Detect the end of a DeflateStream

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I've been reading stuff from a stream using BinaryReader in the normal way and I don't know how big the stream is - I don't care but I need to know when I get to the end, so I've been doing this:

C#

while (reader.BaseStream.Position < reader.BaseStream.Length)
{
    // do stuff
}

Now, as an enhancement I've compressed the data coming in and have attached a DeflateStream (with option inflate) between the previous stream and the reader:

using (DeflateStream inflation = new DeflateStream(stream, CompressionMode.Decompress, true))
{
    // create reader etc. as before
}

But now this doesn't work as neither Position or Length is supported on a DeflateStream. That makes sense as you'll never know how big it is until you've finished decompressing it. What I would expect to be able to do is tell whether I'm at the end or not.

At the moment, I know because it throws an exception. There has to a better way?

Posted 2-Sep-13 2:32am

Rob Philpott

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Bernhard Hiller 2-Sep-13 10:44am

What do you think of reader.Peek()?

Rob Philpott 2-Sep-13 11:05am

Thanks for the suggestion, but unfortunately that always returns -1 when the underlying stream doesn't support seeking, which DeflateStream doesn't. Hence it always reports end of stream!

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Keith Barrow · Accepted Answer · 2013-09-02T06:54:00

As you say the stream can't know it's size so the usual strategy for reading from a stream won't work. I found this SO solution http://stackoverflow.com/questions/1528508/uncompress-data-file-with-deflatestream[^].

Inside an "infinite" loop you keep reading:

C#

using (DeflateStream inflation = new DeflateStream(stream, CompressionMode.Decompress, true))
{
    byte[]  buffer = new byte[BUF_SIZE];
    while(true)
    {
        int lengthRead = inp.Read(buffer, 0, buffer.Length)
        if(lengthRead <= 0)
             break;
        // Transfer from buffer, but only transfer the first "lengthRead" number of bytes to prevent "overruns" in the final iteration.
    }
}

BUF_SIZE is the size of the buffer you want to use. I haven't used this before, so apologies in advance if it fails (can't test right now) but hopefully this should get you re-started.