Re: LARGE_READX / LARGE_WRITEX support

I am going to place this patch in a patches directory. I have removed
the Encdec change however. I believe the correct fix for that issue is
the following in doRecv:

  int size = Encdec.dec_uint16be( BUF, 2 ) & 0xFFFF;

It's correct for dec_uint16be to return a short. We just need to ensure
that the value bahaves as if it were unsigned which is a simple matter
of masking out the lower 16 bits.

Mike

On Wed, 19 Oct 2005 17:03:34 +0200
Thomas Krammer <Thomas_Krammer@xxxxxxxx> wrote:

> Hi,
> 
> the attached patch adds LARGE_READX / LARGE_WRITEX support to jCIFS 
> 1.2.6. It also fixes some problems I found along the way.
> 
> 1) Debug output in Transport.java
> 
> The patch removes some debug output that is printed to stdout.
> 
> 2) Integer overflow in SmbTransport.java
> 
> If you execute the following code:
> 
> SmbFile serverFile = ....
> SmbRandomAccessFile ra = new SmbRandomAccessFile(serverFile, "rw");
> 
> int BUFFER_SIZE = Short.MAX_VALUE;
> 
> byte[] buffer = new byte[BUFFER_SIZE];
> 
> ra.read(buffer);
> 
> you will get the following exception:
> 
> jcifs.util.transport.TransportException: Transport1 timedout waiting for 
> response to 
> SmbComReadAndX[command=SMB_COM_READ_ANDX,received=false,errorCode=0,flags=0x0018,flags2=0xC003,signSeq=0,tid=2048,pid=10207,uid=2048,mid=475,wordCount=12,byteCount=0,andxCommand=0xFF,andxOffset=0,fid=16384,offset=0,maxCount=32767,minCount=32767,openTimeout=-1,remaining=0,offset=0]
>          at jcifs.util.transport.Transport.sendrecv(Transport.java:74)
>          at jcifs.smb.SmbTransport.send(SmbTransport.java:580)
>          at jcifs.smb.SmbSession.send(SmbSession.java:229)
>          at jcifs.smb.SmbTree.send(SmbTree.java:102)
>          at jcifs.smb.SmbFile.send(SmbFile.java:688)
>          at jcifs.smb.SmbRandomAccessFile.read(SmbRandomAccessFile.java:86)
>          at jcifs.smb.SmbRandomAccessFile.read(SmbRandomAccessFile.java:69)
> 
> The reason for this error is an integer overflow in 
> SmbTransport.doRecv() line 422. If the specified buffer size is greater 
> than Short.MAX_VALUE - SMB_HEADER_LENGTH the package size gets negative 
> and the package is rejected. That's because Encdec.dec_uint16be returns 
> a short instead of an int.
> 
> Please note that there are more similar errors in Encdec (for example 
> dec_uint32be returns an int instead of a long). I didn't fix those 
> additional errors.
> 
> 3) LARGE_READX and LARGE_WRITEX support
> 
> The patch adds LARGE_READX and LARGE_WRITEX support for 
> SmbFileInputStream, SmbFileOutputStream and SmbRandomAccessFile. This 
> significantly increases the performance when transferring files from and 
> to Windows servers.
> 
> For example transferring a 183 MB file (using streams):
> 
>                 modified 1.2.6   original 1.2.6
> Download             23 sec           39 sec
> Upload                       26 sec           40 sec
> 
> Client: Windows XP SP 2, Java 1.4.2_08
> Server: Windows XP SP 2
> 
> The test used a 128k buffer to transfer the data from the InputStream to 
> the OutputStream.
> 
> 
> Bye,
> 
>    Thomas
> 
>