private HeapOnNodeBlockData GetBlockDataUnbuffered(int blockIndex)
{
DataBlock block = DataTree.GetDataBlock(blockIndex);
if (blockIndex == 0)
{
HeapOnNodeFirstBlockData heapFirstBlock = new HeapOnNodeFirstBlockData(block.Data);
return(heapFirstBlock);
}
else
{
// HNBITMAPHDR appears at data block 8 (zero-based) and thereafter every 128 blocks.
// (that is, data block 8, data block 136, data block 264, and so on).
if (blockIndex % 128 == 8)
{
HeapOnNodeBitmapBlockData bitmapBlock = new HeapOnNodeBitmapBlockData(block.Data);
return(bitmapBlock);
}
else
{
HeapOnNodePageBlockData pageBlock = new HeapOnNodePageBlockData(block.Data);
return(pageBlock);
}
}
}
public HeapID AddItemToHeap(byte[] itemBytes)
{
if (itemBytes.Length > MaximumAllocationLength)
{
throw new ArgumentException("Maximum size of a heap allocation is 3580 bytes");
}
if (itemBytes.Length == 0)
{
return(HeapID.EmptyHeapID);
}
// We can use the Header / BitmapHeader to locate available space,
// but the final authority is HNPAGEMAP located at the end of each block
// Note: we are only required to maintain HNPAGEMAP
for (int blockIndex = 0; blockIndex < m_dataTree.DataBlockCount; blockIndex++)
{
HeapOnNodeBlockData blockData = GetBlockData(blockIndex);
// We need space for the item itself and for a place for it in the page map (2 bytes)
// We also have to make sure we do not allocate more items then can be represented by hidIndex
if (blockData.AvailableSpace > itemBytes.Length + 2 && blockData.HeapItems.Count < HeapID.MaximumHidIndex)
{
blockData.HeapItems.Add(itemBytes);
UpdateBuffer(blockIndex, blockData);
// hidIndex is one-based
ushort hidIndex = (ushort)(blockData.HeapItems.Count);
return(new HeapID((ushort)blockIndex, hidIndex));
}
}
// no space found in existing blocks, we need to allocate new data block
int newBlockIndex = m_dataTree.DataBlockCount;
HeapOnNodeBlockData newBlockData;
if (newBlockIndex % 128 == 8)
{
newBlockData = new HeapOnNodeBitmapBlockData();
}
else
{
newBlockData = new HeapOnNodePageBlockData();
}
newBlockData.HeapItems.Add(itemBytes);
this.DataTree.AddDataBlock(newBlockData.GetBytes());
// hidIndex is one-based
return(new HeapID((ushort)newBlockIndex, 1));
}
