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:
“I were content to wearie out my paine,
To bee Narsissus so she were a spring
To drowne in hir those woes my heart do wring:
And more I wish transformed to remaine:
That whilest I thus in pleasures lappe did lye,
I might refresh desire, which else would die.”
—Thomas Lodge (1558?–1625)
“A woman does not have to make decisions based on the need to survive. She can cut through issues, call shots as she sees them.... Many bad decisions are made by men in government because it is good for them personally to make bad public decisions.”
—Dianne Feinstein (b. 1933)