Stream downloader of web resources, based on mikeal's request, but processed first through zlib if necessary

requestGzip.js

var request = require('request');
var zlib = require('zlib');

// A two-way passthrough Stream, made by @felixge
// https://github.com/felixge/node-passthrough-stream/blob/master/lib/passthrough_stream.js
var PassthroughStream = function () {
  this.writable = true;
  this.readable = true;
}
util.inherits(PassthroughStream, streams.Stream);
PassthroughStream.prototype.write = function(data) {
  this.emit('data', data);
};
PassthroughStream.prototype.end = function() {
  this.emit('end');
};
PassthroughStream.prototype.destroy = function() {
  this.emit('close');
};


// returns a Readable Stream from the resource, unzipping it if necessary
var requestGzip = function (requestOpts) {
	var gzipHeaders = ['application/x-gzip', 'application/gzip'];
	var req = request( requestOpts );
	var out = new PassthroughStream();
	req.on( 'response', function (res) {
		if (gzipHeaders.indexOf( res.headers['content-type'] ) !== -1) {
			return req.pipe(zlib.createGunzip()).pipe(out);
		}
		else {
			return req.pipe(out);
		}
	});
	return out;
};

// module api
module.exports = requestGzip