@johngw/stream/dist/transformers/buffer.js

Reactive programming tools using the WHATWG Streams API.

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();
        },
        cancel() {
            abortController.abort();
        },
    });
}
//# sourceMappingURL=buffer.js.map