public void StartDownload()
{
if (Token == null)
{
Token = TransferService.RequestDownloadToken(ResourceId, false);
}
while (true)
{
IDataBlockInfo blockInfo;
string transferId = Token.TransferId;
long nextBlock = 0;
if (Token.LastTransmittedBlockInfo != null)
{
nextBlock = Token.LastTransmittedBlockInfo.BlockNumber + 1;
}
if (UseStreamingTransfer)
{
StreamedDataBlock block = TransferService.ReadBlockStreamed(transferId, nextBlock);
block.Data.WriteTo(OutputStream);
blockInfo = block;
}
else
{
BufferedDataBlock block = TransferService.ReadBlock(transferId, nextBlock);
OutputStream.Write(block.Data, 0, block.Data.Length);
blockInfo = block;
}
//update the token, get independent file info without data or stream
Token.LastTransmittedBlockInfo = DataBlockInfo.FromDataBlock(blockInfo);
Token.LastBlockTransmissionTime = SystemTime.Now();
if (blockInfo.IsLastBlock)
{
//we're done - update token data
Token.CompletionTime = Token.LastBlockTransmissionTime;
TransferService.CompleteTransfer(transferId);
Token.Status = TransferStatus.Completed;
break;
}
}
}
/// <summary>
/// Adds a <see cref="DataBlockInfo"/> instance to the internal
/// list of registered data blocks.
/// </summary>
/// <param name="dataBlock"></param>
public void RegisterBlock(DataBlockInfo dataBlock)
{
Ensure.ArgumentNotNull(dataBlock, "dataBlock");
transferredBlocks[dataBlock.BlockNumber] = dataBlock;
}
/// <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);
}
}
/// <summary>
/// Handles the creation of an actual data block based on the underlying resource.
/// </summary>
/// <param name="transfer">The processed transfer.</param>
/// <param name="blockNumber">The number of the downloaded block.</param>
/// <param name="previouslyTransferredBlock">If this data block was already transferred, this parameter
/// contains the information about the block. Can be used in order to ensure proper retransmission in case
/// of variable block sizes.</param>
/// <returns>A data block which exposes the data as a resource-friendly stream
/// (<see cref="BufferedDataBlock.Data"/>).</returns>
protected abstract StreamedDataBlock CreateStreamedDataBlockImpl(TTransfer transfer, long blockNumber,
DataBlockInfo previouslyTransferredBlock);
/// <summary>
/// Handles locking, validation and stream preparation of a given transfer in order to read
/// a given block of data. The actual reading (either into a buffer, or a returned
/// stream) is being delegated via the <paramref name="dataReaderFunc"/>.
/// </summary>
/// <typeparam name="T">The type of <see cref="IDataBlockInfo"/> that is being returned.</typeparam>
/// <param name="transferId">The transfer token ID.</param>
/// <param name="blockNumber">The block number to be read.</param>
/// <param name="dataReaderFunc">A function that receives the <see cref="DownloadTransfer"/> and
/// the designated stream offset, and returns the required <see cref="IDataBlockInfo"/> that
/// provides the block's data.</param>
/// <returns>The <see cref="IDataBlockInfo"/> that is being created by the <paramref name="dataReaderFunc"/>.</returns>
private T PrepareBlockReading <T>(string transferId, long blockNumber, Func <DownloadTransfer, long, T> dataReaderFunc) where T : IDataBlockInfo
{
DownloadTransfer transfer = GetCachedTransfer(transferId, true);
DownloadToken token = transfer.Token;
if (!File.Exists(transfer.File.FullName))
{
string msg = "Resource [{0}] of transfer [{1}] was not found.";
msg = String.Format(msg, transfer.Token.ResourceName, transferId);
throw new VirtualResourceNotFoundException(msg);
}
lock (transfer.SyncRoot)
{
//make sure the transfer is active
if (!transfer.Status.Is(TransferStatus.Starting, TransferStatus.Running, TransferStatus.Paused))
{
string msg = String.Format("Transfer is not active anymore - status is [{0}].", transfer.Status);
throw new TransferStatusException(msg);
}
long position = blockNumber * token.DownloadBlockSize.Value;
//in case of an invalid position, throw error
if (position > token.ResourceLength)
{
string msg = "Cannot deliver block {0} - invalid block number.";
msg = String.Format(msg, blockNumber);
throw new DataBlockException(msg);
}
if (transfer.Stream == null)
{
//open stream, share read access
transfer.Stream = transfer.File.Open(FileMode.Open, FileAccess.Read, FileShare.Read);
}
//reposition stream if necessary
if (position != transfer.Stream.Position)
{
transfer.Stream.Seek(position, SeekOrigin.Begin);
}
T dataBlock = dataReaderFunc(transfer, position);
if (dataBlock.IsLastBlock)
{
//assume the last block will be processed successfully and
//already close the stream (don't wait for the transfer to be
//close by client)
transfer.Stream.Close();
transfer.Stream.Dispose();
transfer.Stream = null;
}
//update status
transfer.Token.Status = TransferStatus.Running;
//maintain local (unshared) copy of the block info without the data
transfer.Token.LastTransmittedBlockInfo = DataBlockInfo.FromDataBlock(dataBlock);
return(dataBlock);
}
}
