internal static ulong HashWordIgnoreCaseUnderscoreIsSpace(ReadOnlySpan <char> word, ulong lexID, ulong uniqueId)
{
unchecked
{
//Implementation of Fowler/Noll/Vo (https://en.wikipedia.org/wiki/Fowler%E2%80%93Noll%E2%80%93Vo_hash_function), also used by the Roslyn compiler: https://github.com/dotnet/roslyn/blob/master/src/Compilers/Core/Portable/InternalUtilities/Hash.cs
const ulong fnv_prime = 1099511628211LU;
const ulong fnv_offset_basis = 0xcbf29ce484222325;
ulong hash = fnv_offset_basis;
for (int i = 0; i < word.Length; i++)
{
var c = word[i];
if (c == '_')
{
c = ' ';
}
if (char.IsUpper(c))
{
c = char.ToLowerInvariant(c);
}
hash = (hash ^ c) * fnv_prime;
}
return(Hashes.Combine(Hashes.Combine(hash, lexID + 1UL), uniqueId + 1UL));
}
}
