1var Stream = require('stream'); 2if (process.env.READABLE_STREAM === 'disable' && Stream) { 3 module.exports = Stream; 4 exports = module.exports = Stream.Readable; 5 exports.Readable = Stream.Readable; 6 exports.Writable = Stream.Writable; 7 exports.Duplex = Stream.Duplex; 8 exports.Transform = Stream.Transform; 9 exports.PassThrough = Stream.PassThrough; 10 exports.Stream = Stream; 11} else { 12 exports = module.exports = require('./lib/_stream_readable.js'); 13 exports.Stream = Stream || exports; 14 exports.Readable = exports; 15 exports.Writable = require('./lib/_stream_writable.js'); 16 exports.Duplex = require('./lib/_stream_duplex.js'); 17 exports.Transform = require('./lib/_stream_transform.js'); 18 exports.PassThrough = require('./lib/_stream_passthrough.js'); 19} 20