Create a stream from an ArrayBuffer

arrayBufferStream.ts

import * as Stream from 'stream';

class ArrayBufferStream extends Stream.Readable {
    constructor(private _arrayBuffer: ArrayBuffer, opts?: Stream.ReadableOptions) {
        super(opts);
    }

    private _chunk_size = 1024 * 16;
    private _pointer = 0;

    _read(size: number) {
        size = size || this._chunk_size;

        if (this._pointer + size >= this._arrayBuffer.byteLength) {
            size = this._arrayBuffer.byteLength - this._pointer;
        }

        const from = this._pointer;
        this._pointer += size;

        // we use setTimeout here to yield to the UI thread, prevent it from locking up
        setTimeout(() => {
            if (size) {
                this.push(Buffer.from(this._arrayBuffer, from, size));
            } else {
                this.push(null);
            }
        }, 0);
    }
}

I use this with node-csvtojson to efficiently stream large csv files (500MB / 2,000,000 records) into ag-grid.