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- 'use strict';
- const {Transform} = require('stream');
-
- class ObjectTransform extends Transform {
- constructor() {
- super({
- objectMode: true
- });
- }
- }
-
- class FilterStream extends ObjectTransform {
- constructor(filter) {
- super();
- this._filter = filter;
- }
-
- _transform(data, encoding, callback) {
- if (this._filter(data)) {
- this.push(data);
- }
-
- callback();
- }
- }
-
- class UniqueStream extends ObjectTransform {
- constructor() {
- super();
- this._pushed = new Set();
- }
-
- _transform(data, encoding, callback) {
- if (!this._pushed.has(data)) {
- this.push(data);
- this._pushed.add(data);
- }
-
- callback();
- }
- }
-
- module.exports = {
- FilterStream,
- UniqueStream
- };
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