[Box Backup] Experimental questions on boxbackup

[Ben Summers]

On 1 Jul 2005, at 16:32, Noah yan wrote:

> Dear All,
>
> I am doing some experiment on boxbackup for its performance. Several
> questions about the rollingchecksum of rsync: thanks in advance for
> answering

see notes/encrypt_rsync.txt which explains what's going on in the  
algorithm. It's not the same as rysnc. The concept is almost the  
same, but the actual algorithms are quite different. Encryption makes  
things difficult.

> 1. What the block size of each file are splited to calculate its
> checksum? Or what is the range if it is fixed

see BackupStoreFileEncodeStream::CalculateBlockSizes() in lib/ 
backupclient/BackupStoreFileEncodeStream.cpp

> 2. What if there are overflow when calcualting the sum, such as the a
> and b in rollingchecksum algorithm. I noticed that a is 16bit as sum
> for 8bit data, how overflow is handled if have in the algorithm, or
> other ways to avoid this?

see lib/crypto/RollingChecksum.h / .cpp

That's the lovely thing about open source. You have the source! And  
in this case, documentation too.

Ben