Am Mon, 01 May 2017 21:01:43 +0000 schrieb notna <notna.remove.t...@ist-einmalig.de>:
> Hi Dlander's. > > Found some interesting reads ([1] [2] [3]) about the $SUBJECT and > wonder if there is anything available in the Dland?! > > If yes, pls. share. > If not, how could it be done (D'ish) > > [1] - > https://moinakg.wordpress.com/2013/06/22/high-performance-content-defined-chunking/ > - > https://github.com/moinakg/pcompress/blob/master/rabin/rabin_dedup.c > > [2] - > https://restic.github.io/blog/2015-09-12/restic-foundation1-cdc > > [3] - http://www.infoarena.ro/blog/rolling-hash > > Thanks & regards Interesting concept. I'm not aware of any D implementation but it shouldn't be difficult to implement this in D: https://en.wikipedia.org/wiki/Rolling_hash#Cyclic_polynomial There's a BSD licensed haskell implementation, so a BSD licensed port would be very easy to implement: https://hackage.haskell.org/package/optimal-blocks-0.1.0 https://hackage.haskell.org/package/optimal-blocks-0.1.0/docs/src/Algorithm-OptimalBlocks-BuzzHash.html To make an implementation D'ish it could integrate with either std.digest or process input ranges. If you want to use it exclusively for chunking your code can be more efficient (process InputRange until a boundary condition is met). When using input ranges, prefer some kind of buffered approach, Range!ubyte[] instead of Range!ubyte for better performance. If you really want the rolling hash value for each byte in a sequence this will be less efficient as you'll have to enter data byte-by-byte. In this case it's extremely important for performance that your function can be inlined, so use templates: ubyte[] data; foreach(b; data) { // This needs to be inlined for performance reasons rollinghash.put(b); } -- Johannes