public IEnumerable <T> Items()
{
for (var i = StartIndex; ; ++i)
{
if (LastIndex != null && i >= LastIndex)
{
break;
}
if (i >= state.WaveIndex)
{
state.CheckNext();
}
if (LastIndex == null || i < LastIndex)
{
yield return(state.cache[i]);
}
}
}