public ChainLoopDetector(long rawSize, BlockStore blockStore)
{
this.blockStore = blockStore;
int numBlocks = (int)Math.Ceiling(1.0 * (rawSize / blockStore.GetBlockStoreBlockSize()));
used_blocks = new bool[numBlocks];
}
/**
* Updates the contents of the stream to the new
* Set of bytes.
* Note - if this is property based, you'll still
* need to update the size in the property yourself
*/
public void UpdateContents(byte[] contents)
{
// How many blocks are we going to need?
int blockSize = blockStore.GetBlockStoreBlockSize();
int blocks = (int)Math.Ceiling(((double)contents.Length) / blockSize);
// Make sure we don't encounter a loop whilst overwriting
// the existing blocks
ChainLoopDetector loopDetector = blockStore.GetChainLoopDetector();
// Start writing
int prevBlock = POIFSConstants.END_OF_CHAIN;
int nextBlock = startBlock;
for (int i = 0; i < blocks; i++)
{
int thisBlock = nextBlock;
// Allocate a block if needed, otherwise figure
// out what the next block will be
if (thisBlock == POIFSConstants.END_OF_CHAIN)
{
thisBlock = blockStore.GetFreeBlock();
loopDetector.Claim(thisBlock);
// We're on the end of the chain
nextBlock = POIFSConstants.END_OF_CHAIN;
// Mark the previous block as carrying on to us if needed
if (prevBlock != POIFSConstants.END_OF_CHAIN)
{
blockStore.SetNextBlock(prevBlock, thisBlock);
}
blockStore.SetNextBlock(thisBlock, POIFSConstants.END_OF_CHAIN);
// If we've just written the first block on a
// new stream, save the start block offset
if (this.startBlock == POIFSConstants.END_OF_CHAIN)
{
this.startBlock = thisBlock;
}
}
else
{
loopDetector.Claim(thisBlock);
nextBlock = blockStore.GetNextBlock(thisBlock);
}
// Write it
//byte[] buffer = blockStore.CreateBlockIfNeeded(thisBlock);
ByteBuffer buffer = blockStore.CreateBlockIfNeeded(thisBlock);
int startAt = i * blockSize;
int endAt = Math.Min(contents.Length - startAt, blockSize);
buffer.Write(contents, startAt, endAt);
//for (int index = startAt, j = 0; index < endAt; index++, j++)
// buffer[j] = contents[index];
// Update pointers
prevBlock = thisBlock;
}
int lastBlock = prevBlock;
// If we're overwriting, free any remaining blocks
NPOIFSStream toFree = new NPOIFSStream(blockStore, nextBlock);
toFree.free(loopDetector);
// Mark the end of the stream
blockStore.SetNextBlock(lastBlock, POIFSConstants.END_OF_CHAIN);
}