/// <summary>
/// Writes a block to its correct place in the file.
/// The block's TotalStreamLength is saved as the total length of the stream IF AND ONLY IF the written block is the last block in the stream.
/// </summary>
public void WriteBlock(EncryptedFile.Block block, long size)
{
if (isReadonly)
throw new InvalidOperationException("The current stream is read-only.");
lock (locker)
{
if (block == null)
throw new ArgumentNullException("block");
if (block.BlockNumber < 0)
throw new ArgumentOutOfRangeException("block", "Block number be non negative.");
if (block.Data == null || block.Data.Length != header.DecryptedBlockSize)
throw new ArgumentException("Block must have data with length == " + header.DecryptedBlockSize);
long position = header.GetPhysicalPositionFromBlockNumber(block.BlockNumber);
if (stream.Length - EncryptedFile.Footer.FooterSize < position)
throw new InvalidOperationException("Write past end of file.");
stream.Position = position;
var encrypted = settings.Codec.EncodeBlock(key, block.Data);
Debug.Assert(encrypted.Data.Length == header.EncryptedBlockSize);
stream.Write(encrypted.IV, 0, encrypted.IV.Length);
stream.Write(encrypted.Data, 0, encrypted.Data.Length);
totalUnencryptedSize += size;
if (stream.Length <= stream.Position + EncryptedFile.Footer.FooterSize)
{
footer.TotalLength = block.TotalEncryptedStreamLength;
WriteFooterInCurrentPosition(footer);
}
}
}
private void WriteHeaderInCurrentPositionIfNotReadonly(EncryptedFile.Header fileHeader, ulong magicNumber)
{
if (isReadonly)
return;
var headerSize = GetHeaderSizeByMagicNumber(magicNumber);
var headerBytes = StructConverter.ConvertStructToBits(fileHeader, headerSize);
stream.Write(headerBytes, 0, headerSize);
}
private void WriteFooterInCurrentPosition(EncryptedFile.Footer footer)
{
var footerBytes = StructConverter.ConvertStructToBits(footer);
if (!isReadonly)
stream.Write(footerBytes, 0, EncryptedFile.Footer.FooterSize);
}
private void WriteHeaderInCurrentPositionIfNotReadonly(EncryptedFile.Header fileHeader)
{
if (isReadonly) return;
var headerBytes = StructConverter.ConvertStructToBits(fileHeader);
stream.Write(headerBytes, 0, EncryptedFile.Header.HeaderSize);
}