public BlockReaderWriter(EncryptionSettings encryptionSettings, string key, Stream stream, int defaultBlockSize)
{
if (encryptionSettings == null)
throw new ArgumentNullException("encryptionSettings");
if (key == null)
throw new ArgumentNullException("key");
if (stream == null)
throw new ArgumentNullException("stream");
if (!stream.CanRead)
throw new ArgumentException("The Underlying stream for a BlockReaderWriter must always be either read-only or read-write. Write only streams are not supported.");
if (!stream.CanSeek)
throw new ArgumentException("The Underlying stream for a BlockReaderWriter must be seekable.");
isReadonly = !stream.CanWrite;
this.settings = encryptionSettings;
this.key = key;
this.stream = stream;
this.header = ReadOrWriteEmptyHeader(defaultBlockSize);
this.footer = ReadOrWriteFooter();
totalUnencryptedSize = 0;
}
private EncryptedFile.Footer ReadOrWriteFooter()
{
lock (locker)
{
if (stream.Length >= EncryptedFile.Header.HeaderSize + EncryptedFile.Footer.FooterSize)
{
// Read footer
stream.Position = stream.Length - EncryptedFile.Footer.FooterSize;
var footerBytes = stream.ReadEntireBlock(EncryptedFile.Footer.FooterSize);
var footer = StructConverter.ConvertBitsToStruct <EncryptedFile.Footer>(footerBytes);
// Sanity check that the footer has some value that could be correct
var streamBlockLength = (stream.Length - (EncryptedFile.Header.HeaderSize + EncryptedFile.Footer.FooterSize)) / header.DiskBlockSize;
var footerBlockLength = footer.TotalLength / header.DecryptedBlockSize;
if (footerBlockLength != streamBlockLength - 1 && footerBlockLength != streamBlockLength)
{
throw new InvalidDataException("File is corrupted: the length written to the file doesn't match the number of blocks in it.");
}
return(footer);
}
else
{
// Write footer
stream.Position = EncryptedFile.Header.HeaderSize;
var footer = new EncryptedFile.Footer {
TotalLength = 0
};
WriteFooterInCurrentPosition(footer);
return(footer);
}
}
}
public BlockReaderWriter(EncryptionSettings encryptionSettings, string key, Stream stream, int defaultBlockSize)
{
if (encryptionSettings == null)
{
throw new ArgumentNullException("encryptionSettings");
}
if (key == null)
{
throw new ArgumentNullException("key");
}
if (stream == null)
{
throw new ArgumentNullException("stream");
}
if (!stream.CanRead)
{
throw new ArgumentException("The Underlying stream for a BlockReaderWriter must always be either read-only or read-write. Write only streams are not supported.");
}
if (!stream.CanSeek)
{
throw new ArgumentException("The Underlying stream for a BlockReaderWriter must be seekable.");
}
isReadonly = !stream.CanWrite;
this.settings = encryptionSettings;
this.key = key;
this.stream = stream;
this.header = ReadOrWriteHeader(defaultBlockSize);
this.footer = ReadOrWriteFooter();
}
private void WriteFooterInCurrentPosition(EncryptedFile.Footer footer)
{
var footerBytes = StructConverter.ConvertStructToBits(footer);
if (!isReadonly)
{
stream.Write(footerBytes, 0, EncryptedFile.Footer.FooterSize);
}
}
private EncryptedFile.Footer ReadOrWriteFooter()
{
lock (locker)
{
if (stream.Length >= EncryptedFile.Header.HeaderSize + EncryptedFile.Footer.FooterSize)
{
// Read footer
stream.Position = stream.Length - EncryptedFile.Footer.FooterSize;
var footerBytes = stream.ReadEntireBlock(EncryptedFile.Footer.FooterSize);
var footer = StructConverter.ConvertBitsToStruct<EncryptedFile.Footer>(footerBytes);
// Sanity check that the footer has some value that could be correct
var streamBlockLength = (stream.Length - (EncryptedFile.Header.HeaderSize + EncryptedFile.Footer.FooterSize)) / header.DiskBlockSize;
var footerBlockLength = footer.TotalLength / header.DecryptedBlockSize;
if (footerBlockLength != streamBlockLength - 1 && footerBlockLength != streamBlockLength)
throw new InvalidDataException("File is corrupted: the length written to the file doesn't match the number of blocks in it.");
return footer;
}
else
{
// Write footer
stream.Position = EncryptedFile.Header.HeaderSize;
var footer = new EncryptedFile.Footer { TotalLength = 0 };
WriteFooterInCurrentPosition(footer);
return footer;
}
}
}
