@barchart/common-node-js/stream/IteratorReadStream.js

Common classes, utilities, and functions for building Node.js servers

const assert = require('@barchart/common-js/lang/assert'),
	object = require('@barchart/common-js/lang/object');

const Stream = require('stream');

module.exports = (() => {
	'use strict';

	class IteratorReadStream extends Stream.Readable {
		constructor(iterator, options) {
			super(object.merge({ objectMode: true }, (options || { })));

			this._iterator = iterator;
		}

		_read() {
			let next = this._iterator.next();
			let value;

			if (next.done) {
				value = null;
			} else {
				value = next.value;
			}

			this.push(value);
		}

		/**
		 * @param {Array<Object>} a
		 * @returns {IteratorReadStream}
		 */
		static fromArray(a) {
			assert.argumentIsArray(a, 'a');

			return new IteratorReadStream(a[Symbol.iterator]());
		}

		/**
		 * @param {Map} m
		 * @returns {IteratorReadStream}
		 */
		static fromMap(m) {
			assert.argumentIsRequired(m, 'm', Map, 'Map');

			return new IteratorReadStream(m.values());
		}

		toString() {
			return '[IteratorReadStream]';
		}
	}

	return IteratorReadStream;
})();