Content Based Slicing Using Rabin-Karp Hash
One of the interesting use cases of the rolling hash function is that it can create dynamic, content-based chunks of a stream or file. This is especially useful when it is required to send only the changed chunks of a large file over a network and a simple byte addition at the front of the file would cause all the fixed size windows to become updated, while in reality, only the first ‘chunk’ has been modified.
The simplest approach to calculate the dynamic chunks is to calculate the rolling hash and if it matches a pattern (like the lower N bits are all zeroes) then it’s a chunk boundary. This approach will ensure that any change in the file will only affect it’s current and possibly the next chunk, but nothing else.
When the boundaries are known, the chunks need to be compared by their hash values to detect which one was modified and needs transfer across the network.
Read more about this topic: Rolling Hash
Famous quotes containing the words content and/or based:
“First it must be known that only a spoken word or a conventional sign is an equivocal or univocal term; therefore a mental content or concept is, strictly speaking, neither equivocal nor univocal.”
—William of Occam (c. 1285–1349)
“Whoever invented the meeting must have had Hollywood in mind. I think they should consider giving Oscars for meetings: Best Meeting of the Year, Best Supporting Meeting, Best Meeting Based on Material from Another Meeting.”
—William Goldman (b. 1931)