zlib.unzip gives me an empty result

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Feb 1, 2012, 11:01:55 AM2/1/12
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Please help I don't know what's happening. 
I'm connecting to Gnip stream api which emits json messages using gzip. But when I try to unzip incoming data, I get an empty buffer!

This is the code that makes the request. Basically it's the same as the example given in http://nodejs.org/docs/latest/api/zlib.html#zlib.Unzip

var options = {
host : 'stream.gnip.com',
port : 443,
method : 'get',
path : '/track/prod.json',
headers : {
'Authorization' : self._basicAuth(self.options.username, self.options.password),
'User-Agent' : self.options.userAgent,
'Accept-Encoding' : 'gzip,deflate'

self._req = https.request(options, function(res) {
res.on('data', function(chunk) {
console.log(chunk.toString()) // this prints a lot of strange stuff
zlib.unzip(chunk, function(err, res) {
console.log(res.toString()) // empty!
if (err) self.emit('error', err);
else self.parser.receive(res);
res.on('end', function() {
self._req.on('error', function(e) {
self.emit('error', e);

Isaac Schlueter

Feb 1, 2012, 2:03:17 PM2/1/12
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The zlib.unzip() method assumes that you have *all* the data. HTTP
requests in node send the data bit by bit. It's possible that what
you have in that first chunk isn't the whole gzip'ed file.

If you want to process it one chunk at a time (which is probably best)
use a zlib.Unzip() object rather than the convenience method.

var unzipper = zlib.Unzip()
req.on("data", function (c) {
req.on("end", function () {
unzipper.on("data", function (c) {
// some unzipped data
unzipper.on("end", function () {
// no more unzipped data is coming

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Isaac Schlueter

Feb 1, 2012, 2:04:07 PM2/1/12
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Oops, pedantic error. Should be:

var unzipper = new zlib.Unzip()

(Though, the function detects this and does the right thing anyway.)

Demián Andrés Rodriguez

Feb 1, 2012, 2:12:19 PM2/1/12
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Thanks. I've just done that and it seems to work!
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