/// <summary>
/// Gets information about all blocks that have been transferred so far.
/// This information can be used to resume a transfer that spawns several
/// sessions on the client side.<br/>
/// In case of retransmissions of blocks, this method returns only the
/// <see cref="DataBlockInfo"/> instance per block number that corresponds
/// to the most recent transfer.
/// </summary>
/// <param name="transferId">Identifies the transfer and resource.</param>
/// <returns>All transferred blocks (without data).</returns>
/// <exception cref="UnknownTransferException">In case no such transfer
/// is currently maintained.</exception>
/// <remarks>Implementing classes might decide to discard cached block information
/// once a transfer was completed, and throw exceptions or just return an empty list.</remarks>
public IEnumerable <DataBlockInfo> GetTransferredBlocks(string transferId)
{
var context = IsUploadService
? FileSystemTask.UploadedBlockInfosRequest
: FileSystemTask.DownloadedBlockInfosRequest;
TTransfer transfer = GetCachedTransfer(transferId, true, context);
var blocks = transfer.TransferredBlocks;
Auditor.AuditTransferOperation(context, AuditEvent.TransferredBlockInfoRequest, transferId, transfer.FileItem);
return(blocks);
}
private Stream DownloadFileImpl(string transferId)
{
const FileSystemTask context = FileSystemTask.StreamedFileDownloadRequest;
//get the cached transfer
TTransfer transfer = GetCachedTransfer(transferId, true, context);
if (transfer.Token.TotalBlockCount == 0)
{
//if we don't have any blocks, return a null stream
Auditor.AuditTransferOperation(context, AuditEvent.FileDataDownloaded, transfer.TransferId, transfer.FileItem);
return(Stream.Null);
}
//we don't expose the underlying stream directly, but rather use blocks again,
//which disconnects the exposed stream from the underlying resource and allows for simple
//aborting
long resourceLength = transfer.FileItem.ResourceInfo.Length;
// ReSharper disable UseObjectOrCollectionInitializer
var stream = new StreamedBlockInputStream(blockNumber => ReadBlockStreamed(transferId, blockNumber),
resourceLength);
// ReSharper restore UseObjectOrCollectionInitializer
//assign the stream the transfer object in order so it can query the status during reading
stream.Transfer = transfer;
//reading the last block closes the transfer automatically..
transfer.AutoCloseAfterLastBlockDelivery = true;
//...and so does disposing the stream at any time
var closingStream = new ClosingActionStream(stream, () => CompleteTransfer(transferId));
Auditor.AuditTransferOperation(context, AuditEvent.FileDataDownloaded, transfer.TransferId, transfer.FileItem);
return(closingStream);
}
/// <summary>
/// Orchestrates common block reading procedures for the <see cref="ReadBlock"/> and
/// <see cref="ReadBlockStreamed"/> methods.
/// </summary>
protected virtual T OrchestrateBlockReading <T>(TTransfer transfer, long blockNumber,
Func <TTransfer, long, DataBlockInfo, T> readerImplFunc) where T : IDataBlock
{
const FileSystemTask context = FileSystemTask.DataBlockDownloadRequest;
if (blockNumber < 0)
{
string msg = "Invalid block number [{0}] requested - block numbers cannot be negative.";
msg = String.Format(msg, blockNumber);
throw new DataBlockException(msg);
}
if (blockNumber >= transfer.Token.TotalBlockCount)
{
string msg = "Invalid block number [{0}] requested - the total number of blocks is [{1}].";
msg = String.Format(msg, blockNumber, transfer.Token.TotalBlockCount);
throw new DataBlockException(msg);
}
//make sure the file still exists
if (!transfer.FileItem.Exists)
{
Auditor.AuditRequestedFileNotFound(transfer.FileItem, context);
string msg = "Resource [{0}] of transfer [{1}] was not found.";
msg = String.Format(msg, transfer.Token.ResourceName, transfer.TransferId);
throw new VirtualResourceNotFoundException(msg)
{
IsAudited = true
};
}
lock (transfer.SyncRoot)
{
//make sure the transfer is active
if (!transfer.Status.Is(TransferStatus.Starting, TransferStatus.Running, TransferStatus.Paused))
{
string msg = String.Format("Transfer [{0}] is not active anymore - status is [{1}].", transfer.TransferId,
transfer.Status);
if (transfer.AbortReason.HasValue)
{
msg += String.Format(" Transfer abort reason: [{0}].", transfer.AbortReason);
}
Auditor.AuditDeniedOperation(context, AuditEvent.DownloadNoLongerActive, transfer.FileItem, msg);
throw new TransferStatusException(msg)
{
IsAudited = true, EventId = (int)AuditEvent.DownloadNoLongerActive
};
}
//check whether we already transferred this block once
DataBlockInfo transferredBlock = transfer.TryGetTransferredBlock(blockNumber);
T dataBlock = readerImplFunc(transfer, blockNumber, transferredBlock);
//update status
transfer.Status = TransferStatus.Running;
//store copy of the downloaded block that doesn't contain any data
transfer.RegisterBlock(DataBlockInfo.FromDataBlock(dataBlock));
//audit download
Auditor.AuditTransferOperation(context, AuditEvent.FileBlockDownloaded, transfer.TransferId, transfer.FileItem);
return(dataBlock);
}
}