private const int BlockRequestSize = 16384; // 16 kB
public IEnumerable <BlockRequest> BlocksToRequest(IReadOnlyList <Piece> incompletePieces,
Bitfield availability,
IReadOnlyCollection <PeerConnection> peers,
IBlockRequests blockRequests)
{
var toRequest = new List <BlockRequest>();
int maxToRequest = MaxOutstandingRequests - blockRequests.RequestedBlocks.Count;
foreach (var piece in incompletePieces)
{
if (toRequest.Count >= maxToRequest)
{
break;
}
if (!availability.IsPieceAvailable(piece.Index))
{
continue;
}
var block = NextBlockForPiece(piece, blockRequests);
if (block != null)
{
toRequest.Add(block);
}
}
return(toRequest);
}
private BlockRequest NextBlockForPiece(Piece piece, IBlockRequests blockRequests)
{
for (int blockOffset = 0; blockOffset < piece.Size; blockOffset += BlockRequestSize)
{
int blockSize = blockOffset < piece.Size - BlockRequestSize ? BlockRequestSize : piece.Size - blockOffset;
var blockToRequest = new BlockRequest(piece.Index, blockOffset, blockSize);
if (!blockRequests.RequestedBlocks.Contains(blockToRequest) &&
!blockRequests.DownloadedBlocks.Contains(blockToRequest))
{
return(blockToRequest);
}
}
// No blocks to request for specified piece
return(null);
}
