Transaction.java

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.ObjectOutputStream;
import java.util.ArrayList;
import java.util.Iterator;


public class Transaction implements Iterable<Write>{
	
	public static final Sector COMMIT = new Sector("Commit".getBytes());

	private ArrayList<Write> writes;

	public Transaction() {
		this.writes = new ArrayList<Write>();
	}

	public void add(int sectorNum, byte[] buffer) throws IndexOutOfBoundsException, IllegalArgumentException{
		if (writes.size() == Common.MAX_WRITES_PER_TRANSACTION)
			throw new ResourceException();
		writes.add(new Write(sectorNum, buffer));
	}

	public Iterator<Write> iterator() {
		return writes.iterator();
	}
	
	//Return the size of the transaction, in sectors
	public int size() {
		return this.writes.size() + 2;
	}
	
	public ArrayList<byte[]>getSectors() throws IOException {
		ArrayList<byte[]> bytes = new ArrayList<byte[]>();
		ByteArrayOutputStream buff = new ByteArrayOutputStream(Disk.SECTOR_SIZE);
		ObjectOutputStream oos = new ObjectOutputStream(buff);		
		ArrayList<Integer> sectorNums = new ArrayList<Integer>();
		
		for (Write w : this)
			sectorNums.add(w.sectorNum);
		oos.writeObject(sectorNums);
		bytes.add(new Sector(buff.toByteArray()).array);

		for (Write w : this)
			bytes.add(w.buffer);
		bytes.add(Transaction.COMMIT.array);
		return bytes;
	}
}

class Write {
	public int sectorNum;
	public byte[] buffer;
	
	Write(int sectorNum, byte buffer[]) throws IllegalArgumentException, IndexOutOfBoundsException{
		if (sectorNum < 0 || sectorNum >= ADisk.size() )
			throw new IndexOutOfBoundsException();
		
		if (buffer.length != Disk.SECTOR_SIZE)
			  throw new IllegalArgumentException();
		this.sectorNum = sectorNum;
		this.buffer = buffer.clone();
	}
}