Asynchronous Streaming Adapter
Explore how to build a StreamAdapter that converts a legacy callback-based file reader into an async iterable using the async iterator protocol. Understand managing internal queues, resolving iteration promises, and bridging incompatible interfaces while maintaining seamless data flow for modern Node.js applications.
Problem statement
You maintain a legacy file reader utility that processes data in chunks. It uses a callback pattern to push each chunk of data, as shown:
legacyReader.readFile('log.txt', chunk => { ... });
Modern code in your app expects an async iterator that it can loop over using:
for await (const chunk of reader) { ... }
You need to write an adapter that makes the legacy callback-based reader compatible with this newer iteration model—without modifying the original code.
Goal
Implement a StreamAdapter class that wraps a legacy reader and exposes an async iterable interface.
for await (const chunk of new StreamAdapter(legacyReader, 'file.txt')) { ... }