Duplexer.js for node v0.10

duplexer.js

var vNext = !!require('stream').Duplex;
var DuplexBase = require(vNext ? 'stream' : 'readable-stream').Duplex;
var Readable = require(vNext ? 'stream' : 'readable-stream').Readable;

function Duplex(writer, reader, options) {
  DuplexBase.call(this, options);
  var _reader = new Readable();
  _reader.wrap(reader);
  reader = _reader;
  var self = this;
  this._read = function (size) {
    var buf;
    read();
    function read() {
      while (buf = reader.read(size))
        if (!self.push(buf)) return;
      reader.once('readable', read);
    }
  };
  reader.on('end', function () {
    self.push(null);
  });

  this._write = function (chunk, encoding, callback) {
    if (writer.write(chunk, encoding)) {
      callback();
    } else {
      writer.once('drain', callback);
    }
  };
  this.on('finish', function () {
    writer.end();
  });

  reader.on('error', function (err) {
    self.emit('error', err);
  });
  writer.on('error', function (err) {
    self.emit('error', err);
  });
}
Duplex.prototype = Object.create(DuplexBase.prototype);
Duplex.prototype.constructor = Duplex;