Release 1.02 part 6 page 40

The text says:

<blockquote>
The formula to calculate the amount of padding depends on the amount of data that needs to be sent (called BytesToWrite). The sender shall first calculate the maximum amount of space available in the MessageChunk (called MaxBodySize) using the following formula:

MaxBodySize = PlainTextBlockSize * Floor((MessageChunkSize –

HeaderSize – SignatureSize - 1)/CipherTextBlockSize) –
SequenceHeaderSize;

</blockquote>

In fact, this maxBodySize might be underestimated , a better formula would be :

    this.maxBlock     =  Math.floor( ( this.chunkSize - this.headerSize ) / this.cipherBlockSize);
    this.maxBodySize  = this.plainBlockSize * this.maxBlock - this.sequenceHeaderSize - this.signatureLength - 1 ;