/// <summary>
/// Reads a file.
/// </summary>
/// <param name="type"> The type of the file. </param>
/// <param name="id"> The id of the file. </param>
/// <returns> A <seealso cref="ByteBuffer" /> containing the contents of the file. </returns>
/// <exception cref="IOException"> if an I/O error occurs. </exception>
public ByteBuffer Read(int type, int id)
{
if ((type < 0 || type >= indexChannels.Length) && type != 255)
{
throw new FileNotFoundException();
}
var indexChannel = type == 255 ? metaChannel : indexChannels[type];
long ptr = id * Index.SIZE;
if (ptr < 0 || ptr >= indexChannel.size())
{
throw new FileNotFoundException();
}
var buf = ByteBuffer.allocate(Index.SIZE);
FileChannelUtils.ReadFully(indexChannel, buf, ptr);
var index = Index.Decode((ByteBuffer)buf.flip());
var data = ByteBuffer.allocate(index.GetSize());
buf = ByteBuffer.allocate(Sector.SIZE);
int chunk = 0,
remaining = index.GetSize();
ptr = index.GetSector() * Sector.SIZE;
do
{
buf.clear();
FileChannelUtils.ReadFully(dataChannel, buf, ptr);
var sector = Sector.Decode((ByteBuffer)buf.flip());
if (remaining > Sector.DATA_SIZE)
{
data.put(sector.GetData(), 0, Sector.DATA_SIZE);
remaining -= Sector.DATA_SIZE;
if (sector.GetType() != type)
{
throw new IOException("File type mismatch.");
}
if (sector.GetId() != id)
{
throw new IOException("File id mismatch.");
}
if (sector.GetChunk() != chunk++)
{
throw new IOException("Chunk mismatch.");
}
ptr = sector.GetNextSector() * Sector.SIZE;
}
else
{
data.put(sector.GetData(), 0, remaining);
remaining = 0;
}
}while (remaining > 0);
return((ByteBuffer)data.flip());
}
/// <summary>
/// Writes a file.
/// </summary>
/// <param name="type"> The type of the file. </param>
/// <param name="id"> The id of the file. </param>
/// <param name="data"> A <seealso cref="ByteBuffer" /> containing the contents of the file. </param>
/// <param name="overwrite">
/// A flag indicating if the existing file should be
/// overwritten.
/// </param>
/// <returns> A flag indicating if the file was written successfully. </returns>
/// <exception cref="IOException"> if an I/O error occurs. </exception>
private bool Write(int type, int id, ByteBuffer data, bool overwrite)
{
if ((type < 0 || type >= indexChannels.Length) && type != 255)
{
throw new FileNotFoundException();
}
var indexChannel = type == 255 ? metaChannel : indexChannels[type];
var nextSector = 0;
long ptr = id * Index.SIZE;
ByteBuffer buf;
Index index;
if (overwrite)
{
if (ptr < 0)
{
throw new IOException();
}
if (ptr >= indexChannel.size())
{
return(false);
}
buf = ByteBuffer.allocate(Index.SIZE);
FileChannelUtils.ReadFully(indexChannel, buf, ptr);
index = Index.Decode((ByteBuffer)buf.flip());
nextSector = index.GetSector();
if (nextSector <= 0 || nextSector > dataChannel.size() * Sector.SIZE)
{
return(false);
}
}
else
{
nextSector = (int)((dataChannel.size() + Sector.SIZE - 1) / Sector.SIZE);
if (nextSector == 0)
{
nextSector = 1;
}
}
index = new Index(data.remaining(), nextSector);
indexChannel.write(index.Encode(), ptr);
buf = ByteBuffer.allocate(Sector.SIZE);
int chunk = 0,
remaining = index.GetSize();
do
{
var curSector = nextSector;
ptr = curSector * Sector.SIZE;
nextSector = 0;
Sector sector;
if (overwrite)
{
buf.clear();
FileChannelUtils.ReadFully(dataChannel, buf, ptr);
sector = Sector.Decode((ByteBuffer)buf.flip());
if (sector.GetType() != type)
{
return(false);
}
if (sector.GetId() != id)
{
return(false);
}
if (sector.GetChunk() != chunk)
{
return(false);
}
nextSector = sector.GetNextSector();
if (nextSector < 0 || nextSector > dataChannel.size() / Sector.SIZE)
{
return(false);
}
}
if (nextSector == 0)
{
overwrite = false;
nextSector = (int)((dataChannel.size() + Sector.SIZE - 1) / Sector.SIZE);
if (nextSector == 0)
{
nextSector++;
}
if (nextSector == curSector)
{
nextSector++;
}
}
var bytes = new byte[Sector.DATA_SIZE];
if (remaining < Sector.DATA_SIZE)
{
data.get(bytes, 0, remaining);
nextSector = 0; // mark as EOF
remaining = 0;
}
else
{
remaining -= Sector.DATA_SIZE;
data.get(bytes, 0, Sector.DATA_SIZE);
}
sector = new Sector(type, id, chunk++, nextSector, bytes);
dataChannel.write(sector.Encode(), ptr);
}while (remaining > 0);
return(true);
}
