feat(lp32): Implement Chrome host message protocol
MODIFY
package.json
package.json
"packages/endo",
"packages/eslint-config",
"packages/eslint-plugin",
+ "packages/lp32",
"packages/netstring",
"packages/promise-kit",
"packages/ses",

ADD
packages/lp32/LICENSE
+ Apache License
+ Version 2.0, January 2004
+ http://www.apache.org/licenses/
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ADD
packages/lp32/NEWS.md
packages/lp32/NEWS.md
ADD
packages/lp32/README.md
+# LP32
+
+Also known as the web extension "Native Host Message" protocol, this package
+implements async iterator streams for reading and writing with 32-bit
+host-byte-order length-prefix message envelopes for binary data, represented
+with Uint8Arrays.
+
+These streams are "hardened" and depend on Hardened JavaScript.
+Most JavaScript environments can be locked down with the
+[SES shim](https://github.com/endojs/endo/blob/master/packages/ses/README.md).

ADD
packages/lp32/index.d.ts
+export { makeLp32Reader } from './reader.js';
+export { makeLp32Writer } from './writer.js';

ADD
packages/lp32/index.js
+export { makeLp32Reader } from './reader.js';
+export { makeLp32Writer } from './writer.js';

ADD
packages/lp32/jsconfig.json
+{
+ "compilerOptions": {
+ "target": "esnext",
+ "module": "esnext",
+ "noEmit": true,
+ "downlevelIteration": true,
+ "strictNullChecks": true,
+ "moduleResolution": "node"
+ },
+ "include": ["src/**/*.js", "index.d.ts"]
+}

ADD
packages/lp32/package.json
+{
+ "name": "@endo/lp32",
+ "version": "0.2.13",
+ "description": "32 bit unsigned host byte order length prefix message streams as async iterators",
+ "keywords": [
+ "stream",
+ "endo",
+ "chrome",
+ "extension",
+ "native",
+ "host",
+ "messaging",
+ "length-prefix",
+ "async",
+ "iterator"
+ ],
+ "author": "Endo contributors",
+ "license": "Apache-2.0",
+ "homepage": "https://github.com/endojs/endo/tree/master/packages/netstring#readme",
+ "repository": {
+ "type": "git",
+ "url": "git+https://github.com/endojs/endo.git"
+ },
+ "bugs": {
+ "url": "https://github.com/endojs/endo/issues"
+ },
+ "type": "module",
+ "main": "./index.js",
+ "module": "./index.js",
+ "types": "./index.d.ts",
+ "exports": {
+ ".": "./index.js",
+ "./reader.js": "./reader.js",
+ "./writer.js": "./writer.js",
+ "./package.json": "./package.json"
+ },
+ "scripts": {
+ "build": "exit 0",
+ "cover": "c8 ava",
+ "lint": "yarn lint:types && yarn lint:js",
+ "lint-fix": "eslint --fix .",
+ "lint:js": "eslint .",
+ "lint:types": "tsc --build jsconfig.json",
+ "test": "ava"
+ },
+ "dependencies": {
+ "@endo/stream": "^0.1.0",
+ "ses": "^0.15.3"
+ },
+ "devDependencies": {
+ "@endo/eslint-config": "^0.3.20",
+ "@endo/ses-ava": "^0.2.13",
+ "ava": "^3.12.1",
+ "babel-eslint": "^10.0.3",
+ "c8": "^7.7.3",
+ "eslint": "^7.23.0",
+ "eslint-config-airbnb-base": "^14.0.0",
+ "eslint-config-prettier": "^6.9.0",
+ "eslint-plugin-eslint-comments": "^3.1.2",
+ "eslint-plugin-import": "^2.19.1",
+ "eslint-plugin-prettier": "^3.1.2",
+ "prettier": "^1.19.1",
+ "typescript": "^4.0.5"
+ },
+ "files": [
+ "LICENSE*",
+ "index.d.ts",
+ "index.js",
+ "reader.js",
+ "writer.js"
+ ],
+ "publishConfig": {
+ "access": "public"
+ },
+ "eslintConfig": {
+ "extends": [
+ "@endo"
+ ]
+ },
+ "prettier": {
+ "trailingComma": "all",
+ "singleQuote": true
+ },
+ "ava": {
+ "files": [
+ "test/**/test-*.js"
+ ],
+ "timeout": "2m"
+ }
+}

ADD
packages/lp32/reader.js
+// @ts-check
+/// <reference types="ses"/>
+
+// We use a DataView to give users choice over endianness.
+// But DataView does not default to host-byte-order like other typed arrays.
+
+import { hostIsLittleEndian } from './src/host-endian.js';
+
+const { details: X, quote: q } = assert;
+
+/**
+ * @param {Iterable<Uint8Array> | AsyncIterable<Uint8Array>} reader
+ * @param {Object} [opts]
+ * @param {string=} [opts.name]
+ * @param {number} [opts.maxMessageLength] - defaults to 1MB
+ * @param {boolean=} [opts.littleEndian]
+ * @param {number=} [opts.initialCapacity]
+ * @returns {import('@endo/stream').Reader<Uint8Array, undefined>}
+ */
+async function* makeLp32Iterator(
+ reader,
+ {
+ name = '<unknown>',
+ initialCapacity = 1024,
+ maxMessageLength = 1024 * 1024, // 1MB
+ littleEndian = hostIsLittleEndian,
+ } = {},
+) {
+ let capacity = Math.max(4, initialCapacity);
+ let length = 0;
+ let array8 = new Uint8Array(capacity);
+ let data = new DataView(array8.buffer);
+ let offset = 0;
+
+ for await (const chunk of reader) {
+ if (length + chunk.byteLength >= capacity) {
+ while (length + chunk.byteLength >= capacity) {
+ capacity *= 2;
+ }
+ const replacement = new Uint8Array(capacity);
+ replacement.set(array8, 0);
+ array8 = replacement;
+ data = new DataView(array8.buffer);
+ }
+ array8.set(chunk, length);
+ length += chunk.byteLength;
+
+ let drained = false;
+ while (!drained && length >= 4) {
+ const messageLength = data.getUint32(0, littleEndian);
+ assert(
+ messageLength <= maxMessageLength,
+ X`Messages on ${q(
+ name,
+ )} must not exceed ${maxMessageLength} bytes in length`,
+ );
+ const envelopeLength = 4 + messageLength;
+ drained = envelopeLength > length;
+ if (!drained) {
+ // Must allocate to support concurrent reads.
+ yield array8.slice(4, envelopeLength);
+ // Shift
+ array8.copyWithin(0, envelopeLength);
+ length -= envelopeLength;
+ offset += envelopeLength;
+ }
+ }
+ }
+
+ if (length > 0) {
+ throw new Error(
+ `Unexpected dangling message of length ${length} at offset ${offset} of ${name}`,
+ );
+ }
+}
+
+/**
+ * @param {Iterable<Uint8Array> | AsyncIterable<Uint8Array>} reader
+ * @param {Object} [opts]
+ * @param {string=} [opts.name]
+ * @param {number=} [opts.capacity]
+ * @returns {import('@endo/stream').Reader<Uint8Array, undefined>} reader
+ */
+export const makeLp32Reader = (reader, opts) => {
+ return harden(makeLp32Iterator(reader, opts));
+};
+harden(makeLp32Reader);

ADD
packages/lp32/src/host-endian.js
+// @ts-check
+
+const isHostLittleEndian = () => {
+ const array8 = new Uint8Array([1, 0]);
+ const array16 = new Uint16Array(array8.buffer);
+ return array16[0] === 1;
+};
+
+export const hostIsLittleEndian = isHostLittleEndian();

ADD
packages/lp32/test/lockdown.js
+lockdown();

ADD
packages/lp32/test/test-lp32.js
+/* global setTimeout */
+// @ts-check
+
+import 'ses';
+import './lockdown.js';
+
+import rawTest from 'ava';
+import { wrapTest } from '@endo/ses-ava';
+
+import { makePipe } from '@endo/stream';
+import { makeLp32Reader } from '../reader.js';
+import { makeLp32Writer } from '../writer.js';
+import { hostIsLittleEndian } from '../src/host-endian.js';
+
+const encoder = new TextEncoder();
+const decoder = new TextDecoder();
+
+const test = wrapTest(rawTest);
+
+/**
+ * @param {import('@endo/stream').Stream<T, U, V>} reader
+ */
+async function arrayFromAsync(reader) {
+ const array = [];
+ for await (const chunk of reader) {
+ // Capture current state, allocating a copy.
+ array.push(chunk.slice());
+ }
+ return array;
+}
+
+test('read null message', async t => {
+ const r = makeLp32Reader([new Uint8Array([0, 0, 0, 0])], {
+ capacity: 1,
+ });
+ const array = await arrayFromAsync(r);
+ t.deepEqual(
+ [''],
+ array.map(chunk => decoder.decode(chunk)),
+ );
+});
+
+test('read null message across chunk boundary', async t => {
+ const r = makeLp32Reader([new Uint8Array([0, 0, 0]), new Uint8Array([0])], {
+ capacity: 1,
+ });
+ const array = await arrayFromAsync(r);
+ t.deepEqual(
+ [''],
+ array.map(chunk => decoder.decode(chunk)),
+ );
+});
+
+test('read messags of varying length at arbitrary chunk boundaries', async t => {
+ const order = [];
+
+ // Create a template of data to put in each message, as sequential numbers.
+ const template = new Uint8Array(10);
+ for (let i = 0; i < 10; i += 1) {
+ template[i] = i + 1;
+ }
+
+ // Measure out how long the whole stream will be.
+ let totalLength = 0;
+ for (let i = 0; i < 100; i += 1) {
+ const length = i % 10;
+ totalLength += 4 + length;
+ }
+
+ // Construct a scratch space of expected byte sequence of the entire stream.
+ const scratch = new Uint8Array(totalLength);
+ const data = new DataView(scratch.buffer);
+ {
+ let offset = 0;
+ for (let i = 0; i < 100; i += 1) {
+ const length = i % 10;
+ data.setUint32(offset, length, hostIsLittleEndian);
+ offset += 4;
+ const message = scratch.subarray(offset, offset + length);
+ message.set(template.subarray(0, length));
+ order.push(message.slice());
+ offset += length;
+ }
+ }
+
+ // Cut chunks along entirely different boundaries.
+ // Specifically Fibonacci lengths.
+ const chunks = [];
+ {
+ let offset = 0;
+ for (let i = 1, j = 1; offset < totalLength; [i, j] = [j, j + i]) {
+ const length = Math.min(i, totalLength - offset);
+ chunks.push(scratch.slice(offset, offset + length));
+ offset += length;
+ }
+ }
+
+ const totalChunkLength = chunks.reduce(
+ (length, chunk) => length + chunk.length,
+ 0,
+ );
+ t.is(totalChunkLength, totalLength);
+
+ const r = makeLp32Reader(chunks, {
+ capacity: 1,
+ name: '<fib-chunks>',
+ });
+ const array = await arrayFromAsync(r);
+ t.deepEqual(order, array);
+});
+
+/** @param {number} ms */
+function delay(ms) {
+ return new Promise(resolve => {
+ setTimeout(resolve, ms);
+ });
+}
+
+const makeArrayWriter = () => {
+ const array = [];
+ const writer = makeLp32Writer({
+ /**
+ * @param {Uint8Array} value
+ */
+ async next(value) {
+ // Provide some back pressure to give the producer an opportunity to make
+ // the mistake of overwriting the given slice.
+ await delay(10);
+ // slice to capture before yielding.
+ array.push(value.slice());
+ return { done: false };
+ },
+ async return() {
+ return { done: true };
+ },
+ async throw() {
+ return { done: true };
+ },
+ });
+ return { array, writer };
+};
+
+test('round-trip short messages', async t => {
+ const { array, writer } = makeArrayWriter();
+ await writer.next(encoder.encode(''));
+ await writer.next(encoder.encode('A'));
+ await writer.next(encoder.encode('hello'));
+ await writer.return();
+
+ t.deepEqual(
+ [encoder.encode(''), encoder.encode('A'), encoder.encode('hello')],
+ await arrayFromAsync(makeLp32Reader(array)),
+ );
+});
+
+test('concurrent writes', async t => {
+ const { array, writer } = makeArrayWriter();
+ await Promise.all([
+ writer.next(encoder.encode('')),
+ writer.next(encoder.encode('A')),
+ writer.next(encoder.encode('hello')),
+ writer.return(),
+ ]);
+
+ t.deepEqual(
+ [encoder.encode(''), encoder.encode('A'), encoder.encode('hello')],
+ await arrayFromAsync(makeLp32Reader(array)),
+ );
+});
+
+test('round-trip varying messages', async t => {
+ const array = ['', 'A', 'hello'];
+
+ for (let i = 1020; i < 1030; i += 1) {
+ array.push(new Array(i).fill(':').join(''));
+ }
+ for (let i = 2040; i < 2050; i += 1) {
+ array.push(new Array(i).fill(':').join(''));
+ }
+
+ t.plan(array.length);
+
+ const [input, output] = makePipe();
+
+ const producer = (async () => {
+ /** @type {import('@endo/stream').Writer<Uint8Array, undefined>} */
+ const w = makeLp32Writer(output);
+ for (let i = 0; i < array.length; i += 1) {
+ // eslint-disable-next-line no-await-in-loop
+ await w.next(encoder.encode(array[i]));
+ // eslint-disable-next-line no-await-in-loop
+ await delay(10);
+ }
+ await w.return();
+ })();
+
+ const consumer = (async () => {
+ /** @type {import('@endo/stream').Reader<Uint8Array, undefined>} */
+ const r = makeLp32Reader(input);
+ let i = 0;
+ for await (const message of r) {
+ await delay(10);
+ t.is(array[i], decoder.decode(message));
+ i += 1;
+ }
+ t.log('end');
+ })();
+
+ await Promise.all([producer, consumer]);
+});

ADD
packages/lp32/writer.js
+// @ts-check
+/// <reference types="ses"/>
+
+import { hostIsLittleEndian } from './src/host-endian.js';
+
+const { details: X, quote: q } = assert;
+
+/**
+ * @param {import('@endo/stream').Writer<Uint8Array, undefined>} output
+ * @param {Object} [opts]
+ * @param {number} [opts.maxMessageLength] - defaults to 1MB
+ * @param {string} [opts.name]
+ * @param {boolean} [opts.littleEndian] - defaults to host byte order
+ * @returns {import('@endo/stream').Writer<Uint8Array, undefined>}
+ */
+export const makeLp32Writer = (
+ output,
+ {
+ name = '<unknown-lp32-writer>',
+ maxMessageLength = 1024 * 1024, // 1MB
+ littleEndian = hostIsLittleEndian,
+ } = {},
+) => {
+ const writer = harden({
+ /** @param {Uint8Array} message */
+ async next(message) {
+ assert(
+ message.byteLength <= maxMessageLength,
+ X`Messages on ${q(
+ name,
+ )} must not exceed ${maxMessageLength} bytes in length`,
+ );
+ const array8 = new Uint8Array(4 + message.byteLength);
+ const data = new DataView(array8.buffer);
+ data.setUint32(0, message.byteLength, littleEndian);
+ array8.set(message, 4);
+ return output.next(array8);
+ },
+ async return() {
+ return output.return(undefined);
+ },
+ /** @param {Error} error */
+ async throw(error) {
+ return output.throw(error);
+ },
+ [Symbol.asyncIterator]() {
+ return writer;
+ },
+ });
+ return writer;
+};
+harden(makeLp32Writer);

feat(lp32): Implement Chrome host message protocol