strata/lib/gzip.js

A modular, streaming HTTP server

var util = require('util');
var zlib = require('zlib');
var Request = require('./request');

/**
 * A middleware that gzip encodes the body of the response on the fly if the
 * client accepts gzip encoding. The options may be any of node's zlib
 * options (see http://nodejs.org/api/zlib.html) or any of the following:
 *
 *   - types  A regular expression that is used to match the Content-Type
 *            header to determine if the content is able to be gzip'd or
 *            not. Defaults to `/text|javascript|json/i`.
 */
module.exports = function (app, options) {
  options = options || {};

  var typeMatcher;
  if (util.isRegExp(options.types)) {
    typeMatcher = options.types;
    delete options.types;
  } else {
    typeMatcher = /text|javascript|json/i;
  }

  function gzip(env, callback) {
    app(env, function (status, headers, body) {
      var type = headers['Content-Type'];

      if (type && typeMatcher.exec(type)) {
        var req = new Request(env);

        // Make sure the client accepts gzip encoding first.
        if (req.acceptsEncoding('gzip')) {
          var gzip = zlib.createGzip(options);

          if (typeof body === 'string') {
            gzip.end(body);
          } else {
            body.pipe(gzip);
          }

          if ('Content-Length' in headers) {
            delete headers['Content-Length'];
          }

          headers['Vary'] = 'Accept-Encoding';
          headers['Content-Encoding'] = 'gzip';
          body = gzip;
        }
      }

      callback(status, headers, body);
    });
  }

  return gzip;
};