Stream.Read sometimes returns -1, what to do?

[mirzapirza]

It's not documented in the MSDN. The Read method is supposed to return the number of bytes read from the stream, or 0 if there's no more data.

Here's what I'm currently doing..

// reader is a Stream
using(reader = new WebClient().OpenRead(url))
{
	int read = 1;
	byte[] buff = new byte[4096];
	while(read != 0)
	{
		read = reader.Read(buff, 0, buff.Length);

		if(read > 0)
			writer.Write(buff, 0, read);
	}
}

Any ideas on how this -1 should be handled? I can't seem to find it documented anywhere.

http://mirzapirza.com/

 

[chiph]

I think you might have found a bug. The return value is definitely a count of bytes read, and you can't have a negative count of anything.

I would just test for it being less than 1.

Chip H.


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[obislavu]

I don't think the Stream.Read() returns -1.
The Stream.ReadByte{} could return -1 when the end stream.
You should write:
while(read >= 0)
{
...
}
-obislavu-

 

[mirzapirza]

obislavu, it does. Even when I use WebClient.DownloadFile I sometimes catch exceptions with an inner ArgumentException coming from the Stream.Read saying that the parameter 'count' can't be negative.

I was wondering how i should interpret this? Should I treat -1 like 0 and assume there's no more?

I guess I'll look around a bit and then send something to microsoft's newsgroups and see if they're fixing this.

 

[mirzapirza]

Uhm, Stream.Write that is..