On 12/6/24 12:22, Julien Blanc via Boost wrote:
6 décembre 2024 à 09:31 "Alexander Grund via Boost" a écrit:
The proposed library currently consists of two things :
* a concept that hashers must use (for hash implementors) * an hash_append helper to ease the use of hash functions with objects
As far as I understood this is exactly how the library is implemented: It is not `boost::hash2::update( h, span )` but `boost::hash2::hash_append( h, {}, span )` but thats minor.
I have a different understanding.
Quoting the doc, “This library addresses two major use cases: hashing an untyped sequence of bytes, and hashing C++ objects.”.
But for the former, the library relies on the user to directly call the hasher object update function. This is the part i don't feel comfortable, with, i think a hasher completly opaque for the user of the library would be a better design. That's just a minor change in term of implementation.
A hasher must expose a common public interface anyway to be compatible with hash_append, and at this point why not use the interface in the user types hash functions directly? What value a free hash_append function would bring? The only thing that comes to mind is it could have a more flexible interface, as Vinnie suggested, to keep the hasher interface minimal, but that's about it. I do think though that whether or not a free hash_append function is provided, using the hasher directly through its public interface should be allowed. This would allow the user types' hash functions not depend on Boost.Hash2 and therefore make support for hashing more lightweight and potentially compatible with std::hash2, if one ever comes to light.