BinaryIn.java

package joshua.util.io;

import java.io.DataInput;
import java.io.Externalizable;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.ObjectInput;
import java.io.ObjectStreamConstants;
import java.io.RandomAccessFile;

import joshua.corpus.vocab.Vocabulary;

public class BinaryIn<E extends Externalizable> extends RandomAccessFile implements DataInput, ObjectInput {

	private final Class<E> type;
	
	public static BinaryIn<Vocabulary> vocabulary(String filename) throws FileNotFoundException {
		return new BinaryIn<Vocabulary>(filename, Vocabulary.class);
	}
	
	public BinaryIn(String filename, Class<E> type) throws FileNotFoundException {
		super(filename, "r");
		this.type = type;
	}

	public int available() throws IOException {
		long pos = getFilePointer();
		long length = length();
		
		long bytesAvailable = length - pos;
		
		if (bytesAvailable > Integer.MAX_VALUE) {
			return Integer.MAX_VALUE;
		} else {
			return (int) bytesAvailable;
		}
	}

	public E readObject() throws ClassNotFoundException, IOException {

		int b = peek();
		
		if (b == ObjectStreamConstants.TC_NULL) {
			
			return null;
			
		} else {
			
			E obj;
			try {
				obj = type.newInstance();
				obj.readExternal(this);
				return obj;
			} catch (InstantiationException e) {
				throw new RuntimeException(e);
			} catch (IllegalAccessException e) {
				throw new RuntimeException(e);
			}

			
		}
	}
	
	public long skip(long n) throws IOException {
		
		long bytesSkipped = 0;
		
		while (n > 0) {
			if (n > Integer.MAX_VALUE) {
				bytesSkipped += skipBytes(Integer.MAX_VALUE);
				n -= Integer.MAX_VALUE;
			} else {
				bytesSkipped = skipBytes((int) n);
				n = 0;
			}
		}
		
		return bytesSkipped;
	}
	
	

	private int peek() throws IOException {
		long pos = getFilePointer();
		int b = read();
		seek(pos);
		return b;
	}
}