOENT', path, syscall);
+	}
+
+	protected create(syscall: string, path: string, stats: Partial<StatsLike<number>> = {}): Element {
+		if (this.existsSync(path)) throw ErrnoError.With('EEXIST', path, syscall);
+		const node = this.document.createElement('file');
+		node.setAttribute('paths', JSON.stringify([path]));
+		set_stats(node, stats);
+		this.document.append(node);
+		return node;
+	}
+}
+
+const _XML = {
+	name: 'XML',
+	options: {
+		parent: { type: 'object', required: false },
+	},
+	isAvailable(): boolean {
+		return true;
+	},
+	create(options: XMLOptions) {
+		return new XMLFS(options.parent);
+	},
+} satisfies Backend<XMLFS, XMLOptions>;
+
+type _XML = typeof _XML;
+// eslint-disable-next-line @typescript-eslint/no-empty-object-type
+export interface XML extends _XML {}
+/**
+ * @experimental
+ */
+export const XML: XML = _XML;