stream-switcher

stream-switcher is a utility function that provides a flexible mechanism to dynamically switch between active streams while maintaining seamless data flow. It allows you to designate one active stream at a time, forwarding data and handling connections without interference from previously connected streams. The utility also supports optional buffering when paused, preventing data loss during stream transitions.

Usage

Importing stream-switcher

import { createStreamSwitcher } from 'stream-switcher';

Basic Example

Initialize createStreamSwitcher with an initial stream, allowing data to flow through it:

import { PassThrough } from 'streamx';
import { createStreamSwitcher } from 'stream-switcher';

const initialStream = new PassThrough();
const switcher = createStreamSwitcher(initialStream);

// Capture data from the active stream
switcher.on('data', (chunk) => {
  console.log('Received:', chunk.toString());
});

// Write data to the initial stream
initialStream.write('Hello from the initial stream!');

Switching to a New Stream

Use the switch method to replace the active stream with a new one, seamlessly transferring data flow to the new stream:

const newStream = new PassThrough();
switcher.switch(newStream);

newStream.write('Hello from the new stream!');

Writing to the Active Stream

The switcher can also function as a writable stream, where data sent to switcher.write() will be forwarded to the current active stream:

switcher.write('Forwarded to active stream');

Handling Buffering When Paused

You can configure createStreamSwitcher to buffer data when no active stream is set:

const switcher = createStreamSwitcher(null, { bufferWhenPaused: true, maxBufferSize: 50 });

// Data written while paused will be buffered
switcher.write('Buffered data');

// Set an active stream to flush buffered data
const activeStream = new PassThrough();
switcher.switch(activeStream);

Features

• Dynamic Stream Switching: Easily swap active streams without disrupting data flow from previous connections.
• Bi-directional Data Forwarding: switcher relays data to and from the active stream seamlessly.
• Configurable Buffering: Optionally buffer data when no active stream is set, with customizable buffer limits.
• Automatic Listener Management: Only the active stream pushes data to switcher, ensuring data consistency and efficient resource management.

Special Behavior with null or undefined

Calling switcher.switch(null) or switcher.switch(undefined) will pause the stream and, if bufferWhenPaused is enabled, data written to the switcher will be buffered until a new active stream is set.

API

createStreamSwitcher(initialStream, config)

Creates a new Duplex instance output stream that facilitates stream switching.

• initialStream (optional): The first stream to connect to the switcher.
• config (optional): The configuration supplied to the output stream.
  • bufferWhenPaused (boolean, default: false): Whether to buffer data when paused.
  • maxBufferSize (number, default: 100): The maximum number of items to buffer when paused.

switcher.switch(newStream)

Changes the active stream to the provided newStream.

• newStream: The new stream that becomes the active stream for switcher.

License

MIT License. See LICENSE file for full details.

For questions, issues, or contributions, feel free to reach out or create a pull request!