Lightweight 8 byte hash function algorithm

Question

I need to extract an 8 byte digest from a variable length string so I\'m looking for such an algorithm that I will implement in c/c++. That will be part of a digital signatu

Answer 1

I had the exact same requirement, and I settled for FNV-1A, after dismissing SIP hash (implemented by bloomberg here).

I found an FNV implementation here:

https://github.com/foonathan/string_id/blob/master/hash.hpp

which is:

constexpr uint64_t fnv_basis = 14695981039346656037ull;
constexpr uint64_t fnv_prime = 1099511628211ull;

// FNV-1a 64 bit hash of null terminated buffer
uint64_t fnv1a_hash(const char* str, uint64_t hash = fnv_basis)
{
    return *str ? fnv1a_hash(str + 1, (hash ^ *str) * fnv_prime) : hash;
}

It appears he is looping using tail recursion. And stop condition is the null byte.
(boost uses hash_range which is hash_combining each element in chain I guess.)

License is zlib and copyright is Jonathan Müller. Though I'm not convinced a oneliner can be legally licensed if it implements research by other persons (Fowler-Noll-Vo).