setup-node/node_modules/get-stream/buffer-stream.js

'use strict';
const {PassThrough} = require('stream');

module.exports = options => {
	options = Object.assign({}, options);

	const {array} = options;
	let {encoding} = options;
	const buffer = encoding === 'buffer';
	let objectMode = false;

	if (array) {
		objectMode = !(encoding || buffer);
	} else {
		encoding = encoding || 'utf8';
	}

	if (buffer) {
		encoding = null;
	}

	let len = 0;
	const ret = [];
	const stream = new PassThrough({objectMode});

	if (encoding) {
		stream.setEncoding(encoding);
	}

	stream.on('data', chunk => {
		ret.push(chunk);

		if (objectMode) {
			len = ret.length;
		} else {
			len += chunk.length;
		}
	});

	stream.getBufferedValue = () => {
		if (array) {
			return ret;
		}

		return buffer ? Buffer.concat(ret, len) : ret.join('');
	};

	stream.getBufferedLength = () => len;

	return stream;
};