private RegionState GetBlock(int position, bool addIfMissing = true)
{
if (position <= 0)
{
throw new ArgumentException("Position must be greater than 0.");
}
if (_lastAccessedBlock != null && _lastAccessedBlock.ContainsPosition(position)) // performance improvement to remember last block
{
return(_lastAccessedBlock);
}
var blockKey = GetBlockKey(position);
RegionState block;
if (!_regionLookup.TryGetValue(blockKey, out block))
{
if (!addIfMissing)
{
return(null);
}
block = CreateOrReuseBlock((blockKey - 1) * _regionSize + 1, blockKey * _regionSize);
_regionLookup[blockKey] = block;
}
_lastAccessedBlock = block;
return(block);
}
/// <summary>
/// Get block by either reusable one that is available for reuse, or creating a new one if non available for reuse.
/// </summary>
/// <param name="startPosition"></param>
/// <param name="endPosition"></param>
/// <returns></returns>
private RegionState CreateOrReuseBlock(int startPosition, int endPosition)
{
RegionState block;
if (_reusableBlocks.Any())
{
block = _reusableBlocks.Pop();
block.Reset(startPosition, endPosition);
}
else
{
block = new RegionState(startPosition, endPosition);
}
return(block);
}
