Smack's IBB sends too much data in a packet

I tried to send a file from Smack to SleekXMPP.

SleekXMPP currently supports only IBB (In-band Bytestream), the negotiation works fine.

But when Smack sends its first data packet, SleekXMPP shows the following message:

Bad file transfer packet received! Terminating session with SENDER_JID

seq 0: expected seq: 0

packet size: 5400 Max Block size: 4096

I checked org/jivesoftware/smackx/bytestreams/ibb/InBandBytestreamSession.java class

It turns out to be Smack that use a wrong buffer size.

XEP-0047 said "The base64-encoded data to be sent, prior to any wrapping in the <data/> element and IQ or message stanza, MUST NOT be larger' than the 'block-size' determined in the bytestream negotiation."

I think that block-size should be the length of 'base64-encoded data', which is longer than the actual data itself.

So, if we let the block-size=4096, the buffer size should be (4096 / 4)*3  = 3072 bytes.

(3 bytes of data will be encoded as 4 characters in base64 encoding)

I'd like to submit a patch to org/jivesoftware/smackx/bytestreams/ibb/InBandBytestreamSession.java (Smack 3.2.1)

with following buffer size calculation:

/* Old */

          public IBBOutputStream() {

             this.buffer = new byte[byteStreamRequest.getBlockSize()];

          }

/* New */

           public IBBOutputStream() {

             int maximumBytesPerPacket = (byteStreamRequest.getBlockSize() / 4) *3;

             this.buffer = new byte[maximumBytesPerPacket];

          }