FriendCloudProto/src/main/java/moe/nekojimi/friendcloud/FilePieceAccess.java

package moe.nekojimi.friendcloud;

import moe.nekojimi.friendcloud.objects.NetworkFile;

import java.io.Closeable;
import java.io.File;
import java.io.IOException;
import java.io.RandomAccessFile;

public class FilePieceAccess implements Closeable
{
	private final NetworkFile networkFile;
	private final File file;
	private final RandomAccessFile randomAccessFile;
	private final OpenMode openMode;

	public FilePieceAccess(NetworkFile networkFile, OpenMode openMode) throws IOException
	{
		this.networkFile = networkFile;
		this.file = networkFile.getOrCreateLocalFile();
		this.randomAccessFile = new RandomAccessFile(file,openMode == OpenMode.READ_WRITE ? "rw" : "r");
		this.openMode = openMode;
		if (openMode == OpenMode.READ_WRITE)
			randomAccessFile.setLength(file.length());
	}

	public long getPieceOffset(int index)
	{
		return (index * networkFile.getPieceSize());
	}

	public int getPieceSize(int index)
	{
		if (index != networkFile.getPieceCount()-1)
			return Math.toIntExact(networkFile.getPieceSize());
		int ret = Math.toIntExact(networkFile.getSize() % networkFile.getPieceSize());
		if (ret == 0)
			ret = Math.toIntExact(networkFile.getPieceSize());
		return ret;
	}

	public byte[] readPiece(int index) throws IOException
	{
		if (index >= networkFile.getPieceCount())
			throw new IllegalArgumentException("Piece index out of range!!");
		if (index < 0)
			throw new IllegalArgumentException("Piece index is negative!!");
		if (!networkFile.hasPiece(index))
			return null;

		int pieceSize = getPieceSize(index);
		byte[] buffer = new byte[pieceSize];
		long pieceOffset = getPieceOffset(index);
		System.out.println("Reading piece " + index + " from file " + file.getName() + " (offset=" + pieceOffset + ", size=" + pieceSize + ")");
		randomAccessFile.seek(pieceOffset);
		randomAccessFile.read(buffer);
		return buffer;
	}

	public void writePiece(int index, byte[] buffer) throws IOException
	{
		if (openMode == OpenMode.READ_ONLY)
			throw new IllegalStateException("File was opened read-only!");
		else if (buffer.length != getPieceSize(index))
			throw new IllegalArgumentException("Received a file piece that's the wrong size!! Length = " + buffer.length + " != Piece Size = " + getPieceSize(index));
		else if (index >= networkFile.getPieceCount())
			throw new IllegalArgumentException("Received a file piece with an index past the end of the file!!");

		randomAccessFile.seek(getPieceOffset(index));
		randomAccessFile.write(buffer);

		networkFile.setHasPiece(index, true);
	}

	@Override
	public void close() throws IOException
	{
		randomAccessFile.close();
	}

	public enum OpenMode
	{
		READ_ONLY,
		READ_WRITE;
	}
}