Question

I am using a slightly modified version of the DotZlib which is part of the contrib directory with the zlib source code to inflate a realtime data stream.

Instead of the regular inflateInit I need to use InflateInit2 – but this the only difference to the provided library.

Netherlesse after a couple of reads I receive error code 1 from the zlib and do not manage to recover when adding bytes.

The original code from the zlib contrib directory is:

    public override void Add(byte[] data, int offset, int count)
        {
            if (data == null) throw new ArgumentNullException();
            if (offset < 0 || count < 0) throw new ArgumentOutOfRangeException()
;
            if ((offset+count) > data.Length) throw new ArgumentException();

            int total = count;
            int inputIndex = offset;
            int err = 0;

            while (err >= 0 && inputIndex < total)
            {
                copyInput(data, inputIndex, Math.Min(total - inputIndex, kBufferSize));
                err = inflate(ref _ztream, (int)FlushTypes.None);
                if (err == 0)
                    while (_ztream.avail_out == 0)
                    {
                        OnDataAvailable();
                        err = inflate(ref _ztream, (int)FlushTypes.None);
                    }

                inputIndex += (int)_ztream.total_in;
            }
            setChecksum( _ztream.adler );
        }

BTW Does anyone know how to contribute improved code? The implementation is nicely designed, but incomplete from my point of view.

Answer 1

I think that

            err = inflate(ref _ztream, (int)FlushTypes.None);
            if (err == 0)
                while (_ztream.avail_out == 0)
                {
                    OnDataAvailable();
                    err = inflate(ref _ztream, (int)FlushTypes.None);
                }

should be

            while (_ztream.avail_in > 0)
            {
                err = inflate(ref _ztream, (int)FlushTypes.None);
                if (err!=0)
                    break;
                OnDataAvailable();
            }

There are two problems I see with the first version of the code:

1. if inflate() produces data but does not produce enough data to make avail_out be 0, you won’t call OnDataAvailable, even though data is available.
2. you might call inflate() even though avail_in is 0, which I could easily imagine might produce a stream-end error.

(NB: I suspect that you know me in a professional capacity. This answer is given in a private capacity and is not related to my work for my employer.)