compress bug?

testcase.js

var fs = require('fs');
var url = require('url');
var path = require('path');
var http = require('http');
var mime = require('mime');
var zlib = require('zlib');

// Define compression types
var compressors = {
  gzip: zlib.createGzip,
  deflate: zlib.createDeflate
};

var server = http.createServer();

server.on('request', function (req, res) {
  if (req.url === '/favicon.ico') {
    res.end();
    return;
  }

  route(req, res);
});

server.listen(8000, '127.0.0.1');

function route(req, res) {
  var pathname = path.join(
    path.dirname(module.filename),
    '../../project/static',
    url.parse(req.url).pathname
  );

  // set response code
  res.statusCode = 200;

  // Set cache control headers
  res.setHeader('Expires', 'Mon, 26 Jul 1997 05:00:00 GMT');
  res.setHeader('Cache-Control', 'no-cache, private, must-revalidate, ' +
                                 'max-stale=0, post-check=0, pre-check=0 no-store');
  res.setHeader('Pragma', 'no-cache');

  // get content type header
  var type = mime.lookup(pathname);
  var charset = mime.charsets.lookup(type);

  // assume charset is UTF-8 if is handled by a compress stream
  if (!charset && /json|text|javascript/.test(type)) {
    charset = 'UTF-8';
  }

  // set mime and charset
  res.setHeader('Content-Type', type + (charset ? '; charset=' + charset : ''));

  // create read stream and add to domain
  var file = fs.createReadStream(pathname);
      file.pause();

  fs.stat(pathname, function (error, stat) {
    if (error) return file.emit('error', error);

    file.mtime = stat.mtime;
    file.size = stat.size;
    file.emit('ready');
  });

  file.once('ready', function () {
    // set mtime and size headers
    res.setHeader('Last-Modified', file.mtime.toUTCString());
    res.setHeader('Content-Length', file.size); // don't do this - bug

    var stream = open(req, res);
    // HEAD request, nothing should be writen
    if (stream === false) {
      file.destroy();
    }

    // pipe file content to http response stream
    else {
      file.pipe( stream );
      file.resume();
    }
  });
}

function open(req, res) {
  // set Date header
  res.setHeader('Date', new Date().toUTCString());

  // do only compress plain text
  if (/json|text|javascript/.test(res.getHeader('Content-Type')) === false) {
    return res;
  }

  // get accept encodeing
  var accept = req.headers['accept-encoding'];

  // Indicate the the respons is depends on accept-encoding
  res.setHeader('Vary', 'Accept-Encoding');

  // get compressor
  var method = null;
  if (accept === undefined) {
    method = null;
  } else if (accept.trim() === '*') {
    method = 'gzip';
  } else if (accept.indexOf('deflate') !== -1) {
    method = 'gzip';
  } else if (accept.indexOf('gzip') !== -1) {
    method = 'deflate';
  }

  // set content-encoding if possible
  if (method) {
    res.setHeader('Content-Encoding', method);
  }

  // http HEAD means that no respons is wanted,
  // but the header should be the same as it GET coresponding request
  if ('HEAD' == req.method) {
    res.end();
    return false;
  }

  // return write stream
  if (method) {
    var stream = compressors[method]();
    stream.pipe(res);

    return stream;
  }

  // default to identity encodeing
  return res;
}