bundles/org.eclipse.core.runtime/src/org/eclipse/core/internal/runtime/CipherInputStream.java

package org.eclipse.core.internal.runtime;

/*
 * (c) Copyright IBM Corp. 2000, 2001.
 * All Rights Reserved.
 */

import java.io.*;

/**
 * Decrypts a stream of data that was encrypted using the
 * <code>Cipher</code> or <code>CipherOutputStream</code>.
 *
 * @see Cipher
 * @see CipherOutputStream
 */
public class CipherInputStream extends FilterInputStream {
	private static final int SKIP_BUFFER_SIZE = 2048;
	private Cipher cipher;
/**
 * Constructs a new <code>CipherInputStream</code> that decrypts the
 * data in the given <code>InputStream</code>.  The data can only be
 * decrypted if the given password is the same as that which was used
 * to encrypt it.
 *
 * @param is
 * @param password
 */
public CipherInputStream(InputStream is, String password) {
	super(is);
	cipher = new Cipher(Cipher.DECRYPT_MODE, password);
}
/**
 * @see InputStream#markSupported
 */
public boolean markSupported() {
	return false;
}
/**
 * @see InputStream#read
 */
public int read() throws IOException {
	int b = super.read();
	if (b == -1)
		return -1;
	try {
		return ((int) cipher.cipher((byte) b)) & 0x00ff;
	} catch (Exception e) {
		throw new IOException(e.getMessage());
	}
}
/**
 * @see InputStream#read(byte, int, int)
 */
public int read(byte b[], int off, int len) throws IOException {
	int bytesRead = in.read(b, off, len);
	if (bytesRead == -1)
		return -1;
	try {
		byte[] result = cipher.cipher(b, off, bytesRead);
		for (int i = 0; i < result.length; ++i)
			b[i + off] = result[i];
		return bytesRead;
	} catch (Exception e) {
		throw new IOException(e.getMessage());
	}
}
/**
 * @see InputStream#skip(long)
 */
public long skip(long n) throws IOException {
	byte[] buffer = new byte[SKIP_BUFFER_SIZE];

	int bytesRead = 0;
	long bytesRemaining = n;

	while(bytesRead != -1 && bytesRemaining > 0){
		bytesRead = read(buffer, 0, (int)Math.min(SKIP_BUFFER_SIZE, bytesRemaining));
		if(bytesRead > 0){
			bytesRemaining -= bytesRead;
		}
	}

	return n - bytesRemaining;
}
}