void MoveFileBlock(FileDataBlock fileBlock, long dataOffset)
{
// First, determine whether the next file block needs to move before this one.
long nextDataOffset;
FileDataBlock nextFileBlock = GetNextFileDataBlock(fileBlock, dataOffset, out nextDataOffset);
if (nextFileBlock != null && dataOffset + fileBlock.Length > nextFileBlock.FileOffset)
{
// The next block needs to move first, so do that now.
MoveFileBlock(nextFileBlock, nextDataOffset);
}
// Now, move the block.
if (fileBlock.FileOffset > dataOffset)
{
// Move the section to earlier in the file stream (done in chunks starting at the beginning of the section).
byte[] buffer = new byte[COPY_BLOCK_SIZE];
for (long relativeOffset = 0; relativeOffset < fileBlock.Length; relativeOffset += buffer.Length)
{
long readOffset = fileBlock.FileOffset + relativeOffset;
int bytesToRead = (int)Math.Min(buffer.Length, fileBlock.Length - relativeOffset);
_fileStream.Position = readOffset;
_fileStream.Read(buffer, 0, bytesToRead);
long writeOffset = dataOffset + relativeOffset;
_fileStream.Position = writeOffset;
_fileStream.Write(buffer, 0, bytesToRead);
}
}
else
{
// Move the section to later in the file stream (done in chunks starting at the end of the section).
byte[] buffer = new byte[COPY_BLOCK_SIZE];
for (long relativeOffset = 0; relativeOffset < fileBlock.Length; relativeOffset += buffer.Length)
{
int bytesToRead = (int)Math.Min(buffer.Length, fileBlock.Length - relativeOffset);
long readOffset = fileBlock.FileOffset + fileBlock.Length - relativeOffset - bytesToRead;
_fileStream.Position = readOffset;
_fileStream.Read(buffer, 0, bytesToRead);
long writeOffset = dataOffset + fileBlock.Length - relativeOffset - bytesToRead;
_fileStream.Position = writeOffset;
_fileStream.Write(buffer, 0, bytesToRead);
}
}
// This block now points to a different position in the file.
fileBlock.SetFileOffset(dataOffset);
}
