Functions
LuidH	buildHash (string const &sym, HashVal seed=0)
	build up a hash value, packaged as LUID. More...

Variables
const size_t	KNUTH_MAGIC = 2654435761
	lousy old tinkerer's trick: hash values with poor distribution can be improved by spreading the input with something close to the golden ratio. More...

Function Documentation

◆ buildHash()

LuidH lib::idi::anonymous_namespace{entry-id.hpp}::buildHash	(	string const &	sym,
		HashVal	seed = `0`
	)

inline

build up a hash value, packaged as LUID.

Parameters

sym	symbolic ID-string to be hashed
seed	(optional) hash value to combine with the sym.

Note: This is a half baked preliminary solution. The issue here is that LUID has a fixed size of 128bit, whereas the hash values of the std library (and boost) have the smaller and platform dependent type of size_t. This hack here assumes that size_t corresponds to void*, which is correct for i386 and AMD64. LUID provides a hook for embedding a void* (setting the trailing bits to zero). Finally we reinterpret the char[] of the LUID as a LuidH class, which is ugly, but granted to work.

Todo:: several unsolved design problems. How to deal with std hash values in conjunction with LUID. How to create a LuidH instance, if not generating a new random value. How to make EntryID and asset::Ident interchangeable, /////////TICKET #739 which would require both to yield the same hash values....

Warning: there is a weakness in boost::hash for strings of running numbers, causing collisions already for a small set with less than 100000 entries. To mitigate the problem, we hash in the trailing digits, and spread them by the KNUTH_MAGIC /////////TICKET #865; this code isn't portable and breaks if sizeof(size_t) < sizeof(void*)