streampunk

This project is an experimental "classical" Flow-based programming-like system for JavaScript, providing an idiomatic JavaScript API requiring minimal boilerplate, implemented using standard JavaScript constructs. It aims to support major JavaScript platforms, including Node.js and browsers.

The core API uses Streams (and eventually here) and Promises. It also supports coroutines via ECMAScript 6 generator functions and yield, providing a style familiar to users of other classical-FBP systems.

It is implemented in ECMAScript 6, via Babel.

This project is inspired by J. Paul Morrison's jsfbp project, and, of course, his larger body of work on FBP.

Usage
-----

npm install
npm test

npm install -g babel
babel-node examples/reverse

To try a browser example, run make then open "examples/browser/index.html" in the browser.

Features
--------

* "classical mode" components: traditional FBP send and recieve API (returns a promise, which can be yielded in a generator function)
* "reactive mode" components: Node.js Stream API (e.x. pipe, .on("data", ...), .write(...), etc)
* mix and match classical and reactive components.
* compatibility with Node.js text/binary streams via StreamAdapter
* array ports, as well as named and nested ports
* rich object IPs (e.x. all types supported by JSON: strings, numbers, boolean, array, object)

Example Components
------------------

The following are examples of a trivial "copier" component written in 3 different styles:

$3

async function copier() {
let ip;
while ((ip = await this.input('IN').receive()) !== null) {
await this.output('OUT').send(ip);
}
}

Note the use of a generator function, which allows yielding of the Promises returned by send and receive. These methods use Stream's backpressure facilities (write() returning false and the drain event) internally to pause execution. The process ends when the generator function returns (regardless of whether the output streams have been closed).

$3

Ports are just Node Streams, so you can pipe between them:

function copier() {
this.input("IN").pipe(this.output("OUT"));
}

This uses Stream's pipe API to pipe the input to the output (automatically handling back-pressure, and closing the output stream when the input stream ends)

The StreamAdapter component (and WrapIP and UnwrapIP Transform streams) can be used to adapt Node streams.

$3

The following is much more verbose, but demonstrates using the raw EventEmitter/Stream API:

function copier() {
let IN = this.input("IN");
let OUT = this.output("OUT");
IN.on("data", (ip) => {
if (OUT.write(ip) === false) {
IN.pause();
}
});
IN.on("finish", () => OUT.end());
OUT.on("drain", () => IN.resume());
}

Note this version must manually handle back-pressure via the input port's pause() and resume() functions, and the output port's write() return value and drain event.

Example Networks
----------------

function delay_example() {
let sender0 = this.proc(Emitter(["a","b","c"]), "sender0");
let delay0 = this.proc(delay, "delay0", { "INTVL": 1000 });
let receiver0 = this.proc(StreamAdapter(process.stdout), "receiver0");

this.connect(sender0.output("OUT"), delay0.input("IN"));
this.connect(delay0.output("OUT"), receiver0.input("IN"));
}

This network defines 3 processes, a sender which simply sends 3 hard-coded IPs, a delay componenent which delays IPs for 1 second (configured with the INTVL port), and a receiver which sends the IPs' contents to the stdout stream.

TODO
----

* deadlock detection
* back pressure support is experimental/work-in-progress