[jbosscache-dev] Re: Any reason not to use ExposedByteArrayOutputStream instead of ByteArrayOutputStream ?

[Bela Ban]

Manik Surtani wrote:
> cc'ing JBC-dev.
>
> The stream looks good, except that getting the raw buffer would mean 
> that the buffer returned would "almost certainly be longer than the 
> data written to it" (quoted from Brian's excellent javadocs).  Bela, 
> how would JGroups behave with this?  Would it attempt to stream the 
> entire buffer, including uninitialized values?

Yes, good point, this is not good !  You would have to return an 
org.jgroups.util.Buffer which has the byte[] buffer but also offset and 
length:

public class Buffer {
    private final byte[] buf;
    private final int offset;
    private final int length;

    public Buffer(byte[] buf, int offset, int length) {
        this.buf=buf;
        this.offset=offset;
        this.length=length;
    }

    public byte[] getBuf() {
        return buf;
    }

    public int getOffset() {
        return offset;
    }

    public int getLength() {
        return length;
    }

    public Buffer copy() {
        byte[] new_buf=buf != null? new byte[length] : null;
        int new_length=new_buf != null? new_buf.length : 0;
        if(new_buf != null)
            System.arraycopy(buf, offset, new_buf, 0, length);
        return new Buffer(new_buf, 0, new_length);
    }

    public String toString() {
        StringBuilder sb=new StringBuilder();
        sb.append(length).append(" bytes");
        if(offset > 0)
            sb.append(" (offset=").append(offset).append(")");
        return sb.toString();
    }

}


In addition, I would have to change Marshaller to use a Buffer :
 public interface Marshaller {
        *Buffer* objectToByteBuffer(Object obj) throws Exception;
        Object objectFromByteBuffer(*Buffer* buf) throws Exception;
    }


This should have far-reaching consequences as I'm not aware of anyone 
else but JBossCache to use Marshaller. Or maybe, to be on the safe side, 
I could create a Marshaller2 so existing code doesn't break (extending 
Marshaller)... http://jira.jboss.com/jira/browse/JGRP-796That should

> Will need to see how this gets de-serialized as well.  Also, since all 
> cacheloaders use the same marshaller, will need to see how they deal 
> with this as well.  Any code that relies on buf.length may end up at 
> best writing unnecessary data and at worst breaking when deserializing. 
That shouldn't be an issue because your JBC marshalling code creates 
local variables, and doesn't reuse ByteArrayOutputStream instances


-- 
Bela Ban
Lead JGroups / Clustering Team
JBoss - a division of Red Hat