Fwd: [RFC] HashContext as Object

On Mon, Dec 26, 2016 at 7:35 PM, Sara Golemon wrote: > I was trawling through Pull Requests and found #660 which I think is a > nice idea and deserves some attention. It involves minor BC however, > so I've updated the patch and presented it for your discussing > pleasure. > Specifically, I should say I'm eager to hear thoughts on the item listed as an Open Issue. That is: Currently hash_final() destroys the existing HashContext resource immediately. No hope of continuing or even just reissuing the result. I'm quite tempted atm, to go the "copy the context, finalize to get a digest, then restoring to the saved context state". For most use cases of this API this is a slight overhead add since the context is being duplicated then shortly thereafter discarded. (Bear in mind though, that the hash_init->hash_update->hash_final API is the edge case already compared to the all-in-one hash() and hash_hmac() functions). What doing this does offer, however, is a pathway to reasonable APIs for streaming hash functions (see SHA3/Keccak Sponge Functions). As a minor side benefit, we also get an idempotent hash_final(). So even though there's a VERY minor BC break involved, I think it's the right thing to do. If others agree, I'll update the diff to reflect. -Sara