plugins/org.eclipse.epp.sfx.archive/src/org/eclipse/epp/installer/internal/archive/sfx/BoundedInputStream.java

/**
 * 
 */
package org.eclipse.epp.installer.internal.archive.sfx;

import java.io.IOException;
import java.io.InputStream;
import java.io.RandomAccessFile;


/**
 * @author itsuart
 *
 */
public class BoundedInputStream extends InputStream {

	private RandomAccessFile file;
	private long dataLeft;
	/**
	 * 
	 */
	public BoundedInputStream(RandomAccessFile source, long maxSize) {
		file = source;
		dataLeft = maxSize;
	}
	/* (non-Javadoc)
	 * @see java.io.InputStream#read()
	 */
	public int read() throws IOException {
		if (dataLeft == 0)
			return -1;
		int result = file.read();
		if ( result != - 1)
			dataLeft--;
		return result;
	}
	/* (non-Javadoc)
	 * @see java.io.InputStream#available()
	 */
	public int available() throws IOException {
		return (int) dataLeft;
	}
	/* (non-Javadoc)
	 * @see java.io.InputStream#markSupported()
	 */
	public boolean markSupported() {
		return false;
	}
	/* (non-Javadoc)
	 * @see java.io.InputStream#read(byte[], int, int)
	 */
	public int read(byte[] b, int off, int len) throws IOException {
		if (dataLeft == 0)
			return -1;
		if (dataLeft >= len)
		{
			int dataRead = file.read(b, off, len);
			if ( dataRead == -1 )
			{
				dataLeft = 0;
				return -1;
			}
			dataLeft -= dataRead;
			return dataRead;
		}
		else
		{
			//read only allowed num of bytes
			int dataRead = file.read(b, off, (int) dataLeft);
			if ( dataRead == -1 )
			{
				return -1;
			}
			dataLeft -= dataRead;
			return dataRead;
		}
	}
	/* (non-Javadoc)
	 * @see java.io.InputStream#read(byte[])
	 */
	public int read(byte[] b) throws IOException {
		return read(b,0,b.length);
	}
	/* (non-Javadoc)
	 * @see java.io.InputStream#skip(long)
	 */
	public long skip(long n) throws IOException {
		if (dataLeft == 0)
			return -1;
		long bytesToSkip = dataLeft >= n ? n : dataLeft;
		int skipped = file.skipBytes((int) bytesToSkip);
		if (skipped == -1)
			return -1;
		else
		{
			dataLeft -= skipped;
			return skipped;
		}
	}
	
	

}