/// <summary>
/// Attempts to retrieve the next item to be taken without removing it.
/// </summary>
/// <param name="item">The item retrieved.</param>
/// <returns>
/// <c>true</c> if an item was retrieved; otherwise, <c>false</c>.
/// </returns>
public bool TryPeek(out T item)
{
item = default;
var index = Interlocked.Add(ref _indexDequeue, 0);
return(index < Capacity && index > 0 && _entries.TryGetInternal(index, out item));
}
/// <summary>
/// Retrieve or creates a new item at the specified index.
/// </summary>
/// <param name="index">The index.</param>
/// <returns>The value.</returns>
/// <exception cref="ArgumentOutOfRangeException">index;index must be greater or equal to 0 and less than capacity</exception>
public T Get(int index)
{
if (index < 0 || index >= _entries.Capacity)
{
throw new ArgumentOutOfRangeException(nameof(index), "index must be greater or equal to 0 and less than capacity");
}
// Using TryGetValue first just avoid wasting a needle
if (_entries.TryGetInternal(index, out var found))
{
// Null resistant
found.TryGetValue(out var previous);
return(previous);
// We don't donate because we didn't remove
}
var newNeedle = _needleIndexFactory(index);
if (_entries.InsertInternal(index, newNeedle, out found))
{
return(newNeedle.Value);
}
// we just failed to insert, meaning that we created a useless needle
// donate it
Reservoir.DonateNeedle(newNeedle);
return(found.Value);
}
