hashmap Files

• fix hashing on ARM CPUs
• optimize hashing by using specialized xxhash implementations
• reduce variable allocations in get functions
• removed obsolete 0 length checks

It is noticeable faster than the current version of HaxMap is able to handle collisions of valid 0 hash values:

BenchmarkReadHashMapUint-8                   1314156           955.6 ns/op
BenchmarkReadHaxMapUint-8                     872134          1316 ns/op (can not handle hash 0 collisions)

// works for this library, fails for HaxMap
func TestHash0Collision(t *testing.T) {
    m := New[string, int]()
    staticHasher := func(key string) uintptr {
        return 0
    }
    m.SetHasher(staticHasher)
    m.Set("1", 1)
    m.Set("2", 2)
    _, ok := m.Get("1")
    if !ok {
        t.Error("1 not found")
    }
    _, ok = m.Get("2")
    if !ok {
        t.Error("2 not found")
    }
}