/// <summary>
/// Makes a shadow copy of a data cluster.
/// </summary>
/// <param name="sourceClusterAddress">the address of the first block in the cluster.
/// If address is zero, it simply creates an empty cluster.</param>
/// <param name="indexValue">the index value of this first block</param>
/// <param name="destinationClusterAddress">the first block of the destination cluster</param>
private void ShadowCopyDataCluster(uint sourceClusterAddress, uint indexValue, uint destinationClusterAddress)
{
//if source exist
if (sourceClusterAddress != 0)
{
DiskIoSession sourceData = m_ioSessions.SourceData;
DiskIoSession destinationData = m_ioSessions.DestinationData;
sourceData.ReadOld(sourceClusterAddress, BlockType.DataBlock, indexValue);
destinationData.WriteToNewBlock(destinationClusterAddress, BlockType.DataBlock, indexValue);
Memory.Copy(sourceData.Pointer, destinationData.Pointer, sourceData.Length);
m_ioSessions.SwapData();
}
//if source cluster does not exist.
else
{
m_ioSessions.SourceData.WriteToNewBlock(destinationClusterAddress, BlockType.DataBlock, indexValue);
Memory.Clear(m_ioSessions.SourceData.Pointer, m_ioSessions.SourceData.Length);
}
}
/// <summary>
/// Makes a shadow copy of the indirect index passed to this function. If the block does not exists, it creates it.
/// </summary>
/// <param name="sourceBlockAddress">The block to be copied</param>
/// <param name="indexValue">the index value that goes in the footer of the file.</param>
/// <param name="blockType">Gets the expected block type</param>
/// <param name="remoteAddressOffset">the offset of the remote address that needs to be updated.</param>
/// <param name="remoteBlockAddress">the value of the remote address.</param>
/// <returns>Returns true if the block had to be shadowed, false if it did not change</returns>
private bool ShadowCopyIndexIndirect(ref uint sourceBlockAddress, uint indexValue, BlockType blockType, int remoteAddressOffset, uint remoteBlockAddress)
{
uint indexIndirectBlock;
//Make a copy of the index block referenced
//if the block does not exist, create it.
if (sourceBlockAddress == 0)
{
DiskIoSession buffer = m_ioSessions.SourceIndex;
indexIndirectBlock = m_fileHeaderBlock.AllocateFreeBlocks(1);
m_subFileHeader.TotalBlockCount++;
buffer.WriteToNewBlock(indexIndirectBlock, blockType, indexValue);
Memory.Clear(buffer.Pointer, buffer.Length);
WriteIndexIndirectBlock(buffer.Pointer, remoteAddressOffset, remoteBlockAddress);
sourceBlockAddress = indexIndirectBlock;
return(true);
}
//if the data page is an old page, allocate space to create a new copy
else if (sourceBlockAddress <= m_lastReadOnlyBlock)
{
indexIndirectBlock = m_fileHeaderBlock.AllocateFreeBlocks(1);
m_subFileHeader.TotalBlockCount++;
ReadThenWriteIndexIndirectBlock(sourceBlockAddress, indexIndirectBlock, indexValue, blockType, remoteAddressOffset, remoteBlockAddress);
sourceBlockAddress = indexIndirectBlock;
return(true);
}
//The page has already been copied, use the existing address.
else
{
ReadThenWriteIndexIndirectBlock(sourceBlockAddress, sourceBlockAddress, indexValue, blockType, remoteAddressOffset, remoteBlockAddress);
return(false);
}
}
/// <summary>
/// Makes a shadow copy of an index indirect block and updates a remote address.
/// </summary>
/// <param name="sourceBlockAddress">the address of the source.</param>
/// <param name="destinationBlockAddress">the address of the destination. This can be the same as the source.</param>
/// <param name="indexValue">the index value that goes in the footer of the file.</param>
/// <param name="blockType">Gets the expected block type</param>
/// <param name="remoteAddressOffset">the offset of the remote address that needs to be updated.</param>
/// <param name="remoteBlockAddress">the value of the remote address.</param>
private void ReadThenWriteIndexIndirectBlock(uint sourceBlockAddress, uint destinationBlockAddress, uint indexValue, BlockType blockType, int remoteAddressOffset, uint remoteBlockAddress)
{
DiskIoSession bufferSource = m_ioSessions.SourceIndex;
if (sourceBlockAddress == destinationBlockAddress)
{
if (*(int *)(bufferSource.Pointer + (remoteAddressOffset << 2)) != remoteBlockAddress)
{
bufferSource.WriteToExistingBlock(destinationBlockAddress, blockType, indexValue);
WriteIndexIndirectBlock(bufferSource.Pointer, remoteAddressOffset, remoteBlockAddress);
}
}
else
{
bufferSource.ReadOld(sourceBlockAddress, blockType, indexValue);
DiskIoSession destination = m_ioSessions.DestinationIndex;
destination.WriteToNewBlock(destinationBlockAddress, blockType, indexValue);
Memory.Copy(bufferSource.Pointer, destination.Pointer, destination.Length);
WriteIndexIndirectBlock(destination.Pointer, remoteAddressOffset, remoteBlockAddress);
m_ioSessions.SwapIndex();
}
}
