@johngw/stream
Version:
Reactive programming tools using the WHATWG Streams API.
48 lines • 1.42 kB
JavaScript
import { write } from '@johngw/stream-common/Stream';
/**
* Buffers the source stream chunks until `notifier` emits.
*
* @group Transformers
* @example
* ```
* --a--b--c--d--e--f--g--h--i--|
*
* buffer(
* --------B--------B--------B--|
* )
*
* --------[a,b,c]--[d,e,f]--[g,h,i]-|
* ```
*/
export function buffer(notifier, maxBuffer = Number.MAX_SAFE_INTEGER) {
const abortController = new AbortController();
let buffer = [];
return new TransformStream({
start(controller) {
notifier
.pipeTo(write(() => {
if (buffer.length) {
controller.enqueue(buffer);
buffer = [];
}
}), { signal: abortController.signal })
.then(() =>
// Typescript still thinks that `flush` may not be set.
// eslint-disable-next-line @typescript-eslint/no-non-null-assertion
this.flush(controller))
.catch((error) => controller.error(error));
},
transform(chunk) {
if (buffer.length === maxBuffer)
buffer.shift();
buffer.push(chunk);
},
flush(controller) {
if (buffer.length)
controller.enqueue(buffer);
controller.terminate();
abortController.abort();
},
});
}
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