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

Standard library for Node.js

import { Transform } from 'node:stream';
/**
 * Similar to RxJS bufferCount(),
 * allows to "chunk" the input stream into chunks of `opt.chunkSize` size.
 * Last chunk will contain the remaining items, possibly less than chunkSize.
 *
 * `chunkSize` indicates how many items to include in each chunk.
 * Last chunk will contain the remaining items, possibly less than chunkSize.
 */
export function transformChunk(chunkSize, opt) {
    let buf = [];
    return new Transform({
        objectMode: true,
        highWaterMark: 1,
        ...opt,
        transform(chunk, _, cb) {
            buf.push(chunk);
            if (buf.length >= chunkSize) {
                cb(null, buf);
                buf = [];
            }
            else {
                cb();
            }
        },
        final(cb) {
            if (buf.length) {
                this.push(buf);
                buf = [];
            }
            cb();
        },
    });
}