[Nbserver-devel] Re: question

[Attila S. <sze...@fr...>]

the pipe's "auto-transfer" feature is useful when you want to have th=
e pipe
attempt writing to its associated auto-write channel whenever you wri=
te to
the pipe. If you want to transfer a file that is readily available (i=
.e. it
resides on a hard drive instead of being dinamically generated conten=
t)
you'd be better off by writing a protocol handler that opens a channe=
l to
the file, and whenever your protocol handler's "tryToWrite" method is
called, call fileChannel.transferTo(socketChannel, offset, length),
adjusting the offset along the way.

A minimalistic protocol handler that - after a client connects - send=
s over
a file would look like the code below. Note that you needn't use the
nonblocking pipe - this is because nonblocking pipe is for situations=
 where
your code generates the data. When the data is readily available in a=
 file,
you can send it over more efficiently.

public class FileSendProtocolHandler
implements
    ProtocolHandler
{
    private final FileChannel fileChannel;
    private final SocketChannel socketChannel
    private long offset =3D 0;
    private final long length;

    public FileSendProtocolHandler(File file, SocketChannel socketCha=
nnel)
    throws
        IOException
    {

        length =3D file.length();
        fileChannel =3D new FileInputStream(file).getChannel();
        this.socketChannel =3D socketChannel;
    }

    public int validOps()
    {
        return SelectionKey.OP_WRITE;
    }

    public boolean tryToRead()
    throws
        IOException
    {
        return true;
    }

    public boolean tryToWrite()
    throws
        IOException
    {
        boolean endWrite =3D false;
        try
        {
            while(offset < length)
            {
              int written =3D fileChannel.transferTo(offset, 4096,
socketChannel);
              if(written =3D=3D 0) break;
              offset +=3D written;
            }
            endWrite =3D offset =3D=3D length;
        }
        catch(IOException e)
        {
            endWrite =3D true;
            e.printStackTrace();
            throw e;
        }
        finally
        {
            if(endWrite)
            {
                fileChannel.close();
            }
        }
        return endWrite;
    }


--
Attila Szegedi
home: http://www.szegedi.org

----- Original Message -----
=46rom: ivanwang
To: sze...@us...
Sent: 2002. =E1prilis 22. 18:05
Subject: question


hi,szegedia

I have study the code of nbserver, but i have some questions about it=
.

I want to send a huge file and I have done as the following:
1) create a GlobalByteBufferPool object--pool
2)according to MEMORY_BLOCKSIZE,separate the huge file into blocks, a=
nd call
pool.putbuffer to be a ByteBuffer list.
3) create a NonblockingPipe object pipe=3D NonblockingPipe(pool)
4)call pipe.setAutoWriteChannel() and pipe.autoTransferTo() to send o=
ut the
huge file.

Is it okay? would you please give me some ideas?

Thank you very much!

ivan