zlib deflate/inflate failure

[jeffrson]

Hi,

I reported an issue against ws (websockets/ws#1669) which actually can be traced back to NodeJS (851a691678 - #26363), introduced from 11.10.1 to 11.11.0.

Essentially there is some deflate'd data that cannot be uncompressed successfully. I hope it's okay to point to related issue for code samples and further discussion. If not please tell - I'll extend this report.

[lpinca]

Here is a test case:

const zlib = require('zlib');

const data = zlib.deflateRawSync('Welcome');

const chunks = [];
const inflate = zlib.createInflateRaw();

inflate.on('data', function(chunk) {
  chunks.push(chunk);
});

inflate.write(data);
inflate.write(Buffer.from([0x00, 0x00, 0xff, 0xff]));
inflate.flush(function() {
  const buf = Buffer.concat(chunks);
  console.log(buf.toString());
});

The problem is that inflate.flush() callback is not called. This used to work before 28db96f.

Decompression follows the RFC 7692 specifications.

It is possible to use the 'end' event, for example if

inflate.on('end', function() {
  const buf = Buffer.concat(chunks);
  console.log(buf.toString());
});

is added to the above example it will work as expected but is it intended?

[lpinca]

cc: @addaleax

[addaleax]

This isn’t specific to flushes – in

const zlib = require('zlib');

const data = zlib.deflateRawSync('Welcome');

const inflate = zlib.createInflateRaw();

inflate.resume();
inflate.write(data, () => console.log('write 1 done'));
inflate.write(Buffer.from([0x00]), () => console.log('write 2 done'));
inflate.write(Buffer.from([0x00]), () => console.log('write 3 done'));

only the first two writes finish. I’ll try to figure out why that is.

[lpinca]

I did not investigate but I think it's because the inflate stream is no longer readable after a block with the BFINAL bit set to 1 is received.

[addaleax]

@lpinca Yeah, but other Transform streams seem to still allow writes to finish, even after .push(null). So I’ll look into that.