@naturalcycles/nodejs-lib/dist/stream/transform/transformLimit.js

Standard library for Node.js

import { Transform } from 'node:stream';
import { PIPELINE_GRACEFUL_ABORT } from '../stream.util.js';
import { transformNoOp } from './transformNoOp.js';
export function transformLimit(opt) {
    const { limit, signal, objectMode = true, highWaterMark = 1 } = opt;
    if (!limit) {
        return transformNoOp();
    }
    let i = 0; // so we start first chunk with 1
    let ended = false;
    return new Transform({
        objectMode,
        highWaterMark,
        transform(chunk, _, cb) {
            if (ended) {
                return;
            }
            i++;
            if (i === limit) {
                ended = true;
                this.push(chunk);
                this.push(null); // tell downstream that we're done
                cb();
                queueMicrotask(() => {
                    signal.abort(new Error(PIPELINE_GRACEFUL_ABORT));
                });
                return;
            }
            cb(null, chunk);
        },
    });
}